Opportunistic Energy-Aware Amplify-and-Forward Cooperative Systems With Imperfect CSI

Abstract

Recently, much attention has been paid to the green design of wireless communication systems using energy efficiency (EE) metrics that should capture all energy consumption sources to deliver the required data. In this paper, we design an energyefficient relay assisted communication system based on estimated channel state information (CSI). It employs amplify-andforward relaying and switches between different communication schemes, which are known as direct-transmission, two-hop and cooperative-transmission schemes, using the estimated CSI in order to maximize the EE. Two estimation strategies are assumed, namely disintegrated channel estimation and cascaded channel estimation. To formulate an accurate EE metric for the proposed opportunistic amplify-and-forward system, the channel estimation cost is reflected on the EE metric by including its impact in the signal-to-noise ratio term and in the energy consumption during the channels estimation phase. Based on the formulated EE metric, we propose an adaptive power allocation algorithm to maximize the EE of the proposed opportunistic amplify-andforward system with channel estimation. Furthermore, we study the impact of the estimation parameters on the proposed system via simulation examples.

Energy-Efficient Resource Allocation for Phantom Cellular Networks With Imperfect CSI

“…According to the maximum power budget parameters, the simulation results indicate that increasing number of pilots will be an energy inefficient choice. It is worth to mention that such trend depends mainly on the maximum power budget available for the pilot, which may result in a unimodal behavior for low pilot power budget as discussed in [26]. The simulation also indicates that the relative EE performance of the three strategies is independent of changing the number of pilots.…”

Energy-Efficient Channel Estimation

“…The bandwidth of the channel is 180 kHz. σ 2 h = G, σ 2 e = 0.5 G [21], and the cross correlation between h i and h 0 is considered as ρ i = exp(−i). The number of the maximum data slots L is 128.…”

“…To model the relationship between h i and h 0 , we employ the time-varying channel feedback error model to express the channel coefficient as [21]…”

“…Similar to [21], the downlink channel is estimated by the uplink feedback channel in our model. Compared with [22], the pilot power and the transmission power in each data slot are coupled together in our objective function, which is more complex and harder to solve.…”

An Energy Efficient Cooperative Communication Scheme in Ambient RF Powered Sensor Networks

“…The basic modes of CC include amplify-and-forward (AF) and decode-andforward (DF). For AF mode [5], the relays just amplify the signal received from the source, then forward the amplified signal directly to the destination; whereas for DF mode [6], relays decode the received signal, and re-encode it before forwarding to the destination. Both AF and DF mode are considered in a distributed approach [7], which solves the relay node selection problem in CC.…”