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CHAPTER 2

LITERATURE SURVEY

The survey consists of research papers of various authors.

Communication Protocol for Wireless Sensor Networks

Heinzelman et al (2000) Energy-efficient communication protocol

for wireless sensor networks. Here communication protocols are considered,

which can have significant impact on the overall energy dissipation of these

networks. Based the findings that the conventional protocols of direct

transmission, minimum-transmission-energy, multi-hop routing, and static

clustering may not be optimal for sensor networks, The author propose

LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based

protocol that utilizes randomized rotation of local cluster based station

(cluster-heads) to evenly distribute the energy load among the sensors in the

network. LEACH uses localized coordination to enable scalability and

robustness for dynamic networks, and incorporates data fusion into the

routing protocol to reduce the amount of information that must be transmitted

to the base station. Simulations show the LEACH can achieve as much as a

factor of 8 reductions in energy dissipation compared with conventional

outing protocols. In addition, LEACH is able to distribute energy dissipation

evenly throughout the sensors, doubling the useful system lifetime for the

networks were simulated.

Wadaa et al (2005) Training a wireless sensor network, in this

proposed a simple, energy-efficient protocol to aid sensor-field sampling by a

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mobile object. The protocol exploits the concept of bands to limit the

propagation of sensor data broadcasting, providing a form of directional

broadcast based on software control. Methods for defining and using bands

were presented. Extensive simulations under two communication models

were conducted to evaluate the performance and trade-offs of our band-based

scheme. His first communication model assumed no collisions and a binary

sensor-to-sensor communication model. The second communication model

assumed collisions, and a decay communication model. The simulations

indicated that the band-based scheme is quite efficient in directional

broadcast, and moreover, performs much better than default broadcast.

Hu et al (2003) On mitigating the broadcast storm problem with

directional antennas, in this paper broadcast transmission is used extensively

during the route discovery process and by some applications (especially by

the ones that are developed for VANET), the routing protocols should be

designed to address the broadcast storm problem to avoid unnecessary loss of

urgent data packets during the period of broadcast storm. In this paper, the

authors have proposed three novel techniques which depend only on the local

positions of the receiver and the transmitter nodes. The algorithms are

completely distributed and computationally efficient in that they require only

minor computations. In the absence of the GPS information, it is shown that

the proposed algorithms can also be modified to use the RSS of the packet

received to determine whether or not the packet should be retransmitted. The

proposed schemes are tested against both one dimensional highway and

generic 2-dimensional square topologies. The results show that the proposed

slotted persistence schemes can reduce the broadcast redundancy and packet

loss ratio by up to 90% in a highway network while they can still offer an

acceptable end-to-end delay for most applications; e.g. using roadside unit to

inform drivers about the detour, construction, etc. In a 2-dimensional

topology, on the other hand, the proposed schemes do not offer much

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improvement in terms of packet loss rate, but they can be used to guide the

routing protocol to select a route with fewer hops.

Wireless Ad-hoc Networks

Elnahrawy (2004), The limits of localization using signal strength:

a comparative study, in this paper, author has presented a secure and efficient

position verification approach for the wireless ad-hoc networks. A group of

position-verifier nodes estimate the distance to the announcing node using the

received signal strength intensity. They elect a leader that computes if the

announcing node is cheating in its position or not. Upon detection of

malicious node, secure warning protocol is presented, where the leader sends

a warning-of malicious node to all the other nodes in the network. All the

communications between the nodes and the position verifiers is secured using

the PKI infrastructure. The proposed approach is immune to both the internal

and external attacks; it is using the minimal traffic overhead; and requires no

extra hardware. The future directions may include extending this work for

specific wireless ad-hoc networks for example VANET, WSN and WMN.

Juzheng Li and Sol (2004), A band based Approach for multicast

system, in this paper the author proposed an energy-efficient protocol to aid in

sensor-field sampling. The concept of bands is exploited to limit the

propagation of sensor data broadcasting, providing a form of directional

broadcast. Methods for defining and using bands are presented, and

simulation results are provided to show the effectiveness of the approach. Due

to space limitations, all details associated with the approach cannot be

explored. One important future work is to perform further simulations under

non-perfect MAC layer protocols. Since our scheme prunes many rebroadcast

packets, it reduces opportunities for packet collisions. It may be further

optimized with respect to this property. Also, further study can be done on the

analysis of energy concerns under error conditions.

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Zhang and Huang (2006) a learning-based adaptive routing tree for

wireless sensor networks, the author describes type of reinforcement-based

meta-routing strategy for the constraint-based routing. Author have studied

the properties of such protocol and shown in our experiments that the adaptive

tree protocol is robust for un-predicable link failures and mobile sinks. Here

the use of different routing objectives for achieving load balancing and

reducing congestion is demonstrated. The parameters in the protocol, such as

learning rates for Q-values, update rates for NQ-values, parent reset threshold,

and the maximum number of retransmissions for failed confirmations, can be

tuned to make the routing best for a particular application. Lots of research

still needs to be done on the selection of parameter values and understanding

the relationship between different parameters.

Xu et al (2001) Geography-informed energy conservation for Ad-

hoc routing, introduce a geographical adaptive fidelity (GAF) algorithm that

reduces energy consumption in ad hoc wireless networks. GAF conserves

energy by identifying nodes that are equivalent from a routing perspective and

then turning off unnecessary nodes, keeping a constant level of routing

fidelity. GAF moderates this policy using application- and system-level

information; nodes that source or sink data remain on and intermediate nodes

monitor and balance energy use. GAF is independent of the underlying ad hoc

routing protocol; here simulation for GAF over unmodified AODV and DSR

is done. Analysis and simulation studies of GAF show that it can consume

40% to 60% less energy than an unmodified ad hoc routing protocol.

