Final Year IEEE Project 2013-2014 - Networking Project Title and Abstract
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Elysium Technologies Private Limited Singapore | Madurai | Chennai | Trichy | Coimbatore | Cochin | Ramnad | Pondicherry | Trivandrum | Salem | Erode | Tirunelveli http://www.elysiumtechnologies.com , [email protected]13 Years of Experience Automated Services 24/7 Help Desk Support Experience & Expertise Developers Advanced Technologies & Tools Legitimate Member of all Journals Having 1,50,000 Successive records in all Languages More than 12 Branches in Tamilnadu, Kerala & Karnataka. Ticketing & Appointment Systems. Individual Care for every Student. Around 250 Developers & 20 Researchers
Answering ―What-If‖ Deployment and Configuration Questions With WISE:
Techniques and Deployment Experience,
Abstract: Designers of content distribution networks (CDNs) often need to determine how changes to
infrastructure deployment and configuration affect service response times when they deploy a new data center, change ISP peering, or change the mapping of clients to servers. Today, the designers use coarse,
back-of-the-envelope calculations or costly field deployments; they need better ways to evaluate the
effects of such hypothetical “what-if” questions before the actual deployments. This paper presents What-
If Scenario Evaluator (WISE), a tool that predicts the effects of possible configuration and deployment changes in content distribution networks. WISE makes three contributions: 1) an algorithm that uses
traces from existing deployments to learn causality among factors that affect service response time
distributions; 2) an algorithm that uses the learned causal structure to estimate a dataset that is representative of the hypothetical scenario that a designer may wish to evaluate, and uses these datasets to
predict hypothetical response-time distributions; 3) a scenario specification language that allows a
network designer to easily express hypothetical deployment scenarios without being cognizant of the dependencies between variables that affect service response times. Our evaluation, both in a controlled
setting and in a real-world field deployment on a large, global CDN, shows that WISE can quickly and
accurately predict service response-time distributions for many practical what-if scenarios.
ETPL
NT-002
Complexity Analysis and Algorithm Design for Advance Bandwidth Scheduling in
Dedicated Networks
Abstract: An increasing number of high-performance networks provision dedicated channels through
circuit switching or MPLS/GMPLS techniques to support large data transfer. The link bandwidths in such
networks are typically shared by multiple users through advance reservation, resulting in varying bandwidth availability in future time. Developing efficient scheduling algorithms for advance bandwidth
reservation has become a critical task to improve the utilization of network resources and meet the
transport requirements of application users. We consider an exhaustive combination of different path and bandwidth constraints and formulate four types of advance bandwidth scheduling problems, with the
same objective to minimize the data transfer end time for a given transfer request with a prespecified data
size: fixed path with fixed bandwidth (FPFB); fixed path with variable bandwidth (FPVB); variable path
with fixed bandwidth (VPFB); and variable path with variable bandwidth (VPVB). For VPFB and VPVB, we further consider two subcases where the path switching delay is negligible or nonnegligible. We
propose an optimal algorithm for each of these scheduling problems except for FPVB and VPVB with
nonnegligible path switching delay, which are proven to be NP-complete and nonapproximable, and then tackled by heuristics. The performance superiority of these heuristics is verified by extensive
experimental results in a large set of simulated networks in comparison to optimal and greedy strategies
ETPL
NT-003
Diffusion Dynamics of Network Technologies With Bounded Rational Users:
Aspiration-Based Learning
Abstract: Recently, economic models have been proposed to study adoption dynamics of entrant and
incumbent technologies motivated by the need for new network architectures to complement the current
Internet. We propose new models of adoption dynamics of entrant and incumbent technologies among bounded rational users who choose a satisfying strategy rather than an optimal strategy based on
aspiration-based learning. Two models of adoption dynamics are proposed according to the characteristics
of aspiration level. The impacts of switching cost, the benefit from entrant and incumbent technologies,
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] and the initial aspiration level on the adoption dynamics are investigated.
ETPL
NT-004 Delay-Based Network Utility Maximization
Abstract: It is well known that max-weight policies based on a queue backlog index can be used to
stabilize stochastic networks, and that similar stability results hold if a delay index is used. Using
Lyapunov optimization, we extend this analysis to design a utility maximizing algorithm that uses explicit delay information from the head-of-line packet at each user. The resulting policy is shown to ensure
deterministic worst-case delay guarantees and to yield a throughput utility that differs from the optimally
fair value by an amount that is inversely proportional to the delay guarantee. Our results hold for a
general class of 1-hop networks, including packet switches and multiuser wireless systems with time-varying reliability .
ETPL
NT-005 A Distributed Control Law for Load Balancing in Content Delivery Networks
Abstract: In this paper, we face the challenging issue of defining and implementing an effective law for load balancing in Content Delivery Networks (CDNs). We base our proposal on a formal study of a CDN
system, carried out through the exploitation of a fluid flow model characterization of the network of
servers. Starting from such characterization, we derive and prove a lemma about the network queues
equilibrium. This result is then leveraged in order to devise a novel distributed and time-continuous algorithm for load balancing, which is also reformulated in a time-discrete version. The discrete
formulation of the proposed balancing law is eventually discussed in terms of its actual implementation in
a real-world scenario. Finally, the overall approach is validated by means of simulations.
ETPL
NT-006 Efficient Algorithms for Neighbor Discovery in Wireless Networks
Abstract: Neighbor discovery is an important first step in the initialization of a wireless ad hoc network.
In this paper, we design and analyze several algorithms for neighbor discovery in wireless networks. Starting with a single-hop wireless network of n nodes, we propose a Θ(nlnn) ALOHA-like neighbor
discovery algorithm when nodes cannot detect collisions, and an order-optimal Θ(n) receiver feedback-
based algorithm when nodes can detect collisions. Our algorithms neither require nodes to have a priori
estimates of the number of neighbors nor synchronization between nodes. Our algorithms allow nodes to begin execution at different time instants and to terminate neighbor discovery upon discovering all their
neighbors. We finally show that receiver feedback can be used to achieve a Θ(n) running time, even when
nodes cannot detect collisions. We then analyze neighbor discovery in a general multihop setting. We establish an upper bound of O(Δlnn) on the running time of the ALOHA-like algorithm, where Δ denotes
the maximum node degree in the network and n the total number of nodes. We also establish a lower
bound of Ω(Δ+lnn) on the running time of any randomized neighbor discovery algorithm. Our result thus implies that the ALOHA-like algorithm is at most a factor min(Δ,lnn) worse than optimal.
ETPL
NT-007 Stochastic Game for Wireless Network Virtualization
Abstract: We propose a new framework for wireless network virtualization. In this framework, service
providers (SPs) and the network operator (NO) are decoupled from each other: The NO is solely responsible for spectrum management, and SPs are responsible for quality-of-service (QoS) management
for their own users. SPs compete for the shared wireless resources to satisfy their distinct service
objectives and constraints. We model the dynamic interactions among SPs and the NO as a stochastic game. SPs bid for the resources via dynamically announcing their value functions. The game is regulated
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] by the NO through: 1) sum-utility optimization under rate region constraints; 2) enforcement of Vickrey-
Clarke-Groves (VCG) mechanism for pricing the instantaneous rate consumption; and 3) declaration of
conjectured prices for future resource consumption. We prove that there exists one Nash equilibrium in the conjectural prices that is efficient, i.e., the sum-utility is maximized. Thus, the NO has the incentive to
compute the equilibrium point and feedback to SPs. Given the conjectural prices and the VCG
mechanism, we also show that SPs must reveal their truthful value functions at each step to maximize their long-term utilities. As another major contribution, we develop an online learning algorithm that
allows the SPs to update the value functions and the NO to update the conjectural prices iteratively. Thus,
the proposed framework can deal with unknown dynamics in traffic characteristics and channel
conditions. We present simulation results to show the convergence to the Nash equilibrium prices under various dynamic traffic and channel conditions.
ETPL
NT-008 ABC: Adaptive Binary Cuttings for Multidimensional Packet Classification,
Abstract: Decision tree-based packet classification algorithms are easy to implement and allow the tradeoff between storage and throughput. However, the memory consumption of these algorithms remains
quite high when high throughput is required. The Adaptive Binary Cuttings (ABC) algorithm exploits
another degree of freedom to make the decision tree adapt to the geometric distribution of the filters. The three variations of the adaptive cutting procedure produce a set of different-sized cuts at each decision
step, with the goal to balance the distribution of filters and to reduce the filter duplication effect. The
ABC algorithm uses stronger and more straightforward criteria for decision tree construction. Coupled
with an efficient node encoding scheme, it enables a smaller, shorter, and well-balanced decision tree. The hardware-oriented implementation of each variation is proposed and evaluated extensively to
demonstrate its scalability and sensitivity to different configurations. The results show that the ABC
algorithm significantly outperforms the other decision tree-based algorithms. It can sustain more than 10-Gb/s throughput and is the only algorithm among the existing well-known packet classification
algorithms that can compete with TCAMs in terms of the storage efficiency.
ETPL
NT-009
A Utility Maximization Framework for Fair and Efficient Multicasting in Multicarrier
Wireless Cellular Networks
Abstract: Multicast/broadcast is regarded as an efficient technique for wireless cellular networks to
transmit a large volume of common data to multiple mobile users simultaneously. To guarantee the
quality of service for each mobile user in such single-hop multicasting, the base-station transmitter
usually adapts its data rate to the worst channel condition among all users in a multicast group. On one hand, increasing the number of users in a multicast group leads to a more efficient utilization of spectrum
bandwidth, as users in the same group can be served together. On the other hand, too many users in a
group may lead to unacceptably low data rate at which the base station can transmit. Hence, a natural question that arises is how to efficiently and fairly transmit to a large number of users requiring the same
message. This paper endeavors to answer this question by studying the problem of multicasting over
multicarriers in wireless orthogonal frequency division multiplexing (OFDM) cellular systems. Using a
unified utility maximization framework, we investigate this problem in two typical scenarios: namely, when users experience roughly equal path losses and when they experience different path losses,
respectively. Through theoretical analysis, we obtain optimal multicast schemes satisfying various
throughput-fairness requirements in these two cases. In particular, we show that the conventional multicast scheme is optimal in the equal-path-loss case regardless of the utility function adopted. When
users experience different path losses, the group multicast scheme, which divides the users almost equally
into many multicast groups and multicasts to different groups of users over nonoverlapping subcarriers, is optimal .
