Radio systems, one of the earliest forms of telecommunication, required users to communicate on distinct frequencies. Frequency Division Multiple Access (FDMA), one form of early wireless communication, only allowed users to operate on a single frequency. When tuning in to a radio to get sound, for instance, the listener must select one frequency or another, and must tune the frequency to filter out noise in the spectrum. Another form of early radio communication was Time Division Multiple Access (TDMA). In this case, users could not share a frequency, and each user had to coordinate his or her turn on that frequency in order to communicate.
Both FDMA and TDMA posed restrictions for early users, particularly the military. As early as World War II, militaries recognized the high value in using wireless technology to communicate across vast distances. Military communication units did not always have the time to wait their turn to transmit sound, or to find the right frequency.
Some telecommunication systems allowed military communication units to transmit sound into the same spectrum their adversaries used. Military signals needed a unique identification through a distinct code to avoid interference from enemy communication. The receiver of that message on the other end could then retrieve the message based on its unique code in the spectrum.
Just as the radio moved from military use to commercial use, so too was the case with the wireless technology. CDMA became the early choice for personal communication because it could allow multiple users to communicate within the spectrum, avoiding interference or blocking among users. In 1999, CDMA became the standard technology for the telecommunications industry for its growing wireless systems. Since there are large numbers of users in the system communicating at the same time, code division ensures that each user’s signal remains separate in the spectrum.