Moreover, simulations of GAP suggest that network lifetime increases

proportionally to node density; in one example, a four-fold increase in node

density leads to network lifetime increase for 3 to 6 times (depending on the

mobility pattern). More generally, GAF is an example of adaptive fidelity, a

technique proposed for extending the lifetime of self-configuring systems by

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exploiting redundancy to conserve energy while maintaining application

fidelity.

Polastre et al (2005) enabling ultralow power wireless research,

presented the design and implementation of Telos, the latest generation in a

family of motes from UC Berkeley, which shows the Telos is the lowest

power mote to date. Telos includes numerous enhancements that enable

research in wireless sensor networks while making the devices easier to use

and lowering the per-module cost. Other features, like hardware write

protection and radio signal stability, closely map to current research.

Researchers may experiment with the new IEEE 802.15.4 standard and use

existing work in Tiny OS. Additional flexibility allows software to configure

or disable hardware modules. Telos is a robust module with lower power

consumption yet greater performance than existing designs.

Elnahrawy et al (2004), the limits of localization using signal

strength: a comparative study, in this paper the author presented a secure and

efficient position verification approach for the wireless ad-hoc networks. A

group of position-verifier nodes estimate the distance to the announcing node

using the received signal strength intensity. They elect a leader that computes

if the announcing node is cheating in its position or not. Upon detection of

malicious node, author presented a secure warning protocol, where the leader

sends a warning-of malicious node to all the other nodes in the network. All

the communications between the nodes and the position verifiers is secured

using the PKI infrastructure. The proposed approach is immune to both the

internal and external attacks; it is using the minimal traffic overhead; and

requires no extra hardware. The future directions may include extending this

work for specific wireless ad-hoc networks for example VANET, WSN and

WMN.

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Study of Directional Antennas

Hu et al (2003), describes on mitigating the broadcast storm

problem with directional antennas, which present three directional antenna-

based schemes to mitigate the broadcast storm problem. In the on/off

directional broadcast scheme, on receipt of a broadcast packet that has not

been forwarded before, a node only forwards it in the three directions other

than the direction in which the packet arrives. This is achieved by setting the

directional antennas in the active/passive mode. In the relay-node-based

directional broadcast scheme, a node forwards a broadcast the relay node in

the Angle-Of-Arrival (AOA).

Determination of relay nodes is facilitated by a neighbour discovery

mechanism and is determined the relative signal strength of received packets.

In the location-based directional broadcast scheme, the delay in forwarding

broadcast packets in each of the three directions other than AOA is

determined by the location information of both the immediate upstream

sender and the node. The simulation using QualNet is used to evaluate the

three proposed schemes, with the conventional omni-directional broadcast

scheme as the base line. The simulation results indicate that by using

directional antennas, the broadcast storm problem can be mitigated to a great

extent. Specifically, in static wireless networks, the performance

improvement with respect to coverage, redundancy, and collision is on

average 6~18%, 36~80%, and 21~46%, respectively.

The performance with respect to latency is comparable or

mariginally improved, except for the location based directional broadcast

scheme. All the relative performance, except the coverage under the relay-

node-based directional broadcast scheme, exhibits the same trend in the case

of mobility. The several avenues for future research have identified. The rule

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for selecting relay nodes in the relay-node-based directional broadcast scheme

is refined and also the performance of the proposed schemes (as well as the

omni-directional broadcast scheme) in conjunction with power management is

studied. Note that in power-managed MANETs, some of the nodes may be

put into sleep and awakened periodically to check for transmission activities.

How the proposed schemes perform in a power managed MANET and how

they should be modified is a subject of future study.

Ammari and Das (2008), promoting heterogeneity, mobility, and

energy-aware Voronoi diagram in wireless sensor networks, referred to prove

that the energy sink-hole problem can be solved provided that sensors adjust

their communication ranges so they can send data over distances less than the

radii of their nominal communication range. This solution, however, imposes

a severe restriction on the size of a monitored field. To overcome this

limitation, a sensor deployment strategy based on energy heterogeneity is

proposed with a goal that all sensors deplete their energy simultaneously.

Simulation results of the research show that such a sensor deployment

strategy helps all sensors deplete their initial energy at the same time. To

solve the energy sink-hole problem for homogeneous WSNs, where all

sensors have the same initial energy, a localized energy-aware Voronoi

diagram-based data forwarding (EVEN) protocol is proposed. EVEN

combines sink mobility with a new concept, called energy-aware Voronoi

diagram whose virtual sites (i.e., virtual sensors locations) are computed

based on the remaining energy of the corresponding sensors. Through

simulations, the EVEN outperforms the similar greedy geographical data

forwarding protocols and has performance that is comparable to that of an

existing data collection protocol that uses a joint mobility and routing

strategy. Precisely, EVEN yields an improvement of more than in terms of

network lifetime has been found.

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Broadcasting techniques

Williams and Camp (2002), comparison of broadcasting techniques

for mobile ad hoc networks, describes the adaptability greatly improves the

performance of a broadcast protocol, the three ways in which machine

learning can be applied to broadcasting in a mobile ad hoc network (MANET)

is identified. The broadcasting technique is chosen because of it functions as a

foundation of MANET communication. Unicast, multicast, and geocast

protocols utilize broadcasting as a building block, providing important control

and route establishment functionality. Therefore, any improvements to the

process of broadcasting can be immediately realized by higher-level MANET

functionality and applications. While efficient broadcast protocols have been

proposed, no single broadcasting protocol works well in all possible MANET

conditions. Furthermore, protocols tend to fail catastrophically in severe

network environments. Our three classes of adaptive protocols are pure

machine learning, intra-protocol learning, and inter-protocol learning. In the

pure machine learning approach, a new approach to the design of a broadcast

protocol is exhibited: the decision of whether to rebroadcast a packet is cast as

a classification problem. Each mobile node (MN) builds a classifier and trains

it on data collected from the network environment. Using intra-protocol

learning, each MN consults a simple machine model for the optimal value of

one of its free parameters. Lastly, in inter-protocol learning, MNs learn to

switch between different broadcasting protocols based on network conditions.

