Downlink Capacity Evaluation of Cellular Networks with Known Interference Cancellation

Recently the capacity region of a multi-input (MIMO) Gaussian broadcast channel, with Gaussian codebooks and known-interference cancellation through dirty paper coding (DPC), was shown to equal the union of the capacity regions o a collection of MIMO multiple access channels (MAC). We use this duality result to evaluate the system capacity achievable in a cellular wireless network with multiple antennas at the base station and multiple antennas at each terminal. 

Some fundamental properties of the rate region are exhibited, and algorithms for determining the optimum weighted rate sum and the optimal covariance matrices for achieving a given rate vector on the boundary of the rate region are presented. These algorithms are then used in a simulation study to determine potential capacity enhancements to a cellular system through known-interference cancellation. 

We study both the circuit data scenario in which each user requires a constant data rate in every frame, and the packet data scenario in which users can be assigned a variable rate in each frame so as to maximize the long-term average throughput. In the case of circuit data, the outage probability as a function of the number of active users served at a given rate is determined through simulations. 

For the packet data case, long term average throughputs that can be achieved using the proportionally fair scheduling algorithm are determined. We generalize the zero- forcing beam-forming technique to the multiple receive antennas case and use this as the baseline for the packet data throughput evaluation.