Improved Model for Transmission and Interference Ranges

Report, 2007

Transmission range (Rtx), carrier sensing range (Rcs), and interference range (Ri) are three important radio ranges in wireless networks. These parameters are defined in [1] and the authors proposed the first analytical model for the interference range based on which new protocols has been proposed [2]–[5]. In this paper, we improve on this model by relaxing some of the simplifying assumptions. A new formula for interference range is derived, where noise is not ignored as it was done in [1]. Our formula shows that interference range obtained by ignoring the noise is a good approximation, only for receivers close to the transmitter. While for receivers closer to the transmission range, which suffer from hidden terminal problem, ignoring the noise results in substantially underestimating the interference range. We also study the effect of physical layer parameters on Rtx and Ri, by introducing more general definitions for these ranges. Our study indicates that both Rtx and Ri are influenced by variations in packet size, modulation, and coding. This implies that RTS/CTS packets may have a different Rtx and Ri compared to data packets. Thus, we expect the performance analysis based on the assumption of similar Rtx and Ri for RTS/CTS and data packets, to be inaccurate. Moreover, effects of small-scale fading on Rtx and Ri for the case where fading value is constant during a packet investigated.Our case study indicates that Rayleigh fading has a negative effects on both Rtx and Ri.