Research Of Distributed Wireless Network MAC Protocol

Distributed Wireless Network is a distributed self-organized network which is composed of wireless mobile nodes, without fixed infrastructure, robust and deployed quickly. It is especially attractive to military tactical and disastrous rescue cases and remote regions. MAC protocol controls network nodes access to the sharing broadcast channel. The special properties of wireless channel such as half-duplex mode, time-varying channel and burst channel errors make the designing of MAC protocol very challenging. Furthermore, the multi-hop structure brings the hidden terminal and exposed terminal problem, making the work more difficult.MAC protocols for wireless networks can be divided into three classes: fixed allocation,random access and demand assignment. This paper analyzed the three kinds of protocols in detail and summed up the advantages and disadvantages. According to the characteristic without a center in distributed wireless network, adopts random access protocols which nodes contends the channel in an asynchronous manner and using carrier sense, collision avoidance methods and random retransmitting, transmitting information in some conditions can abtain an good effect. So random access protocols is generally used in distributed wireless network.This paper is focused on random access protocols and analyzed two kinds of MAC protocols in detail which used in military tactical wireless network: FAMA protocols and the MAC protocols in MIL-STD-188-220C. FAMA protocol is a high speed tactical packet radio network MAC protocol, and 220C protocol is a low speed tactical packet radio network MAC protocol. We studied FAMA protocol in detail and compared with 802.11 MAC protocols. The simulation results shown that FAMA protocol with packet trains can greatly improve on performance. In heavy load and short packet's intervals conditions, FAMA protocol with packet trains is superior to IEEE 802.11 MAC protocols. So we can draw a conclusion that FAMA protocol with packet trains is a good protocol for a heavy load and short packet's intervals network.This thesis not only analyses 220C protocols in particularly, but also introduces a new algorithm with carrier sensing mechanism and token mechanism based on 220C for the general utilization of algorithm. Meantime, we offered the simulation result of four protocols (pure ALOHA,1- persistent CSMA,220C R-NAD,CSMA/Token Ring). The simulation results show that CSMA/Token Ring protocol performs particularly well in small network and upwards of middle load condition.