Migration from 2G to 3G - Options:
Evolution of Mobile Technologies: The Migration Path
This is a brief overview of what has been already done and possible expected migration path of mobile operators.
At the 2G phase, there were three major dominant systems in market:
a) GSM operating in 900, 1800 and 1900MHz band,
b) TDMA operating in 800MHz, 1900MHz and 850MHz (North America), and
c) CDMA (IS-95) operating in 1900 and 800MHz band.
2G systems offered enhanced voice services and improved capacity to its customers.
With the growing demand in mobile services and the need to connect corporate networks for data communications, an intermediate generation (2.5G) of technologies were developed: GPRS and EDGE (both in the GSM family), and cdma2000 1X-RTT. While migrating from 2G to 2.5G, operators made decisions based on their future planning and business interests targeting third generation (3G) networks.
From 2G to 2.5G, GSM operators migrated to GPRS and EDGE systems with some of the TDMA operators also migrating to GSM/GPRS systems (see figure 1). Among them * Vodafone is the largest player with a global foot print in offering GSM/GPRS ser-vices. * Prominent TDMA operators in the United States include AT&T Wireless and Cingular Wireless. * Another major operator includes T-Mobile-USA, offering GSM/GPRS services. * In India, Bharti Cellular (AirTel), IDEA Cellular, Hutchison are some of the GPRS operators whose GPRS networks are in commercial and other GSM operators have announced their support for the same (see figure 2).
On the other hand, CDMA operators migrated to cdma2000 1X-RTT (see figure 1).
Some of the major CDMA operators include Verizon Wireless, Sprint PCS in North America, and SK Telecom (South Korea). Migrating from 2G to 2.5G, no new spectrum was required: in the case of an existing spectrum, and overlay approach was used.
This stage of migration did not require major capital investment, exception being migrating from GSM/GPRS to GSM/GPRS/EDGE (see figure 2). As of May 2005, 51 networks are offering EDGE enabled services in 36 countries and many more are in deployment phase. * In North America, Cingular Wireless launched EDGE services in the US Virgin Islands and * T-Mobile USA is in the deployment phase and plans to launch in 2005. * In India, Bharti AirTel, IDEA Cellular, and Hutchison Max Telecom launched EDGE services in 2004.
Many researchers consider EDGE as a 2.75G technology, as it offers higher data rates in comparison to 2.5G technologies. On the other hand, upgrade to EDGE required changes in both hardware and software. * The highlights of the migration from 2G to 2.5G were packet switched data and improved data rates (from 14.4Kbps to 160Kbps (GPRS), to 473.6Kbps (EDGE)). * Intermediate 2.5G systems were seen as a platform for providing data services and as an initial step towards offering enhanced wireless data services.
In the 3G wireless market, two dominant technologies emerged: * WCDMA, as the default evaluation of GSM operators and * The cdma2000 evolution for CDMA operators.
3G technologies adhere to requirements of ITU to be labeled as 3G mobile technologies. Under ideal circumstances, GSM operators would migrate to WCDMA and CDMA operators would migrate to cdma2000 systems (see figure 1). * NTT DoCoMo, Japan and Vodafone, Japan were the first to deploy WCDMA systems in 2001 (see fig. 2). * 38 operators were offering UMTS/WCDMA services in a total of 23 countries in Asia, Europe, and the Arab states as of April 2004. * As of June 2005, 126 operators have launched 123 cdma2000 1X and 22 1xEV-DO commercial networks across Asia, Europe and the Americas (see figure 2). * 20 1X and 20 1xEV-DO networks are scheduled to be deployed in 2005. * In North America, Verizon Wireless offers Wireless Internet Broadband access based on cdma2000 1xEV-DO in more than 30 markets nationwide at a monthly rate of $79.99 for unlimited access.
An operator that migrates from 2.5G to 3G faces several critical issues e.g., * new spectrum requirements, * capital investment, * backward compatibility of handhelds, * new handhelds, and * Applications to be offered, etc.
For example, a GSM operator migrating to WCDMA would require new spectrum allocation and new cell phones that makes the migration a capital intensive project. A CDMA operator on the other hand, can build on the existing spectrum “spectrum re-farming” (see figure 1).

