Power Consumption in Spatial Cognitive Scenarios

Multiple Input Multiple Output (MIMO) adds a new dimension to be exploited in Cognitive Radio (CR) by simultaneously serving several users. The spatial domain that is added through MIMO is another system resource that has to be optimized, and shared when possible. In the current paper, we present a spatial sharing that is carried out through Zero Forcing beamforming (ZFB). The power consumption in such a scenario is mathematically formulated and compared to single user case, to check the feasibility of employing spatial cognition from the power´s perspective. Interesting conclusions are obtained about the utility of spatial cognition thanks to the derived closed form expressions for the data rate and consumed power. To provide a comprehensive measure of the expediency of spatial cognitive scenario, a joint power and rate metric is also proposed and analyzed.