CHAPTER 2 BASIC CONCEPTS: CROSS LAYER ARCHITECTURE...

CHAPTER 2

BASIC CONCEPTS:

CROSS LAYER

ARCHITECTURE,

Congestion

Control & QoS IN

WSN

Chapter 2

Basic Concepts: Cross Layer Architecture, Congestion Control and

QoS in Wireless Sensor Networks

2.1 Overview of Conventional Layer and Cross Layer Architecture

2.1.1 OSI (Open Systems Interconnection) Model:

2.1.2 Paradigm of Cross-Layering

2.2 Overview of Cross Layer Architecture

2.2.1 Cross-Layer Design:

2.2.2 Drivers for Cross-Layer Approaches

2.3 Cross-Layer Signaling Architecture

2.4 Congestion Control

2.4.1 Causes of Losses

2.4.2 Types of Congestion

2.4.3 Important Factors to Detect Congestion Controlling

2.5 Quality of Service in Wireless Sensor Networks (QoS)

2.5.1 Limitations for QoS Support in Wireless Sensor Networks

2.5.2 Techniques to Achieve QoS in WSNs

2.6 Conclusion

2.7 References

2.1 Overview of Conventional Layer and Cross Layer Architecture

2.1.1 Open Systems Interconnection ( OSI) Model:

Over a network, applications can communicate using Open Systems

Interconnection, i.e. OSI is a reference model. To understand the relationships OSI

reference model is used as a conceptual framework.

OSI model is a set of layers in which seven logical layers are present. Each

layer gets service from layer below it and each layer serves the layer above it. Each

layer is responsible for communication system with specific function. Non-adjacent

layers interaction is never allowed. In short, from one to another next layer control is

passed. Starting from application layer and processing towards the bottom, i.e.

physical layer.

In a telecommunication network the main function of OSI model is that the

communication process between two points and model divides in seven layers. All

layers of OSI model having functions provided at a computer by communicating user.

If source user requires to communicate and transfer message to the destination user

then flow of data down through the layers in the source computer then through

network and then through layers in the destination computer.

Thus OSI model is used for users if software and hardware elements work together.

Troubleshooting is also easier if network is separated into different manageable

pieces. User easily understands the big networking structure using this model.

Chapter 2 Basic Concepts: Cross Layer Architecture, Congestion Control and QoS in WSN

Application Protocol

7 APDU

Presentation Protocol

6 PPDU

Session Protocol

5 SPDU

Transport Protocol

4 TPDU

Routers Routers

3 Packet

2 Frame

1 Bit

Host A Subnet limit Host B

Fig. 2.1 : OSI Reference Model


Network Network

Application

Presentation

Session

Transport Transport

Session

Presentation

Application

Data link Data link

Physical Physical

Conventional layered architecture prepares designs for system which

exchanges the data and for fast implementation. Open system interconnection

reference model is used for network architecture using layered type architecture.

Using protocol data units same protocol is designed by software or hardware, which is

used for communication on another network system. Using layered architecture

features such as modularity, interoperability, improved protocols are developed.

Performance of layered architecture has limitations because of lack of coordination

among the layers.

Cross layer architecture is a solution to avoid the drawbacks of layered architecture.

Using cross layer architecture improved communication protocols, interoperability is

possible. The basic concept of cross layer design is to acknowledge synchronization,

conversation and by intersecting different layers joint optimization of protocols and

supports the basic functionality of original layers.

Paper published “Standardization and Optimization Of Cross Layer Design for

Wireless Sensor Networks” International Journal of Computer Networking, Wireless

and Mobile Communications; (IJCNWMC) Vol. 3, Issue 4, Oct 2013, pp 103-110

ISSN (Print): 2250-1568;E-ISSN:2278–9448 Impact Factor(JCC): 5.2749; IC value

(Index Copernicus): 2.4


2.1.2 Paradigm of Cross-Layering

Standardization of layered protocol stacks are used for fast development in

transmitting and receiving of data systems, but at the same time there are some

limitations on the execution of the whole architecture, due to the defect of

coordination among layers.

Alteration or adjustment in design of layered architecture structure is known as Cross

layer design. Wireless execution limitation problems such as bandwidth limitation,

severe interference, propagation environment are due to physical nature of the

transmission medium.

Generally there are two approaches of cross layering defined as:

Weak cross-layering– It is ‘nonadjacent’ interaction. It is the capability to

make the conversation among protocol’s various layers.

