Half Direct-Link Setup (H-DLS) for Fairness between External and Local TCP Connections in IEEE 802.11e Wireless LANs

The IEEE 802.11e standard supports a direct-link setup (DLS) mechanism optionally to improve the throughput. Using this mechanism, IEEE 802.11e stations in proximity can directly exchange frames with no intervention of an access point. However, extensive simulations reveal the severe unfairness between external and local TCP connections in the IEEE 802.11e DLS mode due to the characteristics of TCP: a window-based flow control mechanism. This paper first analyzes why a fairness problem happens between external and local TCP connections in the IEEE 802.11e DLS mode. Then, we seeks to achieve fairness between them by introducing a novel mechanism dubbed half direct-link setup plus (H-DLS) which differentiates the paths for TCP DATA and ACK packets of local TCP connections. Simulation results reveal that H-DLS achieves the fairness between external and local TCP connections while keeping the aggregate throughput higher than the original IEEE 802.11 infrastructure.