For each class of learning method, a prototypical protocol is created and its

performance is examined by simulation.

Peng and Lu (2000) on the reduction of broadcast redundancy in

mobile ad hoc networks, the author describes the network wide broadcasting

is a fundamental operation in ad hoc networks. In broadcasting, a source node

ends a message to all the other nodes in the network. In this paper, the

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problem of collision-free broadcasting in ad hoc wireless networks is

considered. The objective is to minimize the latency and the number of

retransmission in the broadcast. That shows minimum latency broadcasting i

NP-hard for ad hoc wireless networks. A simple and distributed collision-free

broadcasting algorithm for broadcasting a message is also presented. For

networks with bounded node transmission ranges, our algorithm

simultaneously guarantees that the latency and the number of retransmission

are within O (1) times their respective optimal values. Our algorithm and

analysis extends to the case when multiple messages are broadcast from

multiple sources. Experimental studies indicate that our algorithm perform

much well in practice than the analytical guarantee provided for the worst

case.

Sensor Networks

Wadaa et al (2005) training a wireless sensor network, in this work,

The author consider a large-scale geographic area populated by tiny sensors

and some more powerful devices called actors, authorized to organize the

sensors in their vicinity into short-lived, actor-centric sensor networks. The

tiny sensors run on miniature of non-rechargeable batteries, are anonymous,

and are unaware of their location. The sensors differ in their ability to

dynamically alter their sleep times. Indeed, the periodic sensors have sleep

periods of predefined lengths, established at fabrication time; by contrast, the

free sensors can dynamically alter their sleep periods, under program control.

The main contribution of this work is to propose an energy-efficient location

training protocol for heterogeneous actor-centric sensor networks where the

sensors acquire coarse-grain location awareness with respect to the actor in

their vicinity. Our theoretical analysis, confirmed by experimental evaluation,

shows that the proposed protocol outperforms the best previously known

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location training protocols in terms of the number of sleep/awake transitions,

overall sensor awake time, and energy consumption.

Tian et al (2009) querying Sensor Networks Using Ad-hoc Mobile

Devices: A Two Layer Networking Approach, used to interplay between

mobile devices and static sensor nodes are envisioned in the near future. This

will enable a heterogeneous design space that can offset the stringent resource

and power constraints encountered in traditional static sensor networks by

taking advantage of the more powerful mobile devices. The systematic

framework for end-to-end query processing is presented, using a two-layer

architecture that consists of mobile devices at the upper layer and static sensor

nodes at the bottom layer. The framework employs a ''PULL'' query model

that contains staged operations including query generation, query routing,

query injection, and query result routing. Each of these stages of query

processing is discussed with an emphasis on techniques for energy-efficient

query injection and query result routing with location-ignorant sensor nodes.

The techniques leverage the mobility and transmission flexibility of mobile

objects at the upper layer. Numeric and simulation results are provided to

support the proposed methods.

Heinzelman et al (2000) Energy-efficient communication protocol

for wireless sensor networks, in this paper wireless distributed micro sensor

systems will enable the reliable monitoring of a variety of environments for

both civil and military applications. In this paper, the communication

protocols are considered, which can have significant impact on the overall

energy dissipation of these networks. Based on our findings that the

conventional protocols of direct transmission, minimum-transmission-energy,

multi-hop routing, and static clustering may not be optimal for sensor

networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy),

a clustering-based protocol that utilizes randomized rotation of local cluster

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based station (cluster-heads) to evenly distribute the energy load among the

sensors in the network. LEACH uses localized coordination to enable

scalability and robustness for dynamic networks, and incorporates data fusion

into the routing protocol to reduce the amount of information that must be

transmitted to the base station. Simulations show the LEACH can achieve as

much as a factor of 8 reductions in energy dissipation compared with

conventional outing protocols. In addition, LEACH is able to distribute

energy dissipation evenly throughout the sensors, doubling the useful system

lifetime for the networks are simulated.

Xu et al (2001) Geography-informed energy conservation for ad

hoc routing, the idea of using mobile objects to gather samples from a sensor

field has been recently proposed. A key challenge is how to gather the sensor

data in a manner that is energy efficient with respect to the sensor nodes that

serve as sources of the sensor data. In this paper, an algorithmic technique

called Band-based Directional Broadcast is introduced to control the direction

of broadcasts that originate from sensor nodes. The technique is studied by

simulations that consider energy consumption and data deliverability.

Wireless Sensor Networks

Ekici et al (2006) mobility-based communication in wireless sensor

networks, describes the properties of mobile wireless sensor networks

(MWSNs) are inherited from static wireless sensor networks (WSNs) and

meanwhile have their own uniqueness and node mobility. Sensor nodes in

these networks monitor different regions of an area of interest and collectively

present a global overview of monitored activities. Since failure of a sensor

node leads to loss of connectivity, it may cause a partitioning of the network.

Adding mobility to WSNs can significantly increase the capability of the

WSN by making it resilient to failures, reactive to events, and able to support

disparate missions with a common set of sensor nodes. In this paper, a new

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algorithm based on the divide-and-conquer approach is proposed, in which

the whole region is divided into sub-regions and in each sub-region the

minimum connected sensor cover set is selected through energy-aware

selection method. Also, a new technique for mobility assisted minimum

connected sensor cover considering the network energy is proposed. We

provide performance metrics to analyze the performance of our approach and

the simulation results clearly indicate the benefits of our new approach in

terms of energy consumption, communication complexity, and number of

active nodes over existing algorithms.

