The Evolution of Cellular Data: on the Road to 3G Published by Intel
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The Evolution of Cellular Data: On the Road to 3G Published by Intel Corporation. Peter Rysavy, Rysavy Research Copyright 1999. All rights reserved. Introduction Wireless phone use is taking off around the world. Many of us would no longer know how to cope without our cellphones. Always being connected offers us flexibility in our lifestyles, makes us more productive in our jobs, and makes us feel more secure. So far, voice has been the primary wireless application. But with the Internet continuing to influence an increasing proportion of our daily lives, and more of our work being away from the office, it is inevitable that the demand for wireless data is going to ignite. Already, in those countries that have cellular-data services readily available, the number of cellular subscribers taking advantage of data has reached significant proportions. We want wireless Internet, we want our organizational data from anywhere, and we want it now. But to move forward, the question is whether current cellular-data services are sufficient, or whether the networks need to deliver greater capabilities. The fact is that with proper application configuration, use of middleware, and new wireless- optimized protocols, today’s cellular-data can offer tremendous productivity enhancements. But for those potential users who have stood on the sidelines, subsequent generations of cellular data should overcome all of their objections. These new services will roll out both as enhancements to existing second- generation cellular networks, and an entirely new third generation of cellular technology. Our job here is to describe this road to the third generation (3G), as well as to show you how these services will allow new applications never before possible. The World Today Before we peek into the future, let’s quickly look at where we are today. In 1999, the primary cellular-based data services are Cellular Digital Packet Data (CDPD), circuit-switched data services for GSM networks, and circuit-switched data service for CDMA networks. Some brave souls connect their PC Card modems to their analog cellphones, but this approach is not very popular because it is tricky to configure. All of these services offer speeds in the 9.6 Kbps to 14.4 Kbps range. Why such low speeds? The basic reason is that in today’s cellular systems, data is allocated to the same radio bandwidth as a voice call. Since voice encoders (vocoders) in current cellular networks digitize voice in the range of 8 to 13 Kbps, that’s about the amount available for data. Remember, too, that today’s digital and PCS technology designs started over five years ago. Back then, 9.6 Kbps was considered more than adequate. Today, it can seem slow with graphical or multimedia content, though it is more than adequate for text-based applications and carefully configured applications. There are two basic ways that the cellular industry is currently delivering data services. One approach is with smart phones, which are cellular phones that include a microbrowser. With these, you can view specially formatted Internet information. The other approach is through wireless modems, supplied either in PC Card format or by using a cellphone with a cable connection to a computer. See Figure 1. Figure 1: Smart phone versus phone connected to laptop Both approaches can give you access to Internet sites and corporate systems, including e-mail, databases, or host-based systems. But both approaches also require that the user take throughput and latency of the network into account. In contrast, next generation networks promise throughput, global coverage, and ease- of-use that will greatly expand your mobile computing options. The World Tomorrow Before diving into details of different network technologies, we need to realize that from a user perspective, the offerings from all of these networks will be largely comparable. Introduction dates of services may vary by up to a year, and exact data rates may differ by 20 or 30%. But just as voice users today may be hard- pressed to distinguish between the quality of an IS-136 call using AT&T’s wireless network, a GSM call using Omnipoint’s network, or a CDMA call using Sprint PCS network, data users will notice great similarity between the new cellular-data services. In thinking about the rollout of next generation services, consider what features can be added to existing networks, and what features will require vastly new network infrastructure. Since we refer to the current generation of cellular as second generation, then new feature advancements to the current network are sometimes called 2.5G. Generally, 2.5G technologies have been developed for third generation (3G) networks, but they are applied incrementally to existing networks. This approach