On Maximum of Energy-Efficiency in Amplify-and-Forward Relay Networks Under Channel Estimation Errors

Abstract

In this paper, we investigate the energy-efficiency for amplify-and-forward relay networks in the presence of channel estimation errors. Two kinds of transmission strategies, i.e., direct transmission (DT) and relay transmission (RT), are dealt with for the energy-efficient communication system design. The energy cost function in DT or RT is defined as the total energy consumption for transmitting one bit data successfully, in which the channel estimation error, the channel estimation cost (i.e., energy consumed for pilot transmission) and the outage probability are included. As the power allocation plays a crucial role in implementing relay networks in an energy-efficient manner, we propose a theoretical framework for energyefficient power allocation in DT and RT strategies to minimize the energy cost. By simulation, we compare the two transmission strategies according to the energy cost under various network scenarios. Our results provide several insights into the choice between DT and RT strategies if some transmission parameters are known.INDEX TERMS Amplify-and-forward, channel estimation, energy consumption, energy-efficient power allocation, relay network.

Energy-efficient amplify-and-forward full-duplex transmission strategy

“…With relay technique, the energy-efficient transmission can be achieved. Energy-efficient relay network in the presence of channel estimation errors has been investigated to minimize energy cost [2]. Energy-efficient resource allocation in the downlink relay networks has been studied to maximize the system average EE [3].…”

“…However, in [10]- [12], to simplify the analysis, the direct link (DL) in relay transmission has not been considered with the assumption of deeply channel fading. Actually, considering the existence of DL in relay transmission can achieve further performance gain [2]. At the same time, some works have been done on it, i.e., the sum-rate performance of simultaneous relay and direct MIMO with imperfect channel state information (CSI) case have been investigated in [13]; and a FD transmitter cooperative scheme to improve achievable rate for multiple access channels has been proposed in [14].…”

“…At the same time, the 𝑔 can be reexpressed as 𝑔 =2 𝛼 3.2 𝛼 − 1 + 2 2(2 2𝛼 − 2 𝛼 ) (2 3𝑅 1 − 1) − 2 2𝛼+2 (2 4𝑅 1 ) − 1.When the 𝛼 has been known, the 𝑔 is a function of 𝑅 and the 𝑔 is a function of 𝑅 can be found. When 𝛼 ∈[2,4], 𝑔 (𝑅 ) < 0 and 𝑔 (𝑅 ) < 0 can be obtained. Thus, 𝑔 (𝑅 ) is a decreasing function of 𝑅 , 𝑔 (𝑅 ) is a decreasing function of 𝑅 , and the maximum of 𝑔 (𝑅 ) and 𝑔 (𝑅 ) can be obtained when 𝑅 = 𝑅 = 0.…”