Performance improvements of integrating ad hoc operations into infrastructure IEEE 802.11 wireless local area networks

In the infrastructure configuration, the standard IEEE 802.11 wireless LAN employs an access point (AP) to forward all packets regardless of their destinations, resulting in significant system performance degradation in terms of throughput and packet delay when a significant portion of packets have intra-cell destinations. These intra-cell packets could be more efficiently delivered to the destinations directly in an ad hoc manner. In this paper, we propose methods to seamlessly integrate such ad hoc operations into the infrastructure mode. By inserting a 2 beta delay in the frame exchange sequence, the proposed 2 beta ad hoc awareness direct connection (2 beta AHADC) scheme brings ad hoc awareness to the infrastructure setting and minimizes the number of packets forwarded by the AP. Furthermore, a direct cut-through forwarding (DCTF) scheme is introduced to-minimize the intra-cell packet forwarding delay. We evaluate the performance of the proposed methods by theoretical analysis and simulations. Numerical results show that in systems with significant fraction of intra-cell packets, the DCTF and 2 beta AHADC schemes effectively reduce packet delays and increase system throughput. The proposed methods extend the capability and performance of existing standards in a backward compatible manner, by introducing minor modifications that do not require explicit mode switching or extra modules. (c) 2004 Elsevier B.V. All rights reserved.