Signal Processing

In engineering, some of the most basic concepts are often the most powerful. Take BPSK (binary phase shift keying), for example. We can encode a binary message by simply changing the phase of a carrier signal from 0 degrees to 180 degrees. BPSK is used in GPS, satellite TV, and modern communication systems. The figure shows a BPSK message of 101110.

I found it interesting that CDMA signals have a rounded shape due to bandpass filtering. The rounded shape allows overlapping CDMA signals (orange and blue) to be detected because when one signal is low, the other has an opportunity to peak through and be detected, even in the presence of noise (green).

I was curious how the detection quality of CDMA signals at a receiver would change as the receiver moved away from one transmitter toward another (i.e., same frequency, same transmit power, different pseudo-random noise (PRN) codes). Logically, when the receiver is halfway between two transmitters, the received power levels would be the same. Would the signals then interfere with each other and cause both to drop out, or is CDMA robust enough to handle the interference and al