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CDMA2000 technology tutorial
- a guide or summary of the evolution of CDMA2000 technology from cdmaOne through CDMA2000 1X to CDMA2000 1xEV-DO and CDMA2000 1xEV-DV, UMB and beyond
This 3GPP / CDMA2000 tutorial tutorial is split into several pages each of which addresses different aspects of the CDMA2000 system from cdmaOne through CDMA2000 1X to CDMA2000 1x EV-DO and UMB:
[1] CDMA2000 technology overview[2] IS 95 cdmaOne
[3] CDMA2000 1x EV-DO
[4] UMB Ultra-Mobile Broadband
One of the major cell / mobile phone or cellular telecommunications technologies today is the cdmaOne / CDMA2000 system. One of its strengths is that it has focussed on being an evolutionary technology moving from standards such as IS-95 (IS-95A and IS-95B) for cdmaOne through to standards including IS-2000 and IS-856 for CDMA2000 1X, 1xEv, 1xEV-DO and 1xEV-DV. Currently the standard uses one standard channel under a system known as 1X RTT, although for the future three channels (3X RTT) may be used).
In view of the fact that the CDMA2000 system has been designed to be an evolutionary standard, it is relatively easy to introduce upgrades to the system. This has made it particularly popular with operators because the cost of upgrading to the new standards is much less, and they can have users with a variety of types of phone on the same network. Thus users may operate cdmaOne phones on the same network as CDMA2000 1X or CDMA2000 1xEV-DV phones.
The story of how the system was developed is particularly interesting, and it reveals much about the nature of the system as well as telling its significant successes.
In the beginning .....
The idea for using the form of modulation known as direct sequence spread spectrum (DSSS) for a multiple access system for mobile telecommunications came from a California based company called Qualcomm in the 1980s. Previously DSSS had been mainly used for military or covert communications systems as the transmissions were hard to detect, jam and eavesdrop.
The system involved multiplying the required data with another data stream with a much higher data rate. Known as a spreading code, this widened the bandwidth required for the transmission, spreading it over a wide frequency band. Only when the original spreading code was used in the reconstruction of the data, would the original information be reconstituted. It was reasoned that by having different spreading codes, a multiple access system could be created for use in a mobile phone system.
In order to prove that the new system was viable a consortium was set up and Qualcomm was joined by US network operators Nynex and Ameritech to develop the first experimental code division multiple access (CDMA) system. Later the team was expanded as Motorola and AT&T (now Lucent) joined to bring their resources to speed development. As a result the new standard was published as IS-95A in 1995 under the auspices of the Cellular Telecommunications Industry Association (CTIA) and the Telecommunications Industry Association (TIA). As part of the development of CDMA an organisation called the CDMA Development Group (CDG) was formed from the founding network and manufacturers. Its purpose is to promote CDMA and evolve the technology and standards, although today most of the standards work is carried out by 3GPP2.
It then took a further three years before Hutchison Telecom became the first organisation to launch a system. It is now widely deployed in North America, and the Asia Pacific region, but there are also networks in South America, Africa, and the Middle East as well as some in Eastern Europe.
System Basics
The CDMA system was totally unlike any system used before. In the UK the original TACS system had used a channel spacing of 25 kHz and AMPS in the US had used 30 kHz. The new GSM system used 200 kHz channels whilst the US -TDMA standard kept compatibility with AMPS and was based around 30 kHz channels. CDMA, IS-95A, used a 1.25 MHz bandwidth and this was much wider than anything that had been used before. CDMA operates well with a wide bandwidth, but it was limited to 1.25MHz to remain compatible with the spectrum allocations that were available.