The Research On The Multi-Channel Medium Access Control Protocols In WLAN

With the development of wireless communication technology, wireless LAN (WLAN) gradually comes into use by millions of households for its flexibility and mobility features. However, the traditional medium access control (MAC) mechanism which occupies the entire channel for data transmission has not been able to meet the growing demand for multi-user access. On the contrary, multi-channel frequency division multiplexing technology may improve the performance of the system in the case of multi-users to some extent.Therefore, according to the concept of multi-channel, this paper proposes a multi-channel MAC mechanism that allows multiple users to transmit data in different sub-channels simultaneously, thereby increasing the throughput of the wireless communication system. The concept of multi-channel is extracted by orthogonal frequency division multiple Access (OFDMA), OFDMA divides the subcarriers in the system into multiple sub-channels, which allows users to compete for the right to transfer data on different sub-channels. When users contend for sub-channels, we take use of the carrier sense multiple access (CSMA/CA) with RTS/CTS (request to send/clear to send) mechanism to avoid collision and hidden terminals. What’s more, the protocol allows users to set a back-off counter on each sub-channel, so that the collision which occurs when a user competes for a sub-channel will not affect users to access other sub-channels. In this paper, the performance of the proposed mechanism for multi-channel MAC is analyzed through the theoretical derivation as well as the simulation software. It is proved that the simulation results are consistent with theoretical analysis. At last, how to select the number of sub-channels in this multi-channel mechanism is discussed and we compare the saturation throughput of the system under different number of sub-channels. As we can see from the simulation results, multi-channel MAC mechanism improves the system performance to meet the system requirements in the case of amount of users.