CDMA Technology
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Beyond Words

By Jeffrey A. Schlesinger, UBS

If voice services become standard, data and information could be selling points of the future. In fact cdmaOne’s robustness and bandwidth could mean that, for future investors, its real benefit could be data rather than voice.

For the best part of a decade, the CDMA/TDMA battle has centered around which of these air-interface techniques is best suited for high-mobility voice communications. Wireless technologists will likely declare at the end of the day a truce (in the form of third generation mobile standards) and conclude that there are only marginal differences between the current implementations of these technologies, at least as they pertain to mobile voice communication. For fixed-based wireless services, CDMA is likely to prove more spectrally efficient and cost-effective than current high-mobility implementations of TDMA.

During this lengthy debate, perhaps the experts lost sight of the fact that society was undergoing a fundamental shift in how it was choosing to communicate information. With the rapid development of the Internet, e-mail, and corporate Intranets, society has become increasingly dependent on data, as opposed to voice, as a means of communicating information. As data becomes more and more a part of our daily lives, mobile communications traffic will also migrate from voice to data. In fact, some industry pundits believe that data traffic will account for almost 30% of network traffic by the end of the decade.

While this prediction may seem a bit aggressive given its late start, data is certainly going to play an important role in the next phase of the industry’s development. For, in an increasingly competitive services environment, voice services will ultimately become a commodity. Operators will look to data and information services as a means to differentiate their networks and create brand loyalty. It is here, in the area of mobile data and information access, not voice, that CDMA is likely to prove a more robust technology than current TDMA-based technologies.

As the world migrates from voice to data, and correspondingly from circuits to packets, the real virtues of CDMA become apparent. IS-95-based CDMA is inherently a wideband packet radio system with an intrinsic data format that essentially packetizes voice traffic. The relatively broadband nature of CDMA and its high channel data rate, makes this air-interface technology very well suited for data communications. Assuming you could use the entire CDMA channel, you would have essentially a T1 in the palm of your hand. While this is not possible today, the point is that data applications, whether wired or wireless, require significantly more bandwidth than voice.

The wideband channel structure of IS-95 CDMA relative to TDMA-based systems like GSM, PDC, and IS-136 is better suited for delivering faster and more efficient mobile data communications.

Aside from the obvious difference in air-interface technique and channel size, today’s CDMA systems are architecturally different in other ways. Many of the IS-95 CDMA systems being constructed today incorporate network backbones that utilize packet-based technologies, such as Asynchronous Transfer Mode (ATM) and Frame Relay, for transmission of voice traffic between base stations and mobile switches and base station controllers (by comparison, today’s TDMA systems utilize circuit-switched technologies to connect base stations and mobile switches and controllers).

ATM/Frame Relay backbone architectures give these systems truly broadband capability, which, as air-interface technology continues to evolve will be able to support high-speed data applications (database query, broadcast data, file transfer and Internet access) and ultimately video telephony. Today, Lucent and Nortel offer packet-based backbone architectures for their CDMA product offerings.

In terms of additional network hardware to support CDMA data services, carriers only have to add Interworking Function equipment to their voice networks. Interworking Function hardware is essentially a modem pool that sits behind the switch and converts the data information from CDMA packets to the public network format. Today, only a limited number of North American CDMA systems can support packet data transmission with speeds up to 14.4 kpbs. This service offering should be widely available by the end of 1997. Faster data communications is on the horizon, as a new CDMA standard for high-speed data services (64 kbps ISDN B channel service plus a D channel for signaling) has recently been approved. This new standard will allow seamless connectivity to both ISDN and High Speed Asynchronous Circuit Switched Data applications. It should be noted that many of these high-speed applications will require end-user devices be stationary — probably a good idea given the trouble some people have with just talking and driving. High-speed CDMA network services should be available late in 1998 or 1999.

