Higher rate packet transmission scheduling for enhancing TCP performance by smoothing of queuing time in wireless LAN

Recently, wireless LANs are utilized in various situations. However, inefficient channel utilization is still a serious problem. One of effective solutions is to prevent packet loss and to transmit packets at a higher rate. While the backoff algorithm in IEEE 802.11 avoids only the packet loss caused by collision, other existing works tackle the packet loss caused by channel fading by transmitting packets at a lower rate. The authors have proposed a transmission scheduling algorithm which avoids decreasing transmission rate and improves channel utilization. However, these previous methods do not consider influence to TCP performance. In this paper, we propose a novel packet transmission scheduling which enhances TCP performance by effectively utilizing higher channel transmission rate and by keeping TCP congestion window size large. The proposed scheduling at MAC level avoids retransmission time out (RTO) of TCP ACK and duplicate ACK, without modifying TCP itself and adopting complicated cross-layer approaches. Evaluation results demonstrate that total throughput which aggregates all transferred TCP flows and the minimum throughput among the TCP flows are enhanced by explicitly decreasing the frequencies of duplicate ACK and RTO.