/ 4 - dqpsk which is a modification of qpsk modulation . it is a linear narrowband technology which has been widely employed in mobile communication system , satellite communication system . it possesses features of high spectrum utilization ratio , better spectrum specification , stronger anti - fading performance and applicability to non - coherent detection / 4 - dqpsk是qpsk改进方式,它是一种线性窄带数字调制技术,被广泛应用于移动通信和卫星通信中,其突出特点是频带利用率高、频谱特性好、抗衰落性能强、可进行非相干解调。
Among the non - coherent transmit diversity technologies , differential transmit diversity is a remarkable technique . in this thesis we consider the combining diversity of the differential transmit diversity and receive diversity . the potential of space diversity was discussed and the error performance of combining diversity system was investigated 本论文采用联合分集的方式将差分发送分集技术与接收分集技术相结合，进一步探讨了空间分集在抗衰落方面的潜力，并对基于联合分集技术的多天线通信系统进行了研究。
The problem of signal processing for direct - sequence code - division - multiple - access ( ds - cdma ) signal over multipath frequency - selective mobile channels is considered . a new blind receiver is proposed . without the knowledge of the multiple - access interference users spreading code and the channel characteristics , the receiver achieves blind detection with prior knowledge of only the desired users spreading code and approximate timing . by using reduced rank adaptive decorrelating filter and adaptive multipath combiner which is based on decision - directed algorithm , the receiver gets the ability to combat both fading and the near - far effect at low cost . simulation results demonstrate that the proposed receiver offers high performance 本文研究多径频率选择性衰落信道下直接序列扩频码分多址（ ds - cdma ）信号的处理问题，提出了一种新型的盲接收机.该接收机不需预知多址干扰用户的扩频码，不需预知信道参数，只需已知期望用户的扩频码和粗略的定时，就可以完成用户的盲检测.同时，该接收机通过降维自适应去相关滤波和基于判决指导的自适应多径合并，来获得低成本和良好的抗衰落、抗远近效应性能.仿真结果验证了本文提出的接收机的优良性能