Bo Tang (2006), A Novel Reliable & Efficient Data Harvesting

Mechanism in Wireless Sensor Networks with Path- Constrained Mobile

Sink, in this paper, a novel reliable and efficient data harvesting mechanism

named Economical & Manageable Sub-sinks Mechanism (E&MSM) is

proposed for WSNs with path-constrained mobile sink. Its innovation idea is

to combine randomly deployed sensors with regularly deployed wireless

nodes to achieve reliable and efficient data harvesting. To illustrate this

mechanism in detail, the possible potential problems and pose corresponding

solutions have analysed. Simulation results validate our proposed mechanism

and prove that E&MSM can improve network lifetime dramatically. By

simulating this mechanism, some rules for constructing such a network have

been detected and the theoretical reference for practical applications is

provided. E&MSM could have good performance in realistic applications.

Heinzelman et al (2000), Energy-efficient communication protocol

for wireless microsensor networks, clustering provides an effective way to

prolong the lifetime of wireless sensor networks. One of the major issues of a

clustering protocol is selecting an optimal group of sensor nodes as the cluster

heads to divide the network. Another is the mode of inter-cluster

communication. In this paper, an energy-balanced unequal clustering (EBUC)

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protocol is proposed and evaluated. By using the particle swarm optimization

(PSO) algorithm, EBUC partitions all nodes into clusters of unequal size, in

which the clusters closer to the base station have smaller size. The cluster

heads of these clusters can preserve some more energy for the inter-cluster

relay traffic and the ‘hot-spots’ problem can be avoided. For inter-cluster

communication, EBUC adopts an energy-aware multihop routing to reduce

the energy consumption of the cluster heads. Simulation results demonstrate

that the protocol can efficiently decrease the dead speed of the nodes and

prolong the network lifetime.

Sinchan Roychowdhury and Chiranjib Patra (2010), Geographic

Adaptive Fidelity and Geographic Energy Aware Routing in Ad Hoc Routing,

in this paper both GAF and GEAR are location based protocols, although

GAF can also be classified as hierarchical protocol, with limited power usage.

As they operate on the basis of the geographic or location information for

routing, data aggregation at any point is absent. Although GAF is highly

scalable, GEAR faces a problem of limited scalability and is often identified

as one of the major disadvantages of GEAR. Another problem faced by both

the protocols is that both the mechanisms have moderately high overhead

which affects the energy efficiency. A major difference in between the two

protocols is in their respective data delivery model. GAF follows the virtual

grid data delivery model and the data is transmitted by the operations

performed by the master nodes and the slave nodes. On the other hand, GEAR

operates on the principle of demand driven data delivery model. Although

neither of the two protocols take care of QoS, but this provides scope for

future research to be conducted to enable QoS in GAF and GEAR protocols

during data transmission.

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Ad-hoc sensor networks

Ossama Younis and Sonia Fahmy (2004) HEED: A Hybrid,

Energy-Efficient, Distributed Clustering Approach for Ad Hoc Sensor

Networks, refers the topology control in a sensor network balances load on

sensor nodes and increases network scalability and lifetime. Clustering sensor

nodes is an effective topology control approach. In this paper, a novel

distributed clustering approach for long-lived ad hoc sensor networks is

proposed. Our proposed approach does not make any assumptions about the

presence of infrastructure or about node capabilities, other than the

availability of multiple power levels in sensor nodes. This paper present a

protocol, HEED (Hybrid Energy-Efficient Distributed clustering), that

periodically selects cluster heads according to a hybrid of the node residual

energy and a secondary parameter, such as node proximity to its neighbors or

node degree. HEED terminates in O(1) iterations, incurs low message

overhead, and achieves fairly uniform cluster head distribution across the

network. This paper prove that, with appropriate bounds on node density and

intracluster and intercluster transmission ranges, HEED can asymptotically

almost surely guarantee connectivity of clustered networks. Simulation results

demonstrate that our proposed approach is effective in prolonging the network

lifetime and supporting scalable data aggregation.

Katayoumn et al (2004), in distributed wireless sensing applications

such as unattended ground sensor systems, remote planetary exploration, and

condition-based maintenance, where the deployment site is remote and/or the

scale of the network is large, individual emplacement and configuration of the

sensor nodes is difficult. Hence, network self-assembly and continuous

network self-organization during the lifetime of the network in a reliable,

efficient, and scalable manner are crucial for successful deployment and

operation of such networks. This paper provides an overview of the concept

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of network self-assembly for ad hoc wireless sensor networks at the link

layer, with descriptions of results from implementation of a novel network

formation mechanism for wireless unattended ground sensor applications

using a multicluster hierarchical topology and a novel dual-radio architecture.

Jain et al (2006), Exploiting Mobility for Energy Efficient Data

Collection in Sensor Networks, referred to analyze an architecture based on

mobility to address the problem of energy efficient data collection in a sensor

network. Our approach exploits mobile nodes present in the sensor field as

forwarding agents. As a mobile node moves in close proximity to sensors,

data is transferred to the mobile node for later depositing at the destination.

An analytical model to understand the key performance metrics such as data

transfer, latency to the destination, and power is presented in this paper.

Parameters for our model include: sensor buffer size, data generation rate,

radio characteristics, and mobility patterns of mobile nodes. Through

simulation we verify our model and show that our approach can provide

substantial savings in energy as compared to the traditional ad-hoc network

approach.

Chakrabarti et al (2006), Communication Power Optimization in a

Sensor Network with a Path-Constrained Mobile Observer, this paper presents

a procedure for communication power optimization in a network of randomly

distributed sensors with an observer (data collector) moving on a fixed path.

