Energy efficiency analysis of soft and hard cooperative spectrum sensing schemes in cognitive radio networks

Cooperative spectrum sensing (CSS) represents a key factor in the success of cognitive radio networks. CSS implies that users report their local sensing results to a fusion center in order to process them. The two popular reporting schemes are soft and hard schemes. In hard scheme, local sensing result is conveyed by a single bit, whereas the sensing result is reported as it is in the soft scheme. The more detection accuracy attained by soft scheme is confronted by more resource efficiency in hard scheme. This paper provides analytic comparison between both schemes in terms of throughput, energy consumption and energy efficiency. Our work includes deriving the sufficient conditions on the frame length by which the hard scheme outperforms soft scheme for each comparison aspect. Our results show that hard scheme always achieves higher throughput, while, at short frames and large number of users, it consumes less energy and attains higher energy efficiency.