Optimal power allocation for two-way decode-and-forward relay networks with equal transmit power at source nodes

Abstract

This paper proposes an optimal power allocation method for two-way decode-and-forward (DF) relay networks when transmit power values at source nodes are the same. In this paper we consider the multiple access (MAC) capacity for DF relaying scheme. Using case studies, it analytically determines the optimal power values for the two source nodes and one relay node. The achievable sum rate is maximized under a sum power constraint for given squared magnitude of the channel coefficients. Finally, numerical results show that the achievable sum rate for proposed optimum power allocation is greater than or equal to that for equal power allocation.Index Terms-Two-way relay channel, power allocation, decode-and-forward, network coding, sum rate. I. INTRODUCTIONIn a two-way relay channel (TWRC), two source nodes exchange messages with each other via a common relay. The two source nodes transmit messages to the relay through the multiple access (MAC) in the first time slot, and the relay transmits received messages to both source nodes through the broadcast (BC) in the second time slot. Amplify-and forward (AF) and decode-and-forward (DF) are typical relay ing schemes [1]-[4]. This paper assumes the DF relay. The each source node removes its own information, called self interference, and decodes the other source node ' s information.In order to maximize the achievable rate, the signal-to-noise ratio (SNR) of the received signal should be the maximum. By allocating the sum power to the sources and relay nodes in an optimal way, a maximum achievable rate can be obtained. To maximize an achievable rate, an optimal power allocation method for a one-way relay channel using DF was presented in [5]. The outage probability of a TWRC with a DF strategy was studied in [6]. An optimal power allocation scheme for a TWRC using AF and DF with data rate fairness was proposed in [7]. The physical-layer network coding (PNC) technique is presented in [8], and the optimal power allocation scheme for a TWRC using PNC has been presented in [9]. While the paper [9] does not consider a MAC capacity, this paper considers the MAC capacity and for the sake of simplicity assumes that transmit power at the two source nodes are the

Resource Management Based on Security Satisfaction Ratio with Fairness-Aware in Two-Way Relay Networks

“…exponentially distributed random variables in a six-tap channel; the path loss exponent is set to 3. Figure 4 illustrates the average SSR of JRASSFA using CHA (JRASSFA C), JRASSFA using suboptimal subchannel pairing (JRASSFA S), and equal power allocation (EPA) [22] algorithms for different security preference parameters, assuming that the eavesdropper exists between 100 m and 450 m from the RN. We can see that the average SSR of PMUs increases when the eavesdropper is far away from the RN, particularly when the eavesdropper is far away from relay node at a distance within 250 m. There are two reasons that can explain this result:…”

“…Figure 4 illustrates the average SSR of JRASSFA using CHA (JRASSFA_C), JRASSFA using suboptimal subchannel pairing (JRASSFA_S), and equal power allocation (EPA) [22] algorithms for different security preference parameters, assuming that the eavesdropper exists between 100 m and 450 m from the RN. We can see that the average SSR of PMUs increases when the eavesdropper is far away from the RN, particularly when the eavesdropper is far away from relay node at a distance within 250 m. There are two reasons that can explain this result: (1) the farther the distance between eavesdroppers and relay nodes, the worse the SINR eavesdropper received and thus the less the communication information the eavesdropper eavesdrop, so the security satisfaction ratio of users increases; (2) the path loss is a major factor deteriorating the received signal of the eavesdropper within 250 m in the simulation, so the average SSR of PMUs increases rapidly at a distance within 250 m. Moreover, smaller βk result in higher performance of SSR, because user has lower security requirement with a smaller βk; in other words, information security is not important to these users with a smaller βk.…”

Near optimal power allocation in two‐way relay systems with physical layer network coding

“…Pischella and Ruyet [11] proposed a PA scheme to maximise the sum rate under the fairness constraint with the DF protocol. In [12], an optimal PA method for the DF TWR system was proposed under a specific condition where the transmit powers at both the source nodes are the same.…”

Optimal time allocation for two‐way relay channel using physical‐layer network coding

“…An optimal power allocation scheme for a TWRC using the AF MABC and DF MABC protocols with data rate fairness was proposed in [16]. An optimal power allocation was presented in [17] with the assumption that the source nodes have equal transmit power. The optimal power allocation scheme for a TWRC using PNC has been presented in [18].…”