The key challenge in using a mobile observer is that it remains within

communication range of any sensor for a brief duration, and inability to

transfer data in this duration leads to data loss. The process of data collection

can be modeled by a queue with deadlines is established, where arrivals

correspond to the observer entering the range of a sensor and a missed

deadline means data loss. The queuing model is then used to identify the

combination of system parameters that ensures adequate data collection with

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minimum power. The results obtained from the queuing analogy take a simple

form in the asymptotic regime of dense sensor networks. Additionally, for

sensor networks that cannot tolerate data loss, for that a tight bound on

minimum sensor separation that ensures that no data will be lost on account of

mobility has derived. In this paper, the author presents two examples to

illustrate our results, from which it is seen that power reduction by two orders

of magnitude or more is typical relative to a static sensor network. The

scenarios chosen for power comparisons also provide guidelines on the choice

of path, if such a choice is available.

Chakrabarti et al (2006), Communication Power Optimization in a

Sensor Network with a Path-Constrained Mobile Observer, recent work has

shown that sink mobility along a constrained path can improve the energy

efficiency in wireless sensor networks. However, due to the path constraint, a

mobile sink with constant speed has limited communication time to collect

data from the sensor nodes deployed randomly. This poses significant

challenges in jointly improving the amount of data collected and reducing the

energy consumption. To address this issue, a novel data collection scheme,

called the Maximum Amount Shortest Path (MASP) is proposed, that

increases network throughput as well as conserves energy by optimizing the

assignment of sensor nodes. MASP is formulated as an integer linear

programming problem and then solved with the help of a genetic algorithm. A

two-phase communication protocol based on zone partition is designed to

implement the MASP scheme. This paper also presents a practical distributed

approximate algorithm to solve the MASP problem. In addition, the impact of

different overlapping time partition methods is studied. The proposed

algorithms and protocols are validated through simulation experiments using

OMNET++.

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Wang et al (2005), Exploiting sink mobility for maximizing sensor

networks lifetime, this paper demonstrates the advantages of using controlled

mobility in wireless sensor networks (WSNs) for increasing their lifetime, i.e.,

the period of time the network is able to provide its intended functionalities.

More specifically, for WSNs that comprise a large number of statically placed

sensor nodes transmitting data to a collection point (the sink); by controlling

the sink movements, the improvement in lifetime is obtained remarkably. In

order to determine sink movements, first define a Mixed Integer Linear

Programming (MILP) analytical model whose solution determines those sink

routes that maximize network lifetime. Our contribution expands further by

defining the first heuristics for controlled sink movements that are fully

distributed and localized. Greedy Maximum Residual Energy (GMRE)

heuristic moves the sink from its current location to a new site as if drawn

toward the area where nodes have the highest residual energy. A simple

distributed mobility scheme (Random Movement or RM) is also introduced

according to which the sink moves uncontrolled and randomly throughout the

network. The different mobility schemes are compared through extensive ns2-

based simulations in networks with different nodes deployment, data routing

protocols, and constraints on the sink movements. In all considered scenarios,

it has been observe that moving the sink always increases network lifetime. In

particular, our experiments show that controlling the mobility of the sink

leads to remarkable improvements, which are as high as six fold compared to

having the sink statically (and optimally) placed, and as high as twofold

compared to uncontrolled mobility.

Mobile sinks

Papadimitriou and Geogiadis (2005), Maximum life routing to

mobile sink in wireless sensor networks, in this paper, a novel data retrieving

mechanism named Multiple Enhanced Specified-deployed Subsinks (MESS)

mechanism for WSNs with path-limited mobile sink. Its innovation idea is to

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combine randomly deployed sensors with specified deployed wireless nodes

to achieve reliable and efficient data harvesting. To illustrate this mechanism

in detail, the possible and potential problems and pose corresponding

solutions is analysed. Simulation results validate our proposed mechanism

and prove that MESS can improve network lifetime dramatically. By

simulating this mechanism, some rules for constructing such a network has

been detected and the theoretical reference for practical applications is also

provided. MESS could have good performance in practical applications.

Song and Hatzinakos (2007), Architecture of Wireless Sensor

Networks with Mobile Sinks: Sparsely Deployed Sensors, in this paper,

describes to develop wireless sensor networks with mobile sinks (MSSNs).

The proposed MSSN is highly energy efficient, because the multihop

transmissions of high-volume data over the network are converted into single-

hop transmissions. The investigation is focused on sparsely deployed

networks, where single node-to-sink transmission is considered. The

transmission-scheduling algorithm (TSA-MSSN) is proposed, where a

parameter is employed to control the tradeoff between the maximization of

the probability of successful information retrieval and the minimization of the

energy-consumption cost. It is shown that the proposed implementation of the

TSA-MSSN has a complexity of O(1). This paper serves as the foundation for

understanding fundamental laws behind the aforementioned tradeoff with

useful implications for the design of more complex MSSNs.

Rao and Biswas (2008), Data harvesting in sensor networks using

mobile sinks, in this paper data collection architectures for static sensor

networks typically adopt a multipoint-to-point routing model in which data

from individual sensors is routed to strategically placed static sink units. In

spite of its operational simplicity, this model suffers from uneven energy

burden in the network due to the high routing energy expenditure around the

static sink units. This can lead to limited network life caused by sink

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disconnections due to the early energy exhaustion of those energy-strained

nodes near the data sinks. Introducing sink mobility to combat this lifetime

issue has recently generated a lot of interest among the sensor network

research community. The key idea is to avoid routing hotspots using policy

based sink mobility for improving network life. This article first explores and

categorizes the general problem of sink mobility in the context of trade-offs

between data delivery delay and network lifetime. Then it reviews a number

of existing solutions in the literature and their applicability to various

application scenarios. Finally, the article introduces and studies a novel

mobility control solution in which the network nodes cooperatively determine

the sink trajectory, and navigate the mobile sinks for delay and energy

optimized data collection.

