高信噪比下HDAF协议中的最优功率分配的新方案

New Optimal Power Allocation Scheme in HDAF Protocol under High Signal to Noise Ratio Conditions

混合译码放大转发(Hybrid Decode-Amplify-Forward,HDAF)协议与放大转发、译码转发协议相比,能在很大程度上提高系统的性能,成为近年来的研究热点。在此,研究了在混合译码放大转发协议下的最优功率分配问题。首先推导了高信噪比(Signal-to-Noise Ratio,SNR)下混合译码放大转发协议中的误符号率的近似和实用的表达式;然后通过建立数学模型,在满足总功率一定的情况下,以最小化系统的误符号率为目标,优化分配系统的总功率;最后在Matlab环境下验证推导结果并做了大量的仿真实验。实验结果表明,所推导的近似的误符号率的表达式与实际误符号率在稍高的信噪比下具有很好的吻合度。混合译码放大转发协议的最优功率分配因子不仅与源节点到中继节点、中继节点到目的节点的信道质量有关,而且与系统的总功率有关。研究发现,随着系统总功率的增大,最优功率分配因子将趋近于1/2。

The hybrid decode-amplify-forward（HDAF）protocol has recently been proposed in the literature.And it can remarkably outperforms the decode-and-forward and the amplify-and-forward protocol.In this paper,the optimal power allocation problem in hybrid decode-amplify-forward protocol was deeply studied.Firstly,practical formula for the symbol error rate in the hybrid decode-amplify-forward protocol is derived in the literature.Then,the mathematical model of the power allocation problem in the protocol is mathematically formulated,which minimizes the symbol error rate under the total power constraint.Finally,simulations using Matlab programs are designed to verify the proposed formulas and confirm the proposed approach to solve the problem.Numerical results demonstrate that the optimum power allocation factor in the HDAF protocol is not only related to the channel conditions of the source-to-relay channel and the relay-todestination channel,but also related to the total power of system.It is also discovered in our research that with the sufficient increase of the allowed total power,the optimum power allocation factor will asymmetrically approximate 1/2.