Multimedia Channel Allocation in Cognitive Radio Networks using FDM-FDMA   and OFDM-FDMA
  In conventional wireless systems, unless a contiguous frequency band with width at least equal to the required bandwidth is obtained, multimedia communication can not be effected with the desired Quality of Service. We propose here a novel channel allocation technique to overcome this limitation in a Cognitive Radio Network which is based on utilizing several non-contiguous channels, each of width smaller than the required bandwidth, but whose sum equals at least the required bandwidth. We present algorithms for channel sensing, channel reservation and channel deallocation along with transmission and reception protocols with two different implementations based on $FDM-FDMA$ and $OFDM-FDMA$ techniques. Simulation results for both these implementations show that the proposed technique outperforms the existing first-fit and best-fit~\cite{b109, b110} allocation techniques in terms of the average number of attempts needed for acquiring the necessary number of channels for all traffic situations ranging from light to extremely heavy traffic. Further, the proposed technique can allocate the required numbers of channels in less than one second with $FDM-FDMA$ ($4.5$ second with $OFDM-FDMA$) even for $96\%$ traffic load, while the first-fit and best-fit techniques fail to allocate any channel in such situations. 
Ansuman Bhattacharya, Rabindranath Ghosh, Koushik Sinha, Debasish   Datta, and Bhabani P. Sinha
cs.NI