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By Zhu Yu

A series of recent successes in UMTS900 trials represent a milestone for UMTS900, which is well on its way to commercialization, and needless to say, these early successes will have a profound effect on the refarming of 900MHz frequency and the offering of wireless broadband services, and will also serve as a powerful reference for future decision-making by telecom authorities.

The core frequency band of UMTS lies in 2100MHz, but many carriers and equipment vendors around the world are now starting to focus more of their attention on the development and testing of extended frequency bands that lie outside the core band, and a few commercial networks have already begun to use UMTS extended frequency bands. Prior to 2006, frequency bands that had been used in the industry included: 850/1700/1800/1900/2100MHz. However, since the beginning of 2006, more and more news pertaining to the development and testing of 900MHz has attracted a lot of attention, thereby, drawing more emphasis on the use of 900MHz in the UMTS system.


SFR's successful demonstration

Based in Paris, SFR constitutes the second largest mobile communication carrier in France, with 17.3 million subscribers and over 8000 employees. The primary investors in SFR represent two of the most powerful media and telecom giants: Vivendi Universal and Vodafone, who hold a 56% and 44% stake in SFR, respectively.

In 2001, SFR purchased a UMTS license from the French government. In 2004, UMTS officially started its operation in France. In 2006, upon reviewing the control of the 3G license of SFR, French authorities found that SFR's 3G network coverage was not up to the standard specified, and thus, required SFR to implement an enhancement program. At that time, SFR came up with the idea of applying its existing GSM900MHz in the UMTS system.

At about the same time, Huawei had established itself as a major equipment supplier for many well-known carriers such as Vodafone, Telefonica, France Telecom, and Deutsche Telekom in Europe. After several meetings and in-depth discussions, an understanding was finally reached, and SFR formally sent Huawei a test request for UMTS900. Starting in July of 2006, Huawei dispatched engineers to SFR to help them with the construction of their UMTS900 pilot offices.

Huawei's engineers started construction work immediately after arriving in France, and negotiated with SFR to deploy two additional UMTS900 stations in Noirmour and Bordeaux, France. Previously, GSM and 3G devices had already been deployed by other suppliers in these two cities, so Huawei's UMTS900 stations leveraged the existing GSM resources so that they could share stations, the antenna feeder and transmission with GSM stations from other vendors, which greatly helped to reduce construction costs and the amount of installation that was required, and at the same time an IOT (Interoperability test) was conducted on the existing 3G core network equipment supplied by other vendors.

The project was successfully implemented. Shortly thereafter, in October 2006, Huawei engineers made the first lab call for UMTS900, and successfully demonstrated various services in connection to the operability of UMTS900 at the SFR site in November, successfully implementing ordinary calls, videophone and various data services on the UMTS900 network, especially UMTS900's HSDPA 3.6Mbps high speed downloading service.

The news about these successful pilots quickly spread and aroused great interest and response from other people in the industry in France. Top management people from SFR and staff from the French government gathered at SFR's UMTS900 pilot office and tried out the UMTS900 service at the site.

"Testing of the UMTS900 pilot network proved that it was a totally viable service and that it could coexist with the GSM900 network, thus, providing adequate evidence for refarming of the 900MHz frequency. This successful test also indicates that Huawei's UMTS900 solution is fully capable of meeting our needs for commercial construction." a top member of SFR's management team recently stated.


Advantanges of 900MHz frequency band

The 900MHz frequency band is primarily being used for GSM services, although, while it is currently being used to bear GSM services, it is also being considered for UMTS service bearing by carriers and vendors for the following reasons.

The need for reducing costs. Normally, the higher the frequency band, the smaller the coverage, therefore, the coverage of 900MHz is greater than that of 2100MHz. In fact, there is actual test data that backs this up. For service coverage in the same area such as, CS64K service, UMTS2100M is used, with 224 stations; while for UMTS900, 90 stations are used. In this case, stations used in 900MHz represent only 40% of those used for 2100MHz, hence, saving 60% in terms of station resources. As for PS service, it also uses far fewer stations and costs less for 900MHz than for 2100MHz. Moreover, according to a recent estimate made by Australian Optus after construction of its UMTS900 pilot network, it will cost approximately USD 8 million to build a UMTS network, using 2100MHz, in three years, but it will only cost about USD 5 million to construction a 900MHz, thus, saving approximately 37% in terms of CAPEX.

The need for network expansion. Some networks have used 2100MHz as a reference frequency, but with the continuous increase of network subscribers and a switch in consumption practice to data services, this type of frequency is unable to meet the needs for capacity expansion. Under such circumstances, the problem of inadequate capacity can be solved by introducing a new frequency band such as 900MHz, which is able to share part of the capacity.

Individual carriers are not licensed with 2100MHz frequency, but own idle resources in 900MHz. Such carriers have not obtained the 2100MHz frequency band from the appropriate authorities, who are in charge of allocating frequency bands in different countries, due to historical reasons, or other reasons, so instead, they have turned to using the GSM900 frequency which they already own when preparing to build UMTS networks.


Key problems concerned with UMTS900

During the construction of UMTS900 networks, carriers may encounter a few problems that are listed as below, along with solutions that are specifically tailored for such problems.

• Mutual effect on networks
  
  The places where UMTS900 is being deployed are currently covered by UMTS2100 and GSM900 networks. The introduction of UMTS900 will occupy part of the existing GSM900 frequency, which will lead to a degradation of the call quality of GSM subscribers and also cause an increase of call drops if no reasonable frequency allocation is made. Furthermore, the existing GSM network will cause a decline of network KPI on the newly introduced UMTS900 network.
  
