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Enabling UMTS 900 Mobile Broadband
Services with Ditech Networks


October 2007
Enabling UMTS 900 Mobile Broadband Services with Ditech




      Contents


                       Introduction.............
Enabling UMTS 900 Mobile Broadband Services with Ditech


Introduction
        This	paper	provides	a	background	to	the	ben...
Enabling UMTS 900 Mobile Broadband Services with Ditech

                Recent UMTS 900 Developments

                The...
Enabling UMTS 900 Mobile Broadband Services with Ditech




                 																								Figure	3::	Strategies...
Enabling UMTS 900 Mobile Broadband Services with Ditech


               GSM-HR and AMR-HR

               The	use	half-ra...
Enabling UMTS 900 Mobile Broadband Services with Ditech


                  	

 The Ditech Solution for UMTS 900
         ...
Enabling UMTS 900 Mobile Broadband Services with Ditech



                Results from VQA Deployment in GSM Network

   ...
Enabling UMTS 900 Mobile Broadband Services with Ditech



                                                       Estimate...
Enabling UMTS 900 Mobile Broadband Services with Ditech


                 Each	of	the	above	solutions	has	its	own	set	of	...
Enabling UMTS 900 Mobile Broadband Services with Ditech




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Enabling UMTS 900 Mobile Broadband Services with Ditech Networks

