Wireless Systems Design

Will 3G Have To Compete For The Wireless Future?

3G Networks Face Many Challenges, Including Technology, Usage Models, And Existing 802.11b Networks.

Often the simplest questions asked are the hardest ones to answer. For example, ask any group of technology-savvy colleagues if third-generation, or simply 3G, networks exist today. You'll get three different answers: yes, no, and maybe. Why is there this disparity? The definition of 3G has become a moving target. The response therefore depends upon the market segment questioned—whether it's telecom or datacom—and the country in which it's asked.

Why should anyone be concerned about the fate of 3G? Because it may shape the fast-growing 802.11b wireless local-area-network (WLAN) market—and be shaped by it. The struggles of these two powerful, yet quite different wireless networks—the much-heralded 3G and the dark horse known as Wi-Fi—will determine the direction of wireless technology for years to come. As a result, design engineers, market investors, chip manufacturers, and infrastructure vendors are closely watching this evolving struggle.

A ROSE BY ANY OTHER NAME
3G wireless technology is the next evolutionary step in telecom cellular networks. It promises increased bandwidth for the packet-based transmission of digital voice, data, and video communication. The Universal Telecom-munication Union (UMT) has issued guidelines for 3G that specify transmission speeds of 144 Kbps inside a moving vehicle and 2 Mbps at a fixed location.

As an evolving technology, 3G has several variations: Wideband Code Division Multiple Access (W-CDMA), CDMA-2000, and EDGE. Japan's NTT Docomo and Manx Telecom, located in the United Kingdom's Isle of Mann, have deployed W-CDMA networks with limited success.

One of the chief technical problems with the deployment of W-CDMA has been the lack of system testing, notes Dave Whipple, Agilent Technologies' (www.agilent.com) Wireless Industry Technologist. As he states, "It is not clear that lab testing has been done for W-CDMA." Whipple explains that more cooperation is needed between network-equipment vendors and terminal devices to ensure interoperability between the whole system.

Another component of 3G implementation is CDMA-2000. This variation has been deployed by Verizon and Sprint PCS in the U.S., along with several different carriers in Korea.

The third main 3G component, known as EDGE, serves as a follow-on to GPRS and an upgrade to GSM. Its networks are being deployed in the U.S. by AT&T Wireless, Cingular, and Voicestream (now called "T-Mobile"). EDGE allows any user three times the data rate over GPRS. It requires a substantial amount of network reuse, however.

System complexity in both the handset (terminal) and networks (infrastructure) are challenging even the best wireless designers. Many 3G handsets, for example, require two processors: one for the digital baseband and another for applications. Both processors must operate at increased throughput rates, while maintaining a total power consumption that's equivalent to 2G handsets.

These are conflicting requirements. Higher throughput rates typically mean higher processor clock speeds. This, in turn, translates into higher power requirements. Balancing throughput and power rates adds even more pressure to the standard handset design criteria of reduced component size, time-to-market, availability, and cost.

Eva Skoglund, OSE Systems' (www.ose.com) Product Manager of Wireless Communications, agrees that system complexity is a hot issue. She says that designers must decide how many CPUs and DSPs are needed while partitioning the functionality for each processor. "Handset designs must include a very complex baseband chip—Bluetooth chips and high-end parts that must handle multimedia, high-bandwidth data, and Internet connections." This task is certainly not an easy one.

Dual processors also create challenges in the design of subsystem components, like memory. Baseband and application cores, for example, perform different computing tasks. These tasks lead to both volatile and nonvolatile memory requirements, observes Mario Fazio, Micron's (www.micron.com) Director of Strategic Marketing for Wireless Products (see figure). Fortunately, new Flash devices, such as Micron's V-SyncFlash memory, can reside on the synchronous SDRAM bus instead of a separate Flash bus.

Even with dual processors, however, the computing power and throughput may not be enough. Using the traditional approach of a DSP and ASIC combination, how does a designer provide the high capacity needed to handle complex algorithms? Add to this challenge the ever-changing standards specification, and the result is a designer's nightmare.

"It takes too long to get it right using traditional ASIC technologies," observes Bob Plunkett, Director of Product Management for QuickSilver (www.qstech.com). "By the time you have one version figured out, the standards bodies have moved onto the next version." The result, Bob argues, is that only companies with very deep pockets have the resources to develop 3G—and even then they struggle. Quicksilver's adaptive computing machine (ACM) and SilverC languages make it possible to develop new processing technologies that keep pace with evolving standards and design complexities at a reasonable cost.

