Code Division Multiple Access (CDMA)
by Poovamma Konganda
CDMA is a relatively new mobile communications technology. The great attraction of CDMA technology has been because of the extraordinary increase in the system capacity and the service capacity. CDMA is a spread spectrum technology, which means it spreads the information contained in a particular signal of interest over a much greater bandwidth than the original signal.
CDMA was developed by the Allies to resist jamming of the radio signal by the enemy during World War 2.2 The military has been using the technology for communication for decades.3 The use of CDMA for civilian mobile communication did not take place until 40 years later. In November 1989, Qualcomm, a San Diego based company, first successfully demonstrated to the world the usage of CDMA technology for civilian mobile communication. In December of 1991, Qualcomm presented to CTIA the results of some of the first CDMA field trials. The CTIA board of directors adopted a resolution requesting that TIA, the Telecommunication Industry Association, prepare to accept contributions regarding wideband cellular systems. A committee was formed to develop spread spectrum cellular standards and published the CDMA cellular standard in July 1993.
III. Description of CDMA
The CDMA concept can be compared to a situation encountered in a party. At the "CDMA Party" all people are talking in the same room at the same time similar to the technique used in CDMA. If every person is talking in a different language that you don’t understand then all the conversations would sound like noise to you. But, if you knew one of the languages then you would filter out other conversations and listen to the conversation that is of interest to you. A similar technique is applied in CDMA, where both the parties decide on a language and talk to each other.
CDMA has clearly demonstrated its superiority in the second-generation wireless marketplace. In September, 1998, only three years after the first commercial deployment, there were 16 million subscribers on CDMA systems worldwide.4 Due to the full advantages and strong performance of the CDMA technology, CDMA is being deployed in 35 countries around the world.5 In many developing countries, there is a tremendous demand for new business and residential telephone services. More and more operators are looking to wireless technologies to rapidly provide thousands of new subscribers with high quality telephone service at a reasonable price. CDMA is known for its ability to offer coverage, clarity and capacity advantages over other technologies.6 CDMA is far more better than TDMA and GSM in capacity gains and CDMA2000 will increase the benefit in the next generation by doubling the capacity.7
There are many reasons CDMA technology is the choice of the next generation. CDMA filters out background noise, cross- talk, and interference, so that there is crystal clear voice quality, greater privacy and enhanced call quality.8 CDMA’s spread spectrum signal provides the greatest coverage allowing networks to be built with far fewer cell sites than is possible by the other wireless technologies.9 CDMA typically transmits the lowest power levels, allowing for longer battery life which results in longer talk time and standby time and CDMA handsets can also incorporate smaller batteries, resulting in smaller, lighter-weight phones.10 The future generation will opt for something which is easier to carry and easier to use like the CDMA handsets. Designed with about 4.4 trillion codes, CDMA virtually eliminates cloning and other types of fraud.11 Thus improving Security and Privacy.
The following benefits offered by CDMA account for the growing popularity and makes the CDMA technology very marketable:
CDMA’s growing acceptance within the cellular industry is due primarily to the fact that its benefits are dramatic and wide ranging. This new standard should help ease the transition from the current incompatible standards deployed in the United States and Europe.
The actual beneficiaries of CDMA will be the actual users. CDMA is an enabling digital technology that provides enhanced services with higher quality for all customers. Small service providers stand to gain from the introduction of CDMA through enhanced revenue and reduced costs.12 Revenue is enhanced by CDMA’s superior range and thus resulting in greater customer usage. Along with the small service providers, CDMA’s fold capacity increase will provide much needed relief for large service providers in crowded urban areas.13 With CDMA, current allocation of spectrum further increases the system capacity by up to twice the capacity of the original analog system. Licensed manufactures also benefit from their access to the specialized Application Specific Integrated Circuit (ASIC) chip sets that Qualcomm has developed and tested for CDMA wireless applications.14 Manufactures using these devices will not only realize a significant developmental cost savings but are also assured of full system compatibility.
CDMA One, CDMA technology.
Sound Advice, CDMA – The technical side of the story.
Keith Butterworth, CDMA- focusing on in-building wireless communications systems.
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You can have it all, by Perry. M. Laforge, Executive Director CDMA development group.