SAMA: Spectrum Agile Medium Access control for cognitive radios

In this paper we propose a novel medium access control (MAC) protocol that provides spectrum agile bandwidth allocation for cognitive radios. Our MAC protocol, called spectrum agile multiple access or simply SAMA, harnesses the frequency agility of cognitive radios in allocating fair and contention free bandwidth under a heterogeneous spectrum environment. SAMA accomplishes its bandwidth allocation by allowing each radio to synchronize its channel access schedule with its neighbors through the use of TDMA based dynamic control slot scheduling to exchange schedule information. Combining the schedule information with the cross layer information, SAMA establishes a unique communication group called ¿context group (CG)¿ which consists of radios which belong to a common information flow (i.e. intermediate nodes in a route) for optimizing bandwidth allocation and improving end-to-end latency. The establishment of CG leads to a dramatic throughput improvement over a naive approach as shown by our simulation results.