In this paper, we consider the interference caused by a secondary system to the primary system in a cognitive radio network. We consider a secondary system deployed in a field of primary receivers. Primary receivers are assumed to be distributed according to a Poisson point process with a density parameter λp. We assume that the secondary system consists of source, relay, and destination terminals, and the source terminal can communicate with the destination terminal either directly (direct mode) or using the relay (relaying mode). We derive analytical expressions for the outage probability of both modes including pathloss, shadowing and multipath fading, and validate the analytical results by simulation. We also derive analytical expressions for the maximum interference caused by both modes to the primary receivers. The results show that to achieve the same median SNR level, the relaying mode may cause less interference to the primary receivers than the direct mode in high pathloss and low shadowing conditions. However, the relaying mode has much higher interference than the direct mode if both modes have the same capacity performance. The results also show that the capacity of the relaying mode has to be reduced by about one half to provide the same level of interference as the direct mode in a typical channel environment.
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机译：在本文中，我们考虑了认知无线电网络中次系统对主系统的干扰。我们考虑在主要接收器领域中部署的辅助系统。假定主要接收器是根据具有密度参数λ p 的泊松点过程进行分配的。我们假设辅助系统由源终端，中继终端和目标终端组成，并且源终端可以直接与目标终端通信（直接模式），也可以使用中继与中继终端通信（中继模式）。我们推导了包括路径损耗，阴影和多径衰落在内的两种模式的中断概率的解析表达式，并通过仿真验证了解析结果。我们还推导了两种模式对主接收机造成的最大干扰的解析表达式。结果表明，要实现相同的中值SNR水平，在高路径损耗和低阴影条件下，中继模式对直接接收机的干扰可能比直接模式少。但是，如果两种模式具有相同的容量性能，则中继模式比直接模式具有更高的干扰。结果还表明，在典型的信道环境中，中继模式的容量必须减少大约一半，以提供与直接模式相同的干扰水平。
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