NT-010 Achieving Efficient Flooding by Utilizing Link Correlation in Wireless Sensor
Networks,
Abstract: Although existing flooding protocols can provide efficient and reliable communication in
wireless sensor networks on some level, further performance improvement has been hampered by the assumption of link independence, which requires costly acknowledgments (ACKs) from every receiver.
In this paper, we present collective flooding (CF), which exploits the link correlation to achieve flooding
reliability using the concept of collective ACKs. CF requires only 1-hop information at each node, making the design highly distributed and scalable with low complexity. We evaluate CF extensively in
real-world settings, using three different types of testbeds: a single-hop network with 20 MICAz nodes, a
multihop network with 37 nodes, and a linear outdoor network with 48 nodes along a 326-m-long bridge. System evaluation and extensive simulation show that CF achieves the same reliability as state-of-the-art
solutions while reducing the total number of packet transmission and the dissemination delay by 30%-
50% and 35%-50%, respectively
ETPL
NT-011
Random Walks and Green's Function on Digraphs: A Framework for Estimating
Wireless Transmission Costs
Abstract: Various applications in wireless networks, such as routing and query processing, can be
formulated as random walks on graphs. Many results have been obtained for such applications by
utilizing the theory of random walks (or spectral graph theory), which is mostly developed for undirected graphs. However, this formalism neglects the fact that the underlying (wireless) networks in practice
contain asymmetric links, which are best characterized by directed graphs (digraphs). Therefore, random
walk on digraphs is a more appropriate model to consider for such networks. In this paper, by generalizing the random walk theory (or spectral graph theory) that has been primarily developed for
undirected graphs to digraphs, we show how various transmission costs in wireless networks can be
formulated in terms of hitting times and cover times of random walks on digraphs. Using these results, we
develop a unified theoretical framework for estimating various transmission costs in wireless networks. Our framework can be applied to random walk query processing strategy and the three routing paradigms-
best path routing, opportunistic routing, and stateless routing-to which nearly all existing routing
protocols belong. Extensive simulations demonstrate that the proposed digraph-based analytical model can achieve more accurate transmission cost estimation over existing methods.
ETPL
NT-012
A Flexible Platform for Hardware-Aware Network Experiments and a Case Study on
Wireless Network Coding
Abstract: In this paper, we present the design and implementation of a general, flexible, hardware-aware
network platform that takes hardware processing behavior into consideration to accurately evaluate network performance. The platform adopts a network-hardware co-simulation approach in which the NS-
2 network simulator supervises the network-wide traffic flow and the SystemC hardware simulator
simulates the underlying hardware processing in network nodes. In addition, as a case study, we implemented wireless all-to-all broadcasting with network coding on the platform. We analyze the
hardware processing behavior during the algorithm execution and evaluate the overall performance of the
algorithm. Our experimental results demonstrate that hardware processing can have a significant impact on the algorithm performance and hence should be taken into consideration in the algorithm design. We
expect that this hardware-aware platform will become a very useful tool for more accurate network
simulations and more efficient design space exploration of processing-intensive applications.
ETPL
NT-013
Exploring the Design Space of Multichannel Peer-to-Peer Live Video Streaming
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] Abstract: Most of the commercial peer-to-peer (P2P) video streaming deployments support hundreds of
channels and are referred to as multichannel systems. Recent research studies have proposed specific
protocols to improve the streaming quality for all channels by enabling cross-channel cooperation among multiple channels. In this paper, we focus on the following fundamental problems in designing
cooperating multichannel systems: 1) what are the general characteristics of existing and potential
designs? and 2) under what circumstances should a particular design be used to achieve the desired streaming quality with the lowest implementation complexity? To answer the first question, we propose
simple models based on linear programming and network-flow graphs for three general designs, namely
(PCA), and Active Channel-aware bandwidth allocation Approach (ACA), which provide insight into understanding the key characteristics of cross-channel resource sharing. For the second question, we first
develop closed-form results for two-channel systems. Then, we use extensive numerical simulations to
compare the three designs for various peer population distributions, upload bandwidth distributions, and channel structures. Our analytical and simulation results show that: 1) the NBA design can rarely achieve
the desired streaming quality in general cases; 2) the PCA design can achieve the same performance as
the ACA design in general cases; and 3) the ACA design should be used for special applications.
ETPL
NT-014
Secondary Spectrum Trading—Auction-Based Framework for Spectrum Allocation
and Profit Sharing
Abstract: Recently, dynamic spectrum sharing has been gaining interest as a potential solution to scarcity
of available spectrum. We investigate the problem of designing a secondary spectrum-trading market
when there are multiple sellers and multiple buyers and propose a general framework for the trading market based on an auction mechanism. To this end, we first introduce a new optimal auction mechanism,
called the generalized Branco's mechanism (GBM). The GBM, which is both incentive-compatible and
individually rational, is used to determine the assigned frequency bands and prices for them. Second, we assume that buyers of the spectrum are selfish and model their interaction as a noncooperative game.
Using this model, we prove that when the sellers employ the GBM to vend their frequency bands, they
can guarantee themselves the largest expected profits by selling their frequency bands jointly. Third, based on the previous finding, we model the interaction among the sellers as a cooperative game and
demonstrate that, for any fixed strategies of the buyers, the core of the cooperative game is nonempty.
This suggests that there exists a way for the sellers to share the profits from the joint sale of the spectrum
so that no subset of sellers will find it beneficial to vend their frequency bands separately without the remaining sellers. Finally, we propose a profit-sharing scheme that can achieve any expected profit vector
in the nonempty core of the cooperative game while satisfying two desirable properties.
ETPL
NT-015 Towards Practical Communication in Byzantine-Resistant DHTs
Abstract: There are several analytical results on distributed hash tables (DHTs) that can tolerate Byzantine
faults. Unfortunately, in such systems, operations such as data retrieval and message sending incur
significant communication costs. For example, a simple scheme used in many Byzantine fault-tolerant
DHT constructions of n nodes requires O(log3n) messages; this is likely impractical for real-world
applications. The previous best known message complexity is O(log2n) in expectation. However, the
corresponding protocol suffers from prohibitive costs owing to hidden constants in the asymptotic
notation and setup costs. In this paper, we focus on reducing the communication costs against a computationally bounded adversary. We employ threshold cryptography and distributed key generation to
define two protocols, both of which are more efficient than existing solutions. In comparison, our first
protocol is deterministic with O(log2n) message complexity, and our second protocol is randomized with
expected O(logn) message complexity. Furthermore, both the hidden constants and setup costs for our
protocols are small, and no trusted third party is required. Finally, we present results from
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] microbenchmarks conducted over PlanetLab showing that our protocols are practical for deployment
under significant levels of churn and adversarial behavior
ETPL
NT-016
Semi-Random Backoff: Towards Resource Reservation for Channel Access in Wireless
LANs
Abstract: This paper proposes a semi-random backoff (SRB) method that enables resource reservation in
contention-based wireless LANs. The proposed SRB is fundamentally different from traditional random
backoff methods because it provides an easy migration path from random backoffs to deterministic slot
assignments. The central idea of the SRB is for the wireless station to set its backoff counter to a deterministic value upon a successful packet transmission. This deterministic value will allow the station
to reuse the time-slot in consecutive backoff cycles. When multiple stations with successful packet
transmissions reuse their respective time-slots, the collision probability is reduced, and the channel achieves the equivalence of resource reservation. In case of a failed packet transmission, a station will
revert to the standard random backoff method and probe for a new available time-slot. The proposed SRB
method can be readily applied to both 802.11 DCF and 802.11e EDCA networks with minimum modification to the existing DCF/EDCA implementations. Theoretical analysis and simulation results
validate the superior performance of the SRB for small-scale and heavily loaded wireless LANs. When
combined with an adaptive mechanism and a persistent backoff process, SRB can also be effective for
large-scale and lightly loaded wireless networks.
ETPL
NT-017 Entry and Spectrum Sharing Scheme Selection in Femtocell Communications Markets
Abstract: Focusing on a femtocell communications market, we study the entrant network service
provider's (NSP's) long-term decision: whether to enter the market and which spectrum sharing technology to select to maximize its profit. This long-term decision is closely related to the entrant's
pricing strategy and the users' aggregate demand, which we model as medium-term and short-term
decisions, respectively. We consider two markets, one with no incumbent and the other with one
incumbent. For both markets, we show the existence and uniqueness of an equilibrium point in the user subscription dynamics and provide a sufficient condition for the convergence of the dynamics. For the
market with no incumbent, we derive upper and lower bounds on the optimal price and market share that
maximize the entrant's revenue, based on which the entrant selects an available technology to maximize its long-term profit. For the market with one incumbent, we model competition between the two NSPs as
a noncooperative game, in which the incumbent and the entrant choose their market shares independently,
and provide a sufficient condition that guarantees the existence of at least one pure Nash equilibrium. Finally, we formalize the problem of entry and spectrum-sharing scheme selection for the entrant and
provide numerical results to complement our analysis.
ETPL
NT-018 On Replication Algorithm in P2P VoD,
Abstract: Traditional video-on-demand (VoD) systems rely purely on servers to stream video content to clients, which does not scale. In recent years, peer-to-peer assisted VoD (P2P VoD) has proven to be
practical and effective. In P2P VoD, each peer contributes some storage to store videos (or segments of
videos) to help the video server. Assuming peers have sufficient bandwidth for the given video playback rate, a fundamental question is what is the relationship between the storage capacity (at each peer), the
number of videos, the number of peers, and the resultant off-loading of video server bandwidth. In this
paper, we use a simple statistical model to derive this relationship. We propose and analyze a generic replication algorithm Random with Load Balancing (RLB) that balances the service to all movies for both
deterministic and random (but stationary) demand models and both homogeneous and heterogeneous
peers (in upload bandwidth). We use simulation to validate our results for sensitivity analysis and for
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] comparisons to other popular replication algorithms. This study leads to several fundamental insights for
P2P VoD system design in practice.
ETPL
NT-019 Back-Pressure-Based Packet-by-Packet Adaptive Routing in Communication Networks
Abstract: Back-pressure-based adaptive routing algorithms where each packet is routed along a possibly
different path have been extensively studied in the literature. However, such algorithms typically result in
poor delay performance and involve high implementation complexity. In this paper, we develop a new
adaptive routing algorithm built upon the widely studied back-pressure algorithm. We decouple the routing and scheduling components of the algorithm by designing a probabilistic routing table that is used
to route packets to per-destination queues. The scheduling decisions in the case of wireless networks are
made using counters called shadow queues. The results are also extended to the case of networks that employ simple forms of network coding. In that case, our algorithm provides a low-complexity solution
to optimally exploit the routing-coding tradeoff.
