A Study On Limited Ad Hoc Networks' Medium Access Protocol

Wireless mobile Ad hoc networks are networks that do not have any fixed infrastructure. Nodes in the Ad hoc environment must discover communication routes dynamically. Ad hoc applications span several different sectors of society. In the civilian environment they can be used to interconnect workgroups moving in an urban area or a campus and engage in collaborative operation such as distributed scientific experiments and search and rescue. In the military area, the modem communications in a battlefield require extremely sophisticated instant infrastructure with far more complex requirements and constraints than the civilian applications.In this dissertation, we focus on the challenges of the MAC (Media Access Control) protocol in mobile Ad hoc networks. The performance of the MAC protocol has an immediate and fundamental impact on the overall efficiency of the Ad hoc networks. MAC protocols in Ad hoc networks can be divided into four categories: fixed access (FDMA, TDMA), no competition access (WTRP), random access (ALOHA, CSMA and CSMA/CA) and reservation access (MACA, MACAW, FAMA, 802.11DCF, DBTMA and PAMAS). However, many of the proposed MAC protocols employ designs that are not well-suited to cope with the dynamically changing network conditions within the Ad hoc architecture.This dissertation based on a Wireless access system Project. Based on insights into the design of contemporary wireless Ad hoc MAC protocols, a multiple channel MAC protocol-CAMA protocol is proposed. In CAMA, the control channel is used to transmit control frames to reserve data channels. This prevents other nodes from sending data in reserved data channels. CAMA protocol inherits contemporary wireless Ad hoc MAC protocols'RTS/CTS/ACK control frames and enhances with NCTS/DS control frames to solve the hidden terminal and exposed terminal problems. Another increasing efficiency is the spatial slots scheme, which takes into account the fact that radio units are usually spread out geographically. Hence the units with a sufficient spatial separation can use the same time slot for transmission. Network throughput is one of the most important issues when we evaluate the performance of wireless Ad hoc networks. So we used OPNET to build and analyze network models.