Konstantopoulos et al (2012), A Rendezvous-Based Approach

Enabling Energy-Efficient Sensory Data Collection with Mobile Sinks, this

paper refers a large class of Wireless Sensor Networks (WSN) applications

involve a set of isolated urban areas (e.g., urban parks or building blocks)

covered by sensor nodes (SNs) monitoring environmental parameters. Mobile

sinks (MSs) mounted upon urban vehicles with fixed trajectories (e.g., buses)

provide the ideal infrastructure to effectively retrieve sensory data from such

isolated WSN fields. Existing approaches involve either single-hop transfer of

data from SNs that lie within the MS's range or heavy involvement of network

periphery nodes in data retrieval, processing, buffering, and delivering tasks.

These nodes run the risk of rapid energy exhaustion resulting in loss of

network connectivity and decreased network lifetime. Our proposed protocol

aims at minimizing the overall network overhead and energy expenditure

associated with the multi-hop data retrieval process while also ensuring

balanced energy consumption among SNs and prolonged network lifetime.

This is achieved through building cluster structures consisted of member

nodes that route their measured data to their assigned cluster head (CH). CHs

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perform data filtering upon raw data exploiting potential spatial-temporal data

redundancy and forward the filtered information to appropriate end nodes

with sufficient residual energy, located in proximity to the MS's trajectory.

Simulation results confirm the effectiveness of our approach against as well

as its performance gain over alternative methods.

Kim et al (2003), SAFE: a data dissemination protocol for periodic

updates in sensor networks, the author describes group protocol supports

applications with enough quality of service (QoS,) in change of QoS

supported by the underlying network and required by applications. A flexible

group service is supported for applications by cooperation of multiple

autonomous agents. Each agent dynamically and autonomously takes a class

of each protocol function like retransmission which is consistent with the

other agents. Ubiquitous computing holds the promise of a more connected,

more convenient, and more information rich world. However, the limited

number of pervasive devices actually available greatly restricts the range of

functionality currently available to ubiquitous computing applications. This

paper presents an approach whereby legacy devices are revitalized as new,

pervasive artifacts through augmentation by inexpensive sensors and

actuators. While such augmentation is commonplace in prototyping, the

author argues the technique has practical utility, especially with respect to

larger, complex devices. For these devices, often a substantial investment has

already been made and invasive retrofitting or replacement would be

prohibitively expensive. To ground our approach, the use of this technique to

modernize a legacy elevator system at the university has been investigated. In

this paper, technical challenges are described and the report on our experience

in addressing these challenges has been encountered.

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Data transmission

Luo et al (2003), TTDD: Two-tier data dissemination in large-scale

wireless sensor networks, in this paper, the worst-case communication

overhead is analysed, and the state complexity of TTDD. Compared with an

SODD approach, TTDD has asymptotically lower worst case communication

overhead as the sensor network size, the number of sinks, or the moving

speed of a sink increases. TTDD also has a lower state complexity, since

sensor nodes that are not in the grid infrastructure do not need to maintain

states for data dissemination. For a sensor node that is part of the grid

infrastructure, its state complexity is bounded and independent of the sensor

network size or the number of sources and sinks.

Shuai Gao et al (2011), Efficient Data Collection in Wireless

Sensor Networks with Path-Constrained Mobile Sinks, recent work has shown

that sink mobility along a constrained path can improve the energy efficiency

in wireless sensor networks. However, due to the path constraint, a mobile

sink with constant speed has limited communication time to collect data from

the sensor nodes deployed randomly. This poses significant challenges in

jointly improving the amount of data collected and reducing the energy

consumption. To address this issue, a novel data collection scheme, called the

Maximum Amount Shortest Path (MASP) is proposed that increases network

throughput as well as conserves energy by optimizing the assignment of

sensor nodes. MASP is formulated as an integer linear programming problem

and then solved with the help of a genetic algorithm. A two-phase

communication protocol based on zone partition is designed to implement the

MASP scheme. A practical distributed approximate algorithm is developed to

solve the MASP problem. In addition, the impact of different overlapping

time partition methods is studied. The proposed algorithms and protocols are

validated through simulation experiments using OMNET.

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Sink mobility is one of the most comprehensive trends for

information gathering in sensor networks. This way of information gathering

has a prominent role in balancing the energy consumption among sensor

networks, and culling the hotspots problem of sensor networks. In this paper,

a well planned adaptive moving strategy for a mobile sink in large-scale,

hierarchical sensor networks is presented. The mobile sink traverses the entire

network uploading the sensed data from cluster heads in time driven

scenarios. The mobile sink trajectory is planned such that all heads require no

multi-hop relays to reach the mobile sink. The proposed system aims at

extending the lifetime of the sensor network by achieving a high level of

energy efficiency and fair balancing of energy consumption across all

network heads. Furthermore, reducing the loss of data incur due to buffer

overflow. Extensive simulations are conducted in order to validate the

proposed strategy. The adopted data gathering scheme outperforms the static

sink scheme and periphery scheme in terms of life time elongation, and

scalability.

Kansal et al (2004), Intelligent Fluid Infrastructure for Embedded

Networks, the author refers computer networks have historically considered

support for mobile devices as an extra overhead to be borne by the system.

Recently however, researchers have proposed methods by which the network

can take advantage of mobile components. The author exploit mobility to

develop a fluid infrastructure: mobile components are deliberately built into

the system infrastructure for enabling specific functionality that is very hard

to achieve using other methods. Built-in intelligence helps our system adapt to

run time dynamics when pursuing pre-defined performance objectives. Our

approach yields significant advantages for energy constrained systems,

sparsely deployed networks, delay tolerant networks, and in security sensitive

situations. First, the research work show why the proposed approach is

advantageous in terms of network lifetime and data fidelity. Second, present

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adaptive algorithms that are used to control mobility. Third, design the

communication protocol supporting a fluid infrastructure and long sleep

durations on energy-constrained devices. The proposed algorithms are not

based on abstract radio range models or idealized unobstructed environments

but founded on real world behavior of wireless devices. The proposed system

implements a prototype in which infrastructure components move

autonomously to carry out important networking tasks. The prototype is used

to validate and evaluate our suggested mobility control methods.