Strong cross-layering-- In such type of cross layer design get the higher loss in

performance due to increasing complications and cost. Individual structures of

different layers are unable to find due to optimization of cross layers.


2.2 Overview of Cross Layer Architecture

(a) (b) (c)

Fig. 2.2

(a) Layered structure

(b) Cross-layer structure with fused layers (layer 2+ layer 3)

(c) Information exchange between layers using cross layer structure

Paper published on “Energy consumption and congestion avoidance mechanism using

cross layer design approach”, International Journal Enhanced Research in Science

Technology & Engineering, Vol. 3, Issue 10, Oct.2014,pp(177-183) Impact Factor

1.252 available at www.erpublication.com

Layer 3

Layer 1

Layer 2

Layer 3

Layer 4

Layer 2

Layer 1

Layer 4

Layer 4

Layer 2 + Layer 3

Layer 1

Channel Channel Channel


2.2.1 Cross-Layer Design:

Figure 2.2 (a) shows general layered structure for data transmission. As shown in

figure 2.2 (b) layer two and layer three are overlapped to each other and is known as

cross-layer structure for communication. How information is exchange between layers

using cross layer structure is shown in figure 2.2(c). Main purpose of Cross Layer

design is used to take advantage for information from number of layers to jointly

optimize performance of those layers.

Cross layer design is used for System Developer by using static or dynamic

methods. Cross layer design for static or immobile method is implemented by known

characteristics of layers and network. On the other hand, changing network conditions

are used for dynamic or mobile cross layer design.

Using cross layer design OSI layers are converted into new and non-standard

interfaces. Functionality of multiple layers is merged or overlapped. Merged layers

are jointly calibrated and new interfaces are created. Which information required for

cross layer optimization, but initially not approachable then new interfaces reveal

internal information.


2.2.2 Drivers for Cross-Layer Approaches:

In this section we discuss the cross layer design problems for wireless sensor network.

Wireless sensor networks main advantage is that they placed anywhere to monitor the

phenomena. Wireless sensor networks are power dependant so they require a source

of energy. For the design of wireless sensor network care must be taken that it

requires less energy.

There are numbers of restrictions in wireless sensor network. In wireless sensor

network there are a lot of limitations related to routing, quality of service (QoS)

constraints, security, and time synchronization conflict directly with sensors energy

consumption. To handle all these problems across-layer solution is needed. Energy

consumption must be reduced at all costs. It is impossible to avoid the complications

of design with increase in the sensors and it is inversely proportional to the sensors

ability to hold energy.

2.3 Cross-Layer Signalling Architecture

Information exchange between numbers of layers of the stack protocol is required for

different optimization solutions. Cross layer design solution implementation inside

reference model of TCP/IP protocol a common cross-layer signaling model is used for

their interoperability and coexistence.

Chapter 2 Basic Concepts: Cross Layer Architecture, Congestion Control and QoS in WSN Chapter 2 Basic Concepts: Cross Layer Architecture, Congestion Control and QoS in WSN

Several cross-layer signaling architectures have been developed by scientists

1. Signaling pipe by Interlayer: In Interlayer signaling pipe transmission of

signaling messages layer-to-layer along with packet data propagation inside

the protocol stack. It may be in top-down or bottom-up type behavior.

There are two methods of arranging the data into packets which are

transmitted by using given protocol from one layer to another layer, i.e. packet

structures or packet headers.

Top to Bottom Bottom to Top

Fig. 2.3 Signaling pipe by Interlayer

Transport

Application

Network

Link

Physical


Packet structures - In this method, particular section of the packet structure is

entered by signaling data or information. When protocol stack produces packet

then allocation of corresponding organization happened. Packet related

information is included in this structure.

Packet headers – This method is used as message driver for inter-layer.

Disadvantage of packet header is that restriction of signaling for packet flow

direction that is not appropriate for cross layer architecture. Cross layer

scheme require direct communication between opposite direction located

layers. Another drawback is related to overhead of protocol stack processing.

2. Exchanging of data using direct inter-layer – Internet control message protocol

(ICMP) is the pattern of direct interlayer communication. Internet control

message protocol performed at any of the protocol stack, it is not explicit.

