Relay Power Consumption Research Articles

Joint Channel Estimation and Robust Beamforming Design for AF Relaying Using IMM Kalman Filters

This paper addresses the joint problem of recursive channel estimation and robust beamformer design in peer-to-peer communication through a network of relays over time-varying radio channels. Using observed signal samples at the relay and receiver nodes, the Channel State Information (CSI) is estimated centrally by taking advantage of a Markov model for the transmitter-relay and relay-receiver channels, and employing either the Extended Kalman Filter (EKF) or the Cubature Kalman Filter (CKF). Based on the estimated CSI, two robust approaches are conceived for designing the relay beamforming where the aim is to minimize the total transmission power of the relays subject to Signal-to-Interference plus Noise Ratio (SINR) constraints at each of the receiver nodes. Furthermore, the Interacting Multiple Model (IMM) approach for mixing non-stationary and stationary Markov models is employed to extend the time-varying robust beamforming design to non-stationary environments. Through numerical simulations, the recursive CSI estimation methods are shown to be efficient, i.e., unbiased and converging to the Cramer-Rao Lower Bound (CRLB). Furthermore, the results confirm the better performance of the proposed robust relay beamforming design algorithms compared to existing methods in terms of relevant transmission metrics, including relay power consumption and spectral efficiency.

Energy‐efficient communications over multiple access relay channels

SummaryRecently, due to the importance of green communications and power‐limited systems, energy efficiency in vehicular technologies has become a hot research topic. In this paper, we analyze energy‐efficient coding schemes in multiple access relay channels. First, the coding scheme in the multiple access relay channel is introduced. At the desired source rates, 3 optimal sets of resource allocation (the total power consumption, the relay power consumption, and the source power consumption) are given in the closed form. The analysis shows that the proposed energy‐efficient schemes achieve higher data rates and significantly outperform especially by reducing the relay energy consumption, which is useful for the shared relays. Moreover, the results allow a comprehensive description of the power consumption systems and give a detailed understanding of the desired message coding and the resource dedication for every desired sum rate.

Relay Power Control for Two-Way Full-Duplex Amplify-and-Forward Relay Networks

Relay power control for two-way (TW) full-duplex (FD) relay network is studied in this letter. In the prior literature, the relay is assumed to always use its full transmit power in a TW FD relay network. However, high transmit power will increase loopback self-interference at the relay node and thus make the incoming link to the relay become the bottleneck for the end-to-end performance. Therefore, it is suboptimal to always utilize the full power capability of the relay. Thus, we propose three relay power control schemes, which can, respectively, maximize 1) the data rate of an individual end node, 2) the minimum data rate of the two end nodes, and 3) the sum data rate of the two end nodes. Numerical results show that, compared to using full relay power, the proposed relay power control schemes can improve system performance while reducing relay power consumption.

Energy Efficient Scalable Video Coding Based Cooperative Multicast Scheme with Selective Layer Forwarding

Scalable Video Coding (SVC) based multicast schemes have been researched for many years in efforts to simultaneously achieve high throughput and good fairness, which have a trade-off relationship in multicast communication. In an SVC based multicast, all group members in a good channel condition can receive both base layer and enhancement layer information and thus can recover high quality video, while other group members receive the base layer information for guaranteeing basic quality video. However, this causes differentiation of video quality between group members with varying channel conditions, and average video quality is consequently degraded. We propose an Energy Efficient SVC based cooperative multicast (EE-SVC-CM) scheme with selective layer forwarding as a novel approach to mitigate this problem. The performance results reveal that the proposed scheme enhances the overall energy efficiency (throughput per watt) with reduced unnecessary relay power consumption.

Optimal designs of collaborative relay-assisted multiuser beamforming for cellular systems

With careful calculation of signal forwarding weights, relay nodes can be used to work collaboratively to enhance downlink transmission performance by forming a virtual multiple-input multiple-output beamforming system. Although collaborative relay beamforming schemes for single user have been widely investigated for cellular systems in previous literatures, there are few studies on the relay beamforming for multiusers. In this paper, we study the collaborative downlink signal transmission with multiple amplify-and-forward relay nodes for multiusers in cellular systems. We propose two new algorithms to determine the beamforming weights with the same objective of minimizing power consumption of the relay nodes. In the first algorithm, we aim to guarantee the received signal-to-noise ratio at multiusers for the relay beamforming with orthogonal channels. We prove that the solution obtained by a semidefinite relaxation technology is optimal. In the second algorithm, we propose an iterative algorithm that jointly selects the base station antennas and optimizes the relay beamforming weights to reach the target signal-to-interference-and-noise ratio at multiusers with nonorthogonal channels. Numerical results validate our theoretical analysis and demonstrate that the proposed optimal schemes can effectively reduce the relay power consumption compared with several other beamforming approaches. Copyright © 2012 John Wiley & Sons, Ltd.

