Presented by: Dr. Khaled A. Ali

Urgency-based MAC Protocol for WSBANs

WiSense Seminar Series

• Introduction• Wireless Personal Area Networks• WSBAN Application Examples• IEEE 802.15.4 MAC Protocol• Urgency-based MAC Protocol for WSBANs• U-MAC Performance Evaluation and Results• Concluding Remarks

Outline

• Massive deployment of Sensor Networks– Stimulated by numerous industry segments, and government

organizations– Sensors and RFID tags will begin to inhabit every object– Emergence of smart sensors with local intelligence

• Traffic volume increases dramatically– Significant architectural changes to global IT infrastructure is

expected– Process moves to network edge to aggregate and filter traffic– Directional shift in network traffic

Introduction

• Integration of WSNs into 4G Networks– Evolution of current ITU and IEEE standards– Connect sensor world with back-end computing environments– Enable end-to-end solutions

– Mixed Network Traffic of different priority levels and different bandwidth requirements

Introduction

IP Network

4G network

Sensor Net

2G networ

k

3G networ

k

Phone networ

k

Other network

s

Cellular Net

• WPAN (General Description):– Low-rate: (250 kb/s, 40 kb/s and 20 kb/s data rates)– Range: 10-20 meters– Low power consumption– Addresses: short 16-bit or long 64-bit– Channels: 16 channels (2450 MHz band) , 10

channels (915 MHz band ) and 1 channel (868 MHz band)

– Access mechanisms: CSMA/CA or Aloha – Reliability : Fully acknowledgement, error checking– Cost: Low cost of deployment– MAC& PHY: IEEE 802.15.4 and IEEE 802.15.4a

Wireless Personal Area Networks

• WPAN (Network Topology):Wireless Personal Area Networks

FFD (PAN)

RFD

star topology

peer-to-peer topology

• WPAN (Layered Architecture):Wireless Personal Area Networks

Upper Layers

MAC

PHY

Physical Medium

SSCS

802.2 LLC

• Non-invasive WSBANs:– Monitoring and sensing signals from the human

body for medical applications– Distributed communication over the human

body• Invasive (In-Body) WSBANs:

– Connect implanted medical devices (MICS band) and on-body sensors (ISM band)

– Miniature “Pill camera”• Images and medical data are transmitted to a

central WS• View, edit, archive and e-mail the live video,

images and date• Physician can observe and detect exact location

of suspected “in-body” disorder• Patient data can be sent through the network

to establish a diagnosis and trigger the required actions via actuators

WSBAN Application ExamplePersonal Health Care-mixed data rates

• RFID tag integrated in the watch allows entrance in the conference room

• Presentation can be downloaded from nodes in the room

• Business cards are exchanged by handshake

• Additional information can be displayed by video glasses

• Using microphone/motion sensors the main processing unit becomes aware of the meeting and automatically blocks phone calls

WSBAN Application ExampleBusiness Meeting-mixed data rates

• MAC Sublayer

– Generating Network beacons (PAN) – Synchronization– PAN association and disassociation– CSMA-CA – GTS

IEEE 802.15.4 MAC Protocol

INACTIVE

Beacon

Beacon

CFP(GTS)CAP

CAP- Contention Access PeriodCFP- Contention Free PeriodGTS- Guaranteed Time Slots

• Objectives:– Supporting QoS in WSBANs for medical

applications– Increasing network throughput– Minimizing packet rejection rate– Minimizing power consumption

• Approach:– Star network topology – Controlling the number of packet

retransmission • High priority traffic contend more for the transmission

medium than low priority traffic– Slotted Aloha access mechanism

Urgency-based MAC Protocol for WSBANs

• Traffic Classification– Critical Traffic– Non-Critical Traffic

• Arrival Rate– New Packet Arrival

rate (λ)• Critical packet arrival rate• Non critical packet arrival

rate– Retransmitted packet

arrival rate (λr)• Retransmission

Queues

Urgency-based MAC Protocol for WSBANs

U-MAC Block diagram

C1C2C3

Cr

λ λ + λr

Channel

Success

Collision

• Packet Transmission Scenario:– Number of critical packet retransmission s; rc=

3– Number of non critical packet

retransmissions ;rnc= 2

Urgency-based MAC Protocol for WSBANs

Pc

Pnc

3 2rc rnc

2 11 0

• Beacon frame enabled Star network topology

• RFD nodes communicate with a single FFD

• RFD nodes composed of critical nodes and non critical nodes

• Critical nodes contend for the medium rc times

• Non critical nodes contend for the medium rnc times

U-MAC Performance Evaluation and Results

• Maximum number of Critical Nodes• Critical Nodes Packet Arrival Rate• Network Throughput

• Maximum Number of Critical Nodes Nc– Aggrigate Packet Arrival rate G=1

– Number of Critical Nodes

U-MAC Performance Evaluation and Results

• Maximum Number of Critical Nodes Nc (Cont.)– Ntotal=20 G=1– λc=0.05, 0.06– λnc=0.015– rnc= 0, 2, 5– rc= 0- 5

U-MAC Performance Evaluation and Results

• Critical Packet Arrival Rate– Ntotal=20, Nc=5 G=1– λnc=0.015– rnc= 0, 2, 5– rc= 0- 5

U-MAC Performance Evaluation and Results

• Network Throughput– Critical Nodes Throughput

– Non Critical Nodes Throughput

U-MAC Performance Evaluation and Results

• Network Throughput (Cont.)– Nc=10 Nnc=10 rnc=1 10000 time slots

each of 1 sec.

U-MAC Performance Evaluation and Results

λc =λnc=0.025 λc =λnc=0.03

• An Urgency-Based MAC protocol for WSBAN is proposed

• U-MAC protocol differentiates nodal medium access based of the criticality of the reported traffic

• Critical traffic is allowed to retransmit collided packets more than non critical traffic

• U-MAC protocol performance is evaluated mathematically and through simulation

• The performance results show the ability of the proposed protocol to differentiate network traffic

Concluding Remarks

Thank you