  1. 1. | WHITE PAPER | Enabling UMTS 900 Mobile Broadband Services with Ditech Networks October 2007
  2. 2. Enabling UMTS 900 Mobile Broadband Services with Ditech Contents Introduction............................................................................................................................... 3 Background on UMTS 900............................................................................................................3 UMTS 900 Enables Affordable Mobile Broadband Services...............................................................3 Recent UMTS 900 Developments.................................................................................................. 4 UMTS 900 Handset Availability..................................................................................................... 4 The Challenges with UMTS 900....................................................................................................4 Spectrum Issues.......................................................................................................................... 4 Possible Approaches for Clearing 900 MHz Spectrum..................................................................... 4 2G Upgrade Methods – Pros and Cons.......................................................................................... 5 3G Accelerated Migration – Pros and Cons.................................................................................... 6 The Ditech Solution for UMTS 900................................................................................................ 7 VQA™ Overview.........................................................................................................................7 Results from VQA Deployment in GSM Network.............................................................................8 Cost Comparison........................................................................................................................8 Conclusions............................................................................................................................... 9 References................................................................................................................................ 0 1 Copyright © 2007 Ditech Networks 2/14
  3. 3. Enabling UMTS 900 Mobile Broadband Services with Ditech Introduction This paper provides a background to the benefits of deploying UMTS-based mobile broadband services in the GSM 900 MHz band and the current UMTS 900 developments in different countries. Various methods available for clearing spectrum in the often crowded 900 MHz band and the associated costs are discussed, as well as how to minimize disruption to existing GSM services. A comparison that quantifies the costs of the different methods for a typical West European carrier is provided as a summary. The paper also introduces Ditech’s new VQA™ solution for UMTS 900 that frees up spectrum in the 900 MHz band by en- abling increased use of GSM-HR and AMR-HR codecs while maintaining acceptable voice quality, without the need for expen- sive new BTS site construction or upgrades. In addition, the Ditech solution employs capabilities that are already supported by existing handsets, thus it does not require any costly handset subsidies. Background on UMTS 900 UMTS 900 Enables Affordable Mobile Broadband Services UMTS carriers are currently rolling out mobile broadband data services based on the High Speed Downlink Packet Access (HS- DPA) technology which can now deliver peak data rates of up to 7.2 Mbps. The coverage of these services is unfortunately limited in the standard UMTS 2100 MHz band. This results in a significant reduction of the practical data rates that can be delivered, especially inside large buildings as well as in rural areas. One cost- effective way to address this issue is to deploy the mobile broadband services in the GSM 900 MHz band instead, where the propagation characteristics are much more favorable compared to the regular 2100 MHz band. This solution is referred to as UMTS 900. Studies show that the number of base station sites can be reduced by 60% [1], which may result in cost savings on the order of $2 billion in large networks, according to an extensive study published recently by the UK regulator Ofcom on UMTS 900 and the effects of releasing 900 MHz spectrum [2]. Figure 1:: UMTS coverage at 900 MHz and 2100 MHz, respectively [3]. Copyright © 2007 Ditech Networks /14
  4. 4. Enabling UMTS 900 Mobile Broadband Services with Ditech Recent UMTS 900 Developments The use of the 900 MHz band in Europe has until now been reserved exclusively for GSM. However, the European Commission is now proposing a more flexible approach to these frequencies, which would permit their use for 3G/ UMTS as well. UMTS 900 equipment has recently been trialed in Finland, France, Portugal, and the UK with good results. National regulators in Europe are generally expected to consider and authorize UMTS High Speed Packet Ac- cess (HSPA) deployments in the 900 MHz band. UMTS 900 has also been recently trialed in Australia. In New Zeeland, Vodafone is planning to go live with a UMTS 900 service in 2008 [1]. Furthermore, the GSM Association has called on administrations to open up the 900 MHz band to 3G worldwide [4]. UMTS 900 Handset Availability The first UMTS 900 handset, the Nokia 6121 smart-phone was recently announced with shipments starting in Q3 2007 [1]. All leading chipset and handset vendors are planning for UMTS 900, but initial volumes are difficult to predict and may be low, possibly less than a few million handsets produced by 2009, according to an Ovum report [5]. Also, UMTS handsets for the adjacent 850 and1900 MHz bands are already commercially available in the US. The Challenges