Improving the performance of cellular uplinks via power overbooking

The problem of uplink grant under-utilisation, which impacts third generation cellular system performance, is now also emerging in fourth and fifth generation systems, with the introduction of fast uplink access. This study addresses the problem of grant under-utilisation in third generation systems, where these effects are known to be highly significant. Such under-utilisation occurs since mobiles are allowed to use only parts of their granted power resources according to the standard. The inevitable uncertainty introduced by grant under-utilisation is modelled by a grant utilisation probability. This study then proposes the use of statistical overbooking of grants, subject to a pre-specified risk of overload, to mitigate the problem. Two generic overbooking strategies based on this approach are then investigated and it is shown that significant gains in throughput can be achieved. Based on the analysis, a practical overbooking algorithm is described, together with laboratory and field test results. It is shown that very significant performance improvements are obtained, both in terms of throughput and latency.