Hierarchical wireless networks: capacity bounds using the constrained multiple-access relay channel model

A wireless ad hoc network is modeled as a three-tier hierarchical network comprised of low-power source nodes that communicate with a wired access-point via an intermediate relay node. Such a model is appropriate for hybrid ad hoc networks where cooperation between the sources may not be possible or desirable. It is shown that constraining the relay to transmit and receive in either different time slots or frequency bands for a fixed total time and bandwidth yields the same capacity bounds. The rates achieved by cooperative strategies are compared with the rates achieved by traditional multi-hopping and are shown to be substantially better than for certain channels and geometries.