中文摘要：

传统的差分空时分组编码（DSTBC）在QPSK调制时存在着信号星座扩展．文中提出了一种在QPSK调制下新颖的两发射天线差分空时分组编码方案，此方案提供了一定的编码增益，同时也解决了星座扩展问题．在新方案中，改进了从信息块到系数矢量的映射，从而使其性能与相干空时分组编码相比大约只差1dB。同时新方案编码相对简单，在接收端也具有低的解码复杂度．

英文摘要：

The traditional differential space-time block code （DSTBC） suffers from the signal constellation expansion for QPSK modulation. In this paper, a new differential space-time block code for QPSK modulation with two transmit antennas is proposed, which can offer a differential coding gain without constellation expansion. In this scheme, the mapping from the information blocks to the coefficient vectors is improved. As a result, the performance is only about ldB away from the coherent STBC. The new encoding isrelatively simple, and decoding is achieved with low decoding complexity at the receiver.