Three standards have emerged as the front runners in a continuing technological battle of wireless air interfaces. An alphabet soup of acronyms are being used to differentiate new services as proponents and foes of each standard form alliances to market their choice to the consumer. Code Division Multiple Access (CDMA), Global System for Mobiles (GSM), and North American Digital Cellular (NADC) are all competing in the marketplace for acceptance in upgraded cellular and new PCS networks. No longer content to advertise pricing and features, major service providers are now using brand names to build consumer confidence and loyalty. <
Code Division Multiple Access (IS-95)
Code Division Multiple Access is a method by which a number of callers share the same frequency at the same time but are kept separate by the use of pseudo-noise (PN), or spreading, codes. Using these codes, a receiver can "de-spread" the desired signal and recover a particular caller's data (see the February 1997 PCS Front Line column for an introduction to CDMA).
The current CDMA specification, termed IS-95, was originally developed by San Diego-based Qualcomm, Inc., and became an approved Telecommunications Industry Association (TIA) standard in July of 1993. Early CDMA systems were established in Hong Kong and Korea, but are now rapidly being built in the United States. Many existing cellular carriers are converting portions of their 800 MHz spectrum from analog to digital CDMA service, and according to the CDMA Development Group (CDG), an industry association of IS-95 proponents, of the nearly 3,000 PCS licenses granted by the FCC, slightly more than half of the license holders have chosen CDMA, while GSM was selected by 28 percent and TDMA by 20 percent.
The CDG is also attempting to "brand" IS-95 networks under a single term --- cdmaOne. This trademark is supposed to serve as a catch-all term for the family of wireless products using the IS-95 air interface, including cellular, PCS, and wireless local loop.
Major CDMA vendors Lucent Technologies, Motorola, Nortel, and Qualcomm are also working with CDG to develop specifications for a next-generation "wider-band" IS-95-based CDMA technology.
It should be noted that not all proposed CDMA networks follow the IS-95 standard. Ericsson and Nokia, two major European suppliers, are testing a "wideband CDMA" (W-CDMA) not related to IS-95. Optimized for such high speed data applications as Internet access, multimedia electronic mail, high quality voice, and even video, W-CDMA uses a CDMA air interface linked to a GSM network infrastructure. In Japan, Nippon Telephone and Telegraph's DoCoMo is performing experimental field tests on both Ericsson's W-CDMA and an IS-95 follow-on developed by Lucent Technologies.
Global System for Mobiles
The Global System for Mobiles (GSM) is an international air interface and network standard that has been developed and refined over the past decade, primarily in Europe. Several North American GSM service providers have recently formed the GSM Alliance to jointly market digital wireless voice and data services on PCS frequencies (1,900 MHz) and will be working to provide uniform features, roaming rates, and other services across the country. The GSM Alliance includes Aerial Communications, BellSouth Mobility DCS, Microcell Telecommunications, Inc. (Canada), Omnipoint Communications, Pacific Bell Mobile Services, Pocket Communications, Powertel, and Western Wireless. Microprocessor giant Intel is also supporting the alliance through its Mobile Data Initiative in an attempt to boost growth in the wireless data market.
The first commercial PCS network in the United States, American Personal Communications' Sprint Spectrum, uses the GSM standard and will be involved in the Alliance, but is also affiliated with Sprint, which has selected CDMA.
The use of GSM in North American has been limited to PCS frequencies in part because of it's 200 kHz wide channels, and thus cannot be easily retrofitted into the 800 MHz cellular band allocation of 30 kHz wide channels. GSM has also introduced the Subscriber Identity Module, or SIM, to U.S. consumers, containing security, identity, and other information. These programmable smart cards can be easily transferred from one wireless handset to another, allowing a subscriber to quickly change equipment while retaining the same access number and service features.
North American Digital Cellular
North American Digital Cellular (NADC) is based on IS-136, an enhancement of an older standard that makes use of Time Division Multiple Access (TDMA) techniques. NADC was originally slated to be the single digital standard for the United States prior to Qualcomm's IS-95 proposal, and has been in use for several years.
The largest proponent of NADC, AT&T Wireless, is using TDMA in both new PCS frequencies and upgraded analog cellular areas, creating some additional confusion by marketing their 800 MHz NADC service as "Digital PCS." Purists would claim PCS refers to services in the 1,900 MHz band, but AT&T counters that consumers are interested in features and capabilities, not operating frequencies.
All three standards promise increased user capacity, improved sound quality, fewer dropped calls, and broader coverage area than the analog equivalent. The digital nature of the air interface also allows additional services, such as caller ID and paging, to be easily incorporated into the system.
At the end of June there were an estimated 646,000 GSM customers and 420,000 CDMA customers. In the near term, GSM operators appear to be growing quickly. For example, BellSouth Mobility DCS and Pacific Bell Mobile Services both claim more than 100,000 customers, while in seven and a half months Omnipoint has signed up 42,000 customers.
Table 1: Major PCS license holders with service areas and selected technology standard.
Like the gold rush of the mid-1800's, the ones making the money are the equipment providers. PCS and cellular infrastructure revenue in 1996 reached $5.3 billion, up from $3 billion in 1995. PCS equipment alone went from $530 million to $2.8 billion during that period. Lucent Technologies lead the pack with more than a third of the market, followed by Ericsson and Motorola. Nortel had nearly 20 percent of the market and was the only provider to win both CDMA and GSM contracts of significant size.
Cellular and GPS
The Global Positioning System (GPS), operated by the United States Department of Defense, is a constellation of 24 low earth orbit satellites which provide accurate position and time information to military and civilian users. GPS first gained fame during Operation Desert Storm by providing pinpoint accuracy for soldiers and guided munitions. Peacetime uses for accurate location information are now quite numerous, and even more will be found as GPS is combined with wireless communication networks.
Automobile manufacturers are incorporating GPS and cellular technology to provide security, safety, and peace of mind to their customers. The OnStar division of General Motors currently provides cellular communications units and service to more than 12,000 customers, and hopes to install as many as two million OnStar units in more than twenty of GM’s 1998 models. At $270 a year for unlimited service and $900 for installation, the service is not cheap but provides 24 hour monitoring and the ability to remotely lock and unlock doors as well as perform engine diagnostics. Lincoln offers their version, termed remote emergency satellite cellular unit (RESCU), in Continentals at a retail price of $1995. Consumer studies have shown that the primary reason for purchasing a cellular phone is safety, and adding accurate GPS location information to a distress call has clear value. Further advancements in these technologies include sending a cellular message if the air bag is deployed or a major mechanical malfunction occurs.
Smaller devices are also currently in development to provide personal security in a handheld package. When the user presses a panic button the internal GPS receiver sends current position information via a tiny cellular digital packet data (CDPD) modem to an operations center, which can then dispatch emergency services or assistance to the proper location.
That's all for this month. Keep that electronic mail coming to email@example.com, or check the PCS Front Line website at http://www.grove.net/~dan. Until next month, happy monitoring!
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Updated May 1, 2003