with UMTS 900 Spectrum Issues It is clear that there are a lot of advantages with deploying UMTS broadband data services in the 900 MHz band. However, the 900 MHz spectrum is scarce and national regulators have already allocated most of it to existing GSM 900 services. One block of 2 x 5 MHz is required to accommodate a single UMTS frequency carrier. The UMTS Forum suggests the following so-called “sandwich” frequency arrangement to minimize possible interference between UMTS 900 with a 5 MHz frequency carrier and existing GSM 900 services using 200 kHz carriers [6]: GSM UMTS GSM Figure 2:: Suggested deployment of UMTS in the 900 MHz band This means that carriers will have to free up a considerable amount of their 900 MHz spectrum that is already in use while at the same time ensuring that this does not impact their existing GSM voice services. Possible Approaches for Clearing 900 MHz Spectrum There are basically two possible approaches to free up spectrum in the 900 MHz band according to the UK regulator Ofcom [2]: The “2G Upgrade” implements 2G technologies that use the remaining GSM spectrum more efficiently to support the existing GSM users, while the “3G Accelerated Migration” moves the GSM 900 traffic onto an existing UMTS 2100 network by increasing 3G handset subsidies (assuming the carrier operates such a network): Copyright © 2007 Ditech Networks 4/14
  5. 5. Enabling UMTS 900 Mobile Broadband Services with Ditech Figure 3:: Strategies for implementing 900 MHz spectrum release [2] A variant of the 2G Upgrade is the method proposed by the UMTS Forum where the GSM 900 traffic is handed over to a GSM 1800 network (assuming the carrier already has a GSM 1800 network in operation): . Figure 4:: Load balancing between GSM 900 and GSM 1800 in order to re-farm part of GSM 900 spectrum for UMTS 900 deployment [6]. 2G Upgrade Methods – Pros and Cons 2G Upgrade methods increase the capacity of the remaining GSM spectrum and includes Synthesized Frequency Hopping (SFH), increased use of low bit-rate GSM-HR and AMR-HR codecs, and Cell Splitting of macro sites. Synthesized Frequency Hopping SFH is a cost-effective and well-proven method for increasing GSM capacity and spectrum efficiency. Though, it will obvi- ously only work in networks that have not yet deployed this frequency hopping method. SFH requires newer types of base stations that support this feature . Older base stations will require costly hardware upgrades (replacement of cavity combiners with hybrid combiners) as well as software upgrades that together amount to a cost of about $26,000 per site, or about $20-50 million for a typical network in the UK [2]. The actual cost may vary significantly depending on existing GSM traffic loads and number of base stations that require upgrades. Also, SFH must be implemented in whole clusters of cells to get the required capacity gains. Copyright © 2007 Ditech Networks /14
  6. 6. Enabling UMTS 900 Mobile Broadband Services with Ditech GSM-HR and AMR-HR The use half-rate codecs such as GSM Half Rate (HR) and the newer Adaptive Multi Rate (AMR-HR) version allows a carrier to increase capacity during busy hour and improve the utilization of its existing GSM infrastructure with- out the need for new BTS sites and costly hardware upgrades. Half-rate codecs can also be employed locally on a call-by-call basis depending on capacity demands. While half-rate codecs are deployed in many networks and are fully supported by the existing installed base of GSM handsets, carriers tend to use them very cautiously due to voice quality concerns. Although these codecs perform quite well in ideal clean speech conditions, they are optimized for the human voice, and as a result, degrade significantly in the presence of background noise common in busy streets, crowded places, and inside vehicles such as cars, buses, and trains. In addition, non-linear acoustic echo is often created by low-end hand- sets and hands-free kits such as Bluetooth headsets. This tends to further degrade the user experience of calls using low bit-rate codecs. As will be explained later on, GSM-HR and AMR-HR can be combined with advanced network-based voice quality enhancement solutions that include Adaptive Noise Cancellation (ANC), Acoustic Echo Cancellation (AEC), and Enhanced Voice Intelligibility (EVI) to mitigate the degradation in voice quality caused by the use of half-rate co- decs. Thus, advanced voice processing solutions can enable GSM carriers to maintain an acceptable voice quality also during conditions with increased use of HR and AMR-HR codecs. Cell Splitting of Macro Sites Cell splitting of macro sites is the traditional way to increase capacity in a GSM network, and there are no particular technical problems associated with this method. The downside is that cell splitting is a very expensive and time-consuming alternative, as it can take 6-12 months, or even longer, to acquire a new site and obtain the necessary permissions. The construction cost is typically around $200,000 per site with a typical 20 year Net Pres- ent Value (NPV) of about $500,000 in the UK (this is the total cost of building and operating the site including site rents over 20 years) [2]. Micro-Cells and In-Building Solutions The Ofcom study considers other potential capacity solutions such as deployment of micro cells and dedicated in- building systems, but the UK regulator concludes that these solutions have practical limitations that make them less suitable for addressing large-scale capacity demands. 