Even for those with years in the telecom industry, wide area wireless network or wireless WAN technologies present a vast array of protocols and radio technologies, each
This tip is designed to provide you with a quick reference guide to help keep it all straight – a primer, if you will. It also offers an overview of wireless WAN technologies.
Despite the large number of specific protocols and technologies, all of the components can all be assigned to one of three distinct families, which makes keeping track of different versions easier. These broad technology families break out as follows:
While the GSM/UMTS and cdmaOne/CDMA2000 families were originally developed for cell phones, both have added support for data and are widely deployed throughout the world. The WiMAX protocols, however, were specifically developed to support high-speed data with voice carried as VoIP. They are currently deployed in only limited locations.
Wireless WAN -- from generation to generation
The original wireless WAN technologies in both the GSM/UMTS and cdmaOne/CDMA2000 families are now referred to as first generation or 1G. A second generation of technologies in each family replaced analog with digital transmission. These 2G technologies are now being replaced by 3G technologies. 2G provided limited support for data, but 3G provides much higher data rates. Work is currently underway to design and specify the next generation, 4G.
It's not feasible for service providers to upgrade all of their equipment simultaneously across an entire network every time a new protocol is introduced. Network providers typically upgrade in a few large cities first, then smaller metropolitan areas follow. A complete upgrade may require several years, which means network suppliers often support multiple overlapping networks, each based on a different protocol generation.
A confederation of European national phone companies started developing the GSM/UMTS protocols in the early 1980s. As a result, they are used widely by most large European network providers. They are also in wide use throughout the rest of the world. In the U.S., AT&T/Cingular and T-Mobile use GSM/UMTS.
Cingular, now part of AT&T, maintains both the EDGE and BroadbandConnect networks. The EDGE protocol is an early 3G protocol, sometimes described as 2.75G. It was designed to be added to an existing 2G network with minimal effort and expense. The EDGE network is offered throughout the U.S. AT&T advertises typical download and upload rates from 70 to 135 Kbps.
BroadbandConnect service uses a more recent 3G protocol, HSDPA. BroadbandConnect is currently available in major metropolitan areas. AT&T promises download rates from 400 to 700 Kbps and upload rates up to 384 Kbps.
The cdmaONE/CDMA2000 family has developed through a similar sequence of generations. Development began at Qualcomm in the late 1980s. The 2G protocol, IS-95, marketed by Qualcomm as cdma/ONE, was replaced by 1xRTT and subsequently by EV-DO. 1xRTT is considered a 2.5G protocol, and EV-DO is 3G.
Verizon supports two national networks. Its NationalAccess network is based on the older 1xRTT technology. The BroadbandAccess network is based on EV-DO. NationalAccess is supported throughout the U.S.; BroadbandAccess is available only in metropolitan areas.
The original EV-DO Rev 0 technology has been further improved to create EV-DO Rev A. Verizon has now upgraded to EV-DO Rev A in all locations where BroadbandAccess is offered. EV-DO Rev A provides typical download rates from 600 Kbps to 1.4 Mbps and upload rates from 500 to 800 Kbps. Achieving these rates requires that the user have a Rev A-compatible device. Users with Rev 0 devices will be limited to Rev 0 rates. Rev 0 download rates typically vary from 400 to 700 Kbps, with bursts to 2 Mbps. Typical upload rates are 60 to 80 Kbps, with bursts to 144 Kbps.
Sprint is also in the process of upgrading its earlier 1xRTT network with EV-DO. Currently, EV-DO is available in metropolitan areas and in some rural areas. The upgrade from EV-DO Rev 0 to Rev A is currently underway and is expected to be complete by the end of 2007. Sprint reports data rates for both Rev 0 and Rev A similar to those reported by AT&T.
WiMAX developed from work in the mid-90s aimed at reducing the cost of connecting homes and businesses to the Internet by eliminating the cost of running cable or DSL to each location. Instead, a central antenna would provide a high-bandwidth wireless connection to each subscriber. Equipment costs were high due to the lack of an industry standard that would enable manufacturing in high-volume.
As a result, the IEEE chartered a committee to develop standards, and a group of equipment vendors and network providers created the WiMAX Forum to promote standards adoption and to certify equipment designed to meet the standard. The standards committee, IEEE 802.16, produced IEEE 802.16-2004, also known as 802.16d, followed by 802.16e-2005. IEEE 802.16-2004 supports the original goal of the work: to provide wireless communication between fixed locations. IEEE 802.16e supports mobile users.
WiMAX is often described as a 4G technology. Theoretical data rates could be as high as 70 to 75 Mbps, but the WiMAX Forum expects total data rates of approximately 40 Mbps for stations within a radius of three to 10 kilometers of the central antenna. This rate would be shared by all of the stations within the radius. The Forum expects a total of 15 Mbps for mobile users within a three-kilometer radius.
Currently, WiMAX support is offered in the U.S. by Clearwire and Towerstream in a limited number of metropolitan areas. Both support subscribers at fixed locations only. Sprint has announced support for mobile users in 2008. Intel and Motorola have announced PCMCIA cards and chips for embedded laptop support.
Both GSM/UMTS and cdmaONE/CDMA2000 are proven technologies with millions of users worldwide. Some backers of WiMAX have predicted that it will provide performance far superior to the other technology families and eventually replace them. Whatever the outcome, users will benefit from improved data rates and wider availability as the three differing technologies compete.
About the author:
David B. Jacobs of The Jacobs Group has more than 20 years of networking industry experience. He has managed leading-edge software development projects and consulted to Fortune 500 companies as well as software startups.
This was first published in November 2007