Optimal Physical Carrier Sensing Range in Multirate Wireless Ad Hoc Networks: Analytical versus Realistic

In wireless networks with multiple transmitters, sensing range decides the minimum distance between any simultaneous transmissions. A larger sensing range can better protect an ongoing transmission and thus can achieve better per-link transmission speed. However, the aggregate throughput may suffer from the larger sensing range since fewer transmissions can happen at the same time in this case. In this paper, based on the assumption that the sensing range is adjustable, we investigate the optimal physical sensing range both analytically and by simulation. Through analysis for an ideal large scale wireless network, we find that the optimal sensing range lies around 5 times of the transmission range or more. In IEEE 802.11 based multirate ad hoc networks, however, this optimal value is substantially lower than that of the ideal network. This is partially due to the fact that the physical header of any 802.11 frame is always transmitted at the lowest datarate and the CSMA/CA mechanism.