协作式终端直通系统中星座旋转辅助的干扰避免策略
A Scheme to Avoid Interference via Constellation Rotation for Cooperative Device？？to？？Device Systems

针对协作式终端直通(device？？to？？device,D2D)系统中蜂窝链路和D2D链路相互干扰的问题,提出了一种星座旋转辅助的干扰避免策略,以改善系统的误码性能。首先,对系统中各发射节点的信号星座图进行旋转,并对信道相位信息进行预补偿;然后,令不同的发射节点使用相互正交的信道发送信号,利用复信号同相分量和正交分量之间固有的正交性来避免相互干扰;最后,以最大化最小欧氏距离为目标,对星座旋转角度进行优化设计,从而有效降低蜂窝通信和D2D通信的误符号率。仿真结果表明,在系统采用QPSK作为调制方式且平均信噪比大于20 dB的条件下,与传统的协作双向传输策略相比,所提出的策略能够使误符号率由10－1下降至10－3。
A scheme to avoid interference via constellation rotation for cooperative device？？to？？device (D2D) systems is proposed to deal with the cross interference between the cellular link and the D2D link, and to improve the system error performance. The signal constellation is first rotated, and the phase of the channel coefficient is pre？？compensated at each terminal. Then, orthogonal channels at different nodes are used to send their signals. In this manner, the inherent orthogonality between the real and imaginary components of a complex signal can be utilized to avoid the interference. Finally, the value of the rotation angle is carefully designed to maximize the minimum Euclidian distance among the signal points, so that the symbol error probabilities (SEP) for cellular communications as well as D2D communications are effectively reduced. Simulation results and comparisons with the conventional cooperative two？？way transmission scheme show that when QPSK modulation is adopted and the system average signal？？to？？noise ratio is higher than 20 dB, the proposed scheme can reduce the system SEP from 10－1 to 10－3