ETPL
NT-020 Scheduling in a Random Environment: Stability and Asymptotic Optimality
Abstract: We investigate the scheduling of a common resource between several concurrent users when the
feasible transmission rate of each user varies randomly over time. Time is slotted, and users arrive and
depart upon service completion. This may model, for example, the flow-level behavior of end-users in a
narrowband HDR wireless channel (CDMA 1xEV-DO). As performance criteria, we consider the stability of the system and the mean delay experienced by the users. Given the complexity of the problem, we
investigate the fluid-scaled system, which allows to obtain important results and insights for the original
system: 1) We characterize for a large class of scheduling policies the stability conditions and identify a set of maximum stable policies, giving in each time-slot preference to users being in their best possible
channel condition. We find in particular that many opportunistic scheduling policies like Score-Based,
Proportionally Best, or Potential Improvement are stable under the maximum stability conditions,
whereas the opportunistic scheduler Relative-Best or the cμ-rule are not. 2) We show that choosing the right tie-breaking rule is crucial for the performance (e.g., average delay) as perceived by a user. We
prove that a policy is asymptotically optimal if it is maximum stable and the tie-breaking rule gives
priority to the user with the highest departure probability. We will refer to such tie-breaking rule as myopic. 3) We derive the growth rates of the number of users in the system in overload settings under
various policies, which give additional insights on the performance. 4) We conclude that simple priority-
index policies with the myopic tie-breaking rule are stable and asymptotically optimal. All our findings are validated with extensive numerical experiments.
ETPL
NT-021
An Empirical Interference Modeling for Link Reliability Assessment in Wireless
Networks
Abstract: In recent years, it has been widely believed in the community that the link reliability is strongly
related to received signal strength indicator (RSSI) [or signal-to-interference-plus-noise ratio (SINR)] and external interference makes it unpredictable, which is different from the previous understanding that there
is no tight relationship between the link reliability and RSSI (or SINR), but multipath fading causes the
unpredictability. However, both cannot fully explain why the unpredictability appears in the link state. In this paper, we unravel the following questions: 1) What causes frame losses that are directly related to
intermediate link states? 2) Is RSSI or SINR a right criterion to represent the link reliability? 3) Is there a
better measure to assess the link reliability? We first configured a testbed for performing a real measurement study to identify the causes of frame losses, and observed that link reliability depends on an
intraframe SINR distribution, not a single value of RSSI (or SINR). We also learned that an RSSI value is
not always a good indicator to estimate the link state. We then conducted a further investigation on the
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] intraframe SINR distribution and the relationship between the SINR and link reliability with the ns-2
simulator. Based on these results, we finally propose an interference modeling framework for estimating
link states in the presence of wireless interferences. We envision that the framework can be used for developing link-aware protocols to achieve their optimal performance in a hostile wireless environment.
ETPL
NT-022 On Downlink Capacity of Cellular Data Networks With WLAN/WPAN Relays
Abstract: We consider the downlink of a cellular network supporting data traffic in which each user is equipped with the same type of IEEE 802.11-like WLAN or WPAN interface used to relay packets to
further users. We are interested in the design guidelines for such networks and how much capacity
improvements the additional relay layer can bring. A first objective is to provide a scheduling/relay
strategy that maximizes the network capacity. Using theoretical analysis, numerical evaluation, and simulations, we find that when the number of active users is large, the capacity-achieving strategy divides
the cell into two areas: one closer to the base station where the relay layer is always saturated and some
nodes receive traffic through both direct and relay links, and the farther one where the relay is never saturated and the direct traffic is almost nonexistent. We also show that it is approximately optimal to use
fixed relay link lengths, and we derive this length. We show that the obtained capacity is independent of
the cell size (unlike in traditional cellular networks). Based on our findings, we propose simple decentralized routing and scheduling protocols. We show that in a fully saturated network our optimized
protocol substantially improves performance over the protocols that use naive relay-only or direct-only
policies.
ETPL
NT-023
Centralized and Distributed Protocols for Tracker-Based Dynamic Swarm
Management
Abstract: With BitTorrent, efficient peer upload utilization is achieved by splitting contents into many
small pieces, each of which may be downloaded from different peers within the same swarm.
Unfortunately, piece and bandwidth availability may cause the file-sharing efficiency to degrade in small swarms with few participating peers. Using extensive measurements, we identified hundreds of thousands
of torrents with several small swarms for which reallocating peers among swarms and/or modifying the
peer behavior could significantly improve the system performance. Motivated by this observation, we propose a centralized and a distributed protocol for dynamic swarm management. The centralized
protocol (CSM) manages the swarms of peers at minimal tracker overhead. The distributed protocol
(DSM) manages the swarms of peers while ensuring load fairness among the trackers. Both protocols
achieve their performance improvements by identifying and merging small swarms and allow load sharing for large torrents. Our evaluations are based on measurement data collected during eight days
from over 700 trackers worldwide, which collectively maintain state information about 2.8 million unique
torrents. We find that CSM and DSM can achieve most of the performance gains of dynamic swarm management. These gains are estimated to be up to 40% on average for small torrents.
ETPL
NT-024 Localization of Wireless Sensor Networks in the Wild: Pursuit of Ranging Quality
Abstract: Localization is a fundamental issue of wireless sensor networks that has been extensively
studied in the literature. Our real-world experience from GreenOrbs, a sensor network system deployed in a forest, shows that localization in the wild remains very challenging due to various interfering factors. In
this paper, we propose CDL, a Combined and Differentiated Localization approach for localization that
exploits the strength of range-free approaches and range-based approaches using received signal strength indicator (RSSI). A critical observation is that ranging quality greatly impacts the overall localization
accuracy. To achieve a better ranging quality, our method CDL incorporates virtual-hop localization,
local filtration, and ranging-quality aware calibration. We have implemented and evaluated CDL by
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] extensive real-world experiments in GreenOrbs and large-scale simulations. Our experimental and
simulation results demonstrate that CDL outperforms current state-of-art localization approaches with a
more accurate and consistent performance. For example, the average location error using CDL in GreenOrbs system is 2.9 m, while the previous best method SISR has an average error of 4.6 m.
ETPL
NT-025 Control of Wireless Networks With Secrecy
Abstract: We consider the problem of cross-layer resource allocation in time-varying cellular wireless networks and incorporate information theoretic secrecy as a quality-of-service constraint. Specifically,
each node in the network injects two types of traffic, private and open, at rates chosen in order to
maximize a global utility function, subject to network stability and secrecy constraints. The secrecy
constraint enforces an arbitrarily low mutual information leakage from the source to every node in the network, except for the sink node. We first obtain the achievable rate region for the problem for single-
and multiuser systems assuming that the nodes have full channel state information (CSI) of their
neighbors. Then, we provide a joint flow control, scheduling, and private encoding scheme, which does not rely on the knowledge of the prior distribution of the gain of any channel. We prove that our scheme
achieves a utility arbitrarily close to the maximum achievable utility. Numerical experiments are
performed to verify the analytical results and to show the efficacy of the dynamic control algorithm.
ETPL
NT-026 ICTCP: Incast Congestion Control for TCP in Data-Center Networks
Abstract: Transport Control Protocol (TCP) incast congestion happens in high-bandwidth and low-latency
networks when multiple synchronized servers send data to the same receiver in parallel. For many
important data-center applications such as MapReduce and Search, this many-to-one traffic pattern is common. Hence TCP incast congestion may severely degrade their performances, e.g., by increasing
response time. In this paper, we study TCP incast in detail by focusing on the relationships between TCP
throughput, round-trip time (RTT), and receive window. Unlike previous approaches, which mitigate the impact of TCP incast congestion by using a fine-grained timeout value, our idea is to design an Incast
congestion Control for TCP (ICTCP) scheme on the receiver side. In particular, our method adjusts the
TCP receive window proactively before packet loss occurs. The implementation and experiments in our testbed demonstrate that we achieve almost zero timeouts and high goodput for TCP incast.
ETPL
NT-027 Context-Aware Nanoscale Modeling of Multicast Multihop Cellular Networks
Abstract: In this paper, we present a new approach to optimization of multicast in multihop cellular
networks. We apply a hexagonal tessellation for inner partitioning of the cell into smaller subcells of radius r. Subcells may be several orders of magnitude smaller than, e.g., microcells, resulting in what we
refer to as a nanoscale network model (NSNM), including a special nanoscale channel model (NSCM) for
this application. For such tessellation, a spatial interleaving SI MAC protocol is introduced for context-aware interlink interference management. The directed flooding routing protocol (DFRP) and
interflooding network coding (IFNC) are proposed for such a network model including intercell flooding
coordination (ICFC) protocol to minimize the intercell interference. By adjusting the radius of the
subcell r , we obtain different hopping ranges that directly affect the throughput, power consumption, and interference. With r as the optimization parameter, in this paper we jointly optimize scheduling, routing,
and power control to obtain the optimum tradeoff between throughput, delay, and power consumption in
multicast cellular networks. A set of numerical results demonstrates that the NSNM enables high-resolution optimization of the system and an effective use of the context awareness.
ETPL
NT-028
Moment-Based Spectral Analysis of Large-Scale Networks Using Local Structural
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] Abstract: The eigenvalues of matrices representing the structure of large-scale complex networks present
a wide range of applications, from the analysis of dynamical processes taking place in the network to
spectral techniques aiming to rank the importance of nodes in the network. A common approach to study the relationship between the structure of a network and its eigenvalues is to use synthetic random
networks in which structural properties of interest, such as degree distributions, are prescribed. Although
very common, synthetic models present two major flaws: 1) These models are only suitable to study a very limited range of structural properties; and 2) they implicitly induce structural properties that are not
directly controlled and can deceivingly influence the network eigenvalue spectrum. In this paper, we
propose an alternative approach to overcome these limitations. Our approach is not based on synthetic
models. Instead, we use algebraic graph theory and convex optimization to study how structural properties influence the spectrum of eigenvalues of the network. Using our approach, we can compute,
with low computational overhead, global spectral properties of a network from its local structural
properties. We illustrate our approach by studying how structural properties of online social networks influence their eigenvalue spectra
ETPL
NT-029 Internet-Scale IPv4 Alias Resolution With MIDAR
Abstract: A critical step in creating accurate Internet topology maps from traceroute data is mapping IP addresses to routers, a process known as alias resolution. Recent work in alias resolution inferred aliases
based on similarities in IP ID time series produced by different IP addresses. We design, implement, and
experiment with a new tool that builds on these insights to scale to Internet-scale topologies, i.e., millions
of addresses, with greater precision and sensitivity. MIDAR, our Monotonic ID-Based Alias Resolution tool, provides an extremely precise ID comparison test based on monotonicity rather than proximity.
