Abstract
In this paper, we evaluate two-way relay communication systems in cognitive radio environments. The proposed model includes two subsystems: a primary system and a secondary system. The primary system consists of a primary transmitter and a primary receiver while the secondary includes two terminals exchanging their data via an intermediate relay node. Each network node is equipped with a single antenna and operates under a half-duplex mode. The channel state information (CSI) interference from the secondary node to the primary receiver is assumed imperfect. Using analytical methods, this paper derives the interference probability from the secondary system to the primary receiver and an optimal back-off control power coefficient for the secondary transmitter. To evaluate the secondary system quality, an explicit expression for the system outage probability (OP) and its closed form in the high signal-to-noise region (SNR) is presented. Theoretical results are verified using Monte-Carlo simulation.
Highlights
1 Introduction Rapid development of wireless networks coupling with a large number of users and requirements for highspeed wireless services leads to radio frequency spectrum scarcity
It is clear that cognitive radio techniques widen radio spectrum access, where unlicensed users are allowed to operate in the same frequency band allocated to licensed users
Cognitive radio techniques have attracted researchers from academia worldwide and gaining attention from the industry and governments. These techniques have increasingly become one of the main research areas, and many findings have been published on the topic including the use of (i) multiple input, multiple output (MIMO) technologies [4, 5], (ii) relay selection [6, 7], (iii) multi-hop relaying [8, 9], (iv) physical layer security [10], (v) energy harvesting technologies [11, 12], and (vi) a new system model to analyze system quality [13,14,15]
Summary
Rapid development of wireless networks coupling with a large number of users and requirements for highspeed wireless services leads to radio frequency spectrum scarcity. In [20], Duy et al analyzed the quality of two-way relay transmission secondary systems in which their model includes three-phase DF relay intermediate nodes They obtained exact expressions for the system outage probability in Rayleigh fading. To the best of our knowledge, the findings on evaluating two-way relay transmission system’ quality in cognitive radio environments considering interference from the primary transmitters to the secondary system with imperfect CSI from the secondary network nodes to the primary receivers are not yet available. Substituting (36), (37), and (43) into (28), we obtain an exact expression for the secondary system outage probability, when the interference CSI to the primary receiver is imperfect as in (31). It can be shown that over the high SNR region, the system diversity is one
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