UMTSThird generation mobile communications boosting wireless efficiency Publisher: Willtek Communications GmbH Gutenbergstr. 2-4 85737 Ismaning Germany e-mail: [email protected] http://www.willtek.com Co-Author: Helmut Visel, Acterna Eningen GmbH © Copyright 2002 Willtek Communications GmbH. All rights reserved. Willtek Communications, Willtek and its logo are trademarks of Willtek Communications GmbH. All other trademarks and registered trademarks are the property of their respective owners. Content UMTS – a communications revolution 6 Three generations of mobile communications 8 Services – ensuring the success of UMTS 10 New technology, new roles 12 The fundamentals of UMTS 15 3G frequencies 15 Frequency bands for UMTS 18 Minimum bandwidth requirements 20 Inside the UMTS architecture 22 Network overview 24 From handset to network – the user equipment 25 Virtual home environment 30 Service capabilities and APIs 32 UMTS system architecture 34 UTRAN components 35 Node B 38 Serving radio network subsystems and drift radio network subsystems 40 Handovers 41 Hard handovers 42 Softer and soft handovers 43 Role of the Iur interface during handover 45 UMTS logical planes 46 Transport network control plane 46 Control plane 46 Control plane components 47 User plane 50 User plane components 50 ATM in the core network 53 The future – all-IP networks? 55 Key terms 57 UMTS air interface 62 Multiple access routes 63 Frequency division duplex (FDD) 65 Time division duplex (TDD) 66 FDMA-based networks 67 CDMA – it’s party time 68 CDMA-based networks 70 CDMA cells 72 Orthogonal codes and multiplexing 73 Features of the UMTS radio interface 74 Frequency, code, and phase 75 CDMA air interface challenges 76 The “near-far” problem 76 Cell breathing 78 Variable rate transmission 79 Glossary 80 Bibliography 86 Information sources 87 UMTS – a Almost everyone today seems to own at least one mobile device. The growth communications in phone ownership is a relatively new phenomenon and is largely attributa- revolution ble to the quality of the digital radio services like cdmaOne, US-TDMA, PDC and GSM. A new, high capacity mobile infrastructure, universal mobile telecommunications system (UMTS) is poised to change the face of mobile communications. With UMTS, the possibility of making narrowband voice calls and exchanging broadband multimedia content simultaneously becomes reality. In some countries, usage of mobile radio devices has already exceeded 80 percent of the population. The number of mobile telecommunications users looks set to exceed the number of fixed network lines in a number of countries. Meanwhile, the number of Internet users is growing at almost 18 million new subscribers per month, while data traffic is doubling approxi- mately every six months. Given these rates of growth, the mobile Internet underpinned by UMTS transport technology will perform a vital role in mod- ern, high bandwidth communications. 6 UMTS – a guide to the third generation of mobile communications is designed to provide an insight into fundamental aspects of UMTS technology, how it works, and some of the issues that face the industry. Willtek is one of the world’s leading providers of wireless network testing equipment. As a leading member of the telecommunications industry bodies such as ITU-T, ETSI and ANSI, the company is well placed to comment on the emerging broadband mobile market. Willtek provides solu- tions that meet the needs of high bandwidth radio communications today and in the future. figure 1 Development of subscriber count and applications for UMTS 7 Three generations First generation (1G) – analog mobile radio networks of mobile These are still commonplace in some parts of the world, but lack the communications features of modern, digital networks. Because data has to be adapted for analog transmission using a modem, analog networks introduce losses and demand intensive management. Added to this, mobile data traffic is growing at a much faster rate than speech traffic, which means that analog networks are no longer suitable for mobile multimediacommunications. Second generation (2G) – digital mobile radio networks The difference between analog and digital networks is that with digital networks, users are guaranteed a consistently high quality of speech. 2G opened the door to a range of data services such as facsimile, email, text messaging (SMS), and PC connection. In addition, users can exploit features like call forwarding and international roaming. The typical GSM network is a common example of a second-generation mobile radio network. Third generation (2.5G and 3G) – broadband digital mobile networks The first phase in the development of broadband mobile communications is 2.5G, that means an interim step based on 2G technologies. 