Cognitive Two-way Relay Networks Research Articles

Joint Source Power Allocation and Distributed Relay Beamforming Design in Cognitive Two-Way Relay Networks

Joint Source Power Allocation and Distributed Relay Beamforming Design in Cognitive Two-Way Relay Networks

Robust Relay Beamforming in Cognitive Two-Way Relay Networks

We propose a novel restriction and relaxation (RAR) method for robust relay beamforming design in cognitive two-way relay networks with imperfect channel state information (CSI). Due to the uncertainty in CSI, the self-interference cannot be completely canceled. Hence, both channel uncertainties and residual self-interference should be considered. The proposed RAR method aims to minimize the transmit power of relay nodes while guaranteeing the worst-case signal-to-interference plus noise ratio (SINR) of secondary users (SUs) as well as satisfying the interference temperature (IT) constraints. Specifically, in the restriction step of RAR, infinite number of complicated constraints are reformulated into a finite number of linear matrix inequalities (LMIs). In the relaxation step of RAR, the nonconvex robust design problem is transformed into a convex semidefinite program (SDP), which can be efficiently solved by interior-point methods. Simulation results verify the effectiveness and robustness of the proposed method.

Joint power control and relay selection scheme for cognitive two-way relay networks

A joint power control and relay selection scheme is considered for a cooperative and cognitive radio system where a secondary network shares spectrum with the primary network. In the secondary network, two secondary users (SUs) communicate with each other via an assist relay. The main point is to provide the best system performance to SUs while maintaining the interference power at primary user (PU) under a certain level. Using convex optimization, a closed-form solution is obtained when optimizing the power allocation among the two nodes and relay. Based on this result, a joint power control and relay selection scheme with fewer variable dimensions is proposed to maximize the achievable rate of the secondary system. Simulation results demonstrate that the sum rate of the cognitive two-way relay network increases compared with a random relay selection and fixed power allocation.

Outage Analysis of Cognitive Two-Way Relaying Network with Physical-Layer Network Coding in Nakagami-m Fading Channels

In spectrum sharing systems, a secondary user (SU) is permitted to share frequency bands with primary user (PU) as long as its transmission does not interfere with the PU's communication. In this paper, the outage probability is investigated for the physical-layer network coding (PNC) based cognitive two-way relay network over Nakagami-m fading channel. By applying the interference temperature (IT) constraints at the transceiver nodes and relay nodes in secondary systems, we analyze the outage performance in underlay spectrum sharing with the best relay selection criterion. The cumulative distribution function (CDF) of the signal to noise ratio (SNR) for each link is derived to obtain the tight upper bound on the outage probability of the secondary relay system. Simulations results demonstrate the validity and accuracy of the theoretical analysis. Index Terms—Cognitive two-way relay network, physical layer network coding, outage probability, Nakagami-m fading channel.

Optimal Linear Transceiver Designs for Cognitive Two-Way Relay Networks

This paper studies a cooperative cognitive radio network where two primary users (PUs) exchange information with the help of a secondary user (SU) that is equipped with multiple antennas and in return, the SU superimposes its own messages along with the primary transmission. The fundamental problem in the considered network is the design of transmission strategies at the secondary node. It involves three basic elements: first, how to split the power for relaying the primary signals and for transmitting the secondary signals; second, what two-way relay strategy should be used to assist the bidirectional communication between the two PUs; third, how to jointly design the primary and secondary transmit precoders. This work aims to address this problem by proposing a transmission framework of maximizing the achievable rate of the SU while maintaining the rate requirements of the two PUs. Three well-known and practical two-way relay strategies are considered: amplify-and-forward (AF), bit level XOR based decode-and-forward (DF-XOR) and symbol level superposition coding based DF (DF-SUP). For each relay strategy, although the design problem is non-convex, we find the optimal solution by using certain transformation techniques and optimization tools such as semidefinite programming (SDP) and second-order cone programming (SOCP). Closed-form solutions are also obtained under certain conditions. Simulation results show that when the rate requirements of the two PUs are symmetric, by using the DF-XOR strategy and applying the proposed optimal precoding, the SU requires the least power for relaying and thus reserves the most power to transmit its own signal. In the asymmetric scenario, on the other hand, the DF-SUP strategy with the corresponding optimal precoding is the best.

Performance Analysis of Opportunistic Relay Selection for Cognitive Two-Way Relay Networks

Performance Analysis of Opportunistic Relay Selection for Cognitive Two-Way Relay Networks

Optimal spectrum sensing in cooperative cognitive two-way relay networks

This paper investigates a network consisting of some CR terminals distributed between two primary transceivers. In the proposed network model, CR nodes assist the primary transmission as a two-way amplify-and-forward relaying scheme when the primary transceivers are in operation. By using distributed beamforming techniques among CR nodes, we propose an optimal solution to maximize the performance of spectrum sensing in terms of signal-to-noise ratio (SNR) at the CBS while satisfying the quality of service requirements of primary receivers. We demonstrate the superiority of sensing performance in the proposed method by relaxing the problem into the semidefinite form and we achieve the maximum value of SNR in the CBS by using an iterative algorithm.