Generating Pseudo-Random Codes
For each channel the base station generates a unique code that changes for every
connection. The base station adds together all the coded transmissions for every
subscriber. The subscriber unit correctly generates its own matching code and uses it to
extract the appropriate signals. Note that each subscriber uses several independent
channels.
In order for all this to occur, the pseudo-random code must have the following properties:
1. It must be deterministic. The subscriber station must be able to independently generate
the code that matches the base station code.
2. It must appear random to a listener without prior knowledge of the code (i.e. it has the
statistical properties of sampled white noise).
3. The cross-correlation between any two codes must be small (see below for more
information on code correlation).
4. The code must have a long period (i.e. a long time before the code repeats itself).