Fig.2.4 Communication by direct interlayer

Transport

Application

Network

Link

Physical


3. Plane of middle cross-layer – If such type of plane implemented in parallel

structure type then, this is most widely used architecture of cross-layer

signaling. Middle cross layer plane also called as Cross-layer Server which

imparts with clients mean protocol’s at different layers.

Fig.2.5 Plane of middle cross-layer

4. Cross layer communication by Network-wide – At distinct protocol layers of

distributed network nodes cross layer optimization is obtained known as

network wide cross layer communication.

Fig.2.6 Cross layer communication by Network-wide

Transport

Application

Network

Link

Physical

Optimization

plane of

Cross layer

Transport

Application

Network

Link

Physical

Transport

Network

Link

Physical

Application

Router

ICMP

Message

ICMP

Message

PC PC


2.4 Congestion Control

Introduction:

In wireless sensor networks sensor nodes are deployed over large areas. They transmit

collected information to one or multiple central nodes known as base station. The

range of radio may increase in case of distance between a node and base station

increases. In such case intermediate nodes are used to transfer the data at base station.

A sensor node simultaneously collects and transmits information. There are various

ways for getting information from wireless sensor networks efficiently.

When channel or node carries huge data congestion occurs. Due to congestion

throughput and quality of service will decrease. If input data rate increases the

capacity of output channel also increases. Using number of input channels feeding at

the input all channels need the same output. In such case buffer built up and packets

lost due to insufficient memory to hold the packets. Problem cannot be solved by

increasing memory size. As packet waited the queue, they have already timed out.

Duplicate packets added to the buffer by the source as timer goes off. Load will be

increased by repeatedly adding the same packets. Another reason of congestion is

slow processor and slow channels.

Input Lines Output Line

Fig. 2.7 Router for 3 input lines

Router


Stack Model of Network:

OSI reference model is used for communication. Basically congestion occurs at the

time data transmission. Transport layer is used for congestion control implementation.

Rate at which packets are moved from application layer into the network layer can be

controlled. Same network model can be used for various applications because of

executing multiplexing operations.

In sensor networks network layer performs functions like maintenance and

construction of the routing structure. Routes chosen by packets cannot be controlled

therefore generally congestion control implementation work is done independent of

the network layer.

Transport layer consists of congestion control, Network layer consist of routing, Data

link layer consists of MAC protocols

Application Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer

Fig. 2.8 Transport layer consists of congestion control


2.4.1 Causes of Losses

Simultaneous transmission of data causes loss of packets due to number of reasons.

Various ways in which packets can be lost summarised in four ways:

Type 1: If the distance between source and destination node is very large, the

signal will be significantly reduced by the time it reaches the receiver.

Type 2: If number of sensor source nodes in the sensor network transmitting

data simultaneously, interference will occur at the receiving or destination

sensor node that is within range of the transmitting or source nodes. Generally,

sensor nodes can be distant from neighbours is to be considered.

Type 3: The third reason of loss is due to self interference. Sensor source

node’s transmission interferes with itself at the receiver. Such type of

interference is due to multipath effects and Rayleigh fading.

Type 4: When a packet is successfully received by destination sensor node,

but has to be lost due to queue overflow known as loss of type 4.

Type 1 and Type 3 loss is dependent on the specific location, surrounding

environment in which sensor nodes are deployed. Sensor motes may not be able to

hear other motes if placed less than three feet apart due to reflections of the wall.

Type 4 losses mainly due to congestion within the network.

2.4.2 Types of Congestion


Congestion in wireless networks is different from congestion in wired networks.

There are two types of congestion type A and type B.

Type A: Many sensor nodes in a specific region within the range of another

sensor nodes attempt to transmit at the same time resulting in type 2 losses.

Due to this throughput of all sensor nodes are reduced in that specific area.

Specifically local synchronization among neighbouring sensor nodes can

reduce, but cannot eliminate it completely because non-neighbouring sensor

nodes will get involved with transmission.

Type B: To hold the packets which are required to transmit within a specific

node of sensor the queue is used also called as buffer to hold packets.

There is possibility of both types of congestion as Type A and Type-B occurs

simultaneously.

To manage and correct the congestion open loop congestion controlling and closed

loop congestion controlling are used.

Open loop congestion control techniques are used to avoid the congestion

before it happens. This type of congestion control takes place at source or

destination. Various methods such as retransmission technique, window

technique, Acknowledgement technique, Discarding technique, Admission

technique are belongs to open loop congestion control.


