中文摘要：

为了降低码分多址（CDMA）系统中的信号峰平功率比（PAPR），研究了正交可变扩频因子（OVSF）码对下行链路PAPR的影响．推导了使用OVSF码的CDMA系统下行链路信号瞬时功率表达式，分析了OVSF码构成的最大游程长度不小于8的组合码个数对信号PAPR的影响．归纳出组合码最大游程长度与OVSF码下标之间的关系，导出构成最大游程长度不小于8的组合码的码长条件及下标条件．根据3GPP2标准的cdma20001X物理层参数，对不同的OVSF码集合进行了仿真．仿真结果表明，信号PAPR随最大游程长度不小于8的组合码个数增加而增大，该规律为CDMA系统中低PAPR的OVSF码分配算法设计提供了理论依据．

英文摘要：

To reduce the signal peak-to-average power ratio （PAPR） in code-division multiple access （CDMA） system, the effects of orthogonal variable spreading factor （OVSF） codes on PAPR at the down link transmitter were investigated. The expression of down link signal instantaneous power in CDMA systems was deduced, and the influences of the number of the combined codes with maximum run length of 8 or longer on PAPR were observed. After the relationship between the maximum run-length of the combined codes and the index of OVSF codes was concluded, the length and the subscript conditions of combined codes with maximum run-length of 8 or longer were obtained, and different OVSF code sets were simulated according to cdma2000 lx physical layer parameters of 3GPP2 standard. Simulation results show that signal PAPR increases with increasing number of combined codes with maximum run-length of 8 or longer, the proposed conditions can provide theoretical foundation for algorithmic design of OVSF assignment with low PAPR for CDMA systems.