Aggregate Interference of Equidistant Cognitive Radios

In spite of spectrum sensing, aggregate interference from cognitive radios (CRs) remains as a deterring factor to the implementation of spectrum sharing strategies. We provide a systematic approach of evaluating the aggregate interference (I _aggr) experienced at a victim primary receiver (PR). In our approach, we model the received power versus distance relations between a primary transmitter (PT), PR, and CRs. CRs can spatially reuse a channel and thus two adjacent CRs are separated by the co-channel reuse distance (R). Our analytical framework differs from the existing ones in that we have formulated I _aggr in terms of R and sensing inaccuracy. Energy detector is assumed for the purpose of spectrum sensing. I _aggr is expressed explicitly as a function of the number of energy samples collected (N) and the threshold SNR level used for comparison (SNR _ε ). This allows us to assess their impacts on I _aggr. A numerical example is constructed based on the scenario of spectrum sharing between DTV broadcast and IEEE 802.22 Wireless Regional Area Network. Our analysis demonstrates the extents of which I _aggr can be restricted, by increasing R or sensing accuracy (either by increasing N or decreasing SNR _ε ), and the amount of increment required. Conditioned on the example scenario, the critical {N, SNR _ε , R} values that fulfill certain regulatory requirement are revealed.