 | Issue: | Asia-Pacific IV 2001 |
| Article no.: | 11 | |
| Topic: | UMTS Moves from Paper Promises to Provable Performance | |
| Author: | Valy Lev | |
| Title: | Corporate Vice-President and General Manager, GSM/UMTS Systems Division | |
| Organisation: | Global Telecom Solutions Sector, Motorola, Inc. | |
| PDF size: | 24KB |
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Article abstract
Universal Mobile Telecommunications System (UMTS) evolution has been widely anticipated but has yet to be realised in practice. Dr. Valy Lev, Corporate Vice-President and General Manager GSM/EDGE/UMTS Systems Division, Motorola, Inc., here examines some of the key messages for operators to consider when faced with the very difficult and potentially costly decisions that have to be taken when evaluating and implementing UMTS. Radio access networks or ‘starting with UTRAN’ offers food for thought. Downlink shared channels and intelligent coverage offer additional solutions.
Full Article
While Global System for Mobile (GSM) communications operators in the Asia-Pacific region, and worldwide, are committed to evolving their networks to Universal Mobile Telecommunications System (UMTS), to date they have little real-world experience on which to base their infrastructure investment decisions. UMTS solutions haven’t yet been fully tested let alone broadly deployed, so recent Wideband Code Division Multiple Access (W-CDMA) deployments, only now beginning to demonstrate their potential, have been the only experience to consider. Without fully working networks to examine, operators investing in UMTS technology have had no way to physically compare performance, cost-effectiveness and service efficiency-the factors every smart operator dearly wants to compare before putting cash on the line. After all, no one understands better than the telecommunications industry that early standards are often not complete; early-to-market leads can disintegrate quickly as further upgrades are required to remain competitive-or even to achieve already-promised functionality. At the same time, cautious and forward-thinking UMTS solutions vendors have found themselves disadvantaged in the early phases of infrastructure investment. For a prudent vendor, protecting long-term viability demands protecting the balance sheet, avoiding the temptation to over-promise financing and delivery dates. The value of investing time and money in a high-quality, high-performance solution is hard to prove in the very early stages of market introduction. Mobile operators in the Pacific Rim are the early entrants into UMTS. NTT DoCoMo in Japan has launched its version of first generation UMTS. The Freedom of Mobile Multimedia Access (FOMA) 3G system is in limited deployment, but DoCoMo officials have said they expect to sign up to 150,000 3G subscribers by March 2002, and recently announced a new short video-clip service called i-motion, which will deliver news reports, mini music videos and sports highlights on 3G mobile handsets. Additionally, Hutchison Australia has announced that it plans to be the first operator in Asia to launch a full UMTS system, and in China, China Mobile is forging ahead with UMTS trials to be deployed by several vendors throughout 2002. And in Korea, the UMTS licensing and vendor selection process is under way. Other operators in the region and around the globe are choosing a wait and see approach. They are evaluating the current 2.5G market opportunities and trying to differentiate the 3G hype and an actual business case. Factors that will be critically important for UMTS in the long run tend to emerge much later, such as CDMA optimisation experience in a GSM-centric environment. These factors will nonetheless determine the performance of UMTS solutions and the success of operators in the long run. It is time now that operators began to examine the logic of their decision-making process, considering the facts and experience that early deployments have yielded. Logically, UTRAN is Key Where should the process of building a UMTS infrastructure begin? There’s an excellent case to be made-perhaps an incontrovertible case-that the first choice an operator makes should be the UMTS Terrestrial Radio Access Network (UTRAN). The ability to make and receive quality calls in the areas in which they travel is fundamental to end-users. They weigh this ability before they consider feature sets, options or expanded services. Coverage is critical to acquiring and retaining customers, and it is the key to raising both customer satisfaction and annual revenues per user. To take full advantage of UMTS revenue-generating opportunities, an operator’s UTRAN must deliver services to the end user where they are needed, when they are needed. The radio access network can easily account for as much as 70 per cent of the infrastructure cost of a UMTS network. The success of a UMTS solution, therefore, depends directly on the cost/performance ratio of the UTRAN. In addition, the UTRAN also directly contributes to the quality of calls in peak and off-peak usage periods and the number of dropped or blocked calls over a coverage area. Practical CDMA experience is the key to call management between cells as well-for instance, the way in which calls are handed over to busy cells. ‘Start with the UTRAN’ isn’t a message that has been widely considered in UMTS infrastructure planning to date, probably because many vendors underestimate both the importance and the challenges of frequency/power management in a UMTS network. Companies recognise the importance of deep radio frequency planning and CDMA expertise in UMTS deployment. Our UMTS solution has been honed and refined, as well as lessons already learned and models already tested. CDMA Field Experience Works for Operators The W-CDMA standard is extremely broad. As a result, vendors must make many choices/decisions in development to ensure the network performs as projected when implemented. Without prior CDMA field experience, this will be a significant challenge. Both CDMA and W-CDMA networks require, for example, technical expertise in: neighbour list assignment, cell breathing layout, uplink/downlink limitation, power budget planning, hand-off optimisation/ dropped call rate, radio resource management, and determination of optimal amount of messaging between the mobile station, Node B and RNC, so as not to create significant congestion problems. While choosing the right algorithms in these