MIDAR integrates multiple probing methods, multiple vantage points, and a novel sliding-window probe
scheduling algorithm to increase scalability to millions of IP addresses. Experiments show that MIDAR's approach is effective at minimizing the false positive rate sufficiently to achieve a high positive predictive
value at Internet scale. We provide sample statistics from running MIDAR on over 2 million addresses.
We also validate MIDAR and RadarGun against available ground truth and show that MIDAR's results are significantly better than RadarGun's. Tools such as MIDAR can enable longitudinal study of the
Internet's topological evolution.
ETPL
NT-030 Time-Bounded Essential Localization for Wireless Sensor Networks
Abstract: In many practical applications of wireless sensor networks, it is crucial to accomplish the localization of sensors within a given time bound. We find that the traditional definition of relative
localization is inappropriate for evaluating its actual overhead in localization time. To address this issue,
we define a novel problem called essential localization and present the first rigorous study on the essential localizability of a wireless sensor network within a given time bound. Additionally, we propose an
efficient distributed algorithm for time-bounded essential localization over a sensor network and evaluate
the performance of the algorithm with analysis and extensive simulation studies.
ETPL
NT-031 Stability of FIPP -Cycles Under Dynamic Traffic in WDM Networks
Abstract: Application opportunities associated with video, voice, and data triple-play result in a dramatic
demand increase in metro transport networks, with traffic patterns becoming increasingly dynamic and
difficult to predict. This is driving the need of core networks with a high degree of flexibility and multigranularities to carry traffic. We propose to investigate the question of what this means in terms of
dynamic protection provisioning. In other words, we want to study how stable are the protection
structures under dynamic traffic, i.e., how much and how often they need to be updated in a dynamic
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] survivable WDM network. While most studies on the stability of protection structures have been
conducted on p-cycles and link shared protection, we propose to investigate here the stability of failure-
independent path-protecting (FIPP) p-cycles under dynamic traffic. For doing so, we design and develop an original scalable mathematical model that we solve using large-scale optimization tools. Numerical
results show that FIPP p-cycles are remarkably stable under the evaluation of the number of required
optical bypass reconfigurations under dynamic traffic.
ETPL
NT-032 Cooperative Carrier Signaling: Harmonizing Coexisting WPAN and WLAN Devices
Abstract: The unlicensed ISM spectrum is getting crowded by wireless local area network (WLAN) and
wireless personal area network (WPAN) users and devices. Spectrum sharing within the same network of
devices can be arbitrated by existing MAC protocols, but the coexistence between WPAN and WLAN (e.g., ZigBee and WiFi) remains a challenging problem. The traditional MAC protocols are ineffective in
dealing with the disparate transmit-power levels, asynchronous time-slots, and incompatible PHY layers
of such heterogeneous networks. Recent measurement studies have shown moderate-to-high WiFi traffic to severely impair the performance of coexisting ZigBee. We propose a novel mechanism, called
cooperative carrier signaling (CCS), that exploits the inherent cooperation among ZigBee nodes to
harmonize their coexistence with WiFi WLANs. CCS employs a separate ZigBee node to emit a carrier signal (busy tone) concurrently with the desired ZigBee's data transmission, thereby enhancing the
ZigBee's visibility to WiFi. It employs an innovative way to concurrently schedule a busy tone and a data
transmission without causing interference between them. We have implemented and evaluated CCS on
the TinyOS/MICAz and GNURadio/USRP platforms. Our extensive experimental evaluation has shown that CCS reduces collision between ZigBee and WiFi by 50% for most cases, and by up to 90% in the
presence of a high-level interference, all at negligible WiFi performance loss.
ETPL
NT-033 Mobility Increases the Connectivity of Wireless Networks
Abstract: In this paper, we investigate the connectivity for large-scale clustered wireless sensor and ad
hoc networks. We study the effect of mobility on the critical transmission range for asymptotic
connectivity in k-hop clustered networks and compare to existing results on nonclustered stationary networks. By introducing k -hop clustering, any packet from a cluster member can reach a cluster head
within k hops, and thus the transmission delay is bounded as Θ(1) for any finite k. We first characterize
the critical transmission range for connectivity in mobile k-hop clustered networks where all nodes move
under either the random walk mobility model with nontrivial velocity or the i.i.d. mobility model. By the term nontrivial velocity, we mean that the velocity of a node v is ω(r(n)), where r(n) is the transmission
range of the node. We then compare with the critical transmission range for stationary k-hop clustered
networks. In addition, the critical number of neighbors is studied in a parallel manner for both stationary and mobile networks. We also study the transmission power versus delay tradeoff and the average energy
consumption per flow among different types of networks. We show that random walk mobility with
nontrivial velocities increases connectivity in k-hop clustered networks, and thus significantly decreases
the energy consumption and improves the power-delay tradeoff. The decrease of energy consumption per flow is shown to be Θ([(logn)/(nd)]) in clustered networks. These results provide insights on network
design and fundamental guidelines on building a large-scale wireless network.
ETPL
NT-034
Topology Control for Effective Interference Cancellation in Multiuser MIMO
Networks
Abstract: In multiuser multiple-input-multiple-output (MIMO) networks, receivers decode multiple
concurrent signals using successive interference cancellation (SIC). With SIC, a weak target signal can be
deciphered in the presence of stronger interfering signals. However, this is only feasible if each strong
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] interfering signal satisfies a signal-to-noise-plus-interference ratio (SINR) requirement. This necessitates
the appropriate selection of a subset of links that can be concurrently active in each receiver's
neighborhood; in other words, a subtopology consisting of links that can be simultaneously active in the network is to be formed. If the selected subtopologies are of small size, the delay between the
transmission opportunities on a link increases. Thus, care should be taken to form a limited number of
subtopologies. We find that the problem of constructing the minimum number of subtopologies such that SIC decoding is successful with a desired probability threshold is NP-hard. Given this, we propose
MUSIC, a framework that greedily forms and activates subtopologies in a way that favors successful SIC
decoding with a high probability. MUSIC also ensures that the number of selected subtopologies is kept
small. We provide both a centralized and a distributed version of our framework. We prove that our centralized version approximates the optimal solution for the considered problem. We also perform
extensive simulations to demonstrate that: 1) MUSIC forms a small number of subtopologies that enable
efficient SIC operations; the number of subtopologies formed is at most 17% larger than the optimum number of topologies, discovered through exhaustive search (in small networks); 2) MUSIC outperforms
approaches that simply consider the number of antennas as a measure for determining the links that can
be simultaneously active. Specifically, MUSIC provides throughput improvements of up to four times, as compared to such an approach, in various topological settings. The improve- ents can be directly
attributable to a significantly higher probability of correct SIC based decoding with MUSIC.
ETPL
NT-035 Distortion-Aware Scalable Video Streaming to Multinetwork Clients
Abstract: We consider the problem of scalable video streaming from a server to multinetwork clients over heterogeneous access networks, with the goal of minimizing the distortion of the received videos. This
problem has numerous applications including: 1) mobile devices connecting to multiple licensed and ISM
bands, and 2) cognitive multiradio devices employing spectrum bonding. In this paper, we ascertain how to optimally determine which video packets to transmit over each access network. We present models to
capture the network conditions and video characteristics and develop an integer program for deterministic
packet scheduling. Solving the integer program exactly is typically not computationally tractable, so we develop heuristic algorithms for deterministic packet scheduling, as well as convex optimization problems
for randomized packet scheduling. We carry out a thorough study of the tradeoff between performance
and computational complexity and propose a convex programming-based algorithm that yields good
performance while being suitable for real-time applications. We conduct extensive trace-driven simulations to evaluate the proposed algorithms using real network conditions and scalable video streams.
The simulation results show that the proposed convex programming-based algorithm: 1) outperforms the
rate control algorithms defined in the Datagram Congestion Control Protocol (DCCP) by about 10-15 dB higher video quality; 2) reduces average delivery delay by over 90% compared to DCCP; 3) results in
higher average video quality of 4.47 and 1.92 dB than the two developed heuristics; 4) runs efficiently, up
to six times faster than the best-performing heuristic; and 5) does indeed provide service differentiation
among users.
ETPL
NT-036
Combined Optimal Control of Activation and Transmission in Delay-Tolerant
Networks
Abstract: Performance of a delay-tolerant network has strong dependence on the nodes participating in
data transportation. Such networks often face several resource constraints especially related to energy. Energy is consumed not only in data transmission, but also in listening and in several signaling activities.
On one hand these activities enhance the system's performance while on the other hand, they consume a
significant amount of energy even when they do not involve actual node transmission. Accordingly, in order to use energy efficiently, one may have to limit not only the amount of transmissions, but also the
amount of nodes that are active at each time. Therefore, we study two coupled problems: 1) the activation
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] problem that determines when a mobile will turn on in order to receive packets; and 2) the problem of
regulating the beaconing. We derive optimal energy management strategies by formulating the problem as
an optimal control one, which we then explicitly solve. We also validate our findings through extensive simulations that are based on contact traces.
ETPL
NT-037
A Low-Complexity Congestion Control and Scheduling Algorithm for Multihop
Wireless Networks With Order-Optimal Per-Flow Delay
Abstract: Quantifying the end-to-end delay performance in multihop wireless networks is a well-known challenging problem. In this paper, we propose a new joint congestion control and scheduling algorithm
for multihop wireless networks with fixed-route flows operated under a general interference model with
interference degree K. Our proposed algorithm not only achieves a provable throughput guarantee (which
is close to at least 1/K of the system capacity region), but also leads to explicit upper bounds on the end-to-end delay of every flow. Our end-to-end delay and throughput bounds are in simple and closed forms,
and they explicitly quantify the tradeoff between throughput and delay of every flow. Furthermore, the
per-flow end-to-end delay bound increases linearly with the number of hops that the flow passes through, which is order-optimal with respect to the number of hops. Unlike traditional solutions based on the back-
pressure algorithm, our proposed algorithm combines window-based flow control with a new rate-based
distributed scheduling algorithm. A key contribution of our work is to use a novel stochastic dominance approach to bound the corresponding per-flow throughput and delay, which otherwise are often
intractable in these types of systems. Our proposed algorithm is fully distributed and requires a low per-
node complexity that does not increase with the network size. Hence, it can be easily implemented in
practice.
