A review of medium access protocols for mobile ad hoc networks with transmission power control L.M. Patnaik * , S. Hasan Raza Naqvi Microprocessor Applications Laboratory, Department of Computer Science and Automation, Indian Institute of Science, Malleswaram, Bangalore 560012, India Received 2 September 2003; revised 3 March 2004; accepted 18 March 2004 Available online 3 May 2004 Abstract The inadequacy of the classical media access protocols for considering the transmitter power as the critical resource and a tunable parameter for increasing the throughput, conserving the battery power, and providing the quality of service for the communication has given a new perception for the power controlled media access protocols in ad hoc networks. This paper presents an insight into the existing work on the power control at the media access level. Various objectives of the power control, distinct approaches, and the issues related to transmission power control are discussed. q 2004 Elsevier B.V. All rights reserved. Keywords: Ad hoc networks; Media access; Transmission power control; Review 1. Introduction The attractive features of the ad hoc networks like autonomous operation, seamless networking, and easy deployability are the causes of increased interest of the communication and computation research community in ad hoc networks during the past few years. In spite of the significant work on the multihop wireless networks in the early 1980s, ad hoc networks have gained renewed interest ranging from the high density pico-radio networks [24] to the sparse large ad hoc networks spread over miles. A multitude of problems related to connectivity of the network, battery conservation, link quality, capacity enhancement, and quality of service can be easily solved by controlling the transmission power of the mobile nodes. In spite of the fact that the power control in ad hoc networks can be used for multitude of purposes, with the advent of the Code Division Multiple Access technique in ad hoc networks, the power control becomes a necessary requirement. The inadequacy of the classical media access protocols for considering the transmitter power as a critical resource, and a tunable parameter for conserving battery power, managing connectivity, and providing the desired quality of communication, has given a new thought for the design of power controlled protocols. The present commercially available wireless LAN cards have the provision to tune the transmitter power to a few discrete power levels. However, it is sure that wireless LAN cards of the near future will be more sophisticated and will provide low latency, easy and dynamic fine tuning of the transmitter power. The selection of the transmitter power not only decides the coverage area of a mobile node, but the BER (Bit Error Rate) and SNR (Signal to Noise Ratio) values of the received signal also vary according to the transmitted power. Therefore, for supporting different QoS (Quality of Service) levels for the communication, transmission power becomes a crucial parameter. The distinct approach for power control serves different purposes in the network. Primarily, the power control techniques in the literature of ad hoc networks are considered for throughput enhancement, link quality protection, topology control, power conservation and/or a combination of them. The power control at the media access layer can effectively increase the throughput, by allowing more number of concurrent transmissions in the network, if the designed protocol carefully restricts the packet losses on the channel due to the decreased transmission power of the nodes. Moreover, since the transmission power controls 0141-9331/$ - see front matter q 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.micpro.2004.03.021 Microprocessors and Microsystems 28 (2004) 447–455 www.elsevier.com/locate/micpro * Corresponding author. Tel.: þ 91-803600451; fax: þ 91-803600683. E-mail address: lalit@micro.iisc.ernet.in (L.M. Patnaik).