Sundararaman et at (2005), Controllably Mobile Infrastructure for

Low Energy Embedded Networks, the author says security services such as

authentication and pair wise key establishment are critical to sensor networks.

They enable sensor nodes to communicate securely with each other using

cryptographic techniques. This paper proposes two key pre distribution

schemes that enable a mobile sink to establish a secure data-communication

link, on the fly, with any sensor nodes. The proposed schemes are based on

the polynomial pool-based key pre distribution scheme, the probabilistic

generation key pre distribution scheme, and the Q-composite scheme. The

security analysis in this paper indicates that these two proposed pre

distribution schemes assure, with high probability and low communication

overhead, that any sensor node can establish a pair wise key with the mobile

sink. Comparing the two proposed key pre distribution schemes with the Q-

composite scheme, the probabilistic key pre distribution scheme, and the

polynomial pool-based scheme, our analytical results clearly show that our

schemes perform better in terms of network resilience to node capture than

existing schemes if used in wireless sensor networks with mobile sinks.

Luo et al (2006), MobiRoute: Routing towards a Mobile Sink for

Improving Lifetime in Sensor Networks, describes the improving network

lifetime is a fundamental challenge of wireless sensor networks. One possible

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solution consists in making use of mobile sinks. Whereas theoretical analysis

shows that this approach does indeed benefit network lifetime, practical

routing protocols that support sink mobility are still missing. In this paper, in

line with the previous efforts, the approach that makes use of a mobile sink

for balancing the traffic load is investigated and in turn improving network

lifetime. Newly designed routing protocol, MobiRoute that effectively

supports sink mobility. Through intensive simulations in TOSSIM with a

mobile sink and an implementation of MobiRoute, the feasibility of the

mobile sink approach has proved by demonstrating the improved network

lifetime in several deployment scenarios.

Collision avoidance

Hen et al (2008), SELECT, Self-Learning Collision Avoidance for

Wireless Networks, the author discuss the fourth generation (4G) wireless

networks will provide high-bandwidth connectivity with quality-of-service

(QoS) support to mobile users in a seamless manner. In such a scenario a

mobile user will be able to connect to different wireless access networks such

as a Wireless Metropolitan Area Network (WMAN), a 3G cellular network,

and a wireless local area network (WLAN) simultaneously. This research

work presents a game-theoretic framework for radio resource management

(i.e., bandwidth allocation and admission control) in such a heterogeneous

wireless access environment. First, a non cooperative game is used to obtain

the bandwidth allocations to a service area from the different access networks

available in that service area (on a long-term basis). The Nash equilibrium for

this game gives the optimal allocation which maximizes the utilities of all the

connections in the network (i.e., in all the service areas). Second, based on the

obtained bandwidth allocation, to prioritize vertical and horizontal handoff

connections over new connections, a bargaining game is formulated to obtain

the capacity reservation thresholds so that the connection-level quality-of-

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service (QoS) requirements can be satisfied for the different types of

connections (on a long-term basis). Third, a noncooperative game to obtain

the amount of bandwidth allocated to an arriving connection (in a service

area) is formulated by the different access networks (on a short-term basis).

Based on the allocated bandwidth and the capacity reservation thresholds, an

admission control is used to limit the number of ongoing connections so that

the QoS performances are maintained at the target level for the different types

of connections.

Bettstertter et al (2003), The Node Distribution of the Random

Waypoint Mobility Model for Wireless Ad Hoc Networks, illustrates the

random waypoint model (RWP) is one of the most widely used mobility

models in performance analysis of ad hoc networks. The stationary spatial

distribution of a node moving according to the RWP model in a given convex

area is analysed. For this, an explicit expression has been given, which is in

the form of a one-dimensional integral giving the density up to the

normalization constant. This result is also generalized to the case where the

waypoints have a non uniform distribution. As a special case, the modified

RWP model is studied, where the waypoints are on the perimeter. The

analytical results are illustrated through numerical examples. Moreover, the

analytical results are applied to study certain performance aspects of ad hoc

networks, namely, connectivity and traffic load distribution.

Dai and Wu (2006), Efficient Broadcasting in Ad Hoc Networks

Using Directional Antennas, the author implements directional antennas to

conserve bandwidth and energy consumption in ad hoc wireless networks (or

simply ad hoc networks) is becoming popular. However, applications of

directional antennas for broadcasting have been limited. The author proposes

a novel broadcast protocol called directional self-pruning (DSP) for ad hoc

wireless networks using directional antennas. DSP is a nontrivial

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generalization of an existing localized deterministic broadcast protocol using

omni-directional antennas. Compared with its omni-directional predecessor,

DSP uses about the same number of forward nodes to relay the broadcast

packet, while the number of forward directions that each forward node uses in

transmission is significantly reduced. With the lower broadcast redundancy,

DSP is more bandwidth and energy-efficient. DSP is based on 2-hop

neighborhood information and does not rely on location or AoA information.

Two special cases of DSP are discussed: the first one preserves shortest paths

in reactive routing discoveries; the second one uses the directional reception

mode to minimize broadcast redundancy. DSP is a localized protocol. Its

expected number of forward nodes is O (1) times the optimal value. An

extensive simulation study using both custom and ns2 simulators show that

DSP significantly outperforms both omni-directional broadcast protocols and

existing directional broadcast protocols.

