Rate allocation mechanisms for multi-class service transmission over cognitive radio networks

In this paper, we study rate allocation mechanisms that allocate available transmission rate of a particular cognitive radio (CR) user among its different class of services. In particular, we formulate the rate allocation mechanism of a CR user between its two different class of services namely, delay sensitive (DS) and best effort (BE) services as a Markov decision process. Then the optimal rate allocation mechanism that minimizes the average queuing delay of DS service while guaranteeing the packet loss probabilities of both class of services is obtained using a linear programming technique. Since the optimal rate allocation mechanism can be complex to implement in practice, we study a low-complexity suboptimal rate allocation mechanism. For this suboptimal scheme, we develop a queuing analytic model in order to measure different quality parameters. Selected numerical results show that the performance of suboptimal rate allocation mechanism is quite similar to the optimal rate allocation mechanism for the considered system parameters. The developed queuing analytic model is also useful for call admission controller design when the suboptimal scheme is employed.