Costs of inter-system interference: a case study of UWB interference to UMTS

Conditions for allocating spectrum to new wireless systems are conventionally based on carrier-to-interference (C/I) calculations. However, new low power radio technologies, like UWB and Bluetooth, make coexistence more complex, since these technologies exist in, or close to, incumbent systems. Such a situation limits the appropriateness of conventional spatial/frequency separation arguments and metrics. In contrast, the paper describes a methodology for assessing interference while accounting for the spatial and temporal likelihood of coexistence and deriving more representative cost measures. A case study of UWB interference on a hypothetical UMTS network shows a downlink UMTS noise-rise of typically 1 dB and incurred costs to the UMTS operator of tens of millions of pounds.