Performance Improvement of 802.11 Wireless Access Network with TCP ACK Agent and Auto-Zoom Backoff Algorithm

This paper proposes two schemes to improve the TCP performance over 802.11 WLAN access protocol. In the standard 802.11 and TCP protocols, a TCP data segment is acknowledged twice, once at the MAC layer, and once at the TCP layer. By a simple cross-layer design, a TCP ACK agent is installed at the WLAN AP. When a MAC acknowledgment is received by the AP, the AP generates a TCP ACK on behalf of the WLAN stations. Together with the TCP ACK agent scheme, an auto-zoom backoff algorithm is proposed to further improve the access performance. In the auto-zoom backoff, the contention windows can be progressively reduced to a very low value in case of light or asymmetric traffic, and return to normal quickly when collision occurs. With the TCP ACK agent and auto-zoom backoff, we show that significant improvement in TCP throughput performance can be achieved in typical Internet application scenarios.