Asynchronous Requests for Multiple Packet Transmissions in Wireless Networks

Abstract

A multiple packet reception (MPR) capability allows a wireless user and an access point (AP) to receive multiple packets simultaneously. This paper proposes a MAC protocol that takes MPR capability into account. A new mechanism of transmission process and modified frame format of control frames are two main contributions. The new mechanism for request-to-send (RTS) frame transmission allows wireless users to transmit RTS frame while other users are transmitting, under two conditions. The first condition is that the first RTS frame is still ongoing transmission, and the second condition is that the number of ongoing RTS transmission is less than the maximum MPR capability. Moreover, format of the new extended clear-to-send (eCTS) and extended acknowledge (eACK) frames reduce the number of control frames exchanged before data transmissions. A time-driven simulation is developed to evaluate the network throughput. The result shows that throughput obtained by the proposed protocol is about 110 Mbps while those obtained by traditional MAC protocol is about 20 Mbps, when the maximum MPR capability equals 8, minimum contention windows equals 32 and the number of users is 50. However, the throughput is not much increased when increasing the maximum MPR capability, if there are less than 5 users in the network.