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Transmitter and receiver in a system for communicating a sequence of information symbols and the process of transmitting and detecting a sequence of information symbols
Transmitter and receiver in a system for communicating a sequence of information symbols and the process of transmitting and detecting a sequence of information symbols
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机译:用于传达信息符号序列的系统中的发送器和接收器以及发送和检测信息符号序列的过程
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摘要
Information symbols spread using orthogonal or bi-orthogonal codewords are assigned a unique scramble mask that is taken from a set of scramble masks having selected correlation properties. The set of scramble masks is selected such that the correlation between the modulo-2 sum of two scramble masks with any codeword is a constant magnitude, independent of the codeword and the individual masks being compared. In one embodiment, when any two masks are summed using modulo-2 arithmetic, the Walsh transformation of that sum results in a maximally flat Walsh spectrum. For cellular radio telephone systems using subtractive CDMA demodulation techniques, a two-tier ciphering system ensures security at the cellular system level by using a pseudorandomly generated code key to select one of the scramble masks common to all of the mobile stations in a particular cell. Also, privacy at the individual mobile subscriber level is ensured by using a pseudorandomly generated ciphering key to encipher individual information signals before the scrambling operation.
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