Figure 1

Figure 2

Operators in Europe and Scandinavian countries using analogue Nordic Mobile Telephone (NMT) system in 450MHz band did not have a defined evolutionary path. The “Digital Interest Group” (DiG) working group formed by NMT association, formed in 1998, finalized use of cdma2000 system at 450MHz as a replacement for NMT450 systems (see figure 2). An important feature of cdma450 system is that it offers larger coverage area because it operates in a lower frequency band. It requires small chunk of spectrum (1.25MHz) for operation. Furthermore, cdma450 systems require fewer cell sites as compared to systems operating at higher frequency band e.g. UMTS , and a clear evolutionary path to future CDMA systems. * Airvana, Ericsson, Lucent Technologies, Nortel Networks, and Qualcomm are some of the major equipment vendors offering solutions to operators worldwide. As of May 2005, more than 20 commercial networks are offering cdma2000 at 450MHz (cdma450) services across Western Europe, Asia, Latin America, and Africa.
Most wireless mobile service providers adopt a migration path based on their existing technological infrastructure, upgrading to either cdma2000 or UMTS.
BSNL Ltd is one of the few operators around the world who have both the IS-95 (CDMA) and GSM based technology in their portfolio of cellular services. The company has the option to either migrate towards UMTS or cdma2000 (see figure 6). Studying the migration process for BSNL’s two alternatives, we tackle the problem from the perspective of the service provider, the equipment provider and the users, considering the business opportunities for the companies
The Migration Options
In this section we compare the migration process involved in:
a) GSM to UMTS (3G) vs.
b) IS-95A/B to cdma2000 (3G), highlighting the critical points. Migrating from 2G to 3G, we concentrate on three pillars: * New spectrum – * Additional cell sites – * Data Capabilities.
Option A: GSM to UMTS/WCDMA
The migration process from GSM (2G) to UMTS (3G) is not as easy as it seems. It differs depending on the type of operator and the phase of the evolution processes operators are currently in.
Second generation GSM systems introduced digital systems into the market. The systems offered good quality voice services, compared to the analog counterparts, better mobility, and limited data capabilities, i.e., SMS. However, there were serious limitations in the 2G systems, e.g., lack of packet data services, low bandwidth (14.4Kbps), no multimedia services, etc. Improvements to 2G systems were introduction via HSCSD (High Speed Circuit Switched Data), GPRS and EDGE technologies. The improvements were geared towards improved packet data services, more bandwidth, higher data rates, and capacity towards internet services provision (see table 8).
Table 8
Option B: IS 95A/B to cdma2000
The migration step from IS-95A/B to cdma2000 is a not as complex as the case of GSM based systems. A logical migration step would be: from IS-95A (2G) systems to IS-95B (optional) to cdma2000 1x-RTT (3G). The cdma2000 systems can be deployed in the same spectrum as IS-95A and IS-95B. Therefore, no new spectrum is required; unlike the UMTS case (Option A), where new spectrum is required to make the 3G deployment feasible. No new cell sites are required either. Third generation cdma2000 systems can be deployed in lower frequencies capturing the advantage of higher coverage area. In addition, third generation cdma2000 systems offer higher voice capacity and higher data rates.
The next step in the migration process to cdma2000 1xEV-DO, includes evolution of data only. Theoretically, users can achieve peak data rates in the range of 2.4Mbps (data only). It also supports simultaneous voice calls, while in a data call. This evolutionary system can be used to provide data services only; the operator can offer IP based services, support for mobile IP applications, and complete packet switched data services. Therefore, the operator can reap the advantage of lower infrastructure cost for data only solutions. This is an interesting application for an operator to become a regional or national Wireless Internet Service Provider (WISP) (see table 9).