Paul McCartney penned "The Long and Winding Road" a decade before the Advanced Mobile Phone System (AMPS) cellular service was launched, but this lyric perfectly embodies the complex history behind today's 3G wireless. In Part 1 of this tip, we sort out the cellular alphabet soup to understand where 3G came from. In Part 2, we will discuss how to select a 3G wireless service.
In the beginning: 1G
First-generation cellular took off in 1982 with the deployment of commercial AMPS service. AMPS used Frequency Division Multiplexing Access (FDMA) to carry analog voice over several hundred channels within the 800 MHz frequency band. Other incompatible 1G services emerged around the world (e.g., TACS, NMT), and the total number of cellular subscribers grew. But each carrier delivered service to a limited serving area, there were no standards to enable roaming, and channel capacity was rapidly being exhausted.
Going global: 2G
By the early 1990s, carriers began to work together to overcome 1G limitations by defining mobile telephony standards. Two major second-generation technologies emerged: GSM and CDMA. Both increased system capacity by digitizing voice, but each used a different approach to spread digital signals across the available spectrum.
These standards helped bring order to the cellular market -- the same GSM phone could be used in several countries and (later) roam between GSM carrier networks. But there were still other competing services, such as D-AMPS (a North American digital version of AMPS), iDEN (a Motorola/Nextel TDMA-based service), and carriers in the U.S. and elsewhere that deployed GSM on different bands. To bridge this gap, dual and tri-band phones emerged – for example, using PCS 1900 (a North American GSM service) inside the U.S. or GSM at 1800 MHz internationally.
A gradual evolution: 2.5G
In addition to voice, 2G s
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ervices could also carry digital data. For example, GSM networks could use spare bandwidth to support circuit-switched data sessions at 9.6 to 14.4 Kbps. That proved sufficient for short message delivery but far too slow for most Internet applications and multimedia content delivery. To achieve much higher rates and native support for TCP/IP applications, those old 2G networks had to be replaced with new packet-switched networks that employ broadband radio technologies.
While brand-new third-generation standards were being defined to meet those needs, carriers became impatient. As a result, several near-term improvements were made to existing 2G networks, boosting wireless data rates to achieve v.90-like throughput:
Getting there: 3G
Today, many carriers have deployed "true 3G" services in major cities across the world. Those old 2G networks based on GSM and cdmaOne are now being replaced by new 3G networks that employ their descendants: UMTS and CDMA2000.
This evolution is likely to continue with even newer radio network technologies such as High-Speed Uplink Packet Access (HSUPA). Internally, carrier network architectures are expanding the use of IP, guided by IP Multimedia Subsystem (IMS) standards. Eventually, even mobile voice calls will be carried over all-IP carrier networks.
Jumping on the 3G bandwagon
Many consumers find this flood of similar-but-different acronyms terribly confusing, but it really all boils down to a choice between two major technology families, where you join the evolutionary chain, and which products and services you'll choose to support the applications that you intend to use. In Part 2 of this tip (Going 3G: Can you hear me now?, we explore which carriers offer these 2.5 and 3G services and where, and factors to consider when making your selection.
3G resources:
CDMA2000:
Whatis.com definition
http://en.wikipedia.org/wiki/CDMA2000
http://www.3gpp2.org/
UMTS:
Whatis.com definition
http://en.wikipedia.org/wiki/W-CDMA
http://www.3gpp.org/
[TABLE]About the author
Lisa Phifer is vice president of Core Competence Inc., a consulting firm specializing in network security and management technology. Phifer has been involved in the design, implementation, and evaluation of data communications, internetworking, security, and network management products for nearly 20 years. She teaches about wireless LANs and virtual private networking at industry conferences and has written extensively about network infrastructure and security technologies for numerous publications. She is also a site expert to SearchMobileComputing.com and SearchNetworking.com.