The 3G base-station-infrastructure side faces similar problems. Here too, traditional DSP+ASIC combinations are struggling to keep pace with the processing power needed in 3G. In order for equipment manufactures to build profitable businesses, they must use new techniques to drive down the cost-per-channel across the network, explains Ravi Subramanian, President of Morphics Technology (www.morphics.com). Morphics has developed a new class of processor, called the wireless signal processor (WSP), that drastically improves the traditional ASIC+DSP hardware-software partitioning used in 3G baseband processing.

Vendors of existing DSP technology are not standing still, either. In W-CDMA base-station design, for example, power and cost reductions are driving manufacturers to replace much hard-wired logic with software, notes Doug Grant, Analog Devices' (www.analog.com) Director of Business Development for RF and Wireless Systems. Grant explains that this is being accomplished with advanced programmable DSPs, like ADI's TigerSharc family.

FPGA vendors also are rising to meet the challenge of changing system complexity and evolving standards. Paul Ekas, Senior Manager for DSP Marketing at Altera Corp. (www.altera.com), emphasizes that infrastructure-equipment vendors need low-risk, affordable solutions to address 3G's volatility. Because of that fact, 3G equipment designs are moving away from costly ASIC chips and back toward lower-risk FPGA solutions.

3G implementations also require new RF designs. James Spoto, CEO and President for Applied Wave Research (www.appwave.com), points out that unique radio-frequency requirements add to the complexity and cost of 3G, which in turn affect both the design methods and tools. AWR provides an electronic-design-automation (EDA) tool architecture that supports a unified RF systems and circuit design platform.

Satisfying technological complexity is only one of the challenges facing 3G. Equally pressing issues include finding a compelling usage model and competition from existing IEEE 802.11b wireless networks.

If carriers are to remain profitable, they must find a usage model that will interest potential customers enough to buy into 3G products and services. David Chen, a General Partner with OVP Venture Partners (www.ovp.com), notes that one of the main usage scenarios for 3G is to provide a significant increase in bandwidth (up to 384 kbps) to business customers. But is bandwidth really a big driver? It's hard to come up with a scenario in which the typical user would need anything beyond current phone dial-up rates of 50 kbps while in motion.

David Chen believes that many users confuse "mobility" with "mobile." "The word mobility, to me, means anytime, anywhere access to the stuff I want. Mobile means that I'm moving." He notes that mobility data needs are now being met by 802.11b hot-spot technology. In the near term, truly mobile applications can be met by 2.5G technology.

Wi-Fi JOINS THE 3G MOVEMENT
The recent unconfirmed report that the major telecom giants may soon roll out a nationwide 802.11b network in the U.S. adds weight to the argument that 802.11 will play a major role in the shape of 3G development. ADI's Doug Grant sees this as a strategic play by the carriers. They could then offer both flavors of high-speed wireless data access—3G and Wi-Fi. They also would be able to service the very different "mobile" and "portable" usage scenarios.

Goli Ameri, President of eTinium Inc. (www.etinium.net), observes that European and Asian service providers have actively pursued the WLAN option. They recognize that part of the revenue that would have gone to the 3G network will be diverted to WLAN networks. According to Ameri, "British Telecom has a strategy to establish 400 hot spots throughout the next year. Sonera and Telia have both been very active in this area as well."

The U.S. has a high penetration of PCs in both homes and offices. This means that any major carrier offering 3G services may find itself constrained to offering services similar to the models supported by the WLAN operators, explains Guy Singh, NTRU's (www.ntru.com) Director of Wireless. "This will preclude any charge-per-byte revenue models, because they won't be able to compete." In other parts of the world, Singh says that the key to 3G's success will be the speed of deployment. The longer it takes to deploy it, the shorter the window of opportunity before WLAN technologies catch up.

Are 3G and WLAN technologies in competition? Most experts say no—at least for now. Both technologies are seen as complementary, because they service different usage scenarios and business models. Yet the two great market domains of telecom and datacom may be converging. Voice-over-Internet Protocol (VoIP) systems, which bring voice capabilities to WLANs, are seen as a viable and profitable market in the future. IP technologies over cellular systems, like OFDM, will provide WLAN capabilities on cell phones. This merging of 3G and WLAN will undoubtedly change the shape of both technologies—to the eventual benefit of the consumer.

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