Garcia-Luna-Aceves and Tzamaloukas (2002), proposed Receiver-

Initiated Collision Avoidance in Wireless Networks which refers the medium-

access control (MAC) protocols for wireless networks to implement collision-

avoidance handshakes between sender and receiver. In the vast majority of

these protocols, including the IEEE 802.11 standard, the handshake is sender

initiated, in that the sender asks the receiver for permission to transmit using a

short control packet, and transmits only after the receiver sends a short clear-

to-send notification. The effect of making the collision-avoidance handshake

has been analysed, receiver initiated and compare the performance of a

number of receiver-initiated protocols with the performance of sender-

initiated collision avoidance protocols. Analytical and simulation results show

that the best-performing collision avoidance MAC protocol based on receiver-

initiated or sender-initiated collision avoidance is one in which a node with

data to send transmits a dual-purpose small control packet inviting a given

neighbor to transmit and asking the same neighbor for permission to transmit.

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The receiver-initiated protocols make use of carrier sensing, and are

applicable to either baseband or slow frequency-hopping radios in which an

entire packet can be sent within the same frequency hop (which is the case of

frequency hopping spread spectrum (FHSS) commercial radios).

Hu et al (2003), On Mitigating the Broadcast Storm Problem with

Directional Antennas, illustrates the mobile ad hoc networks, network-wide

broadcast is a critical network layer function supporting route discovery and

maintenance in many uni-cast and multicast protocols. A number of broadcast

schemes have been proposed; however, almost all of them assume the usage

of omni-directional antennas and focus on broadcast overhead in terms of the

number of forwarding nodes. Directional antennas have narrow beams and

can potentially reduce broadcast overhead in terms of the ratio of the number

of received duplicate packets to the number of nodes that receive broadcast

packets. In this paper, probability-based directional and omni-directional

broadcast is mapped to bond and site percolation, respectively, and describe a

collection of directional antenna-based broadcast schemes for mobile ad hoc

networks. A thorough and comparative simulation study is conducted to

demonstrate the efficiency of the proposed schemes.

For mobile ad hoc networks, network-wide broadcast is a critical

network layer function supporting route discovery and maintenance in many

uni-cast and multicast protocols. A number of broadcast schemes have been

proposed; however, almost all of them assume the usage of omni-directional

antennas and focus on broadcast overhead in terms of the number of

forwarding nodes. Directional antennas have narrow beams and can

potentially reduce broadcast overhead in terms of the ratio of the number of

received duplicate packets to the number of nodes that receive broadcast

packets. In this paper, the probability-based directional and omni-directional

broadcast is mapped to bond and site percolation, respectively, and describe a

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collection of directional antenna-based broadcast schemes for mobile ad hoc

networks. A thorough and comparative simulation study is conducted to

demonstrate the efficiency of the proposed schemes.

Levis and Culler (2006), A Tiny Virtual Machine for Sensor

Networks, describes the most of the projects the authors have mentioned are

at an early stage, focusing on developing algorithms and components of WSN

middleware. The design of a middleware layer for sensor networks that fully

meets the challenges is now open to discussion. One primordial issue is to

satisfy application QoS requirements while providing a high-level abstraction

that addresses sensor node heterogeneity. Another crucial challenge is

developing an easy-to-use, expressive programming interface while meeting

different sensor network application challenges, such as limited hardware

resources and QoS requirements. Middleware using autonomic computing

could provide more robustness, reliability, and self-management. At this

point, it's unclear whether successful network management and adequate

programming abstractions will stem from the known paradigms of the work

surveyed, or if all-new abstractions and approaches must emerge to

specifically meet WSN goals.

Broadcast redundancy

Peng and Lu (2000), presents the Reduction of Broadcast Redundancy in

Mobile Ad Hoc Networks. In that, the author says mobile objects can be used to

gather samples from a sensor field. Civilian vehicles or even human beings equipped

with proper wireless communication devices can be used as mobile sinks that

retrieve sensor-data from sampling points within a large sensor field. A key

challenge is how to gather the sensor data in a manner that is energy efficient with

respect to the sensor nodes that serve as sources of the sensor data. In this paper, an

algorithmic technique called Band-based Directional Broadcast is introduced to

control the direction of broadcasts that originate from sensor nodes. The goal is to

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direct each broadcast of sensor data toward the mobile sink, thus reducing costly

forwarding of sensor data packets. The technique is studied by simulations that

consider energy consumption and data deliverability.

Sundararaman et al (2005), Clock Synchronization in Wireless

Sensor Networks: A Survey, this paper presents a self-organizing MAC

protocol framework for distributed sensor networks with arbitrary mesh

topologies. The novelty of the proposed ISOMAC (In-band Self-Organized

MAC) protocol lies in its in-band control mechanism for exchanging TDMA

slot information while distributed MAC scheduling. A fixed length bitmap

vector is used in each packet header for exchanging relative slot timing

information across immediate and up to 2-hop neighbors. It is shown that by

avoiding explicit timing information exchange, ISOMAC can work without

network-wide time synchronization which can be prohibitive for severely

cost-constrained sensor nodes in very large networks. A slot-clustering effect,

caused by in-band bitmap constraints, enables ISOMAC to offer better spatial

channel reuse compared to traditional distributed TDMA protocols. ISOMAC

employs partial node wake-up and header-only transmission strategy to adjust

energy expenditure based on the instantaneous nodal data rate. Both analytical

and simulation models have been developed for characterizing the proposed

protocol. Results demonstrate that with in-band bitmap vectors of moderate

length, ISOMAC converges reasonably quickly - approximately within 4 to

8TDMA frame duration. Also, if the bitmap header duration is restricted

within 10% of packet duration, the energy penalty of the in-band information

is quite negligible. It is also shown that ISOMAC can be implemented in the

presence of network time synchronization, although its performance without

synchronization is just marginally worse than that with synchronization.

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Summary of the Chapter

After analyzing the various concepts proposed in research work, the

author clearly overcome the problem in communication protocols for wireless

sensor networks, broadcasting techniques, transmission of data by using

directional antennas, implementation of wireless ad-hoc network, mobile

sinks.