Improving Wireless Communication
Enhancing MAC Layer Protocols and Sectorization


Wireless networking is one of the fastest growing technologies in today's communications scenario. More and more people are becoming active subscribers of wireless based Internet Service Providers that are mushrooming all over. As is well known, the wireless channel is a highly unreliable medium for transmission of information. Deep channel nulls, time varying impulse response of the channel, hidden and exposed nodes in Wireless Local Area Networks (W-LANs), channel access strategies, power control - these are some of the issues and problems related with this type of communication.

One of the major areas of research taking place at the LIST lab deals with the solutions to some of these issues. In particular, the Medium Access Control (MAC) Layer and the related protocols, as applied primarily to Wireless Local Area Networks (W-LANs), are being investigated. Extensive programs to simulate detailed wireless scenarios have been written to study the impact of various network parameters on the system throughput performance. These simulations are being used to fine-tune the already existing recommendations of the 802.11 family of protocols (e.g. the exponential back-off schemes for CSMA/CA). Mathematical analyses to supplement the results of these simulations are being worked out. Recently, a few novel ideas for extracting better throughputs in W-LANs have been suggested for deeper investigation. They include a sectorized access methodology applied to situations with small coverage area and high traffic intensity, and an efficient power control methodology for extending battery life of mobile stations. Current research involves detailed analytical and computer based simulations, and possibly a neural network based optimization, of these. Figure 1 below shows a schematic layout of the sectorized scheme in 802.11 based networks (showing 4 sectors on the access point).

Fig. 1. Sectorization of WLAN with directional Antennae on the Access Point

Figure 2 shows the enhancement of throughput that is effected when the above shown sectorization is applied. It is clear that the sectorized throughput is significantly better for any number of terminals.

Fig. 2. Throughput Comparison between Sectorized and Normal Case