Research Article A Mac Protocol Implementation for Wireless Sensor Network Jamila Bhar 1,2 1 EE Laboratory, Faculty of Science of Monastir, 5019 Monastir, Tunisia 2 Al-Jumum University College, Umm Al-Qura University, P.O. Box 715, Makkah 21421, Saudi Arabia Correspondence should be addressed to Jamila Bhar; jabhar@uqu.edu.sa Received 5 December 2014; Accepted 7 March 2015 Academic Editor: Liansheng Tan Copyright © 2015 Jamila Bhar. Tis 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. IEEE 802.15.4 is an important standard for Low Rate Wireless Personal Area Network (LRWPAN). Te IEEE 802.15.4 presents a fexible MAC protocol that provides good efciency for data transmission by adapting its parameters according to characteristics of diferent applications. In this research work, some restrictions of this standard are explained and an improvement of trafc efciency by optimizing MAC layer is proposed. Implementation details for several blocks of communication system are carefully modeled. Te protocol implementation is done using VHDL language. Te analysis gives a full understanding of the behavior of the MAC protocol with regard to backof delay, data loss probability, congestion probability, slot efectiveness, and trafc distribution for terminals. Two ideas are proposed and tested to improve efciency of CSMA/CA mechanism for IEEE 802.15.4 MAC Layer. Primarily, we dynamically adjust the backof exponent (BE) according to queue level of each node. Secondly, we vary the number of consecutive clear channel assessment (CCA) for packet transmission. We demonstrate also that slot compensation provided by the enhanced MAC protocol can greatly avoid unused slots. Te results show the signifcant improvements expected by our approach among the IEEE 802.15.4 MAC standards. Synthesis results show also hardware performances of our proposed architecture. 1. Introduction IEEE 802.15.4 standard is in increasing use for a diverse range of embedded wireless sensing and control applications. Tis standard [1] is uniquely designed to meet the requirements of the Low Rate Wireless Personal Area Network to enable Wireless Sensor Network (WSN) applications. WSNs are adopted in multiple domains for monitoring industrial, med- ical, or environmental world. In fact, they add capabilities to survey objects and communicate information about them. Sensor networks try to introduce low energy consumption MAC protocols. MAC layer in the sensor nodes presents a number of module consumers of energy. Particularly, to access the channel, the IEEE 802.15.4 MAC protocol employs CSMA/CA algorithm and there is a high probability that col- lision and retransmission occur. Te 802.15.4 beacon enabled mode makes many collisions. If a collision occurs, CSMA/CA algorithm executes retransmission operation. However, in WSNs, transmit operations consume high energy. Many contributions in the literature have been focused on enhancing the MAC protocol in order to minimize energy consumption and improve the network life time. Te research idea proposed in [2] shows that the network lifetime can signifcantly be prolonged by applying a distributed clustering approach that takes the advantage of load balance. Another approach to reduce the number of data transmissions in order to save energy is presented in [3]. Te basic idea of the proposed solution is to prevent unnecessary awakenings of the node by making its wakeup time according to information collected from its neighbors. Te nodes work/sleep schedul- ing strategy is also utilized in [4]. It exploits the dependencies to reduce the number of nodes required to work for sampling and data transmission and prove that such reduction is bound to save energy. Proposed strategies cited below are based on reducing the number of data transmission. To achieve this aim, supplementary exchanges of signalization packet between nodes are needed. In this paper, we demonstrate the importance of decreasing not only data transmission but also retransmission count caused by the behavior of CSMA/CA procedure. Tus, MAC protocol can guaranty energy saving requirements by minimizing congestion probability, backof delay, and a number of retransmission. Hindawi Publishing Corporation Journal of Computer Networks and Communications Volume 2015, Article ID 697153, 12 pages http://dx.doi.org/10.1155/2015/697153