Rate feasibility under medium access contention constraints

Wireless nodes within the same vicinity contend for accessing the shared medium. The contention constraints on sharing the medium depend on the medium access control (MAC) protocol. For example, in IEEE 802.11 MAC protocol-based networks, if node i is in communication with node j, then all nodes within the same transmission range of i or j cannot communicate. On the other hand, if nodes within each other’s transmission range can use different frequencies (e.g., FDMA) or different codes (e.g., CDMA), then neighbor nodes can communicate simultaneously. Furthermore, if nodes are equipped with two radios (e.g., WINS sensor [1] networks), then nodes not only can communicate concurrently but also can receive while they are transmitting. In this paper, we prove a sufficient condition under which a flow rate vector is feasible given the MAC protocol. We also prove that the sufficient condition is necessary for some MAC protocols such as those used by WINS sensor [1] and Bluetooth [2] networks. We give illustrative and real examples for which these conditions apply.