3G Accelerated Migration - Pros and Cons The 3G Accelerated Migration option assumes that a carrier can move the displaced GSM 900 traffic primarily to its UMTS 2100 network. This is possible if the following two conditions hold, there must be adequate 3G cover- age in areas where the GSM capacity is constrained, and there must be sufficient 3G compatible handsets in the subscriber base. However, UMTS 2100 is unlikely to provide the same quality of service inside buildings that GSM 900 could due to the different propagation characteristics of the two bands. The cost of accelerating the migration to 3G using handset subsidies will depend on the percentage of users that already have 3G enabled phones as well as the cost of 3G phones over 2G ones. Ofcom assumes a premium of about $200 for 3G phones compared to 2G ones, and estimates the total cost of an accelerated 3G handset migration to $200 million or more in a typical UK network [2]. Thus, the 3G Accelerated Migration method could be a rather costly alternative, especially if ad- ditional sites will have to be built to compensate for poorer coverage at 2100 MHz. Copyright © 2007 Ditech Networks /14
  7. 7. Enabling UMTS 900 Mobile Broadband Services with Ditech The Ditech Solution for UMTS 900 Ditech’s solution for UMTS 900 employs the company’s award-winning Voice Quality Assurance (VQA™) to increase the use of GSM-HR and AMR-HR for improved capacity while maintaining acceptable voice quality, thus enabling the deployment of UMTS in the GSM 900 MHz band VQA™ Overview VQA is a comprehensive set of industry-leading voice processing algorithms including bi-directional Adaptive Noise Cancellation (ANC), Acoustic Echo Cancellation (AEC), and Enhanced Voice Intelligibility (EVI) that together mitigate the problems of using low bit-rate codecs in noisy environments common in mobile calling. Ditech’s solution is typically deployed on the standard A-interface at the Mobile Switching Center (MSC) and is able to process and enhance all call types including mobile-to-mobile and mobile-to-PSTN calls: Figure 5:: Ditech’s Solution at A-Interface The solution consists of two software packages that are delivered on one of three hardware platforms, where the choice of hardware is based on network interface requirements: • Voice Quality Assurance (VQA™) – improves the speech quality by employing background noise cancellation, speech enhancement for low bitrate GSM codecs, background noise compensation, acoustic echo control, voice level adjustment, and optional hybrid echo cancellation • Experience Intelligence™ (EXi) o Quantifies and categorizes external impairments such as noise and echo that are present on live calls o Generates a call quality score based upon the ITU-T G.107 E-model standard [7]. • Hardware platforms – dependent on network configuration o E1 based A-interface: Quad Voice Processor (QVP) o STM1 based A-interface: Broadband Voice Processor (BVP) A carrier can generally deploy the Ditech solution in the entire network in only 2-4 months with a minimal impact on services. The VQA solution for UMTS 900 can potentially be deployed on a BSC-by-BSC basis in those areas where increased GSM capacity is required. Copyright © 2007 Ditech Networks 7/14
  8. 8. Enabling UMTS 900 Mobile Broadband Services with Ditech Results from VQA Deployment in GSM Network Ditech recently performed an extensive network audit on millions of live calls in a large GSM network in Western Europe. Figure 6 below shows the measured cumulative quality distribution of calls, where almost 50% of the half-rate calls fall below a MOS of 2.7 (or 54 points on the R scale), according to the ITU-T G.107 E-model. It turned out that 30% of the live calls had significant amount of background noise and about 10% had objection- able acoustic echo as defined by the ITU-T G.131 recommendation [8]. Thus, these impairments had a significant impact on customer experience: Figure 6:: Impact of VQA on delivered HR and AMR-HR call quality at 1% FER with 70% HR and 30% AMR-capable handsets As can be seen in the above chart, VQA was able to remove a large amount of the background noise and echo, and as a result, the number of unacceptable calls was reduced to only 10%. Thus, VQA was highly effective in removing external impairments that would otherwise degrade a large percentage of the GSM-HR and AMR-HR calls to an unacceptable quality level. Cost Comparison This section compares the different methods and associated costs for clearing 900 MHz spectrum discussed in previous sections, assuming a typical carrier in the UK. These costs may vary significantly from carrier to carrier depending on the amount of 900 MHz spectrum that needs to be cleared, the current and projected traffic loads in the 900, 1800, and 2100 MHz bands, the number of GSM 900, GSM 1800, and UMTS 2100 base station sites, the hardware and software capabilities of existing GSM base stations, as well as current and projected 3G handset penetration numbers. The following table summarizes the costs associated with the different alternatives. These costs are only approxi- mate but they should at least reflect the order of magnitude of the expenses required for clearing necessary 900 MHz spectrum to deploy UMTS 900 in a mature network in Western Europe (costs for SFH, Cell Splitting and Accelerated 3G Handset Migration based on information provided in [2]): Copyright © 2007 Ditech Networks /14
