Overview

Throughout our previous discussions, we have routinely toggled back and forth between time and frequency domains (temporal space and frequency space) to get a clearer picture of the overall view of our signal. For most seasoned engineers, these are fairly comfortable places almost tangible spaces to some. Though you almost feel like you can put a measuring tape to a sine wave and cut off a millisecond of "x" kHz, frequency is a little more nebulous you can't exactly pour out a gallon of frequency, but yet the concept is fairly routine to most, despite its less-than-tangible nature. Bandwidth is even more ethereal: "yes, I'll take a bushel of 3 ¹/ ₂ kHz bandwidth, and two firkins of the mocha cream." Yet most in the business don't even give it a second thought. With CDMA, we now go one extra notch into the cloud, and introduce what is known as "code space."

In analog broadcasts, each user is assigned a segment in frequency space (i.e., assigned an RF channel) then takes his or her audio (or digital bit stream) and shifts it up to this assigned segment of RF space through the modulation process. In CDMA, we still have to slot our users somewhere in the available frequency space, but we use an extra partitioning technique on top of this RF channel, referred to as "code space." In fact, all our CDMA users can be assigned the same RF channel at the same time, but each user...