Today's GPRS Technology Bridges the Gap to the Next Generation, Says Motorola

November 8, 2001

The much-heralded third-generation (3G) communications networks, with their promises of "always-on" data connections for high-speed mobile Internet access, have claimed most of the public's attention in recent years. However, there is an alternative for consumers who need mobile Internet access, but just can't wait for 3G. Improved wireless technology, called "2.5G" because it spans the gap between the current generation (2G) and the third, is delivering many of the promises of 3G now.

The most widespread of the 2.5G technologies is GPRS, or General Packet Radio Service. GPRS is an upgrade to existing networks based on the leading 2G standard for digital wireless, GSM (Global System for Mobile Communications). Primarily a software upgrade, GPRS requires neither new spectrum nor new networks to be built. Yet it offers much of the speed and increased functionality associated with 3G.

With GPRS available today, the 3G "revolution" looks like more of an "evolution."

"GPRS is really going to have us set up for 3G, because we'll have the servers, the billing engines, all this in place," says Motorola's Bob Schukai, director of 3G Products for Europe, the Middle East, and Africa.

Motorola is a leader in GPRS, delivering a range of technologies including handsets and the underlying handset technology; network infrastructure; and applications. Motorola was the first company to bring to market a commercial GPRS handset, the Motorola Timeport(TM) 260. And now Motorola's semiconductor sector is working to lower the barrier to entry for other manufacturers by offering them a flexible, scalable platform for 2.5G handsets designed to speed time-to-market.

A Solution...and a Revolution

The launch of GPRS networks is likely to lead to the establishment of the kinds of services and service-provider infrastructure that were once known as the hallmarks of 3G. GPRS, then, is the real communications "revolution." Future 3G launches will be distinguished by even faster data rates.

"What's 3G? It's GPRS bandwidth on steroids," says Schukai.

The momentum behind GPRS has increased because the road to 3G has turned out to have quite a few twists and turns. In Japan, Europe, and the U.S., launches of 3G networks have been slower than anticipated, as companies work with new technologies and face the high costs of buying 3G spectrum licenses and building new networks.

According to the GSM Association, more than 60 wireless carriers have now launched commercial GPRS services. BT Cellnet launched the world's first commercial GPRS network, in the U.K., providing customers with the Timeport 260, the only GPRS phone commercially available at the time. Schukai points out that the carrier was also a major customer of Motorola's GSM network infrastructure equipment, which could be readily upgraded to GPRS technology.

More and Faster Services

The kinds of services envisioned for 2.5G and 3G are those that can thrive when users have convenient, high-speed access to the wireless Internet. Short-text messaging, already popular, promises to be better and faster. GPRS networks should also enable the kinds of applications that have struggled to emerge in 2G networks, which use circuit-switched technology optimized for voice calls. Data-friendly GPRS networks may shine, for example, in offering more robust on-the-go e-mail access as well as e-commerce and a wide variety of services through WAP (Wireless Application Protocol) sites.

"There are markets where GPRS is really cruising," says Schukai. "Germany has been up and running quite a while now, Italy is up and running, the Nordic countries are up and running."

WAP promises to bring greater Internet functionality to mobile phones, just as the web browser and HTML opened up the Internet to hundreds of millions of PC users. According to Schukai, WAP got something of a bum rap for a couple of reasons when introduced in 2G networks. "The billing model was dreadful. While reading and thinking about what you have on your screen, you were being charged for it. You had this need to speed through WAP pages as fast as you could."

That problem is a result of the circuit-switched nature of 2G networks. GPRS is different, says Schukai. "GPRS gives the carriers the ability to connect you and only charge you for downloading pages. You're not charged for reading and thinking."

Another problem was the availability of content, or lack therof. "Like in the early days of the Internet, there was not a lot of content. Now there's a lot more content out there," Schukai says.

Although best known for providing handsets and network infrastructure such as the base station equipment owned by carriers, Motorola also brings applications to market.

