Analytical study of the outage probability of ALOHA and CSMA in bounded ad hoc networks

The performance of the ALOHA and CSMA protocols is evaluated within a bounded ad hoc network. Our network model comprises packets being distributed in finite space and time according to a 3-D PPP. Upon the formation of each packet, it is transmitted to its intended destination located a fixed distance away, using a fully-distributed MAC protocol. If the SINR of the received packet falls below a certain threshold any time during its transmission, the packet is received in outage. The evaluation metric of our network is outage probability, which is directly related to throughput. Approximate analytical expressions are derived for the outage probability of the different MAC protocols as a function of the spatial density of transmissions and the physical size of the network, and validated by simulations. Our bounded network is shown to yield a lower outage probability than infinite domains, due to the lower level of interference resulted from edge effects. Furthermore, the performance of the different MAC protocols are compared, and CSMA with receiver sensing [1] is shown to yield the lowest outage probability of all the unslotted protocols.