Carrier-sense medium access control (MAC) protocols such as the IEEE 802.11 distributed coordination function (DCF) avoid collisions by holding up pending packet transmission requests when a carrier signal is observed above a certain threshold. However, this often results in unnecessarily conservative communication, thus making it difficult to maximize the utilization of the spatial spectral resource. This paper shows that a higher aggregate throughput can be achieved by allowing more concurrent communications and adjusting the communication distance on the fly, which needs provisions for the following two areas. On the one hand, carrier sense-based MAC protocols do not allow aggressive communication attempts when they are within the carrier senseable area. On the other hand, the communication distance is generally neither short nor adjustable because multihop routing protocols strive for providing minimum hop paths. This paper proposes a new MAC algorithm, called multiple access with salvation army (MASA), which adopts less sensitive carrier sensing to promote more concurrent communications and adjusts the communication distance adaptively via "packet salvaging" at the MAC layer. Extensive simulation based on the ns-2 has shown MASA to outperform the DCF, particularly in terms of packet delay. We also discuss the implementation of MASA based on the DCF specification

According to the carrier sensing mechanism adopted by distributed coordination function (DCF) in IEEE 802.11 standard, a node defers its communication if it senses the medium busy. However, this deferment might block more concurrent communications than necessary. In addition, in DCF, the time duration of deferment is not delivered to all potential interferers, particularly those in the distance. This paper proposes collision-aware DCF (CAD) that efficiently utilizes the available channel resource along both the spatial and time dimensions. Basically, CAD embeds the spatial and time reservation requirements in the PHY header, which is transmitted at the lower data rate, so that a larger group of potential interferers become aware of the ongoing communication and thus avoid collisions. Extensive simulation based on the ns-2 has shown that CAD offers as much as 21% higher packet delivery rate and 91 % lower packet delay than DCF with the CBR (constant bit rate) traffic

IEEE 802.11 MAC, called the Distributed Coordination Function (DCF), employs carrier sensing to effectively avoid collisions, but this makes it difficult to maximally reuse the spatial spectral resource available for exposed terminals. This paper proposes a new MAC algorithm, called Multiple Access with Salvation Army (MASA), which adopts less sensitive carrier sensing to promote more spatial reuse of the channel. However, this may result in a higher collision probability. MASA alleviates this problem by adaptively adjusting the communication distance via "packet salvaging" at the MAC layer. Extensive simulation based on the ns-2 has shown MASA to offer as much as 25% higher packet delivery rate and 27% higher throughput than the DCF with the CBR (constant bit rate) and TCP traffic, respectively. In particular, a significant reduction in packet delay, 86% and 70% lower packet delay with the CBR and TCP traffic, makes MASA suitable for delay-sensitive applications. For practicality, we discuss the implementation of MASA based on the DCF specification.