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This paper discusses the problem of determining the carrier sense threshold (CS th ) of nodes in a CSMA-based Mobile Ad Hoc Network (MANET) and proposes a practical, fully distributed, CS th adaptation procedure. The procedure enables a node to select its CS th in order to improve the data throughput of the system by maximizing the number of successful transmissions in its neighborhood. Simulation results show that the procedure is able to improve the data throughput in more than 85% of random topologies. The average throughput improvement over all topologies were 11% and 18% in two different scenarios, with some topologies showing up to 75% data throughput gains.

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The ZigBee wireless communication specifications forecast the use of multihop routes between nodes and define that nodes select their routes based on their costs. The specifications define how to compute a route cost from the probability of successfully transmitting on each of the routes’ links; and it is recommended that such probabilities be obtained by counting received link status messages or averaging link quality indicators from received packets. In this paper, we study the performance of these two recommended procedures, show that they can lead to degraded route selections, and propose a procedure that can improve route selections without modifications to the ZigBee protocol or frame formats. Our procedure estimates the probability of successful transmission on each link, based on information from the medium access layer during unicast packet transmissions, and includes a modification into how ZigBee nodes treat routing messages internally in order to reduce variations in the link cost estimates. Focusing on a home environment with one or two hops, our simulation results show that, in several scenarios, our procedure performs better than either of the two procedures recommended in the ZigBee specifications.

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