Dissertação de Mestrado em Engenharia Informática ( 2010 / 2011 )

New applications for wireless sensor networks (WSNs), for instance temperature monitoring for healthcare [1], have been created recently, spreading the use of these networks from the military to many other fields such as industry, surveillance, healthcare, and entertainment [2]. The growing importance of WSNs gives rise to new problems concerning the sensors limited energy and memory capacity, processing, and transmission rates. One trend of solutions that have emerged for these issues is cross-layer design, where the use of parameters that are not visible to a determined layer of the network protocols stack is considered [3]. For instance, the remaining energy at the sensors can be used by routing protocols to forward packets in an energy-efficient manner [4]. Also, parameters from the data link layer, such as retransmission schemes [5] and scheduling [6], are considered in cross-layer proposals. However, these proposals do not agree on the best medium access method for WSNs [7-17]. Some proposals adopt ALOHA as medium access method [7-9], others consider time division multiple access (TDMA) [10-14], and also carrier sense multiple access (CSMA) [15-17] is considered in some other proposals. Thus, this work proposes to investigate the most energy-efficient and fair medium access method for WSNs. Also, as sensors compliant with the IEEE 802.15.4 standard use CSMA [1820], the possibility of implementation of ALOHA and TDMA must be verified and carried out in order to assess the performance of cross-layer proposals based on these medium access methods.