1. Consider the uplink of a single IS-95 cell where all the users are controlled to have the same received power P at the base-station.
a. In the IS-95 system, decoding is done by a conventional CDMA receiver which treats the interference of the other users as Gaussian noise. What is the maximum number of voice users that can be accommodated, assuming capacity-achieving point-to-point codes? You can assume a total bandwidth of 1.25 MHz and a data rate per user of 9.6 kbits/s. You can also assume that the background noise is negligible compared to the intra-cell interference.
b. Now suppose one of the users is a data user and it happens to be close to the base-station. By not controlling its power, its received power can be 20 dB above the rest. Propose a receiver that can give this user a higher rate while still delivering 9.6 kbits/s to the other (voice) users. What rate can it get?