Several works have studied relaying in cognitive radio networks in terms of outage probability. The main challenge in such works is finding a mathematical expression for this performance metric under different system models. This expression can be employed in studying and designing more related systems. In this paper, we consider an underlay cognitive communication system, where each of the primary and secondary networks has two communicating nodes. The secondary nodes communicate, in two directions, through a relay node that employs half-duplex amplify-and-forward relaying scheme. In our study, we presumed having free-space path loss over the channels between the primary and secondary nodes as well as having Nakagami-m fading over the channels between the secondary nodes. To the best of our knowledge, there are no prior works which are similar to ours. In particular, we thoroughly study the proposed model and mathematically derive the outage probability for the whole two-way system in the secondary network under different communication schemes: two time slots, three time slots and four time slots schemes. To verify our mathematical derivations, we conduct thorough simulations under different scenarios. Interestingly, the simulation results show the correctness of our derivation.

几项工作已经从中断概率的角度研究了认知无线电网络中的中继。此类工作的主要挑战是在不同的系统模型下找到针对该性能指标的数学表达式。此表达式可用于研究和设计更多相关的系统。在本文中，我们考虑了一个底层认知通信系统，其中主网络和辅助网络中的每个网络都有两个通信节点。辅助节点在两个方向上通过中继节点进行通信，该中继节点采用半双工放大转发中继方案。在我们的研究中，我们假设在主节点和次节点之间的通道上具有自由空间路径损耗，并且在次节点之间的通道上具有Nakagami-m衰落。据我们所知，没有与我们相似的先前作品。特别是，我们彻底研究了所提出的模型，并在数学上推导了在不同通信方案（两个时隙，三个时隙和四个时隙方案）下二次网络中整个双向系统的中断概率。为了验证我们的数学推导，我们在不同情况下进行了全面的模拟。有趣的是，仿真结果表明了我们推导的正确性。