多输入多输出系统下行链路发射与接收的联合线性预编码

针对多用户多输入多输出系统下行链路线性预编码中的迫零法及正交化法对接收端的噪声有较强放大作用的问题，提出了一种发射与接收联合预编码的波束成形迭代法．该方法把联合预编码直接转变为波束成形问题，以惟一确定的最小范数解作为预编码矩阵，通过迭代得到各用户的预编解码矩阵．由于所得到的解码矩阵具有最小范数的特性，在解码时产生的噪声能量最小，从而有效地减少了对噪声的放大作用．同时，在基站总发射功率一定的条件下，根据用户的信道质量动态地分配功率可以使信道质量较差的用户得到较多的发射功率．仿真实验表明，所提出的方法与迫零法相比，在相同的仿真条件下，在平均误比特率为10^-4时可以获得约9dB的性能增益．

Joint Linear Precoding of Transmit and Receive for Multiple-Input Multiple-Output Downlink System

To solve the problem that zero forcing methods and orthogonalization methods cause severe noise amplifying at the receiver side in multiuser multiple-input multiple-output downlink system, an iterative beamforming method for joint precoding of transmit and receive is proposed. The proposed method directly converts joint precoding and decoding to beamforming problem, and utilizes the unique deterministic minimum norm solution as the precoding matrix, and then precoding and decoding matrix for every user can be got iteratively. The decoding matrix also has the character of minimum norm, and causes the least noise energy in decoding, therefore it efficiently declines the effect on noise amplifying. Under fixed sum transmitting power constraint and according to the channel quality of users, mere transmitting power is dynamically allocated to the user who has relatively poor channel quality. Simulation results prove that, compared to the zero forcing method, the proposed method achieves 9 dB gains under 10^-4 of average bit error rate and similar simulation conditions.