Cellular Telephone Basics continued . . . Code Division Multiple Access has many variants as well. InterDigital, for example, produces a broadband CDMA system called B-CDMA that is different from Qualcomm's narrowband CDMA system. A CDMA system assigns a specific digital code to each user or mobile on the system. It then encodes each bit of information transmitted from each user.
Every cell site can transmit on every frequency available to the wireline or non-wireline carrier.
That's because the specificity of the coded signals helps a CDMA system treat other radio signals and interference as irrelevant noise. Some of the details of CDMA are also interesting. Before we get to them, let's stop here and review, because it is hard to think of the big picture, the overall subject of cellular radio, when we get involved in details. We've discussed, at least in passing, five different cellular radio systems. We looked in particular at AMPS, the mostly analog, original cellular radio scheme.