As a benchmark, the minimum EE obtained when Algorithm 1 is run with perfect, instantaneous CSI is reported.
We assume that the resource allocation period is updated as fast as CSI feedback between CBS and SUs, and perfect instantaneous CSI is assumed available for the CBS.
Perfect instantaneous channel state information (CSI) is assumed in this work for analytic tractability, but imperfect CSI is a relevant extension [45].
However, in the above works [8 11], the perfect instantaneous channel state information (CSI) of all links is needed at the nodes which carry out the optimization procedure.
In particular system, the assumption of having perfect instantaneous CSI is idealistic due to the fact that the CSI at the BS, users, and sensors are obtained by estimation or feedback.
The scalar parameter τ∈[0,1] indicates the quality of the instantaneous CSI, where τ=0 corresponds to perfect instantaneous CSI and τ=1 corresponds to having only statistical channel knowledge.
Motivated by the transmission of training sequences, it is assumed that each receiver has perfect instantaneous knowledge about its own channel gain, which is an acceptable assumption for block fading networks[42 47].
By assuming that each UT has perfect instantaneous CSI, the achievable data rates at the UTs are r_{k} = log_{2}(1+ text{SINR}_{k}), quad k=1,ldots,K.
In many of the works considering resource allocation, perfect instantaneous channel state information (CSI) or channel gain (in the link from the SU transmitter to the PU receiver) was assumed to be available [14 18].
We here assume that the mobile receiver has perfect instantaneous CSI, whereas the BSs only have the statistical CSI including Ut,i, U r, D i and M i (and thus Ω i ) (i = 1, 2,..., m), and this information can be exchanged among the BSs via the wired backbone.