ETPL
NT-038 Measuring Pulsed Interference in 802.11 Links
Abstract: Wireless IEEE 802.11 links operate in unlicensed spectrum and so must accommodate other
unlicensed transmitters that generate pulsed interference. We propose a new approach for detecting the presence of pulsed interference affecting 802.11 links and for estimating temporal statistics of this
interference. This approach builds on recent work on distinguishing collision losses from noise losses in
802.11 links. When the intervals between interference pulses are i.i.d., the approach is not confined to estimating the mean and variance of these intervals, but can recover the complete probability distribution.
The approach is a transmitter-side technique that provides per-link information and is compatible with
standard hardware. We demonstrate the effectiveness of the proposed approach using extensive
experimental measurements. In addition to applications to monitoring, management, and diagnostics, the fundamental information provided by our approach can potentially be used to adapt the frame durations
used in a network so as to increase capacity in the presence of pulsed interference.
ETPL
NT-039 Pricing-Based Decentralized Spectrum Access Control in Cognitive Radio Networks
Abstract: This paper investigates pricing-based spectrum access control in cognitive radio networks,
where primary users (PUs) sell the temporarily unused spectrum and secondary users (SUs) compete via
random access for such spectrum opportunities. Compared to existing market-based approaches with
centralized scheduling, pricing-based spectrum management with random access provides a platform for SUs contending for spectrum access and is amenable to decentralized implementation due to its low
complexity. We focus on two market models, one with a monopoly PU market and the other with a
multiple-PU market. For the monopoly PU market model, we devise decentralized pricing-based spectrum access mechanisms that enable SUs to contend for channel usage. Specifically, we first consider
SUs contending via slotted Aloha. Since the revenue maximization problem therein is nonconvex, we
characterize the corresponding Pareto-optimal region and obtain a Pareto-optimal solution that maximizes
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] the SUs' throughput subject to their budget constraints. To mitigate the spectrum underutilization due to
the “price of contention,” we revisit the problem where SUs contend via CSMA, which results in more
efficient spectrum utilization and higher revenue. We then study the tradeoff between the PU's utility and its revenue when the PU's salable spectrum is controllable. Next, for the multiple-PU market model, we
cast the competition among PUs as a three-stage Stackelberg game, where each SU selects a PU's channel
to maximize its throughput. We explore the existence and the uniqueness of Nash equilibrium, in terms of access prices and the spectrum offered to SUs, and develop an iterative algorithm for strategy adaptation
to achieve the Nash equilibrium. Our findings reveal that there exists a unique Nash equilibrium when the
number of PUs is less than a threshold determined by the budgets and elasticity of SUs.
ETPL
NT-040 Mobile Data Offloading: How Much Can WiFi Deliver?
Abstract: This paper presents a quantitative study on the performance of 3G mobile data offloading
through WiFi networks. We recruited 97 iPhone users from metropolitan areas and collected statistics on
their WiFi connectivity during a two-and-a-half-week period in February 2010. Our trace-driven simulation using the acquired whole-day traces indicates that WiFi already offloads about 65% of the
total mobile data traffic and saves 55% of battery power without using any delayed transmission. If data
transfers can be delayed with some deadline until users enter a WiFi zone, substantial gains can be achieved only when the deadline is fairly larger than tens of minutes. With 100-s delays, the achievable
gain is less than only 2%-3%, whereas with 1 h or longer deadlines, traffic and energy saving gains
increase beyond 29% and 20%, respectively. These results are in contrast to the substantial gain (20%-
33%) reported by the existing work even for 100-s delayed transmission using traces taken from transit buses or war-driving. In addition, a distribution model-based simulator and a theoretical framework that
enable analytical studies of the average performance of offloading are proposed. These tools are useful for
network providers to obtain a rough estimate on the average performance of offloading for a given WiFi deployment condition.
ETPL
NT-041 Quantifying and Verifying Reachability for Access Controlled Networks
Abstract: Quantifying and querying network reachability is important for security monitoring and auditing as well as many aspects of network management such as troubleshooting, maintenance, and design.
Although attempts to model network reachability have been made, feasible solutions to computing
network reachability have remained unknown. In this paper, we propose a suite of algorithms for
quantifying reachability based on network configurations [mainly Access Control Lists (ACLs)] as well as solutions for querying network reachability. We present a network reachability model that considers
connectionless and connection-oriented transport protocols, stateless and stateful routers/firewalls, static
and dynamic NAT, PAT, IP tunneling, etc. We implemented the algorithms in our network reachability tool called Quarnet and conducted experiments on a university network. Experimental results show that
the offline computation of reachability matrices takes a few hours, and the online processing of a
reachability query takes 0.075 s on average.
ETPL
NT-042 Optimal Content Placement for Peer-to-Peer Video-on-Demand Systems,
Abstract: In this paper, we address the problem of content placement in peer-to-peer (P2P) systems, with
the objective of maximizing the utilization of peers' uplink bandwidth resources. We consider system
performance under a many-user asymptotic. We distinguish two scenarios, namely “Distributed Server Networks” (DSNs) for which requests are exogenous to the system, and “Pure P2P Networks” (PP2PNs)
for which requests emanate from the peers themselves. For both scenarios, we consider a loss network
model of performance and determine asymptotically optimal content placement strategies in the case of a
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] limited content catalog. We then turn to an alternative “large catalog” scaling where the catalog size
scales with the peer population. Under this scaling, we establish that storage space per peer must
necessarily grow unboundedly if bandwidth utilization is to be maximized. Relating the system performance to properties of a specific random graph model, we then identify a content placement
strategy and a request acceptance policy that jointly maximize bandwidth utilization, provided storage
space per peer grows unboundedly, although arbitrarily slowly, with system size.
ETPL
NT-043 Content Availability and Bundling in Swarming Systems
Abstract: BitTorrent, the immensely popular file swarming system, suffers a fundamental problem:
content unavailability. Although swarming scales well to tolerate flash crowds for popular content, it is
less useful for unpopular content as peers arriving after the initial rush find it unavailable. In this paper, we present a model to quantify content availability in swarming systems. We use the model to analyze the
availability and the performance implications of bundling, a strategy commonly adopted by many
BitTorrent publishers today. We find that even a limited amount of bundling exponentially reduces content unavailability. For swarms with highly unavailable publishers, the availability gain of bundling
can result in a net decrease in average download time. We empirically confirm the model's conclusions
through experiments on PlanetLab using the Mainline BitTorrent client.
ETPL
NT-044 Model-Driven Optimization of Opportunistic Routing,
Abstract: Opportunistic routing aims to improve wireless performance by exploiting communication opportunities arising by chance. A key challenge in opportunistic routing is how to achieve good,
predictable performance despite the incidental nature of such communication opportunities and the
complicated effects of wireless interference in IEEE 802.11 networks. To address the challenge, we develop a model-driven optimization framework to jointly optimize opportunistic routes and rate limits
for both unicast and multicast traffic. A distinctive feature of our framework is that the performance
derived from optimization can be achieved in a real IEEE 802.11 network. Our framework consists of three key components: 1) a model for capturing the interference among IEEE 802.11 broadcast
transmissions; 2) a novel algorithm for accurately optimizing different performance objectives; and 3)
effective techniques for mapping the resulting solutions to practical routing configurations. Extensive
simulations and testbed experiments show that our approach significantly outperforms state-of-the-art shortest-path routing and opportunistic routing protocols. Moreover, the difference between the achieved
performance and our model estimation is typically within 20%. Evaluation in dynamic and uncontrolled
environments further shows that our approach is robust against inaccuracy introduced by a dynamic network and it also consistently outperforms the existing schemes. These results clearly demonstrate the
effectiveness and accuracy of our approach.
ETPL
NT-045 Opportunistic MANETs: Mobility Can Make Up for Low Transmission Power
Abstract: Opportunistic mobile ad hoc networks (MANETs) are a special class of sparse and disconnected MANETs where data communication exploits sporadic contact opportunities among nodes. We consider
opportunistic MANETs where nodes move independently at random over a square of the plane. Nodes
exchange data if they are at a distance at most r within each other, where r > 0 is the node transmission radius. The flooding time is the number of time-steps required to broadcast a message from a source node
to every node of the network. Flooding time is an important measure of how fast information can spread
in dynamic networks. We derive the first upper bound on the flooding time, which is a decreasing
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] function of the maximal speed of the nodes. The bound holds with high probability, and it is nearly tight.
Our bound shows that, thanks to node mobility, even when the network is sparse and disconnected,
information spreading can be fast.
ETPL
NT-046 Fast Transmission to Remote Cooperative Groups: A New Key Management Paradigm
Abstract: The problem of efficiently and securely broadcasting to a remote cooperative group occurs in
many newly emerging networks. A major challenge in devising such systems is to overcome the obstacles of the potentially limited communication from the group to the sender, the unavailability of a fully trusted
key generation center, and the dynamics of the sender. The existing key management paradigms cannot
deal with these challenges effectively. In this paper, we circumvent these obstacles and close this gap by
proposing a novel key management paradigm. The new paradigm is a hybrid of traditional broadcast encryption and group key agreement. In such a system, each member maintains a single public/secret key
pair. Upon seeing the public keys of the members, a remote sender can securely broadcast to any intended
subgroup chosen in an ad hoc way. Following this model, we instantiate a scheme that is proven secure in the standard model. Even if all the nonintended members collude, they cannot extract any useful
information from the transmitted messages. After the public group encryption key is extracted, both the
computation overhead and the communication cost are independent of the group size. Furthermore, our scheme facilitates simple yet efficient member deletion/addition and flexible rekeying strategies. Its
strong security against collusion, its constant overhead, and its implementation friendliness without
relying on a fully trusted authority render our protocol a very promising solution to many application
ETPL
NT-047
Throughput-Optimal Scheduling in Multihop Wireless Networks Without Per-Flow
Information
Abstract: In this paper, we consider the problem of link scheduling in multihop wireless networks under
general interference constraints. Our goal is to design scheduling schemes that do not use per-flow or per-
destination information, maintain a single data queue for each link, and exploit only local information, while guaranteeing throughput optimality. Although the celebrated back-pressure algorithm maximizes
throughput, it requires per-flow or per-destination information. It is usually difficult to obtain and
maintain this type of information, especially in large networks, where there are numerous flows. Also, the back-pressure algorithm maintains a complex data structure at each node, keeps exchanging queue-length
information among neighboring nodes, and commonly results in poor delay performance. In this paper,
we propose scheduling schemes that can circumvent these drawbacks and guarantee throughput
optimality. These schemes use either the readily available hop-count information or only the local information for each link. We rigorously analyze the performance of the proposed schemes using fluid
limit techniques via an inductive argument and show that they are throughput-optimal. We also conduct
simulations to validate our theoretical results in various settings and show that the proposed schemes can substantially improve the delay performance in most scenarios.
