Uplink admission control in WCDMA based on relative load estimates

When operating a cellular radio system at nearly full capacity, admitting yet another user may jeopardize the stability of the system as well as the performance of the individual users. Therefore, proper admission control is crucial. Prior art includes algorithms which limit the number of users or the uplink interference per cell. Both are known to yield roughly the same performance, but the former is difficult to configure, and the latter is based on a quantity which is hard to measure accurately. The core idea in this work is to predict the relative load of the system directly, given that a user is admitted. Then, the user will be admitted if the predicted load in the specific cell, and in its neighbors, is below some threshold. The proposed uplink relative load estimate is focused on WCDMA. It utilizes measurements readily available in that system, either periodically scheduled or from handover events. Multi-services are naturally handled, and availability of high data-rate services are automatically limited with respect to coverage, compared to services of lower data-rate. Simulations indicate that the admission control operates satisfactorily in different traffic situations with a universal parameter setting. Furthermore, the reporting overhead with periodical measurements can be avoided, since handover event-driven measurements yield roughly the same performance.