Transmitting-collision tradeoff in cognitive radio networks: A flexible transmitting approach

In cognitive radio networks, in order to avoid collision to primary user (PU), cognitive radio (CR) user ought to sense the spectrum periodically to certify that PU is absent. However, the collision to PU also occurs due to imperfect sensing or PU´s returning when CR user is transmitting. In this paper, we study a transmitting-collision tradeoff problem in cognitive radio networks. In particular, we investigate a flexible data transmitting scheme so as to minimize the collision to PU under the probability of detection constrains. In addition, by jointly considering both CR user´s traffic and PU´s state, the probability of collision is derived in detail. Finally, numerical results indicate that the proposed approach can give a superior performance than the fixed frame duration mechanism. The probability of collision for the proposed scheme is lower than conventional mechanism obviously. The conclusion is that the larger traffic parameter of CR user leads to higher collision to PU. By increasing the probability of detection can reduce the collision to PU.