Cooperation and Directionality: Friends or Foes?Zhifeng Tao, Thanasis Korakis, Feilu Liu, Shivendra Panwar, Jinyun Zhang, Leandros Tassiulas

IEEE ICC 2008

Outline

Introduction Proposed Method Performance Evaluation and Comparison Conclusions

Introduction

Benefits of Directional AntennasSpatial reuseLonger transmission and reception rangeHigher network capacityLess interferenceFewer transmission hops

Introduction

Benefits of Cooperative CommunicationSpatial diversityHigher capacityReliabilityExtended coverage

Introduction

DistinctionDirectional antenna relies on directional

transmission of wireless signalCooperative communications depend on the

broadcast nature of wireless channel

Motivation and Goal

Motivation Although a handful of MAC protocols have already

been proposed to support either directional antenna or cooperative communications, nothing exist that can exploit both simultaneously

Goal Proposed a MAC that taps into the combined potential of

both transmission directionality and cooperation diversity

Network Model

Two hosts are said to be neighbors if they can communicate with each other over a wireless link.

We assume that each node knows its neighbors‘ location as well as its own location.

A B

A B

phy layer

MAC layerData Flow

Antenna Model

Proposed Methods

O-CoopMACCooperative MAC with Omni-directional antenna

D-NoopMACNon-Cooperative MAC with Directional antenna

D-CoopMACCooperative MAC with Directional antenna

O-CoopMAC(Cooperative MAC with Omni-directional antenna)

Ss

Sr

Sd

Cooperation Table of Ss

Index (MAC address) Link Rate

Ss Lsr Rsr

Ss Lsd Rsd

Sr Lrd Rrd

… …　 …　Sd Ldr Ldr

…　 …　 　…

RTSHTS

HTSCTS

CTS

1st hop data@Rsr 2nd hop data@Rrd

ACK

D-NoopMAC(Non-Cooperative MAC with Directional antenna)

RTSCTSACK

A B

Data

D-CoopMAC(Cooperative MAC with Directional antenna)

Ss

Sr

Sd

Cooperation Table of Ss

Index (MAC address) Link Rate

Ss Lsr Rsr

Ss Lsd Rsd

Sr Lrd Rrd

… …　 …　Sd Ldr Ldr

…　 …　 　…

RTS HTS

CTS

1st hop data@Rsr

2nd hop data@Rrd

ACK

Performance Simulation and Comparison

Simulation Settings

Baseline IEEE 802.11g

Deployment Random

Network size (in radius) 350m

Radius of omnidirectional antenna 100m

Directional antenna's lobe of radius 119m and 141m

beams number of directional antenna 2 and 4

Throughput versus Number of Stations

Channel access delay

Throughput versus Traffic Load(100 stations)

Throughput versus Traffic Load(300 stations)

Conclusions

This paper has presented three new MAC protocol for ad-hoc networks

To establish a deeper understanding of the relative performance of cooperative communications and directional transmission

Cooperation and directionality can be rather foes than friends

Thank you