Energy Efficient Design for Two-Way AF Relay Networks

Abstract

Conventional designs on two-way relay networks mainly focus on the spectral efficiency (SE) rather than energy efficiency (EE). In this paper, we consider a system where two source nodes communicate with each other via an amplify-and-forward (AF) relay node and study the power allocation schemes to maximize EE while ensuring a certain data rate. We propose an optimal energy-efficient power allocation algorithm based on iterative search technique. In addition, a closed-form suboptimal solution is derived with reduced complexity and negligible performance degradation. Numerical results show that the proposed schemes can achieve considerable EE improvement compared with conventional designs.

Adaptive wireless transmission strategy for maximizing energy efficiency

“…We assume that g s 1 s 2 = |h s 1 s 2 | 2 σ 2 , which reflects the instantaneous channel gain to noise ratio (CNR) [18] from the node S 1 to node S 2 . Then, the transmission rates at the two source nodes can be expressed as…”

“…In [17], it has been demonstrated that the circuit power is consumed by signal processing and the device working in the active mode. The authors in [18] designed an optimal power allocation scheme to maximize EE for two-way amplify and forward (AF) relay networks with consideration of circuit power. Furthermore, the discussions above mainly focus on a fixed transmission mode, in which EE is not always the maximum at a range of transmission rate.…”

Energy Efficient Two-Way Non-Regenerative Relaying for Relays with Multiple Antennas

“…Therefore, problem (8) is a DC problem which is known to be non-convex and NP-hard to solve [21]. Nevertheless, by replacing the concave elements with minus signs by scalar variables, the objective function is turned into a concave function and an equivalent reformulation is given by (9) Compared to (8), the non-convexity in (9) is localized in the inequality constraints , . To deal with the non-convex constraints, we propose to linearize the logarithmic function using its first order Taylor expansion, i.e., the first order Taylor polynomial approximation of at is defined as .…”

“…When two-way relaying (TWR) networks are considered, major contributions to EE optimization deal with power allocation [6]- [10]. More specifically, researches in [6]- [9] study an AF TWR network with only single antenna nodes. Only the work in [10] considers a TWR network with multiple single antenna relays.…”

“…Moreover, all the previous works on the EE of TWR networks solve the bit/Joule EE optimization problem indirectly. That is, first the relationships between EE optimization and spectral efficiency optimization, e.g., [10], or transmit power minimization, e.g., [9] summary, a direct EE optimization for a AF TWR network with multi-antenna nodes has not been well studied. We study the EE optimization problem for a TWR system with a multi-antenna AF relay and multi-antenna users.…”