Research Article MAC Protocol for Ad Hoc Networks Using a Genetic Algorithm Omar Elizarraras, Marco Panduro, Aldo L. Méndez, and Alberto Reyna Universidad Aut´ onoma de Tamaulipas, UAMRR, Carr. Reynosa-San Fernando S/N, Colonia Arcoiris, 88779 Reynosa, TAMPS, Mexico Correspondence should be addressed to Aldo L. M´ endez; almendez@uat.edu.mx Received 23 April 2014; Accepted 4 July 2014; Published 21 July 2014 Academic Editor: T. O. Ting Copyright © 2014 Omar Elizarraras et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. e problem of obtaining the transmission rate in an ad hoc network consists in adjusting the power of each node to ensure the signal to interference ratio (SIR) and the energy required to transmit from one node to another is obtained at the same time. erefore, an optimal transmission rate for each node in a medium access control (MAC) protocol based on CSMA-CDMA (carrier sense multiple access-code division multiple access) for ad hoc networks can be obtained using evolutionary optimization. is work proposes a genetic algorithm for the transmission rate election considering a perfect power control, and our proposition achieves improvement of 10% compared with the scheme that handles the handshaking phase to adjust the transmission rate. Furthermore, this paper proposes a genetic algorithm that solves the problem of power combining, interference, data rate, and energy ensuring the signal to interference ratio in an ad hoc network. e result of the proposed genetic algorithm has a better performance (15%) compared to the CSMA-CDMA protocol without optimizing. erefore, we show by simulation the effectiveness of the proposed protocol in terms of the throughput. 1. Introduction In a wireless ad hoc network, the nodes can communicate with each other without the support of infrastructure. Since the wireless channel is shared by all the nodes in the network, a medium access control (MAC) plays an important role in coordinating access among the nodes so that information gets through from one node to another [1]. Usually each node is able to communicate with each other’s node when all nodes are spread around a geographic range. However, nodes could spread over larger geographic range than the communication signal can reach. In this case, the nodes could have communication over multiple hops. However, there is only one medium that is shared by all the nodes that are in the same radio communication range and the radio frequency bandwidth is limited. Furthermore, packet collisions are unavoidable due to the fact that traffic arrivals are random and there is nonzero propagation time between transmitters and receivers. erefore, MAC schemes are used to coordi- nate the access to the channel in the network [2]. e tendency of the MAC protocols for wireless ad hoc networks is using adaptive systems to adjust the transmission parameters (multirate) and the objective is to maximize the throughput in the use of the channel. Rate adaptation is indispensable to optimally exploit the scarce wireless resources under instable channel conditions. Rate adaptation consists of assessing the wireless channel conditions and selecting the most appropriate data rate. Moreover, in the MAC protocols, the low throughput in the region of low traffic is because there is no more information for sending (this is not due to errors of the multiuser interference). So the system performance is limited by the access technique used in wireless ad hoc networks [3]. To address this problem, we use a rate adaptation to optimize throughput requirements. en, the problem can be formulated as an optimization problem; that is, minimize the resources consumption considering the power, interference, data rate, and energy ensuring the signal to interference ratio in an ad hoc network. e multirate in ad hoc networks has been addressed in [4–9]; these protocols were proposed to maximize the throughput by adapting the rate based on the channel, but they do not address the energy issue. e MAC protocol plays a critical role in a wireless ad hoc network considering bandwidth efficiency, resolving colli- sions, resources allocation, power transmission, interference, energy, data rate, and distance. In most standardized wireless Hindawi Publishing Corporation e Scientific World Journal Volume 2014, Article ID 670190, 9 pages http://dx.doi.org/10.1155/2014/670190