allows carriers to offer new high-speed data and increased voice capacity at much lower cost than deploying all new 3G networks. Plus, they can do so using their existing spectrum. Let’s consider data rates in more detail. The global standards body for communications is the International Telecommunications Union (ITU). The 3G standards effort is called International Mobile Telephone 2000 (IMT-2000). IMT- 2000 mandates data speeds of 144 Kbps at driving speeds, 384 Kbps for outside stationary use or walking speeds, and 2 Mbps indoors. Does this mean that we’ll all be using our cellphones at 2 Mbps? No. The indoor rate will depend on careful frequency planning within buildings, and possibly an organization’s commitment to work closely with a carrier. However, since high-speed services such as wireless LANs already offer speeds of up to 11Mbps, it’s difficult to predict the expected market demand for 2Mbps indoor service when 3G networks roll out. What is of much greater interest is the 384 Kbps data rate for outdoor use, as this IP protocol-based packet service will be available over wide areas. This service is the one that will let us extend our office to any location. And the good news? The technology that will provide 384 Kbps in 3G networks is the same technology that will be deployed in 2.5G networks, albeit at slightly lower data rates in the 50 to 150 Kbps range. But this is still some ten times faster than most options today. More good news? 2.5G services will be released in the year 2000, well in advance of 3G networks that won’t start rolling out until 2002 at the earliest. See Table One. Core Technology Service Data Capability Expected Deployment GSM Circuit-switched data 9.6 Kbps or 14.4 Available worldwide based on the Kbps now standard GSM 07.07 High-speed circuit- 28.8 to 56 Kbps Limited deployment switched data service likely 1999 and 2000 as (HSCSD) many carriers will wait for GPRS General Packet Radio IP and X.25 Trial deployments in Service (GPRS) communications over 2000, rollout of Kbps service 2001 Enhanced Data Rates IP communications to Trial deployment in for GSM Evolution 384 Kbps. Roaming 2001, rollout of (EDGE) with IS-136 networks service 2002 possible. Wideband CDMA Similar to EDGE but Initial deployment in (WCDMA) adds 2Mbps indoor 2002 or 2003 capability. Increased capacity for voice. IS-136 Circuit-switched data 9.6 Kbps Some carriers may based on the offer service, but not standard IS-135 expected on widespread basis because key carriers already offer Cellular Digital Packet Data (CDPD) EDGE IP communications to Initial deployment 384 Kbps. Roaming 2002 or 2003 with GSM networks possible. WCDMA or Similar to EDGE but No stated deployment Wideband TDMA adds 2Mbps indoor plans (WTDMA) capability CDMA Circuit-switched data 9.6 Kbps or 14.4 Available by some based on the Kbps carriers now standard IS-707 IS-95B IP communications to Expected in 64 Kbps Japanese markets by early 2000 CDMA2000 - 1XRTT IP communications to Trial deployment in 144 Kbps 2001, rollout of service 2002 CDMA2000 - 3XRTT IP communications to Initial deployment in 384 Kbps outdoors 2002 or 2003. and 2 Mbps indoors Table One: Summary of forthcoming cellular-data services. Time estimates by Rysavy Research. How the three major cellular technologies will provide these services varies, but all have a similar roadmap. In fact, as we detail in subsequent sections, these technologies are slowly converging, beginning with a convergence of IS-136 and GSM data services, and followed by a harmonization of the 3G versions of GSM and CDMA. By harmonization, we mean that while differences will continue to exist, the systems will interoperate more readily. There are some other important trends to note. The first is that standards bodies are working not just on radio technologies, but also on the networking infrastructure. One objective is to allow users to seamlessly roam from private networks (e.g. Ethernet, WLAN) to public networks. Such roaming will require the implementation of standards such as Mobile IP. Another goal is to simplify the connection between mobile computers and wireless devices through personal-area network (PAN) technologies such as Bluetooth. Yet another trend is voice over IP. As terrestrial networks start using IP for voice and multimedia, it will be important for such IP communications to extend all the way to the wireless device. Perhaps the most important trend of all is for ubiquitous coverage. This will be achieved not just by converging wireless standards, but also by sophisticated new devices that operate in multiple modes and at multiple frequencies. This is the world of tomorrow. To understand how we’ll get there, we will look first at GSM and IS-136 networks, and then CDMA networks. Networks in Detail GSM and IS-136 GSM dominates the world today, with over 200 million users in over a hundred countries.