Joint Transmission Rate, Power, and Carrier Sense Settings: An Initial Measurement Study

A substantial variety of control algorithms to adjust carrier sensing, transmission power, and transmission rate have been proposed for IEEE 802.11 wireless networks in the recent literature. Their objectives range from maximizing throughput, spatial reuse, and fairness to minimizing interference and congestion within the network. However, only a few of these have been implemented and analysed in practice, often because accessing and changing the necessary parameters in the wireless hardware is too difficult. Essentially, there is little understanding about the interactions of jointly adjusted transmission rate, power and carrier sense thresholds, and their impact on the aforementioned objectives. Therefore, in this paper, we focus on transmission rate, power and carrier sensing settings. We provide a detailed description of the common IEEE 802.11 radio hardware, especially in terms of carrier-sensing circuitry. We then present our results from our validation and initial measurement study, which demonstrate interactions between transmit power and rate under different carrier-sensing settings in a two link scenario. Our initial findings indicate there exists a limited number of rate-power combinations that achieve high performance in terms of either throughput and fairness both with and without carrier sensing. Furthermore, in the case of both strong and weak links exist in the network, turning carrier sensing off significantly improves performance.