"We partner to get the best-in-class apps out there," says Schukai. "We've signed up top-branded content such as 'Who Wants to be a Millionaire' and 'Trivial Pursuit,' which we offer through a number of carriers."

The use of Java(TM) in mobile devices -- another area of interest for Motorola -- promises to open up a whole new world of applications. "We help third parties write applications for our phones, such as our iDENŽ phones and the Accompli(TM) 008 device," says Schukai.

Packets are the Key

The emergence of such data services is now more likely because GPRS introduces packet-switching technology to the traditionally circuit-switched GSM network. That allows for better billing -- users can be charged based on actual data use rather than for idle connection time. Just as significantly, GPRS packet-switching allows for an "always-on" connection to data services for the user, and is the key to the much faster data-transfer GPRS offers.

The "always-on" feature of any broadband service is an obvious convenience. Just as a cable modem or corporate network saves a PC user the hassle of logging on with a dial-up modem, GPRS networks allow for quick access for the mobile subscriber. In fact, a user can field a phone call even while using wireless data. The data session is simply paused while the subscriber chats away; the data session resumes when the call is over.

Furthermore, the GPRS method of packet-switching means data rates faster than that available with 2G networks. GPRS data transfer could, in theory, exceed 100 kbps; but for real-world applications, according to Schukai, users can achieve 25 to 35 kbps today.

A Hybrid Network

GPRS implements data-friendly packet-switching through some clever modifications to a network originally designed with voice in mind.

A cellular network such as GSM must accommodate multiple users within the same cell, without letting their phone transmissions interfere with one another. GSM networks accomplish this, in part, by using time-division multiplexing (TDM), in which the ones and zeros of various users' digital phone calls are mixed together on a given radio frequency, but separated and organized by time.

The resulting stream of radio communications is organized into frames -- think of a train consisting of boxcars. The frames, in turn, each contain time slots (eight slots, in the case of GSM), each slot devoted to one user's phone call. From frame to frame to frame, a given user is assigned the first time slot, another user is assigned the second slot, and so on. Digital sampling techniques parcel a continuous voice conversation or data download into these slots. These assigned slots make up a dedicated telephone circuit, and such networks are called circuit-switched networks.

But these time slots are often empty -- due to a pause in the conversation, or Schukai's "reading and thinking" example. That is essentially a waste of network capacity. Packet-switched networks, on the other hand, forego circuits. Instead, they group data into bundles (packets) and multiplex the packets of many users into a network, taking advantage of whatever capacity is available.

If, instead of continuing to dedicate empty slots to a "thinking and reading" user, a circuit network could reclaim those inactive slots to transport some other user's burst of data, then it could operate as a packet-switched network. This is what GPRS does. By placing wireless data into channels where time slots can be bundled for the users who need them at any moment, GPRS serves as a packet-switched overlay to the circuit-switched GSM network.

This also permits the higher GPRS data transfers. During the moments that a user is downloading data, his or her phone may have access to up to three or four time slots per frame (rather than only one as in a 2G network). This allows for a data rate up to three or four times faster than in a 2G system.

Coming to Market

Though the basic idea behind GPRS is relatively simple, any new technology is, of course, a challenge. Even though it does not require the building of entirely new networks, GPRS certainly presents barriers to entry. Motorola expects to benefit from its substantial GPRS experience.

"We have an advantage there because of our technological expertise end-to-end," says Schukai. "We were the first to have a digital phone, a dual-band phone, a tri-band phone, and now a GPRS phone." A leader in semiconductors as well as handsets, Motorola also has announced it will offer a comprehensive silicon-to-software solution for GSM/GPRS handsets. This platform, called i.250, will lower the barriers to entry into the 2.5G market for other handset makers.

But when all is said and done, even the technologists recognize that ultimately, GPRS is all about the service and convenience people want.

"GPRS at the end of the day is just a technology enabler for people to play games, check news, access flight information," says Schukai. "It lets you access pretty cool content really fast."


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