8 The main technologies here are General Packet Radio Service (GPRS) and 1xRTT. These technologies embrace packet switching as opposed to the more traditional circuit-switched networks. GPRS has been built onto existing GSM network infrastructures, so it does not have the bandwidth possibilities of the next phase in broadband mobile: third generation mobile networks (or 3G). While there are other 3G network standards, this guide focuses on just one – UMTS. figure 2 Three generations of mobile radio 9 Services – The mobile communications industry has agreed most of the technical ensuring the success prerequisites for mobile multimedia communications. Soon users will of UMTS combine speech, text, and video in a single call. However, at the beginning of this new era in mobile communications, companies will need to work hard to convince potential users of the benefits of 3G. If UMTS is to be successful, potential subscribers will want access to a much wider range of exciting, cost-effective, and innovative services. The main factors that need to be addressed before this can happen are: – Bandwidth requirements – The need for realtime capabilities – The distinction between point-to-point services for individual communications and point-to-multipoint broadcast services such as mobile TV 10 figure 3 Potential 3G services 11 New technology, Despite some early attempts by new entrants to secure the lucrative new roles services segment of the 1G and 2G mobile communications market, network operators have delivered most of these services alone. With UMTS, the scope for innovative services is such that a redefinition of the traditional roles of many stakeholders is taking place. Subscriber A person or entity deemed as such by law, who has a legal agreement with a service provider on behalf of one or more users. User A person or entity deemed as such by law, who possesses an authorization for usage from a subscriber. In the simplest case, the subscriber is the same as the user. 12 Service provider In Europe, these are the organizations that deliver services to subscribers. A subscriber and service provider enter into a commercial agreement regard- ing specific service provision. The service provider requires the cooperation of the network operator to deliver its services to the subscriber. Service providers manage the profile for each subscriber. The profile details the serv- ices in the customer contract, for example, rates and quality of service. Network operator The network operator combines their own transport, and possibly access services, with those offered by service providers. Network operators may choose to manage the backbone and access networks alone, or to work with another operator. In the US, this term is interchangeable with service provider. Value-added service provider These providers deliver services that extend beyond telecommunications services. Examples of value-added services include mailbox functions and location-based services. Invoices for value-added services may be addressed directly to end-users, or handled by service providers. 13 Content provider A content provider is responsible for content delivery. One example of this would be a video store that provides movies through a streaming video-on- demand service. Service broker These are organizations that act as resellers of products from different serv- ice providers to the end user. They invoice their services directly to the customer. figure 4 How the roles fit together 14 The fundamentals Sections three and four of this guide provide an overview of UMTS architec- of UMTS ture and air interface. This section focuses on fundamental aspects of UMTS – frequencies, frequency bands, and bandwidth requirements. 3G frequencies The body responsible for worldwide radio frequencies’ allocation, the World Administrative Radio Conference (WARC), designated the following frequency bands for worldwide third generation mobile radio systems under the International Mobile Telephony 2000 (IMT-2000) framework thus far: 1885 to 2025 MHz (ITU-specified band for 3G) 2110 to 2200 MHz (ITU-specified band for 3G) 1710 to 1885 MHz (extends the current 2G band for GSM 1800 for 3G use) 2500 to 2690 MHz (new band for future use) 806 to 960 MHz (extends current 2G bands for 3G use) 15 It is expected that new bands will become available around 2010. In Europe, the first 15 MHz of the lower band overlaps with the frequencies reserved for digital enhanced cordless telecommunications (DECT). The industry divided the remaining spectrum into a pair-based division for frequency division duplex (FDD) with 2 x 60 MHz. The range 1920 to 1980 MHz was reserved for the uplink and the range 2110 to 2170 MHz for the downlink. An unpaired spectral band of 35 MHz was reserved for (asymmetrical)