Abstract
In this work, we examine the interference alignment (IA) performance of a multi-input multi-output (MIMO) multi-hop cognitive radio (CR) network in the presence of multiple primary users. In the proposed architecture, it is assumed that linear IA is adopted at the secondary network to alleviate the interference between primary and secondary networks. By doing so, the secondary source can communicate with the secondary destination via multiple relays without causing any interference to the primary network. Even though linear IA can suppress the interference in CR networks considerably, interference leakages may occur due to a fast fading channel. To this end, we focus on the performance of the secondary network for two different cases: (i) the interference is perfectly aligned; (ii) the impact of interference leakages. For both cases, closed-form expressions of outage probability and ergodic capacity are derived. The results, which are validated by Monte Carlo simulations, show that interference leakages can deteriorate both system performance and the diversity gains considerably.
Highlights
As mobile devices become widespread, wireless data traffic has been increasing significantly in the recent years
Without any loss of generality, we assume that the transmit powers at S and Ri are given as PS = PRi = P
As can be seen from the figure, outage probability performance worsens as the number of hops increase
Summary
As mobile devices become widespread, wireless data traffic has been increasing significantly in the recent years. With a rapid increase in the number of connected devices and mobile users, improving spectrum utilization has become an important concern in designing next-generation wireless communication networks [3]. This situation will cause a severe shortage of spectrum resources. CR allows the unlicensed users to exploit the unused frequency bands dynamically without causing harmful interference to the licensed users For this reason, it has been proposed to improve spectral utilization and efficiency [5,6,7,8]. This paper focuses on the interference alignment in CR networks considering multiple hops in the underlay scheme
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