Study on the Uplink Sum Capacity of Single Cell Cellular Systems with Minimum SINR Constraint

This paper studies the uplink information-theoretical sum capacity of single cell, multi-user cellular systems with minimum SINR constraint. The uplink of single cell multiuser systems is interference limited. If one user increases its transmission power, it will bring more interference to other users. Therefore, power control should be used to balance all users´ transmission power. To achieve the maximum system capacity, the optimal power allocation schedules users according to their link gains, which will lead to unfair problem. In order to avoid this problem, a QoS constraint in the form of minimum SINR constraint could be introduced. In previous works, some properties of the optimal allocation under this constraint have been found. However, it is still difficult to get the optimal power allocation. In this paper, we have found some new mathematical properties of the optimal power allocation, and based on these properties, the algorithm for getting the optimal power allocation is proposed. Numerical results are also presented to show the effects of minimum SINR constraint on system capacity.