  9. 9. Enabling UMTS 900 Mobile Broadband Services with Ditech Estimated Estimated Cost Method Assumptions and Comments Total Cost per Subscriber SFH ≥ $25 million ≥ $1.50 About 30% of base stations need hardware upgrades that cost about $26,000 per site. Total cost including frequency planning and optimization is estimated to at least $25 million for an average capacity demand scenario. Method only works if SFH is not yet deployed. Cell Splitting ≥ $200 million ≥ $10 At least 1,000 additional sites required. Construction cost per site is $200,000 (total costs over 20 years estimated to $500,000 per site). Accelerated 3G Handset ≥ $200 million $10 Accelerate migration to UMTS Migration by subsidizing1 million 3G handsets at a $200 premium compared to 2G phones. Increased HR/AMR-HR use $15 million $1.00 Increased use of HR/AMR-HR combined with voice quality combined with network-based enhancement solution such voice quality enhancement as Ditech’s VQATM solution solution deployed in areas where increased GSM voice capacity is required. Table 1:: Approximate costs for clearing spectrum in the 900 MHz band for a mature Western European GSM network Conclusions The ability to deploy UMTS in the 900 MHz band provides mobile carriers with an opportunity to offer more affordable broad- band data services with higher data rates and better coverage compared to deployment in the regular 2100 MHz band. Re-farming the 900 MHz spectrum without disrupting current GSM services can however be a major challenge. UMTS 900 requires at least one block of 2 x 5 MHz spectrum in 900 MHz band. This is a significant amount of spectrum that needs to be cleared from a band that is already heavily used by GSM. There are basically two approaches to mitigate this problem. The “2G Upgrade” implements 2G technologies that use the remaining GSM spectrum more efficiently. These technologies include Synthesized Frequency Hopping (SFH), HR/AMR-HR co- decs, and Cell Splitting, while the “3G Accelerated Migration” moves GSM 900 voice traffic onto an existing 3G UMTS 2100 network by increasing 3G handset subsidies. Copyright © 2007 Ditech Networks /14
  10. 10. Enabling UMTS 900 Mobile Broadband Services with Ditech Each of the above solutions has its own set of advantages and disadvantages and the most suitable solution may vary from carrier to carrier based on each specific situation. Increased usage of HR and AMR-HR codecs is generally a very cost-effective method, provided it is combined with a voice quality enhancement solution to maintain acceptable quality. This method improves utilization of the existing GSM infrastructure without the need for expensive new BTS site construction or upgrades. Nor does it require any costly handset subsidies as GSM-HR and AMR-HR codecs are already supported by the installed base of GSM hand- sets. Also, carriers can easily deploy the solution locally to deal with congestion in e.g. busy urban areas. Ditech’s VQA™ solution for UMTS 900 enables increased use of HR and AMR-HR codecs by removing external impairments such as background noise and acoustic echo that otherwise tend to degrade the quality of these low bit-rate codecs to unacceptable levels. Ditech’s voice quality enhancement solution can be quickly deployed in an entire network within 2-4 months without costly upgrades to BTS sites and with minimal disruption to existing GSM and UMTS services. Finally, carriers have the option to deploy VQA only in select areas on a BSC-by-BSC basis to meet local capacity demands. References [1] Global mobile Suppliers Association (GSA), Information Paper, September 2007. [2] Application of Spectrum Liberalisation and Trading to the Mobile Sector, Office of Communications (Ofcom), UK, September 2007. [3] Huawei contribution to UMTS Forum Workshop, June 20, 2007. [4] GSM Association Press Release, June 25, 2007. [5] Market Study for UMTS900, Ovum, February, 2007. [6] Deployment of UMTS in 900 MHz Band, UMTS Forum White Paper, October 2006. [7] ITU-T Recommendation G.107 (03/2005) The E-model, a computational model for use in transmission planning. [8] ITU-T Recommendation G.131 (11/2003) Talker Echo and Its Control Copyright © 2007 Ditech Networks 10/14
  11. 11. Enabling UMTS 900 Mobile Broadband Services with Ditech Corporate Headquarters US Sales – West Brazil Sales Office Middle East/Africa Sales Office Ditech Networks Ditech Networks Ditech Networks 825 East Middlefield Rd. Alameda Araguaia, 933 21 El-Fawakeh St., 3rd Floor Mountain View, CA 94043 Alphaville Dokki, Giza 12311 USA Barueri, SP 06455-000 Egypt 1-800-234-0884 (Toll Free) Brazil +20 2 336-5100 (Phone) 1-650-623-1300 (Direct) +55 (11) 4208-6266 (Main) +20 2 761-8964 (Fax) 1-650-564-9599 (Fax) +55 (21) 3521-5543 (Sales) MEA-Sales@ditechnetworks.com NA-Sales@ditechnetworks.com Brazil-Sales@ditechnetworks.com South-America-Sales@ditechnetworks.com Spain Sales Office US Sales Office – East and Central Ditech Networks Ditech Networks China Sales Office Torres Quevedo, 1 – (P.T.M.) 8360 Greensboro Dr. Ditech Networks 28760 Tres Cantos – Madrid McLean, VA 22102 Unit 3010, No. 500 Spain USA Xiangyang South Road +34 (91) 803 74 44 (Main) 1-800-234-0884 (Toll Free) Xuhui District +34 (91) 829 26 90 (Sales) 1-650-623-1300 (Direct) Shanghai 200031 Spain-Sales@ditechnetworks.com 1-650-564-9599 (Fax) PRC Europe-Sales@ditechnetworks.com NA-Sales@ditechnetworks.com +86 (21) 5456 0305 (Phone) China-Sales@ditechnetworks.com Canada Sales Office Ditech Networks South-East Asia Sales Office 2275 Lakeshore Blvd West, Suite 500 Ditech Networks Toronto, ON M8V 3Y3 Lippo Plaza 3rd Floor Canada Jl. Jend. Sudirman Kav. 25 1-416-255-7776 (Phone) Jakarta 12920 NA-Sales@ditechnetworks.com Indonesia +62 (21) 5291 3780 (Phone) +62 (21) 522 1977 (Fax) Mexico Sales Office SE-Asia-Sales@ditechnetworks.com Ditech Networks Torcuato Tasso 245-6o. Piso Col. Polanco South Asia Sales Office México, D.F. C.P. 11570 Ditech Networks México No. 8/11, Sarvapriya Vihar +52 (55) 5254-5422 (Main) New Delhi – 110016 +52 (55) 5350-8679 (Sales) India Mexico-Sales@ditechnetworks.com +91 9810372555 (Phone) South-Asia-Sales@ditechnetworks.com Copyright © 2007 Ditech Networks. All rights reserved. Experience Intelligence, Packet Voice Processor, and VQA are trademarks of Ditech Networks. All other brands 11/14 are the property of their respective owners. Specifications may change without notice. This document was last revised 10/07.

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