ETPL
NT-048
Experiences With a Centralized Scheduling Approach for Performance Management
of IEEE 802.11 Wireless LANs
Abstract: We present a centralized integrated approach for: 1) enhancing the performance of an IEEE
802.11 infrastructure wireless local area network (WLAN), and 2) managing the access link that connects the WLAN to the Internet. Our approach, which is implemented on a standard Linux platform, and which
we call ADvanced Wi-fi Internet Service EnhanceR (ADWISER), is an extension of our previous system
WLAN Manager (WM). ADWISER addresses several infrastructure WLAN performance anomalies such as mixed-rate inefficiency, unfair medium sharing between simultaneous TCP uploads and downloads,
and inefficient utilization of the Internet access bandwidth when Internet transfers compete with LAN-
WLAN transfers, etc. The approach is via centralized queueing and scheduling, using a novel,
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] configurable, cascaded packet queueing and scheduling architecture, with an adaptive service rate. In this
paper, we describe the design of ADWISER and report results of extensive experimentation conducted on
a hybrid testbed consisting of real end-systems and an emulated WLAN on Qualnet. We also present results from a physical testbed consisting of one access point (AP) and a few end-systems.
ETPL
NT-049
Geographic Routing in -Dimensional Spaces With Guaranteed Delivery and Low
Stretch
Abstract: Almost all geographic routing protocols have been designed for 2-D. We present a novel geographic routing protocol, named Multihop Delaunay Triangulation (MDT), for 2-D, 3-D, and higher
dimensions with these properties: 1) guaranteed delivery for any connected graph of nodes and physical
links, and 2) low routing stretch from efficient forwarding of packets out of local minima. The guaranteed
delivery property holds for node locations specified by accurate, inaccurate, or arbitrary coordinates. The MDT protocol suite includes a packet forwarding protocol together with protocols for nodes to construct
and maintain a distributed MDT for routing. We present the performance of MDT protocols in 3-D and 4-
D as well as performance comparisons of MDT routing versus representative geographic routing protocols for nodes in 2-D and 3-D. Experimental results show that MDT provides the lowest routing
stretch in the comparisons. Furthermore, MDT protocols are specially designed to handle churn, i.e.,
dynamic topology changes due to addition and deletion of nodes and links. Experimental results show that MDT's routing success rate is close to 100% during churn, and node states converge quickly to a
correct MDT after churn.
ETPL
NT-050 Randomized Information Dissemination in Dynamic Environments,
Abstract: We consider randomized broadcast or information dissemination in wireless networks with switching network topologies. We show that an upper bound for the ε-dissemination time consists of the
conductance bound for a network without switching, and an adjustment that accounts for the number of
informed nodes in each period between topology changes. Through numerical simulations, we show that our bound is asymptotically tight. We apply our results to the case of mobile wireless networks with
unreliable communication links and establish an upper bound for the dissemination time when the
network undergoes topology changes and periods of communication link erasures.
ETPL
NT-051 Towards MIMO-Aware 802.11n Rate Adaptation
Abstract: In this paper, we use real experiments to study multiple-input-multiple-output (MIMO) 802.11n
rate adaptation (RA) on a programmable access point (AP) platform. Our case study shows that existing
RA solutions offer much lower throughput than even a fixed-rate scheme. It is proven that all such algorithms are MIMO-mode oblivious; they do not differentiate spatial diversity and spatial multiplexing
modes. We first design MiRA, a novel MIMO RA scheme that zigzags between intra- and inter-MIMO
modes to address MIMO 802.11n dynamics. Second, we examine a window-based RA solution, which runs an independent RA in each MIMO mode in parallel and a signal-to-noise ratio (SNR)-based MIMO
RA that differentiates modes using SNR measurements. Our experiments show that MIMO-mode aware
designs outperform MIMO-mode oblivious RAs in various settings, with goodput gains up to 73.5% in
field trials.
ETPL
NT-052
Fast Algorithms and Performance Bounds for Sum Rate Maximization in Wireless
Networks
Abstract: In this paper, we consider a wireless network where interference is treated as noise, and we
study the nonconvex problem of sum rate maximization by power control. We focus on finding approximately optimal solutions that can be efficiently computed to this NP-hard problem by studying the
solutions to two related problems, the sum rate maximization using a signal-to-interference-plus-noise
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] ratio (SINR ) approximation and the max-min weighted SINR optimization. We show that these two
problems are intimately connected, can be solved efficiently by algorithms with fast convergence and
minimal parameter configuration, and can yield high-quality approximately optimal solutions to sum rate maximization in the low interference regime. As an application of these results, we analyze the
connection-level stability of cross-layer utility maximization in the wireless network, where users arrive
and depart randomly and are subject to congestion control, and the queue service rates at all the links are determined by the sum rate maximization problem. In particular, we determine the stability region when
all the links solve the max-min weighted SINR problem, using instantaneous queue sizes as weights.
ETPL
NT-053 Privacy Vulnerability of Published Anonymous Mobility Traces
Abstract: Mobility traces of people and vehicles have been collected and published to assist the design and evaluation of mobile networks, such as large-scale urban sensing networks. Although the published
traces are often made anonymous in that the true identities of nodes are replaced by random identifiers,
the privacy concern remains. This is because in real life, nodes are open to observations in public spaces, or they may voluntarily or inadvertently disclose partial knowledge of their whereabouts. Thus, snapshots
of nodes' location information can be learned by interested third parties, e.g., directly through
chance/engineered meetings between the nodes and their observers, or indirectly through casual conversations or other information sources about people. In this paper, we investigate how an adversary,
when equipped with a small amount of the snapshot information termed as side information, can infer an
extended view of the whereabouts of a victim node appearing in an anonymous trace. Our results quantify
the loss of victim nodes' privacy as a function of the nodal mobility, the inference strategies of adversaries, and any noise that may appear in the trace or the side information. Generally, our results
indicate that the privacy concern is significant in that a relatively small amount of side information is
sufficient for the adversary to infer the true identity (either uniquely or with high probability) of a victim in a set of anonymous traces. For instance, an adversary is able to identify the trace of 30%-50% of the
victims when she has collected 10 pieces of side information about a victim.
ETPL
NT-054 Rigorous Statistical Analysis of Internet Loss Measurements
Abstract: Loss measurements are widely used in today's networks. There are existing standards and
commercial products to perform these measurements. The missing element is a rigorous statistical
methodology for their analysis. Indeed, most existing tools ignore the correlation between packet losses
and severely underestimate the errors in the measured loss ratios. In this paper, we present a rigorous technique for analyzing performance measurements, in particular, for estimating confidence intervals of
packet loss measurements. The task is challenging because Internet packet loss ratios are typically small
and the packet loss process is bursty. Our approach, SAIL, is motivated by some simple observations about the mechanism of packet losses. Packet losses occur when the buffer in a switch or router fills,
when there are major routing instabilities, or when the hosts are overloaded, and so we expect packet loss
to proceed in episodes of loss, interspersed with periods of successful packet transmission. This can be
modeled as a simple on/off process, and in fact, empirical measurements suggest that an alternating renewal process is a reasonable approximation to the real underlying loss process. We use this structure to
build a hidden semi-Markov model (HSMM) of the underlying loss process and, from this, to estimate
both loss ratios and confidence intervals on these loss ratios. We use both simulations and a set of more than 18 000 hours of real Internet measurements (between dedicated measurement hosts, PlanetLab hosts,
Web and DNS servers) to cross-validate our estimates and show that they are better than any current
Distributed CSMA Algorithms for Link Scheduling in Multihop MIMO Networks
Under SINR Model
Abstract: In this paper, we study distributed scheduling in multihop multiple-input-multiple-output
(MIMO) networks. We first develop a “MIMO-pipe” model that provides the upper layers a set of rates and signal-to-interference-plus-noise ratio (SINR) requirements that capture the rate-reliability tradeoff in
MIMO communications. The main thrust of this paper is then dedicated to developing distributed carrier
sense multiple access (CSMA) algorithms for MIMO-pipe scheduling under the SINR interference model. We choose the SINR model over the extensively studied protocol-based interference models because it
more naturally captures the impact of interference in wireless networks. The coupling among the links
caused by the interference under the SINR model makes the problem of devising distributed scheduling algorithms very challenging. To that end, we explore the CSMA algorithms for MIMO-pipe scheduling
from two perspectives. We start with an idealized continuous-time CSMA network, where control
messages can be exchanged in a collision-free manner, and devise a CSMA-based link scheduling
algorithm that can achieve throughput optimality under the SINR model. Next, we consider a discrete-time CSMA network, where the message exchanges suffer from collisions. For this more challenging
case, we develop a “conservative” scheduling algorithm by imposing a more stringent SINR constraint on
the MIMO-pipe model. We show that the proposed conservative scheduling achieves an efficiency ratio bounded from below
ETPL
NT-056 An Efficient and Fair MAC Protocol Robust to Reactive Interference
Abstract: Interference constitutes a major challenge to availability for communication networks operating over a shared medium. This paper proposes the medium access (MAC) protocol AntiJam, which achieves
a high and fair throughput even in harsh environments. Our protocol mitigates internal interference,
requiring no knowledge about the number of participants in the network. It is also robust to intentional
and unintentional external interference, e.g., due to coexisting networks or jammers. We model external interference using a powerful reactive adversary that can jam a (1-ε) -portion of the time-steps, where 0 <;
ε ≤ 1 is an arbitrary constant. The adversary uses carrier sensing to make informed decisions on when it is
most harmful to disrupt communications. Moreover, we allow the adversary to be adaptive and to have complete knowledge of the entire protocol history. AntiJam makes efficient use of the nonjammed time
periods and achieves, if ε is constant, a Θ(1)-competitive throughput. In addition, AntiJam features a low
convergence time and has excellent fairness properties, such that channel access probabilities do not
differ among nodes by more than a small constant factor.