Closed loop congestion control technique tries to take away the congestion

after it happens. Backpressure, choke packet, Implicit signaling, explicit

signaling are the examples of closed loop congestion control.

2.4.3 Important Factors to Detect Congestion Controlling

1. Buffer Queue Length: Generally in wireless sensor network queue

management is used for congestion detection. To detect congestion in queue

acknowledgment signal is important. For indication of congestion queue

length cannot be used.

2. End-to-end delay between sources and sink nodes: Sampling rate is used to

identify its own requirements.

3. Processing delay: Using data aggregation method sink collects data from

number of sources. To compromise packet delays which propagate along

different sources, the sink needs to wait until time required getting the reports.

4. Stability - A sink should not react fast to events to avoid unnecessary reaction

to transient phenomena so defined for measurement over long period and

described as “observation period”.

5. Channel Loading: To get the information about busy surrounding network

channel loading is used.


6. Report Rate/Fidelity Measurement- Due to congestion packets are dropped

along the path because sink continuously receives a less than required

acknowledgement rate. To measure the accuracy which requires large time,

but packet transmission time measurement should be less by considering the

parameters such as source-to-destination delay, Processing delay and

Stability.

2.5 Quality of Service (QoS) in Wireless Sensor Networks

Wireless sensor network performs different levels of quality of services based

on the type of applications. Quality of service is a challenging work in wireless sensor

networks because of memory, processing power, sources of power, large scale nature

of wireless sensor networks and bandwidth.

In this section, we discuss current survey on quality of service aware routing

techniques and QoS requirements in wireless sensor networks. Properties of quality of

service are interdependent. Main parameters of quality of service are loss, delay and

jitter. In communication networking, quality of service is described as quality of

service measurement that network performs to the application. A set of services

required to transmit the flow of packets from source to destination is the another way

to describe the Quality of Service.


Provide Quality of Service Quality of Service Request

Fig.2.9 Quality of Service Model

2.5.1 Limitations for QoS Support in Wireless Sensor Networks

For various complicated functions wireless sensor networks are used for many

applications. For success of these missions accurate and reliable data transfer have an

important role in the achievement of target objective. Wireless sensor network

applications have following characteristics:

1. Resource Restrictions: The limitations on resources consist of bandwidth,

queue size, memory, processing capacity and finite transmission power.

Energy is the basic parameter in concern to wireless sensor networks quality of

service because sensor nodes cannot be replaced or recharged.

2. Unequalled traffic mixture: In wireless sensor network applications, generally

traffic flows from large number of sensor nodes to small number of nodes.

This traffic is with combination of periodic or non-periodic data. So quality of

Network

User

or

Application


service mechanism should be designed for unequalled mixture, quality of

service limitations traffic.

3. Excess Data: Wireless sensor networks have features of excess data in the

sensor data. Reliability or robustness of data delivery of WSNs decreases

because of excess data.

4. Wastage of precious energy occurs in this process. To maintain robustness

data fusion is the best solution.

5. Network dynamics: Due to unreliable characteristics of wireless sensor

networks network dynamics occurred. Node mobility, node addition and

failure change the dynamic topology. Highly dynamic networks increase the

complexity of quality of service support.

6. Energy Balance: To increase the lifetime of the network energy must be

equally distributed among all sensor nodes.


2.5.2 Techniques to achieve Quality of Service in WSNs

Following are some techniques to improve the quality of service in wireless sensor

networks.

1. Management of Topology- Energy consumption is more by nodes through

transmission and sensation. To reduce the energy consumption by sensor

nodes, they put in sleep mode when they are not required to sense or transmit

the data. Coordination of sleep schedules of all nodes so that data can be

efficiently forwarded to the sink by using topology management. Topology

management helps to increase the energy efficiency.

2. Localization- In the network physical location of the sensor nodes found by

localization. Localization increases spatial accuracy and reduce energy

efficiency.

3. Controlled mobility- Due to mobility and random deployment of nodes

performance of wireless sensor networks will deteriorate.

4. Data Fusion- Data coming from various sources combined into a single data

packet before the transmission which reduces data redundancy as well as

reduces the number of transmissions required to forward the data to the sink.

Data fusion results in higher latency.

5. Network Topology- In traditional wireless sensor networks centralized single

sink is available and all the source nodes have to send data to the sink

in one direction.


