An Adaptive Power Allocation Scheme for Performance Improvement of Cooperative SWIPT NOMA Wireless Networks

Future wireless networks demand high spectral efficiency,energy efficiency and reliability.Cooperative non-orthogonal multiple access(NOMA)with simultaneous wireless information and power transfer(SWIPT)is considered as one of the novel techniques to meet this demand.In this work,an adaptive power allocation scheme called SWIPT based adaptive power allocation(SWIPT-APA-NOMA)is proposed for a power domain NOMA network.The proposed scheme considers the receiver sensitivity of the end users while calculating the power allocation coefficients in order to prevent wastage of power allocated to user in outage and by offering priority to any one of the users to use maximum harvested power.A detailed analysis on the bit error rate(BER)performance of the proposed scheme is done and closed form expression is obtained.Simulations have been carried out with various parameters that influence the receiver sensitivity and the results show that the network achieves better outage and BER performance using the proposed scheme.It is found that the proposed scheme leads to a ten-fold decrease in transmit power for the same error performance of a fixed power allocation scheme.Further,it offers 96.06%improvement in the capacity for a cumulative noise figure and fading margin of 10 dB.

Adaptive Energy-Efficient Power Allocation for DAS with Imperfect Channel State Information and Antenna Selection

Considering that perfect channel state information(CSI) is difficult to obtain in practice,energy efficiency(EE) for distributed antenna systems(DAS) based on imperfect CSI and antennas selection is investigated in Rayleigh fading channel.A novel EE that is defined as the average transmission rate divided by the total consumed power is introduced.In accordance with this definition,an adaptive power allocation(PA) scheme for DAS is proposed to maximize the EE under the maximum transmit power constraint.The solution of PA in the constrained EE optimization does exist and is unique.A practical iterative algorithm with Newton method is presented to obtain the solution of PA.The proposed scheme includes the one under perfect CSI as a special case,and it only needs large scale and statistical information.As a result,the scheme has low overhead and good robustness.The theoretical EE is also derived for performance evaluation,and simulation result shows the validity of the theoretical analysis.Moreover,EE can be enhanced by decreasing the estimation error and/or path loss exponents.

MULTICARRIER DS-CDMA WITH ADAPTIVE MODULATION AND POWER ALLOCATION

Adaptive modulation and power allocation is introduced into the multicarrier DS-CDMA system to improve the system performance and bandwidth efficiency. First, the systemdesign appropriate for adaptive modulation and power allocation is given, then the algorithmof adaptive modulation and power allocation is applied. Simulation results demonstrate greatperformance improvement compared with the fixed modulated one.

Decentralized beamforming design and power allocation for limited coordinated multi-cell network

Multi-cell processing （MCP） is capable of providing significant performance gain, but this improvement is accompanied by dramatic signaling overhead between cooperative base stations. Therefore, balancing the performance gain and overhead growth is crucial for a practical multi-base cooperation scheme. In this paper, we propose a decentralized algorithm to jointly optimize the power allocation and beamforming vector with the goal of maximizing the system performance under the constraint of limited overhead signal and backhaul link capacity. In particular, combined with calculating the transmission beamforming vector according to the local channel state information, an adaptive power allocation is presented based on the result of sum capacity estimation. Furthermore, by utilizing the concept of cell clustering, the proposed framework can be implemented in a practical cellular system without major modification of network architecture. Simulation results demonstrate that the proposed scheme improves the system performance in terms of the sum capacity and cell-edge capacity.