KING FAHD UNIVIRSITY OF PETROLEUM AND MIERALS

ELECTRICAL ENGINEERING DEPARTMENT

MAC Protocols in ad hoc networks

Rami Bakhsh 200319130 Mohammed Al-Farsi 200164630

References:• http://www.moeforum.net• Mobile Ad Hoc Networks by Faisal Aslam and Chia Ching Ooi• Ad Hoc Wireless Media Access Protocols by Mikko Raatikainen

Introduction

MAC Layer In Ad hoc network

MAC Protocols

Hidden Terminal Problem

Exposed Terminal Problem

MACA Protocol

Conclusions

Definition of the ad hoc networkConsists of mobile nodes which communicate with each other through wireless medium without any fixedInfrastructure.

http://www.moeforum.net

Important Features of ad hoc networks

The network topology Every nodes may be mobile node Limited power Limited wireless bandwidthThe channel quality is varibale No centralized units

MAC Layer In Ad hoc network

MAC Layer:

For sharing a single broadcast medium among multiple users.

Concerned with per-link connections.

Error detection and correction by using Cyclic redundancy checks, Parity

schemes.

Flow control.

There are two types of MAC :

Static MAC

Dynamic MAC

MAC ProtocolsMACMAC

Static MACStatic MAC Dynamic MACDynamic MAC

SchedulingScheduling Random AccessRandom Access

Pure ALOHAPure ALOHA

Slotted ALOHASlotted ALOHA

CSMACSMA

CSMA/CDCSMA/CD

TDMATDMA

FDMAFDMA

CDMACDMA

WDMAWDMA

Collision resolution Collision resolution

MACAMACA

BI-MCMACBI-MCMAC

Hidden Terminal ProblemTwo nodes transmit concurrently data to the same

receiver => collisionUse RTS and CTS control packets.

A B C

Mobile Ad Hoc Networks by Faisal Aslam and Chia Ching Ooi

Exposed Terminal Problemoverhearing data transmission from neighboring nodes.

A B C D

Mobile Ad Hoc Networks by Faisal Aslam and Chia Ching Ooi

MACA Protocol

Inspired by the CSMA/CA method Extension to the CA part of the CSMA/CA Lack of carrier doesn’t always mean it’s OK to transmit Presence of carrier doesn’t always mean it’s bad to

transmit.

MACA and Hidden & Exposed Terminals Problems

Ad Hoc MAC Protocol (Pusan)

Improvements of MACA ProtocolMACA (1990)

No carrier sensing.MACAW (1994)

MACA with Wireless networks.Includes ACK for the fast error recovery.

FAMA (1995)RTS-CTS exchange with non-persistent Carrier Sensing.

MACA-BI (1997)Receiver initiative two-way handshake: RTR-Data.

Different kinds of MAC protocols for different problems.

There are new protocols inspired