Sensor nodes placed near the sink node have to perform more data forwarding

and packet transmissions. This leads to be increased contention and collision

near the sink. Nodes are near the sink having shorter lifetime due to drain up

their energy faster.

6. Cross-Layer design- Information is distributed among different layers and

reduces the cost of interdependency between adjacent layers cross layered

design enhances the network performance.

2.6 Conclusion

In this chapter the OSI reference model architecture and cross layer architecture as

well as drivers for cross-layer approaches and cross layer frameworks are presented.

Also terminologies including causes of packet loss, types of congestion such as type

A, type B were described.

Remaining half of the chapter describes the Quality of Service in wireless

sensor networks. Related to QoS limitations of quality of service, factors affecting on

QoS, and techniques to achieve quality of service in wireless sensor networks are

described.


2.7 References

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consumption in wireless sensor networks” Journal of Theoretical and Applied

Information Technology 20th April 2014. Vol. 62 No.2

[2] W. Su and T. L. Lim, “Cross-layer design and optimization for wireless sensor

networks,” SNPD-SAWN ’06: Proceedings of the Seventh ACIS International

Conference on Software Engineering, Artificial Intelligence, Networking, and

Parallel/ Distributed Computing. Washington, DC, USA: IEEE Computer Society,

2006, pp.278–284.

[3] Divya Sharma, Sandeep Verma, Kanika Sharma, “Network Topologies in

Wireless Sensor Networks: A Review” IJECT Vol. 4, Issue Spl - 3, April - June 2013

[4] MS. Sajjad Ahmad Madani, ‘Cross Layer Design for Low Power Wireless Sensor

Networks” pawis.sourceforge.net/literature

[5] P. Gupta and P.R. Kumar, “The capacity of wireless networks,” IEEE Trans.

Inform. Theory, Vol. 46, pp. 139-157, Jan. 1999.

[6] S. Cho and A. Chandrakasan, “Energy efficient protocols for low duty cycle

wireless microsensor networks,”ICASSP 2001, May 2001.

[7] Q. Ye, Y. Zhang, and L. Cheng, “A study on the optimal time synchronization

accuracy in wireless sensor networks”, submitted to IEEE JSAC, Jul. 2003.

[8] W.R. Heinzelman, J. Kulik, and H. Balakrishnan, “Adaptive protocols for

information dissemination in wireless sensor networks,” Mobi COM '99, pp. 174-185,

Seattle, WA, 1999.

[9] V. Rodoplu and T. H. Meng, “Minimum energy mobile wireless networks,” IEEE

JSAC, Vol. 17, No. 8, pp. 1333-1344, August 1999.


[10] Dzmitry liazovich, Fabrizio Granelli,” Cross Layer Designs in WLAN

Systems,”Book Chapter, Introduction, Why cross layer? Its advantages and

disadvantages.

[11] X.-H. Lin,Y.-K. Kwok, and H.Wang,“Cross-layer design for energy efficient

communication in wireless sensor networks,” Wireless. Comm. Mob. Comp., vol. 9,

no. 2, pp. 251–268, 2009.

[12] R. Madan, S. Cui, S. Lall, and A. J. Goldsmith, “Modeling and optimization of

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[14] D. O’Neill, A. Goldsmith, and S. Boyd, “Wireless network utility maximization,”

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[15] I.Akyildiz,W. Su, Y. Sankarasubramaniam, and E. Cayirci,Wireless sensor

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[16] Morteza Mardani, Seung-Jun Kim, “Cross-layer Design of Wireless Multihop

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[17] Cheng Tien Ee and Ruzena Bajcsy, “Congestion Control and Fairness for Many

to One Routing in Sensor Networks,” SenSys’04, November 35, 2004

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Congestion Detection and Avoidance in Sensor Networks,” SenSys’03, November 5–

7, 2003,


[19] Yuanli Wang, Xianghui Liu, Jianping Yin, “ Requirements of Quality of Service

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[20] Bhaskar Bhuyan, Hiren Kumar Deva Sarma, Nityananda Sarma, Avijit Kar,

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[21] Hwee-Xian Tan, “Quality of Service in Wireless Sensor Networks”, IEEE

Conf.on Networking 2006, Department of Computer Science National University of

Singapore.


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CHAPTER 2 BASIC CONCEPTS: CROSS LAYER ARCHITECTURE...

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