On the bit error probability for interference limited cooperative networks

We derive new upper and lower bounds on the bit error probability (BEP) of a cooperative cellular network. We consider a basic three-cell cluster with three users transmitting to three cooperative base stations. Different from existing works that only consider users within the cooperating cluster, we also take into account the impact of interference originating from users outside the cooperating cluster. For such a network, we derive new closed-form expressions for upper and lower bounds on the BEP of an in-cluster user with arbitrary number of out-of-cluster interfering users. Our results are derived for the following two scenarios: 1) Distinct out-of-cluster interference at each base station, and 2) Identical out-of-cluster interference at each base station. We observe that our lower bound expression accurately approximates the exact simulated BEP at low received signal-to-noise ratios (SNRs). As the SNR increases, the interference power starts to dominate and our upper bound expression accurately describes the exact BEP. By taking into account the impact of out-of-cluster interference, we show that the BEP enters a saturation regime above a certain threshold transmit power. Moreover, we highlight that for a fixed cooperating cluster, the impact of interference is most significant on in-cluster users located at the cluster edge.