qo s based mac protocol for medical wireless body area sensor networks

QoS-based MAC protocol for Medical QoS-based MAC protocol for Medical Wireless Body Area Sensor NetworksWireless Body Area Sensor Networks

Author:Khaled A. Ali,Khaled A. Ali,Jahangir H. Sarker, and Jahangir H. Sarker, and Hussein T. MouftahHussein T. MouftahSchool of Information Technology and EngineeringUniversity of OttawaOttawa, Ontario, K7L 3N6

Presented by:Iffat Anjum(Roll: 16)Iffat Anjum(Roll: 16)Nazia Alam(Roll: 28)Nazia Alam(Roll: 28)15th Batch.

Date: 3rd May 2012.

ContentsContents

Contribution. Problem Definition.

• Background Proposed Protocol

• Network Model• Mathematical analysis

Performance Evaluation.

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Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

ContributionsContributions The paper proposed QoS-based MAC protocol that can be

employed in WBASNs.

This protocol is based on the IEEE 802.15.4 a Ultra Wide Band (UWB) MAC protocol and the sensor nodes utilize the slotted Aloha random access mechanism.

Also prioritizes the critical packets access to the transmission medium by cutting of the number of retransmissions of the collided non critical packets.

The critical traffic throughput is increased and its rejection rate is decreased ,maintaining the non critical traffic QoS parameters above a minimum provisioned level.

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Problem DefinitionProblem Definition Medical information have different urgency levels and timing

constraints that require a sensor to: Sense a physiological phenomenon , Process the sensed value, Communicate the processed value to a central node, in a

bounded and guaranteed time.

For these requirements, A MAC protocol has to , Maximize network throughput, Minimize packet rejection rate and, Differentiate network traffic.

4Green Networking Research GroupDept. of Computer Science and Engineering, University of Dhaka

Problem DefinitionProblem Definition

The medium access mechanism in WBASNs is based on the MAC protocol of Wireless Personal Area Networks (WPANs) standard.

WPAN (extended to UWB) s’ MAC protocol uses, Carrier Sense Multiple Access/Collison Avoidance

(CSMA/CA) and, Aloha access mechanism.

In this standards, star and peer-to-peer both network topologies are supported.

Two communication modes for the star topology, Beacon mode and Non-beacon mode.

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BACKGROUND



In beacon mode, network communications are controlled by the network coordinator.

This coordinator periodically transmits beacon frames for , Device synchronization and network association control.

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BACKGROUND



In Non-beacon mode, a network node can send data to the coordinator using CSMA/CA or Aloha access mechanisms. To receive data from the network coordinator, the node must

power up ,and poll the coordinator. Non-beacon operation mode provides the best performance since,

Sensor nodes’ receivers are not required to power up for receiving the beacon frame.

But the network coordinator cannot communicate with a node unless it has been invited by the node to communicate.

The beacon mode operation is mainly suitable under very tight

data rate restrictions.7

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BACKGROUND



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BACKGROUND


A Distributed Queuing Body Area Network (DQBAN) MAC protocol for healthcare applications, that propose a QoS MAC protocol.

It utilizes two queues: Collision Resolution Queue (CRQ) and, Data Transmission Queue (DTQ).

The CRQ control access requests to the medium, DTQ schedules sensor nodes collision-free packet transmissions. But DQBAN requires the management of different queues and the

logic system implementation in every sensor node.

Proposed ProtocolProposed ProtocolIn the proposed QoS-based MAC protocol, slotted Aloha access mechanism is used,

which sensor nodes contend for the medium only at the beginning of each time slot of the MAC frame.

Network nodes are grouped into,

Sensor nodes with critical information (C1)and ,

Sensor nodes of non critical information (C2).

Sensor nodes have the capability to sense multiple health parameters to indentify the traffic, if it is critical or non critical, Based on a predefined threshold. Traffic is non critical if its sensed value is below the threshold. It becomes critical when such threshold is exceeded.

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Proposed ProtocolProposed Protocol

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Figure: QoS-based MAC Protocol Illustration.

The total number of packets G, ready for transmission at the beginning of a time slot can be defined as,


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Network Model

A star network model composed of, The coordinator node a Full-Function Device (FFD) and, The sensor nodes are composed of Reduced-Function Devices (RFDs).

Figure: WBAN Network for QoS-based MAC protocol Evaluation.


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Mathematical Analysis

N: total number of sensor nodes Nc: sensor nodes of critical informationNnc: sensor nodes of non critical informationG: aggregate packet arrival rate per time slotGc: aggregate critical packet arrival rate per time slotGnc: aggregate non critical packet arrival rate per time slotSc: total critical throughputSnc: total non critical throughput

Definitions


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Rc: total critical rejection rateRnc: total non critical rejection rateλc : critical nodes packet arrival rateλnc: non critical nodes packet arrival raterc: number of allowed packet retransmissions for critical nodesrnc: number of allowed packet retransmissions for non critical nodesrc

min: minimum number of allowed packet retransmissionsfor critical nodesrc

max : maximum number of allowed packet retransmissionsfor critical nodes

Definitions


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Here, Aggregate critical packet arrival rate Gc per time slot is,

The term psucc in Equation (2) defines the probability of asuccessful packet transmission in a time slot.

Equation (2) can be simplified ,


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Equation (4) can be more simplified,

Similarly, Gnc can be written,

The aggregate packet arrival G per time slot can be rewritten,


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Equation (7) can be simplified as in Equation (8)

Substituting the psucc term of Equation (8) ,


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Equation (8) defines the aggregate network traffic generationper time slot ,which is solved numerically to obtained G value.

This G value is used to compute the critical and non critical throughput Sc and Snc respectively,


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Traffic Rejection Rate, the another performance parameterstudied in this paper is the total packet rejection rate.This parameter is defined here for critical and non critical traffic respectively,

Performance EvaluationPerformance Evaluation

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Figure :Aggregate Throughput, λ c = λ nc = 0.02. Figure:Aggregate Throughput, λ c = λnc = 0.025


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Figure :Aggregate Throughput, λ c = λ nc = 0.03. Figure: Packet Rejection Rate, λ c = λnc = 0.02


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Figure: Packet Rejection Rate, λ c = λnc = 0.025 Figure: Packet Rejection Rate, λ c = λnc = 0.03

THANK YOU

Green Networking Research Dept. of Computer Science and Engineering,

University of Dhaka

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qo s based mac protocol for medical wireless body area sensor networks

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