areas to optimise a vendor’s W-CDMA product offering is the ‘name of the game’, the techniques used are very different from what is used in GSM today. In addition, planning tool development/availability is another critical prerequisite investment-one that can be leveraged into W-CDMA from a CDMA vendor’s prior deployment experience. UMTS Provides Improved Performance As UMTS solutions now begin to roll out in real-world applications, smart operators are watching closely, with a checklist in hand. Does the solution leverage legacy equipment but still accommodate all stages of evolution to the UMTS standard? Does the service provider retain the power to choose when and how much to deploy, based on market and business requirements? Is there a clear, intelligent, cost-effective path from current circuit-switched technology to a packet-based architecture? Ultimately, UMTS will offer many advantages, enabling service providers to deliver a wide range of innovative multimedia services supported by multi-rate transmissions. But long-term advantages are even more alluring when the short-term deployment comes with immediate benefits. As the first UMTS deployments are evaluated, the edge will go to the solution that goes beyond tomorrow’s promises to deliver outstanding performance now. An optimum UMTS solution should deliver the following critical capabilities: · Intelligent reliability provides redundancy without additional hardware. · Open- and closed-loop transmit diversity helps to reduce equipment expenditures by as much as 50 per cent. · Packet prioritisation within the GSN complex. · Daisy chaining reduces the number of transmission links, especially in rural areas. · Six-sector support can reduce the number of sites required by 30 percent. · Downlink Shared Channel (DSCH) dynamically reallocates channel resources to speed data transmission and effectively increase network capacity. · Smooth evolution to High-Speed Downlink Packet Access (HSDPA) designed into base stations increases the capacity in the downlink by about 100% depending upon the service mix. The last two features are now standardised following work items we raised in 3GPP based on our experience in CDMA systems. Bringing Proprietary Performance Benefits to a Standards-Compliant Technology One example of how we bring proprietary performance to a standards-compliant technology is the Downlink Shared Channel (DSCH). DSCH, a feature delivered at launch and fully effective only with handsets that support it, is a significantly more efficient resource allocation system than current GSM technology, enabling faster data transmission, higher maximum transmission speeds, better priority handling and increased capacity. Here’s how it works. A user begins a call, initially allocated a data rate of only 16 Kbps. Spare capacity on the network becomes available. Without DSCH it could take several hundred milliseconds to reconfigure the connection to increase the throughput, by which time the excess capacity would likely be gone. With DSCH, however, the call can be reconfigured almost instantaneously (every 10 milliseconds), enabling the user to take advantage of the excess capacity and complete the call more quickly. The DSCH also increases the maximum transmission speeds that an operator can offer. A user can be allocated the maximum data rate whenever there is spare capacity, because the UTRAN can be rapidly reconfigured to allow other users to use the network as they need it. This ‘rapid reassignment’ has the effect of increasing the network’s utilisation, and therefore its capacity. The DSCH also enables better priority handling. Because the network automatically reallocates resource access every 10 milliseconds, operators can ensure that access is assigned according to the prevailing priority ordering of packets queued in the system. The customer who is paying for priority service can get the first call on the available resource. Intelligent Coverage: A Feature of UTRAN Solutions Our depth of experience in radio frequency engineering and CDMA implementation directly contributed to the development of the intelligent coverage capability. In CDMA networks, RF interference creates an inverse relationship between call range and the number of users per cell-a limitation on capacity that must be effectively managed by the UTRAN. Intelligent coverage is designed to help counteract the effect of ‘cell breathing’ on a CDMA network. Here’s a scenario that demonstrates what happens: a base station is performing well, its three sectors covering a road, some offices and a residential area respectively. Suddenly, there is an accident in heavy traffic on the road. Within seconds, many of the drivers are making calls, some to tell colleagues they will be delayed, others to download maps of alternative driving routes. Traffic on the roadway has come to a screeching halt, while traffic on the base station quickly surges. Unfortunately, as the call load increases on the base station so does the radio interference among the multiple mobile stations. As a result of this high-capacity use, the cell ‘inhales’ power, reducing the effective range of all calls to minimise the interference. So just as coverage is most needed, it deteriorates, compounding the motorists’ frustrations. Calls are dropped. Revenue is lost. Customers accustomed to making high-quality calls in this area are not happy. The intelligent coverage system can help mitigate the problem by dynamically optimising the base station’s resources, focusing power and capacity where they are needed to help maintain coverage, capacity-and thus customer satisfaction. Given the higher data rate applications likely to be associated with UMTS traffic, being able to cope effectively with usage peaks is a key advantage. Conclusion Smart wireless operators and service providers are already beginning to look past promised rosy pictures of how quickly and economically they can put a toe in the water, seeking instead a solutions partner who can offer them outstanding performance, significant cost efficiencies and superior end-user experiences. The new winners will be those vendors whose strategy is based on a long-term commitment to high-performance, high-quality products, backed by CDMA expertise. The information presented herein is to the best of our knowledge true and accurate. No warranty or guarantee expressed or implied is made regarding the capacity, performance or suitability of any product.
