EURASIP Journal on Wireless Communications and Networking 
Volume 2006 (2006), Article ID 94235, 7 pages
doi:10.1155/WCN/2006/94235

Traffic Agents for Improving QoS in Mixed Infrastructure and Ad Hoc Modes Wireless LAN

Yang Yang,1 Hai-Feng Yuan,2 Hsiao-Hwa Chen,3 Wen-Bing Yao,2 and Yong-Hua Song2

 1Department of Electronic and Electrical Engineering, University College London, Gower Street, London WC1E 6BT, United Kingdom
2School of Engineering and Design, Brunel University, Uxbridge UB8 3PH, United Kingdom
3Institute of Communications Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan
Received 12 July 2005; Revised 5 December 2005; Accepted 28 December 2005

Abstract

As an important complement to infrastructured wireless networks, mobile ad hoc networks (MANET) are more flexible in providing wireless access services, but more difficult in meeting different quality of service (QoS) requirements for mobile customers. Both infrastructure and ad hoc network structures are supported in wireless local area networks (WLAN), which can offer high data-rate wireless multimedia services to the mobile stations (MSs) in a limited geographical area. For those out-of-coverage MSs, how to effectively connect them to the access point (AP) and provide QoS support is a challenging issue. By mixing the infrastructure and the ad hoc modes in WLAN, we propose in this paper a new coverage improvement scheme that can identify suitable idle MSs in good service zones as traffic agents (TAs) to relay traffic from those out-of-coverage MSs to the AP. The service coverage area of WLAN is then expanded. The QoS requirements (e.g., bandwidth) of those MSs are considered in the selection process of corresponding TAs. Mathematical analysis, verified by computer simulations, shows that the proposed TA scheme can effectively reduce blocking probability when traffic load is light.