Code Division Multiple Access (CDMA)

Techopedia explains Code Division Multiple Access (CDMA)

CDMA technology was initially used in World War II military operations to thwart enemy attempts to access radio communication signals. In the early 1990s, Qualcomm introduced the possibility of using the same concept with publicly-available cellular network technology. During this time, an alternative mobile networking arena digital standard gained traction, proving to be a challenge to CDMA proponents. Despite adamant negativity and discouragement from prominent industry figures, CDMA’s supports successfully convinced these leaders to consider, use and eventually accept the newly introduced CDMA standard. Essentially, CDMA offers more airspace capacity than the time division multiple access (TDMA) based Global System for Mobile Communications (GSM) standard. Furthermore, CDMA also uses less power. Another advantage boasted by CDMA technology is its ability for soft handoffs between base stations, i.e., less likelihood of cut-off calls. The usual analogy given in comparing CDMA with other channel access methods like FDMA or TDMA is that of people each carrying out a conversation with a friend in a crowded room. The room, in this case, represents a channel (a.k.a. carrier frequency). TDMA is likened to the method by which communication is carried out by speaking one at a time (hence the name ‘time division’). FDMA, on the other hand, is likened to the method wherein communication is made by speaking at different pitches (hence, frequency division). Finally, CDMA is likened to people speaking simultaneously but in different languages. Because only those who speak the same language can understand each other, it is possible for multiple conversations to take place in the room at the same time. The basic concept in CDMA is that users who wish to communicate through it are given a shared code. While multiple codes may occupy the same channel, only those users having the same code can communicate with each other. Because CDMA and GSM standards each have unique pros and cons, the preferred technology standard choice is now in the hands of potential subscribers. However, the ultimate choice will depend heavily on the availability of these standards within the localities of subscribers.