CDMA within the European Union, and we’re not talking about the wideband variety? That should give those protectionist senators in the US something to think about. Ian Poole of Racal Instrument Wireless Solutions provides a timely history lesson on CDMA.
Within Europe, GSM and its derivatives have an almost compete monopoly as far as mobile phone systems are concerned — or are at least this is the common belief. However cdmaOne (IS-95) and CDMA2000 are being introduced in a number of European countries including Russia, Romania, Poland, Belarus, Moldova and the Ukraine. This makes CDMA a standard that is being used within Europe, and if Poland’s application for membership succeeds then it will be within the EU itself.
GSM has, by far and away, the greatest use within Europe and also world wide — with a subscriber base set to hit one billion worldwide at the end of the year, of which nearly 400million are within Europe. This makes it the most successful cellular technology of all time. With GPRS data services being rolled out and EDGE able to give even higher data rates, this technology is the natural choice for most operators.
Again for 3G the natural progression is to wideband CDMA (W-CDMA). It is expected that most operators will follow this route. But with IS-95 and CDMA 2000 already gaining a foothold in Eastern Europe it is useful to see how this system has evolved and what major features it possesses.
The DMA family of standards is used worldwide and the number of subscribers has now reached over 147 million. Although North America and the Asia pacific regions are the main areas of use, it is also used in South America, Eastern Europe and new systems are being deployed in areas such as Africa and the Middle East.
The first of the CDMA family of standards to be introduced was IS-95A. The standard was first published in July 1993 as an interim standard and the first revision was released in May 1995. Initially the frequencies it used were in the 60MHz band, but minor changes were introduced to enable it to use other frequencies. This standard allowed for all the basic services for a cellular system including call registration, handoffs, power control and the like. Circuit switched data at rates up to 14.4kbps is allowed and catered for by many operators.
Unlike previous systems that employed a bandwidth of around 30 kHZ — or in the case of GSM a 200 kHZ bandwidth— CDMA used a much wider 1.25MHz bandwidth per channel. The system was first launched in September 1996 when Hutchison Telephone Company went live with their system. This was soon followed by SK telecom in Korea. Now it is deployed in over 40 countries around the globe including those in Eastern Europe.
The basic IS-95A specification underwent an upgrade to take it to IS-95B. This was introduced to satisfy user demands for higher data rates, primarily in Japan and South Korea. By adding further supplemental code channels into the existing CDMA data channels it is possible to carry packet switched data at much higher speeds. Many operators that have commercialised IS-95B systems offer data rates of 64kbps, in addition to voice services. IS-95B was first deployed in September 1999 in South Korea and has since been adopted by operators in Japan and other countries. Today the IS-95A and IS-95B are collectively marketed under the brand name: cdmaOne.
While cdmaOne had been very successful and was introduced in many countries, there was a growing need for higher data rates. The new 1X system provided for this with data rates up to 144kbps in the first release and it provided for other improvements, such as more efficient spectrum usage and improved battery life, while still retaining the 1.25MHz channel bandwidth. As a result a new standard — IS-2000 — was developed. The systems under its control were given the brand CDMA2000. This envisaged and evolution from cdmaOne through to the full 3G standard in a number of stages. The first of these was known as cdma2000 1X. The release of 1X has occurred in two phases. The first of these is known as Revision0 (Rev 0). The second is release A and this increases the data rate by a factor of two over Rev 0 and it adds some more signalling channels as well as providing a few other minor improvements. Of the two releases Rev 0 is the one that is currently more widely used, with Release A following on behind.
CDMA20001X was claimed as the first 3G network to be launched and it is now deployed in 35 countries with 46 operators in all continents of the world. In addition to this there are over 300 devices available on the market allowing the use of a wide range of facilities from colour displays to cameras and GPS capabilities.
With these advantages the number of subscribers is growing every day. In May 2003 there were over 45 million CDMA subscribers world wide. Within Europe 1X systems are currently deployed in Belarus, Moldova, Romania, Russia and the Ukraine.
The 1X standard was further enhanced by what is sometimes referred to as CDMA20001xEv — a data only service. This provides more of a step change than the previous evolutions because it only provides a high speed packet data service. The mobiles for EV-DP are called access terminals because they can only handle data. If voice services are required then a dual mode phone that can handle voice on 1X must be used. The rationale for this is that data and voice services have very different profiles for demand and bandwidth usage. This means that using a single (RF) channel to share these profiles is inefficient.
1xEV-DO is used in a separate RF channel from 1X (which will provide the voice service) and therefore each channel can be optimised independently. The standard is rather a diversion from the main CDMA evolutionary path and this is the reason why it is defined under standard IS-856. The forward channel forms a dedicated variable-rate, packet data channel with signalling and control time multiplexed into it. The channel itself is time-divided and allocated to each user on a demand and opportunity driven basis. By adopting this format the standard is able to provide data speeds at up to 2.4 Mbps in the forward direction, while offering performance in the reverse direction that is the same as 1X.
The first commercial CDMA2000 1xEV-DO network was deployed by SK Telecom in January 2002. Then, four months later, KT Freetel introduced their service in time for the football World Cup. In the USA, Monet Mobile networks was first to launch their DO network in October 2002. Since then other networks have been rolled out in Japan, Korea, Brazil and Indonesia, with Jamaica and Puerto Rico about to launch.
Data and Voice
The logical next progression for the CDMA standard is to have an integrated data and voice service. The service that provides this is known as CDMA2000 1xEV-DV (Evolution data and voice). Although this has not yet been launched, there are currently manufacturers and operators developing the system ready for deployment.
1xEV-DV is essentially 1X with additional high-speed data channels that provide a theoretical maximum data rate of 3.1 Mbps. The system is defined in CDMA2000 Rel C and it builds on the architecture of CDMA 2000 1X while providing backward compatibility not only to 1X but also IS-95A/B. Migration requires upgrades to the BTS, BSC, PDSN, and the AAA. In this way it provides an attractive proposition to many operators. For the future, Release D of the specifications is under way and this provides a number of upgrades including a higher data rate in the reverse channel. This will enable much faster data transfer for applications, including video conferencing and the sending of colour pictures.
Much of the technology and equipment for Eastern Europe is being bought in from outside. Many of the phones are designed and manufactures in countries in the Far East including China. To ensure that these phones are compatible with the networks, in country conformance testing can be undertaken. This will ensure a successful deployment.
CDMA networks operate well. There is a clear migration path through from cdmaOne/ IS-95 to the full 3G networks such as cdma2000 1xEV-DO or EV-DV. This is a distinct advantage for many operators, and this is one of the reasons why CMDA technology is growing fast. Although it currently does not share the same subscriber base as that enjoyed by GSM, it is nevertheless very widespread and it is a successful 3G technology that has been deployed and is being widely used. For CDMA, there are now over 145 million subscribers worldwide and with the roll out of the new 3G technologies this will grow even further, increasing its market share.