Question:

(a) Describe the spreading and dispreading processes of a CDMA system.

(b) Autocorrelation properties are used to recover the signals correctly at the receiver. Explain how this is realised.

(c) A certain CDMA system, using pseudo-random spreading sequences, operates with 128 chips per symbol, and requires a carrier to interference ratio of 8 dB. A salesman, attempting to sell this system, brought along a single base station, and a large number of stationary user terminals to a single room, isolated from the rest of the world.

How many user terminals could be used simultaneously in this case?

(c) Impressed, the operator bought the system, and installed a multi-cellular network, in which the inter-cell interference from all neighbouring cells was one third that of the intra-cell interference from other users in the same cell. Also, due to a slower than ideal power control algorithm, the maximum power control error for moving users was 3 dB.

Estimate the maximum number of users who could use the system for the worst possible case (everyone transmitting with worst-case transmit power error).