Code Division Multiple Access (CDMA) is an industry specification or method used to access wireless communication channels. The technology is patented and owned by Qualcomm, a telecommunications equipment company. As the name suggests, every CDMA-based communication is assigned a unique code so that it’s separated from other communication on the same spectrum. Unlike Global System for Mobile communication (GSM), CDMA-based phones do not have Subscriber Identity Module (SIM) cards – every phone is specifically built for the particular carrier’s network. In other words, specific carrier information is assigned to the particular mobile device’s software itself and not any SIM card. CDMA later introduced a SIM card equivalent called Removable User Identity Module (R-UIM) so that users could change their handsets and keep the same phone number without switching carriers.
CdmaOne is the 2G standard based on CDMA. CDMA is used as base for CDMA2000 and WCDMA (3G mobile standards). CDMA is only the method, like Time Division Multiple Access (TDMA), to access the channel used by several radio communication technologies. GSM is a 2G standard that’s based on TDMA. CDMA and GSM’s primary objectives are the same, but they take different routes to achieve the goal.
CDMA technology has its beginnings in the 1940s when it was used during military operations by the Allies of World War II, as the transmission data were encoded and difficult to decipher or jam. Some decades later, in the 1980s, Qualcomm considered and started working on CDMA as a cellular telecommunications base. Qualcomm saw support from American network operators, Ameritech and Nynex, for developing an experimental CDMA system. The team was later joined by AT&T and Motorola to help speed up the developments.
A set of CDMA network equipment were first ordered in September 1992. In 1993, South Korea adopted CDMA as national-level cellular telephone system. In July 1993, CDMA was recognized as a cellular technology standard by the U.S. Telecommunications Industry Association, which helped CDMA proliferate globally. The first set of commercial CDMA handsets were shipped in December 1995. The same month saw the first commercial CDMA service launch courtesy Hutchinson Telecom (Hong Kong). The first CDMA smartphone was launched in September 1998, which was based on the Palm operating system.
CDMA is referred to as “spread spectrum”, which means it can accommodate much more traffic within a given radio spectrum. In other words, CDMA excels over competing technologies with regard to making maximum use of the bandwidth available and decongesting cellular traffic. Also, CDMA is much more efficient at handing off calls between towers than GSM. This means CDMA phone calls tend to have better clarity, are less likely to drop, and the overall capacity for data communications is also greater. CDMA technology is more secure as there’s inbuilt encryption in CDMA. This means the voice data stays filtered and protected and only people who are a part of the phone conversation get the data.
CDMA standard is handset-based, which means the customer information is not stored on a SIM card but on the device itself. CDMA phone users cannot change phones or switch networks without the permission of the carrier. Buying a new device is the only option if one wants to move over to GSM or another CDMA carrier. For instance, a phone on Verizon’s CDMA network cannot switch to benefit from Sprint’s CDMA offerings despite both using the same wireless communication technology. Though CDMA later came up with R-UIM, it still didn’t turn the tables for CDMA, especially outside the United States.
Since CDMA is not as popular as GSM, and CDMA carriers are under no obligation to accept any or every phone onto their networks, there are limited mobile handset choices for CDMA users. Generally, a phone would either support CDMA or GSM, and not work on both since each have their bands and compatibility specifications.
Making calls and transmitting data simultaneously is not possible with CDMA. In other words, if a voice call has to be made, 3G network would be cut off. Such simultaneous operation is possible on 3G GSM. Also, international roaming is a major concern with CDMA as there aren’t many global networks supporting CDMA. GSM covers more countries across the world.
As aforementioned, CDMA is not as widespread as GSM. It’s found generally in Russia and the United States, and also some African and Asian countries. In the United States, mobile phone network providers such as Sprint and Verizon use CDMA technology.
CDMA not being as popular as GSM has got nothing to do with the core technology used. GSM is more widespread because it was the first to arrive. Moreover, when CDMA technology happened, GSM was already a major wireless communication standard in Europe. Also, GSM is backed by an industry consortium, whereas CDMA is being pushed by a private chip-maker. All these aspects have contributed to CDMA not being the gold standard or being on the same plane as GSM in the world of cellular technology.