High Performance Distributed Coordination Function for Wireless LANs

The performance of DCF, the basic MAC scheme in IEEE 802.11, degrades under larger network sizes, and higher loads due to higher contention and so more idle slots and higher collision rates. We propose a new high-performance DCF (HDCF) protocol that achieves a higher and more stable performance while providing fair access among all users. In HDCF, the transmitting stations randomly select the next transmitter and so active stations do not contend for the channel, and an interrupt scheme is used by newly transmitting stations without contending with the existing active stations. Thus, HDCF achieves collision avoidance and fairness without idle slots added by the backoff algorithm used in DCF. For evaluation, we provide Opnet simulation that considers saturated and non-saturated stations. Results show that HDCF outperforms DCF in terms of throughput, and long-term and short-term fairness with gains up to 391.2% of normalized throughput and 26.8% of fairness index.