Monday, 20 June 2011

What Is CDMA?

What Is CDMA?


If you want to understand digital communication, wireless technology and multiplexing you need to get a handle on CDMA or Code Division Multiple Access. The major difference between traditional communication systems and CDMA is that CDMA employs spread-spectrum multiplexing (various frequencies) to send audio signals.

Interference is significantly reduced with this technology. Requiring a specific code to transmit and receive further enhances signal integrity. CDMA was the popular option for personal communications because a number of users could communicate in the same signal spectrum without interference. This has now become the standard for wireless telecommunications. CDMA competes with Global System for Mobile communication or GSM, the standard for a large portion of the world.


Full understanding of CDMA and its uses is only possible if we also know about Frequency Division Multiple Access or FDMA and Time Division Multiple Access or TDMA. A close look at the full titles shows that separation is achieved in a different way with each process. FDMA divided or separated users only by frequency. It was necessary to carefully select a frequency to take noise and adjoining frequencies out of the audio.

With TDMA, users had to literally take turns using a particular frequency. The separation was provided by using the frequency at different times. Both TDMA and FDMA were in common use in the past but they have now been pressed aside by CDMA. One of the problems for business and military communications was the requirement to take turns – not always a possibility in certain situations. Nor was it possible to devote a lot of time to finding just the right frequency.

Code division protected the integrity of military communications, for example. The receiving station could get the message because of the unique code within the spectrum. Because of the spread-spectrum factor, multiple users could communicate on the same channel, essentially sharing the air. One of the things that make CDMA so “usable” for the mobile Internet is the separation of data through intrinsic codes. This has established CDMA as the standard in the mobile world.

As mentioned earlier, CDMA competes with GSM as a communications standard because GSM is the world standard outside of the United States and Canada. It is a fact that GSM has the lead in global communications coverage. In addition, this technology seems to be the method of contact in the rural United States.

Those who want to know a bit more about the details of coding that allow multiple users should look into digital sequencing that is provided at random for individual conversations. CDMA was first used during World War II and has become the standard half a century later. There have been some patent issues involved with CDMA but most of those have been resolved in recent years. A company called Qualcomm was at the forefront of these issues. The technology provides outstanding audio quality during calls while making relatively low demands on batteries. In addition, CDMA requires fewer cell sites than TDMA and GSM.

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