ETPL
NT-057 Fine-Grained Channel Access in Wireless LAN
Abstract: With the increasing of physical-layer (PHY) data rate in modern wireless local area networks
(WLANs) (e.g., 802.11n), the overhead of media access control (MAC) progressively degrades data throughput efficiency. This trend reflects a fundamental aspect of the current MAC protocol, which
allocates the channel as a single resource at a time. This paper argues that, in a high data rate WLAN, the
channel should be divided into separate subchannels whose width is commensurate with the PHY data rate and typical frame size. Multiple stations can then contend for and use subchannels simultaneously
according to their traffic demands, thereby increasing overall efficiency. We introduce FICA, a fine-
grained channel access method that embodies this approach to media access using two novel techniques.
First, it proposes a new PHY architecture based on orthogonal frequency division multiplexing (OFDM) that retains orthogonality among subchannels while relying solely on the coordination mechanisms in
existing WLAN, carrier sensing and broadcasting. Second, FICA employs a frequency-domain contention
method that uses physical-layer Request to Send/Clear to Send (RTS/CTS) signaling and frequency
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] domain backoff to efficiently coordinate subchannel access. We have implemented FICA, both MAC and
PHY layers, using a software radio platform, and our experiments demonstrate the feasibility of the FICA
design. Furthermore, our simulation results show FICA can improve the efficiency of WLANs from a few percent to 600% compared to existing 802.11.
ETPL
NT-058 A Formal Data-Centric Approach for Passive Testing of Communication Protocols
Abstract: There is currently a high level of consciousness of the importance and impact of formally testing communicating networks. By applying formal description techniques and formal testing
approaches, we are able to validate the conformance of implementations to the requirements of
communication protocols. In this context, passive testing techniques are used whenever the system under
test cannot be interrupted or access to its interfaces is unavailable. Under such conditions, communication traces are extracted from points of observation and compared to the expected behavior formally specified
as properties. Since most works on the subject come from a formal model context, they are optimized for
testing the control part of the communication with a secondary focus on the data parts. In the current work, we provide a data-centric approach for black-box testing of network protocols. A formalism is
provided to express complex properties in a bottom-up fashion starting from expected data relations in
messages. A novel algorithm is provided for evaluation of properties in protocol traces. Experimental results on Session Initiation Protocol (SIP) traces for IP Multimedia Subsystem (IMS) services are
provided.
ETPL
NT-059 QFQ: Efficient Packet Scheduling With Tight Guarantees
Abstract: Packet scheduling, together with classification, is one of the most expensive processing steps in systems providing tight bandwidth and delay guarantees at high packet rates. Schedulers with near-
optimal service guarantees and O(1) time complexity have been proposed in the past, using techniques
such as timestamp rounding and flow grouping to keep their execution time small. However, even the two best proposals in this family have a per-packet cost component that is linear either in the number of
groups or in the length of the packet being transmitted. Furthermore, no studies are available on the actual
execution time of these algorithms. In this paper we make two contributions. First, we present Quick Fair Queueing (QFQ), a new O( 1) scheduler that provides near-optimal guarantees and is the first to achieve
that goal with a truly constant cost also with respect to the number of groups and the packet length. The
QFQ algorithm has no loops and uses very simple instructions and data structures that contribute to its
speed of operation. Second, we have developed production-quality implementations of QFQ and of its closest competitors, which we use to present a detailed comparative performance analysis of the various
algorithms. Experiments show that QFQ fulfills our expectations, outperforming the other algorithms in
the same class. In absolute terms, even on a low-end workstation, QFQ takes about 110 ns for an enqueue()/dequeue() pair (only twice the time of DRR, but with much better service guarantees).
ETPL
NT-060 Spreader Classification Based on Optimal Dynamic Bit Sharing
Abstract: Spreader classification is an online traffic measurement function that has many important
applications. In order to keep up with ever-higher line speed, the recent research trend is to implement such functions in fast but small on-die SRAM. However, the mismatch between the huge amount of
Internet traffic to be monitored and limited on-die memory space presents a significant technical
challenge. In this paper, we propose an Efficient Spreader Classification (ESC) scheme based on dynamic bit sharing, a compact information storage method. We design a maximum likelihood estimation method
to extract per-source information from the compact storage and determine the heavy spreaders. Our new
scheme ensures that false positive/negative ratios are bounded. Moreover, given an arbitrary set of
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] bounds, we develop a systematic approach to determine the optimal system parameters that minimize the
amount of memory needed to meet the bounds. Experiments based on a real Internet traffic trace
demonstrate that the proposed spreader classification scheme reduces memory consumption by 3-20 times when compared to the best existing work. We also investigate a new multi-objective spreader
classification problem and extend our classification scheme to solve it.
Abstract: There has been considerable work developing a stochastic network utility maximization
framework using Backpressure algorithms, also known as MaxWeight. A key open problem has been the
development of utility-optimal algorithms that are also delay-efficient. In this paper, we show that the
Backpressure algorithm, when combined with the last-in-first-out (LIFO) queueing discipline (called LIFO-Backpressure), is able to achieve a utility that is within O(1/V) of the optimal value, for any
scalar V ≥ 1, while maintaining an average delay of O([log(V)]2) for all but a tiny fraction of the network
traffic. This result holds for a general class of problems with Markovian dynamics. Remarkably, the performance of LIFO-Backpressure can be achieved by simply changing the queueing discipline; it
requires no other modifications of the original Backpressure algorithm. We validate the results through
empirical measurements from a sensor network testbed, which show a good match between theory and practice. Because some packets may stay in the queues for a very long time under LIFO-Backpressure, we
further develop the LIFOp-Backpressure algorithm, which generalizes LIFO
p-Backpressure by allowing
interleaving between first-in-first-out (FIFO) and LIFO. We show that LIFOpBackpressure also achieves
the same O(1/V) close-to-optimal utility performance and guarantees an average delay of O([log(V)]2) for
the packets that are served during the LIFO period.
ETPL
NT-060
An Efficient and Robust Addressing Protocol for Node Autoconfiguration in Ad Hoc
Networks
Abstract: Address assignment is a key challenge in ad hoc networks due to the lack of infrastructure. Autonomous addressing protocols require a distributed and self-managed mechanism to avoid address
collisions in a dynamic network with fading channels, frequent partitions, and joining/leaving nodes. We
propose and analyze a lightweight protocol that configures mobile ad hoc nodes based on a distributed address database stored in filters that reduces the control load and makes the proposal robust to packet
losses and network partitions. We evaluate the performance of our protocol, considering joining nodes,
partition merging events, and network initialization. Simulation results show that our protocol resolves all
the address collisions and also reduces the control traffic when compared to previously proposed protocols.
Abstract: Firewalls have been widely deployed on the Internet for securing private networks. A firewall checks each incoming or outgoing packet to decide whether to accept or discard the packet based on its
policy. Optimizing firewall policies is crucial for improving network performance. Prior work on firewall
optimization focuses on either intrafirewall or interfirewall optimization within one administrative
domain where the privacy of firewall policies is not a concern. This paper explores interfirewall optimization across administrative domains for the first time. The key technical challenge is that firewall
policies cannot be shared across domains because a firewall policy contains confidential information and
even potential security holes, which can be exploited by attackers. In this paper, we propose the first cross-domain privacy-preserving cooperative firewall policy optimization protocol. Specifically, for any
two adjacent firewalls belonging to two different administrative domains, our protocol can identify in
each firewall the rules that can be removed because of the other firewall. The optimization process
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] involves cooperative computation between the two firewalls without any party disclosing its policy to the
other. We implemented our protocol and conducted extensive experiments. The results on real firewall
policies show that our protocol can remove as many as 49% of the rules in a firewall, whereas the average is 19.4%. The communication cost is less than a few hundred kilobytes. Our protocol incurs no extra
online packet processing overhead, and the offline processing time is less than a few hundred seconds
ETPL
NT-062 Beyond OFDM: Best-Effort Dynamic Spectrum Access Using Filterbank Multicarrier
Abstract: Orthogonal frequency division multiplexing (OFDM), widely recommended for sharing the
spectrum among different nodes in a dynamic spectrum access network, imposes tight timing and
frequency synchronization requirements. We examine the use of filterbank multicarrier (FBMC), a
somewhat lesser known and understood alternative, for dynamic spectrum access. FBMC promises very low out-of-band energy of each subcarrier signal when compared to OFDM. In order to fully understand
and evaluate the promise of FBMC, we first examine the use of special pulse-shaping filters of the FBMC
PHY layer in reliably transmitting data packets at a very high rate. Next, to understand the impact of FBMC beyond the PHY layer, we devise a distributed and adaptive medium access control (MAC)
protocol that coordinates data packet traffic among the different nodes in the network in a best-effort
manner. Using extensive simulations, we show that FBMC consistently achieves at least an order of magnitude performance improvement over OFDM in several aspects including packet transmission
delays, channel access delays, and effective data transmission rate available to each node in static, indoor
settings. Using measurements of power spectral density and high data rate transmissions from a
transceiver that we build using our National Instruments hardware platform, we show that while FBMC can decode/distinguish all the received symbols without any errors, OFDM cannot. Finally, we also
examine the use of FBMC in a vehicular network setup. We find that FBMC achieves an order of
magnitude performance improvement over large distances in this setup as well. Furthermore, in the case of multihop vehicular networks, FBMC can achieve about 20 × smaller end-to-end data packet delivery
delays and relatively low packet drop probabilities. In summary, FBMC offers a much higher performing
alternative to OFDM for networks that dynamically share the spectrum among multiple nodes.
ETPL
NT-063
An Adaptive System Based on Roadmap Profiling to Enhance Warning Message
Dissemination in VANETs
Abstract: In recent years, new applications, architectures, and technologies have been proposed for
vehicular ad hoc networks (VANETs). Regarding traffic safety applications for VANETs, warning
messages have to be quickly and smartly disseminated in order to reduce the required dissemination time and to increase the number of vehicles receiving the traffic warning information. In the past, several
approaches have been proposed to improve the alert dissemination process in multihop wireless networks,
but none of them were tested in real urban scenarios, adapting its behavior to the propagation features of the scenario. In this paper, we present the Profile-driven Adaptive Warning Dissemination Scheme
(PAWDS) designed to improve the warning message dissemination process. With respect to previous
proposals, our proposed scheme uses a mapping technique based on adapting the dissemination strategy
according to both the characteristics of the street area where the vehicles are moving and the density of vehicles in the target scenario. Our algorithm reported a noticeable improvement in the performance of
alert dissemination processes in scenarios based on real city maps.
