INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS Int. J. Commun. Syst. (2011) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/dac.1301 Busy tone contention protocol: a new high-throughput and energy-efficient wireless local area network medium access control protocol using busy tone M G Jibukumar 1, * ,† , Raja Datta 2 and Prabir Kumar Biswas 2 1 School of Engineering, Cochin University, Cochin-22, India 2 Department of Electronics and Electrical Communication Engineering, Indian Institute of Technology, Kharagpur-72302, India SUMMARY Design of an efficient wireless medium access control (MAC) protocol is a challenging task due to the time-varying characteristics of wireless communication channel and different delay requirements in diverse applications. To support variable number of active stations and varying network load conditions, random access MAC protocols are employed. Existing wireless local area network (WLAN) protocol (IEEE 802.11) is found to be inefficient at high data rates because of the overhead associated with the contention resolution mechanism employed. The new amendments of IEEE 802.11 that support multimedia traffic (IEEE 802.11e) are at the expense of reduced data traffic network efficiency. In this paper, we propose a random access MAC protocol called busy tone contention protocol (BTCP) that uses out-of-band signals for contention resolution in WLANs. A few variants of this protocol are also proposed to meet the challenges in WLAN environments and application requirements. The proposed BTCP isolate multimedia traffics from background data trans- missions and gives high throughput irrespective of the number of contending stations in the network. As a result, in BTCP, admission control of multimedia flows becomes simple and well defined. Studies of the pro- tocol, both analytically and through simulations under various network conditions, have shown to give better performance in comparison with the IEEE 802.11 distributed coordination function. Copyright © 2011 John Wiley & Sons, Ltd. Received 15 June 2010; Revised 9 March 2011; Accepted 7 May 2011 KEY WORDS: wireless LAN; busy tone; MAC; DCF; QoS 1. INTRODUCTION Wireless-enabled communication devices have been widely deployed in places such as airports, corporate offices, academic campuses, and other public areas. Because of mobility issues most of the new-generation electronic equipments such as laptop, personal digital assistant, and household devices use built-in wireless technology. All these devices share the same frequency band and geo- graphical area, where they contend with each other for accessing the channel. As the number of devices increases, the contention for channel also increases. Therefore, the efficiency of a wireless protocol depends on the contention resolution method adopted. The design complexity of wire- less protocol increases further because of diverse QoS requirements. Other issues to be considered are the time-varying characteristics of the wireless media, fairness of the protocol in sharing the resource, and the performance of the protocol under non-ideal channel conditions. With the recent developments in the areas of antenna technology and modulation methods, new medium access protocols that support high data rates are under consideration. *Correspondence to: M G Jibukumar, School of Engineering, Cochin University, Cochin-22, India. † E-mail: jibukumar@cusat.ac.in Copyright © 2011 John Wiley & Sons, Ltd.