A novel scheme for achieving time based in IEEE 802.11 multirate wireless LANs

This paper investigates the issue of fairness in a heterogeneous environment in which stations in IEEE 802.11 based wireless LANs use multiple data rates for transmission. Throughput based fairness does not lead to a fair allocation of the channel time, when stations are transmitting at different physical rates. A new fairness notion called time based fairness has been proposed in which each competing node receives an equal share of the wireless channel occupancy time. We demonstrate that the time based fairness can achieve larger aggregate throughput while still guaranteeing that no node receives worse channel access than it would in a single rate wireless LAN. Using Jain´s fairness index, optimal MAC parameter required to achieve maximum fairness between competing nodes in terms of channel occupancy time is obtained through simulations. The impact of this mechanism on throughput of slow and fast stations is also explored.