ETPL
NT-064 ACORN: An Auto-Configuration Framework for 802.11n WLANs
Abstract: The wide channels feature combines two adjacent channels to form a new, wider channel to
facilitate high-data-rate transmissions in multiple-input-multiple-output (MIMO)-based IEEE 802.11n
networks. Using a wider channel can exacerbate interference effects. Furthermore, contrary to what has
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] been reported by prior studies, we find that wide channels do not always provide benefits in isolation (i.e.,
one link without interference) and can even degrade performance. We conduct an in-depth, experimental
study to understand the implications of wide channels on throughput performance. Based on our measurements, we design an auto-configuration framework called ACORN for enterprise 802.11n
WLANs. ACORN integrates the functions of user association and channel allocation since our study
reveals that they are tightly coupled when wide channels are used. We show that the channel allocation problem with the constraints of wide channels is NP-complete. Thus, ACORN uses an algorithm that
provides a worst-case approximation ratio of O(1/Δ + 1), with Δ being the maximum node degree in the
network. We implement ACORN on our 802.11n testbed. Our evaluations show that ACORN: 1)
outperforms previous approaches that are agnostic to wide channels constraints; it provides per-AP throughput gains ranging from 1.5 × 6×; and 2) in practice, its channel allocation module achieves an
approximation ratio much better than the theoretically predicted O(1/Δ + 1).
ETPL
NT-065 Duty-Cycle-Aware Minimum-Energy Multicasting in Wireless Sensor Networks
Abstract: In duty-cycled wireless sensor networks, the nodes switch between active and dormant states,
and each node may determine its active/dormant schedule independently. This complicates the Minimum-
Energy Multicasting (MEM) problem, which was primarily studied in always-active wireless ad hoc networks. In this paper, we study the duty-cycle-aware MEM problem in wireless sensor networks both
for one-to-many multicasting and for all-to-all multicasting. In the case of one-to-many multicasting, we
present a formalization of the Minimum-Energy Multicast Tree Construction and Scheduling (MEMTCS)
problem. We prove that the MEMTCS problem is NP-hard, and it is unlikely to have an approximation algorithm with a performance ratio of (1 - 0(1)) ln Δ, where Δ is the maximum node degree in a network.
We propose a polynomial-time approximation algorithm for the MEMTCS problem with a performance
ratio of O (H(Δ + 1)), where H(·) is the harmonic number. In the case of all-to-all multicasting, we prove that the Minimum-Energy Multicast Backbone Construction and Scheduling (MEMBCS) problem is also
NP-hard and present an approximation algorithm for it, which has the same approximation ratio as that of
the proposed algorithm for the MEMTCS problem. We also provide a distributed implementation of our algorithms, as well as a simple but efficient collision-free scheduling scheme to avoid packet loss. Finally,
we perform extensive simulations, and the results demonstrate that our algorithms significantly
outperform other known algorithms in terms of the total transmission energy cost, without sacrificing
much of the delay performance.
ETPL
NT-066 Fast Tag Searching Protocol for Large-Scale RFID Systems
Abstract: Fast searching a particular subset in a large number of products attached with radio frequency
identification (RFID) tags is of practical importance for a variety of applications, but not yet thoroughly investigated. Since the cardinality of the products can be extremely large, collecting the tag information
directly from each of those tags could be highly inefficient. To address the tag searching efficiency in
large-scale RFID systems, this paper proposes several algorithms to meet the stringent delay requirement
in developing fast tag searching protocols. We formally formulate the tag searching problem in large-scale RFID systems. We propose utilizing compact approximators to efficiently aggregate a large volume
of RFID tag information and exchange such information with a two-phase approximation protocol. By
estimating the intersection of two compact approximators, the proposed two-phase compact approximator-based tag searching protocol significantly reduces the searching time compared to all
possible solutions we can directly borrow from existing studies. We further introduce a scalable
cardinality range estimation method that provides inexpensive input for our tag searching protocol. We conduct comprehensive simulations to validate our design. The results demonstrate that the proposed tag
searching protocol is highly efficient in terms of both time efficiency and transmission overhead, leading
Pondicherry | Trivandrum | Salem | Erode | Tirunelveli
http://www.elysiumtechnologies.com, [email protected] to good applicability and scalability for large-scale RFID systems.
ETPL
NT-067
Predicting the Impact of Measures Against P2P Networks: Transient Behavior and
Phase Transition
Abstract: The paper has two objectives. The first is to study rigorously the transient behavior of some
peer-to-peer (P2P) networks whenever information is replicated and disseminated according to epidemic-
like dynamics. The second is to use the insight gained from the previous analysis in order to predict how
efficient are measures taken against P2P networks. We first introduce a stochastic model that extends a classical epidemic model and characterize the P2P swarm behavior in presence of free-riding peers. We
then study a second model in which a peer initiates a contact with another peer chosen randomly. In both
cases, the network is shown to exhibit phase transitions: A small change in the parameters causes a large change in the behavior of the network. We show, in particular, how phase transitions affect measures of
content providers against P2P networks that distribute nonauthorized music, books, or articles and what is
the efficiency of countermeasures. In addition, our analytical framework can be generalized to characterize the heterogeneity of cooperative peers
ETPL
NT-068 Realizing the Benefits of Wireless Network Coding in Multirate Settings
Abstract: Network coding has been proposed as a technique that can potentially increase the transport
capacity of a wireless network via mixing data packets at intermediate routers. However, most previous studies either assume a fixed transmission rate or do not consider the impact of using diverse rates on the
network coding gain. Since in many cases, network coding implicitly relies on overhearing, the choice of
the transmission rate has a big impact on the achievable gains. The use of higher rates works in favor of increasing the native throughput. However, it may in many cases work against effective overhearing. In
other words, there is a tension between the achievable network coding gain and the inherent rate gain
possible on a link. In this paper, our goal is to drive the network toward achieving the best tradeoff
between these two contradictory effects. We design a distributed framework that: facilitates the choice of the best rate on each link while considering the need for overhearing; and dictates the choice of which
decoding recipient will acknowledge the reception of an encoded packet. We demonstrate that both of
these features contribute significantly toward gains in throughput. We extensively simulate our framework in a variety of topological settings. We also fully implement it on real hardware and
demonstrate its applicability and performance gains via proof-of-concept experiments on our wireless
testbed. We show that our framework yields throughput gains of up to 390% as compared to what is achieved in a rate-unaware network coding framework.
ETPL
NT-069 On the Discovery of Critical Links and Nodes for Assessing Network Vulnerability
Abstract: The assessment of network vulnerability is of great importance in the presence of unexpected
disruptive events or adversarial attacks targeting on critical network links and nodes. In this paper, we study Critical Link Disruptor (CLD) and Critical Node Disruptor (CND) optimization problems to
identify critical links and nodes in a network whose removals maximally destroy the network's functions.
We provide a comprehensive complexity analysis of CLD and CND on general graphs and show that they still remain NP-complete even on unit disk graphs and power-law graphs. Furthermore, the CND problem
is shown NP-hard to be approximated within Ω([(n-k)/(nε)] ) on general graphs with n vertices
and k critical nodes. Despite the intractability of these problems, we propose HILPR, a novel LP-based rounding algorithm, for efficiently solving CLD and CND problems in a timely manner. The effectiveness
of our solutions is validated on various synthetic and real-world networks.
NT-070 Scheduling Mobile Nodes for Cooperative Data Transport in Sensor Networks
Abstract: Message ferrying has been shown to be an effective approach to support routing in sparse ad
hoc or sensor networks. Considering a generic network model where each node in the network wishes to send data to some (or possibly all) other nodes with known (and possibly different) rates, we propose
three schemes enabling multiple ferries to coordinate in collecting and delivering the data. We analyze the
performance of each scheme and establish bounds on the average and worst-case delay. The latter bounds are useful in offering performance guarantees. We establish that under one of our schemes, constant per-
node throughput is achievable within constant maximum (worst-case) delay as the network size grows.
Using simulation, we compare our proposed schemes with an alternative, the Ferry Relaying algorithm proposed earlier in the literature. The results show that our schemes perform better and provide guidance
on which scheme to use given performance preferences and the number of available ferries.
ETPL
NT-071 Improving Network Agility With Seamless BGP Reconfigurations
Abstract: The network infrastructure of Internet service providers (ISPs) undergoes constant evolution. Whenever new requirements arise (e.g., the deployment of a new Point of Presence or a change in the
business relationship with a neighboring ISP), operators need to change the configuration of the network.
Due to the complexity of the Border Gateway Protocol (BGP) and the lack of methodologies and tools, maintaining service availability during reconfigurations that involve BGP is a challenge for operators. In
this paper, we show that the current best practices to reconfigure BGP do not provide guarantees with
respect to traffic disruptions. Then, we study the problem of finding an operational ordering of BGP reconfiguration steps that guarantees no packet loss. Unfortunately, finding such an operational ordering,
when it exists, is computationally hard. To enable lossless reconfigurations, we propose a framework that
extends current features of carrier-grade routers to run two BGP control planes in parallel. We present a
prototype implementation and show the effectiveness of our framework through a case study.
ETPL
NT-072 Cross-Layer Metrics for Reliable Routing in Wireless Mesh Networks
Abstract: Wireless mesh networks (WMNs) have emerged as a flexible and low-cost network
infrastructure, where heterogeneous mesh routers managed by different users collaborate to extend network coverage. This paper proposes a novel routing metric, Expected Forwarded Counter (EFW), and
two further variants, to cope with the problem of selfish behavior (i.e., packet dropping) of mesh routers
in a WMN. EFW combines, in a cross-layer fashion, routing-layer observations of forwarding behavior
with MAC-layer measurements of wireless link quality to select the most reliable and high-performance path. We evaluate the proposed metrics both through simulations and real-life deployments on two
different wireless testbeds, performing a comparative analysis with On-Demand Secure Byzantine
Resilient Routing (ODSBR) Protocol and Expected Transmission Counter (ETX). The results show that our cross-layer metrics accurately capture the path reliability and considerably increase the WMN
performance, even when a high percentage of network nodes misbehave.
