Two-way transmission capacity of wireless ad-hoc networks

Abstract

The transmission capacity of an ad-hoc network is the maximum density of active transmitters in a unit area, given an outage constraint at each receiver for a fixed rate of transmission. Most prior work on finding the transmission capacity of ad-hoc networks has focused only on one-way communication where a source communicates with destination and no data is sent from destination to the source. In practice, however, two-way or bidirectional data transmission is required to support control functions like packet acknowledgements and channel feedback. This paper develops the concept of transmission capacity for two-way wireless ad-hoc networks, by incorporating the concept of a two-way outage with different rate requirements in both directions. Upper and lower bounds on the two-way transmission capacity are derived for frequency division duplexing, under the assumption that the channel coefficients are independent on different carrier frequencies. The derived bounds are used to derive the optimal solution for bidirectional bandwidth allocation that maximizes the two-way transmission capacity, which is shown to perform better than allocating bandwidth proportional to the desired rate in both directions.