Abstract
Multihop mobile wireless networks have drawn a lot of attention in recent years thanks to their wide applicability in civil and military environments. Since the existing IEEE 802.11 distributed coordination function (DCF) standard does not provide satisfactory access to the wireless medium in multihop mobile networks, we have designed a cross-layer protocol, (CroSs-layer noise aware power driven MAC (SNAPdMac)), which consists of two parts. The protocol first concentrates on the flexible adjustment of the upper and lower bounds of the contention window (CW) to lower the number of collisions. In addition, it uses a power control scheme, triggered by the medium access control (MAC) layer, to limit the waste of energy and also to decrease the number of collisions. Thanks to a noticeable energy conservation and decrease of the number of collisions, it prolongs significantly the lifetime of the network and delays the death of the first node while increasing both the throughput performance and the sending bit rate/throughput fairness among contending flows.
Highlights
Introduction and Problem DefinitionThe IEEE 802.11 [1], standard for wireless local area networks (WLANs) specifies as contention-based medium access control (MAC) mechanism the distributed coordination function (DCF), which is based on carrier sense multiple access with collision avoidance (CSMA/CA)
The IEEE 802.11 [1], standard for wireless local area networks (WLANs) specifies as contention-based MAC mechanism the DCF, which is based on carrier sense multiple access with collision avoidance (CSMA/CA)
In the simulations presented we have investigated the performance of the SNAPdMac protocol against the IEEE 802.11 DCF standard and/or the basic power control protocol from [2]
Summary
The IEEE 802.11 [1], standard for wireless local area networks (WLANs) specifies as contention-based MAC mechanism the DCF, which is based on carrier sense multiple access with collision avoidance (CSMA/CA). One well-known direction in order to save energy and reuse the channel is by manipulating the power (power saving/controlling) or the carrier sense threshold Another direction is focused on enhancements of the IEEE 802.11 MAC since the existing standard does not meet multihop mobile ad hoc network expectations. The weaknesses and unfairness of the binary back-off algorithm (BEB) of the IEEE 802.11 DCF and contention window resetting scheme used by this standard is the reason to improve/change the back-off mechanism and resetting CW algorithm The observation of these two problems led to the design of a novel cross-layer protocol, SNAPdMac. On one hand, our protocol employs tuning of the transmit power based on the level of noise and the collision ratio on the MAC level. The minimum and maximum CW sizes (where CWmin ≤ CW ≤ CWmax) are fixed in the IEEE 802.11 DCF standard independently of the network load and channel conditions
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