The Impact of Edge Effects on the Performance of MAC Protocols in Ad Hoc Networks with Fading

In this paper, the impact of edge effects on the performance of MAC protocols is evaluated. We consider a network where packets are distributed in finite space according to a 2-D PPP, while packets arrive in time according to a 1-D PPP. Each transmitter communicates with its own receiver a fixed distance away using either the ALOHA or CSMA protocol. The metric used for analysis is outage probability, which is the probability that the measured SINR falls below a predefined threshold for the duration of a packet. Approximate analytical expressions are derived for the outage probability of the different MAC protocols assuming a fading channel. Compared to unbounded regions, ALOHA and CSMA are shown to yield lower outage probabilities in finite regions, since the boundedness can be regarded as spatial filtering. Furthermore, the benefit seems to be greater for small outage probabilities, i.e., in the region of practical interest.