Spectrum sharing with adjacent channel constraints

The problem of sharing radio spectrum is analyzed using a multiple server queueing model which represents channels owned by primary users and allowed opportunistic access by a secondary user group. The primary users are constrained to occupy a group of adjacent channels for wideband transmission, whereas the secondary users utilize a single channel for narrowband transmission. The blocking performance of wideband and narrowband users are compared under two policies of channel allocation among the primary and secondary users. These policies differentiate the performance based on allocation of non-overlapping and overlapping blocks of contiguous channels to the wideband and narrowband users. The influence of the number of excess channels that can only be utilized by secondary users is also presented. A computational model developed to estimate the blocking probabilities of NB and WB users is shown to be expressed as a function of the offered loads (ρ_N, ρ_W) and the ratio of the service rates (μ_W/μ_N). The performance impact of providing WB users a block of adjacent channels instead of distributing the requirement across the group of available channels is analyzed. The adjacency constraint will in general decrease the channel availability of WB users, but can improve the probability of channel allocation to NB users. The proposed scheme allows estimation of feasible operating regions of ρ_N, given a WB group size and ρ_W.