Cross-Layer Channel Allocation Protocol for OFDMA Ad Hoc Networks

A new cross-layer design taking advantage of OFDMA in ad hoc networks is presented. OFDMA technology is exploited at the physical layer to improve data rate through multiuser diversity and to enhance network throughput by enabling multiple concurrent transmissions over orthogonal subchannels, each consisting of a group of tones. A new tone-assignment algorithm is presented that takes advantage of channel fading and is adapted to the limitations of ad hoc networks and operates alongside the signaling of the resulting medium access control (MAC) protocol called Concurrent Communication medium Access or CoCo-MAC. The new MAC addresses the synchronization requirements of OFDMA and the tone assignment algorithm´s necessities, and also enables concurrent initiation of data transmissions from multiple nodes to the same receiver or from a single transmitter to multiple receivers. We present simulation results on the throughput advantages of our technique compared to traditional tone assignment algorithms and MAC protocols based on contention-based avoidance of interference.