Research Of Energy-efficient Transmission In Wireless Networks With Cooperative Relay Technique

With the rapid growth of intelligent wireless communication demand and application,the energy consumption of wireless networks is growing at an explosive rate.In such case,to maximize the energy-efficiency(EE)of wireless networks to achieve the energy-efficient transmission(EET)has becoming more and more important,and it is also one of the most important problems that cannot be ignored in the future wireless networks with considering the growth of energy consumption.Cooperative and relay technique has been regared as the effective methods to maximize the EE of wireless networks to realize EET for its property of achieving the diversity,decreasing the power consumption and so on.Combining the cooperative and relay technique with the EET requirements of wireless networks can not only provide diversity against wireless channel fading and establish reliable communication links to promote the further development of wireless networks,but also improve the spectral-efficiency(SE)and EE of wireless networks.Therefore,the research of EET in wireless networks with cooperative and relay techinique has important theoretical value and application prospect.Combining cooperative and relay technique with different optimization methods and communication techniques,such as fractional programming,convex optimization,half-duplex/fullduplex(FD)techinique and so on,this paper focus on the design of energy-efficient buffer-aided relay transmission strategy,the design of energy-efficient adaptive transmission strategy,the achievement of energy-efficient half-duplex transmission with joint optimization of transmission time and transmission power allocation,and the achievement of the energy-efficient FD transmission with joint optimization of transmission time and transmission power allocation four kinds of researchs to achieve EET in the wireless cooperative and relay network.Based on the above four kinds of researchs,the contribution of this paper can be descried as follows:1.This paper proposes a buffer-aided one-way amplify-and-forward(AF)relay transmission strategy to overcome the problem in the traditional two hop one-way AF relay protocol.The problem can be described as the destination node is only to combine a part of the received signals with maximum ratio combining technique,which reduces the resource utilization.At the same time,the analytical expression of the proposed buffer-aided one-way AF relay transmission strategy's and the traditional two hop one-way AF relay protocol's SE analysis are given with the noises normalizetion.In addition,the analytical expressions of the proposed buffer-aided one-way AF relay transmission strategy's and the traditional two hop one-way AF relay protocol's outage probability and downlink transmission EE are further studied under equal power allocation.Finally,simulation results show that the proposed buffer-aided one-way AF relay transmission strategy has performance advantages when comparing with direct transmission(DT)and the traditional two hop one-way AF relay protocol,such as outage probability,bit error rate,and downlink EE.2.This paper proposes a hybrid relay and no-relay adaptive transmission strategy in bidirectional communication situation with considering non-negligible circuit powers consumption.Firstly,through comparing and analyzing the EEs of DT and two-way AF relay transmission,this paper proposes a transmission rate threshold determinating algorithm to find the transmission rate threshold that makes the EEs of DT and two-way AF relay transmission equal.Then,through this transmission rate threshold,this paper proposes a hybrid relay and no-relay adaptive transmission strategy to achiveve adaptive transmission between DT and two-way AF relay transmission aiming at maximizing EE.Finally,the simulation results show that the hybrid relay and no-relay adaptive transmission strategy's EE is always the maximum when comparing with DT and two-way AF relay transmission.3.This paper proposes direct,one-way relay,and two-way relay transmission strategies with considering non-negligible circuit powers consumption,non-ideal power amplifier efficiency,and direct links which directly two source terminals in relay transmission aiming at transmitting the signal as much as possible.In the proposed three transmission strategies,the nodes work in the halfduplex mode and the communication situation is bidirectional transmission.At the same time,this paper gives three transmission strategies' joint optimization of transmission time allocation and transmission power allocation problem.The joint optimization problems are given with three optimization cases:(i)maximizing sum throughput to achieve EET,in such case,optimal transmission time,optimal relay position,and outage probability analysis are given;(ii)minimizing total energy consumption to achieve EET,in such case,optimal transmission power,optimal transmission time with gradient-descent algorithm,optimal relay position and the analysis of asymmetry and asymmetry transmission tasks on EE are given;(iii)maximizing EE to achieve EET,in such case,the optimal solutions with Dinkbach algorithm and the proposed one-by-one optimization iterative algorithm,and the algorithm complexity analysis are given.Finally,the simulation results show that the last optimization case has a higher EE transmission when comparing with the first two optimization cases.4.This paper proposes direct FD,one-way relay FD,and two-way relay FD transmission strategies with considering non-negligible circuit powers consumption,non-ideal power amplifier efficiency,and direct links in relay transmission.In the proposed three transmission strategies,the nodes work in the FD mode and the communication situation is also bidirectional transmission.The design principle of the three FD transmission strategies is transmitting the signal as much as possible with fewer antennas and less self-interference.At the same time,the SE analysis of the three FD transmission strategies under the existence of residual self-interference is given.In addition,the energy consumption analysis,the joint optimization problems and their solutions of three FD transmission strategies are given.Furthermore,a simple EE analysis under zero circuit power consumption and symmetric transmission tasks,non-zero circuit power consumption and symmetric transmission tasks,and non-zero circuit power consumption and asymmetric transmission tasks are given.Finally,the simulation results show that three FD transmission strategies have a higher EE transmission when comparing with the existing half-duplex transmission.