다중홉 Ad-hoc 환경에서 에너지 효율적인 릴레이 선택 방안

릴레이를 사용한 시스템에서 최적의 릴레이 위치에 대한 연구가 많이 진행되어 왔지만, 지금까지는 송신단과 릴레이의 전송 전력의 합이 제한된 경우에 전송 용량을 최대화하는 연구가 대부분이었다. 그러나 Ad-hoc 네트워크와 같이 릴레이가 제한된 용량의 배터리를 에너지원으로 사용하는 경우, 에너지 소모를 효율적으로 절약하는 것이 필요하다. 본 논문은 AF(Amplify-and-Forward) 릴레이를 사용한 두 홉 시스템에서 수신단의 신호 대 잡음비가 고정된 경우, 특정 전송 품질을 만족시키기 위해 릴레이에서 사용하는 전력을 최소화하는 최적 릴레이 위치 선정 방안을 제안한다. 모의실험을 통해 Ad-hoc 환경에서의 제안된 기법이 에너지 소모 측면에서 더 효율적임을 보이고, 다중 홉으로 확장된 시스템에서 제안된 기법의 경우 더 낮은 전송실패확률을 갖는 것을 확인한다. There have been lots of researches on the optimal relay selection in relay-based systems. However, most researches have been focused on the maximization of transmission capacity with a constraint of sum power at both transmitter and relays. In Ad-hoc networks where relays have batteries of limited power, it is imperative to minimize the energy consumption while maintaining the required quality-of-service (QoS). In this paper, we propose an optimal relay selection strategy to minimize the relay power consumption while satisfying the required signal-to-noise ratio (SNR). Through intensive simulations, we show the proposed method is more effective in terms of energy consumption and guarantee lower transmission failure probability in multi-hop Ad-hoc environments.

Energy Efficient Cooperative Multicast Scheme Based on Selective Relay

Multicast communication has been researched for many years in efforts to simultaneously achieve high throughput and good fairness, which have a trade-off relationship. Recently, a cooperative multicast scheduling scheme was proposed. It is considered a promising solution owing to its trade-off characteristics realized by promoting user cooperation among group members. However, it requires significant relay power consumption for user cooperation, since all group members in a good channel condition should relay without checking whether there is at least one user requesting a relay in the transmission boundary. Therefore, in order to resolve this inefficiency, we proposed an energy efficient cooperative multicast scheme (EECM) based on selective relay. We can achieve reduced unnecessary relay power expenditure by selecting relay users with consideration of the condition of nearby users. The performance results derived from a numerical analysis reveal that the proposed scheme requires less energy consumption than the existing solution with almost the same throughput performance.

Linear Relaying Scheme for MIMO Relay System With QoS Requirements

In this letter, we address the problem of fulfilling quality-of-service (QoS) requirements in a multiple-input multiple-output (MIMO) relay system, where a set of target signal-to-noise ratios (SNRs) should be attained on different substreams. By solving a two-step optimization problem, we obtain a power-efficient relaying scheme that can make the SNR requirements asymptotically fulfilled. A simple relay selection method is also proposed such that the relay-power consumption can be largely reduced when there is a large number of relays.

Generalized Circle Diagrams and Their Application to Protective Gear

The common underlying theory of generally used systems of protection involving comparison of two vector quantities is derived by coaxial (bipolar) circles in the complex plane, where amplitude or phase comparison can be used interchangeably to produce any desired circle or straight line characteristic. Practical departure from ideal comparison, resulting from relay power consumption, is considered, and the relationship between this analysis and two currently used methods of distance relaying is pointed out. The basic circuit of a commonly used pilot wire scheme is analyzed and its characteristic considered, and the effect of long pilots with distributed constants is indicated.