Power Switching Protocol for Two-way Relaying Network under Hardware Impairments

In this paper, we analyze the impact of hardware impairments at relay node and source node (i.e. imperfect nodes) on network performance by evaluating outage probability based on the effective signal to noise and distortion ratio (SNDR). Especially, we propose energy harvesting protocol at the relay and source nodes, namely, power switching imperfect relay (PSIR) and power switching imperfect source (PSIS). Aiming to determine the performance of energy constrained network, we first derive closed-form expressions of the outage probability and then the throughput can be maximized in delay-limited transmission mode. The simulation results provide practical insights into the impacts of hardware impairments and power switching factors of the energy harvesting protocol on the performance of energy harvesting enabled two-way relaying network

Wireless Energy Harvesting Assisted Two-Way Cognitive Relay Networks: Protocol Design and Performance Analysis

This paper analyzes the effects of realistic relay transceiver on the outage probability and throughput of a two-way relay cognitive network that is equipped with an energy-harvesting relay. In this paper, we configure the network with two wireless power transfer policies and two bidirectional relaying protocols. Furthermore, the differences in receiver structure of relay node that can be time switching or power splitting structure are also considered to develop closed-form expressions of outage and throughput of the network providing that the delay of transmission is limited. Numerical results are presented to corroborate our analysis for all considered network configurations. This paper facilitates us not only to quantify the degradation of outage probability and throughput due to the impairments of realistic transceiver but also to provide an insight into practical effects of specified configuration of power transfer policy, relaying protocol, and receiver structure on outage and throughput. For instance, the system with multiple access broadcast protocol and the power splitting-based receiver architecture achieves ceiling throughout higher than that of the transmission rate of source nodes. On the contrary, a combination of dual-source energy transfer policy and the time division broadcast protocol is contributed the highest level of limiting factor in terms of transceiver hardware impairments on the network throughput.</p

Power Allocation and Cooperative Diversity in Two-Way Non-Regenerative Cognitive Radio Networks

In this paper, we investigate the performance of a dual-hop block fading cognitive radio network with underlay spectrum sharing over independent but not necessarily identically distributed (i.n.i.d.) Nakagami-$m$ fading channels. The primary network consists of a source and a destination. Depending on whether the secondary network which consists of two source nodes have a single relay for cooperation or multiple relays thereby employs opportunistic relay selection for cooperation and whether the two source nodes suffer from the primary users' (PU) interference, two cases are considered in this paper, which are referred to as Scenario (a) and Scenario (b), respectively. For the considered underlay spectrum sharing, the transmit power constraint of the proposed system is adjusted by interference limit on the primary network and the interference imposed by primary user (PU). The developed new analysis obtains new analytical results for the outage capacity (OC) and average symbol error probability (ASEP). In particular, for Scenario (a), tight lower bounds on the OC and ASEP of the secondary network are derived in closed-form. In addition, a closed from expression for the end-to-end OC of Scenario (a) is achieved. With regards to Scenario (b), a tight lower bound on the OC of the secondary network is derived in closed-form. All analytical results are corroborated using Monte Carlo simulation method

Outage Performance Analysis of Multicarrier Relay Selection for Cooperative Networks

In this paper, we analyze the outage performance of two multicarrier relay selection schemes, i.e. bulk and per-subcarrier selections, for two-hop orthogonal frequency-division multiplexing (OFDM) systems. To provide a comprehensive analysis, three forwarding protocols: decode-and-forward (DF), fixed-gain (FG) amplify-and-forward (AF) and variable-gain (VG) AF relay systems are considered. We obtain closed-form approximations for the outage probability and closed-form expressions for the asymptotic outage probability in the high signal-to-noise ratio (SNR) region for all cases. Our analysis is verified by Monte Carlo simulations, and provides an analytical framework for multicarrier systems with relay selection

Optimal combining and performance analysis for two-way EH relay systems with TDBC protocol

In this paper, we investigate a simultaneous wireless information and power transfer (SWIPT) based two-way decode-and-forward (DF) relay network, where time switching (TS) is employed for SWIPT and time division broadcast (TDBC) is employed for two-way relaying. We focus on the design of a combining scheme that decides how the relay combines the signals received from two terminals through a power allocation ratio at the relay. We formulate an optimization problem to minimize the system outage probability and obtain the optimal power allocation ratio in closed form. For the proposed optimal combining scheme, we derive the expression for the system outage probability. Simulation results verify our derived expressions and show that the proposed scheme achieves a lower system outage probability than the existing schemes

Joint channel pairing and power allocation optimization in two-way multichannel relaying.