  In consideration of this problem, Huawei has conducted in-depth technological analysis on the same-frequency networking of UMTS900 and GSM900 in its UMTS900 solution, and has designed an advanced frequency refarming solution, with optimization of the performance of UMTS stations.
  
  This solution offers two benefits: first, the frequency intervals between two adjacent UMTS and GSM carriers can be smaller than what is required in the protocol, thus, significantly increasing the utilization of frequency; and second, UMTS stations are enhanced against interference from GSM near ends, hence, avoiding a decline of network KPI, which is caused to a great extent by the introduction of UMTS900 and interference from GSM and UMTS.
  
  Moreover, Huawei's UMTS900 is capable of completely reusing the existing GSM900 infrastructure so that it is able to share stations, the antenna feeder and transmission. This not only saves in terms of network construction costs and the speed of deployment of the network, but also saves in regards to the rental expenses of iron towers in certain regions, like Australia.
  
  In December 2006, Huawei successfully completed the phase 1 test of its UMTS900 in Australia. In matter of only three months, Huawei had constructed its UMTS900 pilot network and made its first UMTS900 phone call in Australia and in the southern hemisphere as a whole. In such a network, the above-mentioned technologies have been successfully verified. Moreover, the network quality of carriers is guaranteed, and a great amount of costs are also saved.
  
  
• Interoperability between UMTS900 and existing network
  
  So far, interoperability between UMTS2100 and GSM900 has been achieved, which allows subscribers to roam and switch over and choose between many services which are offered on both networks. After the introduction of UMTS900, problems will arise, which, if not handled properly, will surely affect the use of the UMTS900 network by subscribers.
  
  For such problems, standards have been formulated in both Europe and Asia to ensure interoperability between networks. In addition, Huawei has carried out interoperation and interworking between the core networks and station equipment on both 2G and 3G commercial networks in the pilot networks, for multiple vendors in Europe.
  
  In February 2007, Huawei worked together with Telefonica to successfully complete calls on its UMTS900 commercial network by interoperation, and was able to deliver UMTS900-based HSDPA 3.6Mbps service.
  
  The test results show that the UMTS900 network interworks perfectly with Telefonica's commercialized UMTS/GSM networks, and in particular, the services running on both UMTS900 and GSM900 proved to be both stable and reliable, without any noticeable interference, and subscribers were able to easily switch over between the two networks.
  
  
• Interoperability between UMTS900 and terminals
  
  The interoperation between UMTS900 and the terminals is another issue that must be solved prior to commercialization. At the end of 2006, Huawei successfully completed an IOT between the UMTS900 system and UMTS900 terminals in Shanghai. Huawei subsequently was able to deliver perfect matching with Qualcomm's UMTS900 terminal and the Option's UMTS900 data card in the pilot demonstration which was conducted in Europe, hence, laying a solid foundation for interoperation between UMTS900 and the proper terminals.
  
  
• Deployment of UMTS900
  
  After solving the problems arising from UMTS900 technologies, the next step would be deployment, which needs to be addressed by carriers. In this regard, Huawei suggests that the UMTS900 can be deployed in the following three areas:
  
  1. Rural areas. It will require a lot of stations using the limited coverage of the 2100MHz system, due to the broad scope in rural areas. Therefore, Huawei suggests that 2100MHz should be used in more central areas and the 900MHz system, with wider coverage, should be applied in more remote areas. Currently, Huawei is building a UMTS900 network for Australian Optus, with the aim of solving the coverage problem in local wide areas that have a sparse population.
  
  2. Indoor area in cities. Indoor coverage has always been the key, as well as difficult point in 3G coverage. Hence, using 900MHz frequency can greatly enhance coverage in indoor areas. In such a situation, the cell reselection and handover of the 900MHz and 2100MHz systems should be taken into consideration, for which Huawei has its own solution. 
  
  3. Areas to be expanded. In areas deployed by 2100MHz, demands for capacity are constantly increasing with the rise in number of subscribers, along with the switch to data services. Hence, the introduction of 900MHz tends to ease the bottleneck that has been created in terms of capacity.
  
  With a powerful network planning team, along with an abundance of rich experiences in UMTS900 planning, Huawei is able to deploy UMTS900 quickly, with a high degree of quality.
  
  
• Policies
  
  UMTS900 is a relatively new technology in the industry, and therefore, a lot of governments are still in the middle of establishing pertinent policies regarding UMTS900. However, a series of recent successes in UMTS900 trials represent an important step for UMTS900 on its way to commercialization, and this will no doubt have a profound effect on the redistribution of 900MHz frequency and the offering of wireless broadband services, and it will also serve as a powerful reference for future decision-making by telecom authorities.
  
  In addition to the solutions mentioned above, Huawei's macro stations and distributed stations are all able to support UMTS900. Macro stations support both the UMTS900 and UMTS2100 sharing cabinet (i.e. wireless unit sharing cabinet), with the base band unit fully shared, which can significantly increase the utilization of base band resources. Moreover, the flexible, small-size and easy-to-install distributed stations are equally able to support UMTS900.

The continuous fast development of UMTS900 signifies the basis for UMTS900 application, which has substantially matured, and thus, opens the door a little further in terms of the viability of commercial application.

Just like GSM900 drives the development of GSM1800, hence, UMTS900 has similarly become the driving force behind the UMTS frequency bands, continuously promoting the development of UMTS.

Huawei's UMTS900 solution has now been tested in various situations, and will continue to be tested onsite in multiple networks of Vodafone and French Orange, and is expected to be formally commercialized in the second half of 2007. With the success of HSDPA on UMTS900, Huawei has become the first supplier to provide an HSPA solution which supports 850 /900 /1700 /1800 /1900 /2100MHz and also supports a multi-frequency sharing cabinet. Huawei is now making a substantial amount of progress on its way to providing innovative products and solutions for all its customers.