International Journal of Engineering and Technology

Two types of MAC mechanisms namely, random access and reservation can be employed for OFDMA-based wireless LANs. Reservation-based MAC is more appropriate than random access MAC for connection-oriented applications as connection-oriented applications provide strict requirements of traffic demands. On the other hand, random access mechanism is a preferred choice for bursty traffic i.e., data packets which have no fixed pattern and rate. As OFDMA-based wireless networks promise to support heterogeneous applications, researchers assume that applications with and without traffic specifications will coexist. Thus, both reservation-based and random access schemes are required for an OFDMA-based WLAN. Eventually, OFDMA-based wireless LAN will deploy hybrid MAC mechanisms inheriting traits from random access and reservation. In this article we design a new MAC protocol which employs one kind of hybrid mechanism that will provide high throughput of data as well as maintains improved fair access policy to the medium among the stations. The protocol works in two steps, where in step 1 sub-channels are approximately evenly distributed to the stations and in step 2 stations within in a sub-channel will contend for medium randomly if the total number of stations of the system are larger than the number of sub-channels. The details of the protocol is illustrated in the paper and we analyze the performance of our OFDMA-based multi-channel hybrid protocol using comprehensive computer simulations. Simulation results validate that our proposed protocol is more robust than the conventional CSMA/CA protocol in terms of throughput, collision reduction and fair access. In addition, theoretical analysis of saturation throughput of the protocol is also evaluated using an existing comprehensive model.