We consider two-way amplify-and-forward relaying in a multichannel system with two end nodes and a single relay, using a two-slot multi-access broadcast (MABC) as well as time-division broadcast (TDBC) relaying strategies. We investigate the problem of joint subchannel pairing and power allocation to maximize the achievable sum-rate in the network, under an individual power budget at each node. To solve this challenging joint optimization problem, an iterative approach is proposed to decompose the problem into pairing optimization and joint power allocation optimization, and solve them iteratively. For given power allocation, we first consider the problem of subchannel pairing at the relay to maximize the achievable sum rate in TDBC-based network. Unlike in the one-way relaying case, our result shows that there exists no explicit SNR-based subchannel pairing strategy that is optimal for sum-rate maximization for two-way relaying. Nonetheless, for TDBC-based two way relaying, we formulate the pairing optimization as an axial 3-D assignment problem which is NP-hard, and propose an iterative optimization method to solve it with complexity O(N3). Based on SNR over each subchannel, we also propose sorting-based algorithms for scenarios with and without direct link, with a low complexity of O(N logN). For the joint power allocation at the relay and the two end nodes, we propose another iterative optimization procedure to optimize the power at the two end nodes and at the relay iteratively. By using different forms of optimization parameters, the sum-rate maximization problem turns out to be convex and the optimal solutions can be obtained for each subproblem. The simulation first demonstrates the proposed sorting-based pairing algorithm offers the performance very close to the iterative optimization method. Then, shows the gain of joint optimization approach over other pairing-only or power-allocation-only optimization approaches

Spectrally Efficient Cooperative Relay Networks using Signal Space Diversity

Cooperative relaying has received widespread attention in recent years from both academic and industrial communities. It offers significant benefits in enabling connectivity as well as in increasing coverage, power saving, spatial diversity and channel capacity. However, one of the main limitations of the conventional cooperative relaying system is the repetition of the received data by the relays, which reduces the spectral efficiency and the data rate. In this thesis, signal space diversity (SSD) based technique is proposed to incorporate into the conventional relaying system to enhance spectral efficiency, data rate and system performance. Firstly, SSD is introduced into a two-way cooperative relaying system with three-phase two-way decode-and-forward (DF) protocol. In this system, four symbols are exchanged in three time slots, thereby doubling the spectral efficiency and the data rate compared to the conventional three-phase two-way DF relaying system that uses six time slots to exchange the same four symbols. Next, SSD is employed in a dual-hop relaying system using DF protocol without a direct link between the source and the destination. In this system, two symbols are transmitted in three time slots as compared to four time slots to transmit the same two symbols in the conventional dual-hop DF relaying system. These proposed systems are designed to exploit the inherent diversity in the modulation signal-space by rotating and expanding the ordinary constellation. The improvement in spectral efficiency is achieved without adding extra complexity, bandwidth or transmit power. A comprehensive analysis of these proposed systems is carried out over Rayleigh fading channels, and closed-form expressions for various performance metrics, including error probability, outage probability and channel capacity, are derived and illustrated. An asymptotic approximation for the error probability is obtained and is used to illustrate the impact of system parameters and diversity gain on the system performance. The optimization of relay location and power allocation in these systems is also examined. Extensive Monte Carlo simulations are performed to ascertain the accuracy of the analytical results presented in the thesis. Indeed, it is observed that the use of SSD in cooperative relaying can play a major role in the system design and performance improvement