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首页> 外文期刊>Wireless personal communications >Reference Symbol Assisted Multi-Stage Successive Interference Cancellation for CDMA Wireless Communication: Robustness to Parameter Imperfections with Biphase and Quadriphase Spreading
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Reference Symbol Assisted Multi-Stage Successive Interference Cancellation for CDMA Wireless Communication: Robustness to Parameter Imperfections with Biphase and Quadriphase Spreading

机译：CDMA无线通信中的参考符号辅助的多阶段连续干扰消除：双相和四相扩频对参数缺陷的鲁棒性

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摘要

This paper investigates the sensitivity to system imperfections of a reference symbol assisted multi-stage successive interference cancelling (RAMSIC) receiver. Reverse link of a CDMA system with binary antipodal modulation and coherent detection is considered. Performance of systems using either biphase and quadriphase spreading is compared under different operating conditions. Analysis of a conventional matched filter receiver operating on an AWGN channel reveals that when the number of users is small (such that the multiple access interference cannot be accurately modelled as Gaussian), quadriphase spreading has a significant advantage over biphase spreading. This advantage, however, disappears when the number of users per sector is large (of the order necessary for the multiple access interference to be considered Gaussian). Results for the RAMSIC receiver with quadriphase spreading, on the other hand, show that for hexagonal cell geometry with path loss exponent of 4 and without any forward error correction coding, the traffic capacity is between 1.17 and 1.67 times that of the IS-95. These numbers represent a significant increase over those obtained with biphase spreading. Further investigation with nonidealized cell geometries and other path loss exponents also shows substantial capacity improvement over that of conventional correlator receivers. Performance losses due to nonideal transmitter power amplifier gating, imperfect power control and synchronization errors in the RAKE receiver are also determined. The results for biphase spreading show that for path loss exponent of 4, imperfect amplifier gating causes relatively minor decrease in the traffic capacity, while no such effect is observed for path loss exponents of 2 and 3. As expected, relaxing of power control for both biphase and quadriphase spreading has a similar capacity reducing effect. In spite of these two effects the resultant capacity is still significantly higher than that with the conventional matched filter receiver. Capacity increase with quadriphase over biphase spreading is between 1.4 and 2.0 times. Chip synchronization errors of the order to be expected in a properly designed conventional CDMA system have only minimal effect on performance. Therefore, we conclude that conventional synchronization algorithms should perform adequately with successive interference cancelling receivers considered in the paper.
机译：本文研究了参考符号辅助多级连续干扰消除（RAMSIC）接收机对系统缺陷的敏感性。考虑了具有二进制对映调制和相干检测的CDMA系统的反向链路。比较了在不同操作条件下使用双相和四相扩展的系统的性能。对在AWGN信道上运行的常规匹配滤波器接收机的分析表明，当用户数较少时（使得无法将多路访问干扰准确地建模为高斯模型），四相扩频比双相扩频具有明显优势。但是，当每个扇区的用户数很大时（将多路访问干扰视为高斯所必需的顺序），这种优势就消失了。另一方面，具有四相扩展的RAMSIC接收机的结果表明，对于路径损耗指数为4且没有任何前向纠错编码的六角形六边形几何结构，业务量是IS-95的1.17到1.67倍。这些数字表示比双相扩展获得的数字显着增加。对非理想化的小区几何形状和其他路径损耗指数的进一步研究还显示，与传统的相关器接收器相比，容量有了很大的提高。还确定了由于非理想的发射机功率放大器选通，RAKE接收机中的功率控制不完善和同步错误导致的性能损失。双相扩展的结果表明，路径损耗指数为4时，不完善的放大器门控会导致通信量的下降幅度相对较小，而路径损耗指数2和3则没有观察到这种影响。双相和四相扩展具有类似的容量减少效果。尽管有这两种影响，最终的容量仍明显高于传统的匹配滤波器接收器。四相与双相扩展相比，容量增加了1.4到2.0倍。在适当设计的常规CDMA系统中，预期的芯片同步误差对性能的影响很小。因此，我们得出结论，常规同步算法应与本文中考虑的连续干扰消除接收器充分配合。

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