In fairness to the GSM camp, it is important to note that GSM networks support 9.6 kbps circuit switched data transmission today. In addition, a GSM specification for multi-slot high speed circuit switched data service (HSCSD) was approved last June, with services expected in 1998. HSCSD in conjunction with 14.4 kbps channel coding will provide data speeds up to 57 kbps. Recognizing the need for packet-based communication services, the GSM community has also approved a standard for General Packet Radio Services (GPRS).

Services supporting this packet standard are expected to be available in 1998. GPRS is expected to provide peak data rates of 115 kbps, and is based on data networking standards such as TCP/IP and X.25. Even so, current implementations of GSM are architecturally more limited in terms of data transmission capacity due to the 200 KHz channel structure relative to IS-95 CDMA’s 1.25 MHz channels, everything else being equal.
When discussing mobile data, it is important not to get too bogged-down in technology; technology alone won’t make wireless data a reality. It takes applications in the form of end-to-end solutions. In this regard, the CDMA proponents did something smart in order to insure that the technology would provide a smooth transition path to data applications. In developing the data specification for IS-95 CDMA, the standards committee adopted the TCP/ IP compliant Cellular Digital Packet Data (CDPD) protocol stack for CDMA packet data transmission. TCP/IP compliance not only insures that connectivity to enterprise networks will be seamless but also facilitates third-party application development. In addition, applications that have been or are in the process of being developed for the North American CDPD standard can be ported to IS-95 by modifying the bottom three layers of the protocol stack.

Initially, data applications will focus primarily on specific vertical market solutions, such as field service and field sales. However, over time, wireless data applications will migrate to the general business user and ultimately the mass market.

For this to occur new information appliances will need to be developed. These devices will likely fall into two categories: communication-centric and computing-centric. Communication-centric devices will provide seamless voice and data communications connectivity supporting data applications such as e-mail, WWW access and fax.

Computing-centric devices will be more processing intensive and provide mobile functionality and connectivity to traditional fixed-based computing applications. Either way, computing, networking, telecommunications and Internet content industry groups will have to forge alliances to bring these next-generation devices and applications to market.

The usual suspects such as Intel, Sun, Oracle, and of course Microsoft will almost certainly be a part of the emerging mobile data market. New entrants such as Unwired Planet (mobile access to traditional web sites) and Geoworks (mobile device operating systems and information content services) are also likely play an important role in the development of this market.

The biggest challenge for wireless data may ultimately come in the form of marketing, not technology. Service operators will have to learn how to market and support data applications, which are dramatically different from conventional voice. Customer segmentation for wireless data will be based on vertical market applications which in many instances will require different distribution channels.

New distribution channels will emerge, utilizing system integrators and VARs. In addition, third-party wireless data gateways will be particularly important when dealing with corporate network security and firewall issues. Companies capable of providing these integration and/or gateway services are now emerging (i.e. Wireless Telecom).

So, at the end of the day who wins? The winner is, quite simply, society — which is rapidly migrating to the world of data and information-based services. In the world of data (i.e. computing) society consumes bandwidth — bandwidth for processing, storage, and communications. Over the years the price of the PC hasn’t declined appreciably; instead we buy faster processors, greater storage capacity, and faster modems. Relative to today’s TDMA-based mobile systems, the wider bandwidth and packet nature of the CDMA air-interface makes this technology more robust and better suited to support data applications. In fact, no one in the industry really disputes this; the only thing they disagree on now is the appropriate bandwidth.

All proposed third generation radio mobile systems incorporate radio access systems based on CDMA. The only difference between these systems and presnt-day cdmaOne is that these systems incorporate radio access techniques that utilize significantly wider CDMA radio channels (5 MHz to 15 MHz). As a result, these systems will be capable of significantly faster data communications (380 kbps+) than any of today’s mobile systems, whether they be CDMA or TDMA.

Such third generation mobile networks will be capable of providing the communications bandwidth necessary to seamlessly and cost-effectively extend enterprise networks and Internet-based applications to the mass market. Only then will we truly have ubiquitous any time, any format, anywhere communications.
The future of mobile communications is a function of both data and voice. CDMA technology will make the data side of the equation a reality.