Achieving Secondary Capacity under Interference from a Primary Base Station

Abstract

There are two main challenges for cognitive underlay transmission in a host channel. The first challenge is how to assign a host channel efficiently among a set of cognitive channel applicants such that primary users perceive no harmful interference. Further, the second challenge is how to achieve a good capacity under high power signal from primary transmitter of the host channel. In this paper, we propose a primary interference suppression technique for cognitive underlay transmission in a host channel by using direct sequence spread spectrum. We show that cognitive users can efficiently suppress high power signal from a primary base station by using adequate spreading factors. Further, we propose an adaptive cognitive underlay channel assignment (ACUCHA) algorithm in a host channel for an ad hoc cognitive network which is overlaid with a primary cell. We show that by using the proposed primary interference suppression in cognitive links the proposed secondary channel assignment algorithm achieves 261.14 Mbps capacity when there are 100 cognitive channel applicants and spreading factor is 100. Also, we show that the achieved capacity is gained without producing harmful interference temperature in the host channel and perceptible interference in adjacent channels.