3G Technology

Finally, there’s the ultimate goal of third generation (3G) services, whose principal objectives are the provision of greater user capacity, higher data rates and – hopefully – worldwide compatibility.

The promise of new radio spectrum is a major reason why the world’s telecomms operators have paid such high prices for 3G licences. While existing cellular systems operate either on the very crowded 800MHz and 900MHz wavebands or at the less crowded 1800MHz and 1900MHz wavebands, many 3G systems will operate at 2GHz, the IMT-2000 core band. This waveband is being cleared of existing traffic, promising 3G licensees plenty of scope for future expansion, especially (they hope) in the area of the new value-added data services.

Europe has settled on the Universal Mobile Telephone System (UMTS), with WCDMA as the chosen 3G protocol. CDMA is generally accepted within the industry as a superior air interface technology, compared with that used in GSM/TDMA. However, what makes GSM popular is its international roaming feature. Advocates of CDMA deny that this is an important sales driver and at the same time argue that future CDMA will include roaming capabilities!

European licensees are not, however, expecting services to be available until 2004. Using packet-switching, UMTS will deliver up to 384 Kbit/s to high-mobility users (those in cars or trains), and as much as 2 Mbit/s to low-mobility users wandering around in offices or in urban areas. These super high-capacity services won’t be deployed everywhere. UTMS, for example, will only be deployed in areas of high demand, such as city centres. Outside of these areas, mobile users will seamlessly be catered for by existing 2.5 Generation infrastructure.

Japan has been at the forefront of the research, development and deployment of trial technology for 3G systems and has also focussed on WCDMA as the multiple access technology. It has also played an important role in helping forge a single global standard, having initiated a process of co-operation and harmonisation of WCDMA with ETSI’s UTRA proposal.

The phenomenal uptake of digital mobile telephony in Japan (over 40 million subscribers by mid-2000) created a situation in which 3G was seen as a way to solve network capacity problems, as well as providing opportunities for new services through enhanced data rates. Unlike in those parts of the world in which GSM is the foundation of present 2G systems, the Japanese PDC system has no scheduled enhancements for bridging the gap to 3G. For these reasons, Japan is expected to be the first country to introduce 3G technology, with widespread implementation expected by 2002. There, the Association of Radio Industry Businesses (ARIB) performs an equivalent function to that performed by UMTS in Europe.

In North America, as in Europe, the provision of an evolutionary path from 2G legacy networks is an important issue in order for existing operators to protect their infrastructure and spectrum investments. However, with no common 2G standard and no national network operators, the situation is even more complicated. There, three competing 2G systems are widely deployed, and each has its own transition path to 3G. IS-136 is a TDMA-based standard and IS-95 a CDMA-based standard – both deployed in the cellular and PCS bands – and PCS1900 is a GSM derivative, deployed in the PCS band only. The networks that use the IS-95 standard – referred to as cdmaOne networks – will upgrade to cdma2000, a similar standard to WCDMA.

Under WCDMA protocols, each conversation or data transfer is split into separate packets that are transmitted together, as on a computer network. The packets contain an identifying code, allowing reassembly at the network’s receiving end. The main problem with CDMA is that, as more users communicate concurrently with the base station, they compete for finite power at the transmitter. This reduces the range of the cell, a phenomenon known as cell breathing. WCDMA and cdma2000 have been designed to manage this process. They also make more efficient use of the available spectrum because all base stations can use the same frequency. The coding identifies the conversation and eliminates interference from adjoining base stations.

In Europe, the UTMS implementation of WCDMA will operate in two modes, each using 5MHz carriers. The first mode uses paired bands, one for the uplink and the other for the down. It chops up its 5MHz carrier pairs using frequency duplex division (FDD). The second mode chops an unpaired 5MHz carrier into time slots to carry both uplink and downlink data, using time duplex division (TDD).

The Operators Harmonisation Group (OHG) is an independent, operator-driven organisation representing a significant percentage of the worldwide wireless industry and committed to the promotion the rapid development and commercialisation of globally-harmonised IMT-2000 wireless systems and operations. Its efforts have played a significant role in the unification of the various ITU IMT-2000 3G CDMA proposals. The resulting Global Third Generation (G3G) will ensure inter-operability and inter-working between 3G systems worldwide.

As the expected launch of their 3G networks in late-2002 approached, the problems facing UK network operators showed little sign of abating. As well as facing mounting stakeholder pressure to deliver a return on the estimated £40bn spent on 3G licenses in the spring of 2000 and the subsequent development of network infrastructure, concerns remained both about the technical hurdles that were yet to be negotiated and consumers’ continued lukewarm response to the technology.

Handset makers admitted that the task of integrating receivers for both 2.5G and 3G networks onto a single piece of silicon had proved to be more difficult than first anticipated, with the result that phones were likely to be bigger and more expensive than hoped. Furthermore, it was accepted that users would experience dropped calls as they moved away from areas covered by 3G masts, requiring that they log back in before then having to tolerate a slower 2.5G connection.

Research also indicated that consumers harboured a number of concerns about the technology, including:

  • the security of 3G services, including fears that sensitive information could go astray and that costly mistakes could be made in performing phone-based transactions
  • the increased risk of mobile phone muggings
  • worries about receiving large volumes of junk mail via their phones.

As if all that wasn’t enough were the fears that consumers’ sentiment was unlikely to change until the long-sought killer application for 3G was identified and that the success of Wi-Fi made it an increasingly credible alternative delivery technology for the type of services 3G had been designed for!