SPREADING .....

There are various ways used by CDMA to "spread" the original message. The term spread refers to method of scrambling with certain pattern and both party (sender & receiver) able to de-scrambler the coded message.



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walsh code is generated by chipset which produced by Qualcom. You don't need to be confused by huge matrix and one-zero waving numbers . It's all qualcom secret, and every cdma handset and BTS channel card involve qualcom chipset. One user use one walsh code, and since the matrix is huge, the probability of same walsh code use at one place is one to million



Short PN is use at BTS part, to differentiate every subcell ( sector) of the BTS. This code is re-useable.


Long code is equal with ESN ( electronics serial numbers) plus A-key (authentication key). CDMA handset has different ESN and some operator apply A-key to avoid handset fraud or cloning.