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Mamoru Sawahashi has been driving in circles for 16 months, but he feels like he's making plenty of headway. Sawahashi is an engineer studying the potential of hyperfast 4G, or fourth-generation, cellular service for Japan's NTT DoCoMo Inc (DCM
). Since July, 2003, he and his team have been driving an Isuzu van in an 800-meter loop around the verdant Miura peninsula south of Tokyo 250 times a week to test the reception from a nearby cellular antenna. ``There are many problems to be solved, but we have made a lot of progress,'' says Sawahashi. That's right: 4G. Sure, most of the world has yet to adopt 3G and the high-speed data services it makes possible, but in Japan 3G cellular is a reality that millions use every day to make videophone calls, download clips of soccer games, check traffic, and send animated e-mails to friends. So DoCoMo is going full bore to develop the Next Big Thing in mobile telecommunications. The company may have little choice. On Oct. 29, DoCoMo said profits for the first half of fiscal 2004 had fallen by 6% from the year-earlier period, while sales slid by 3.3% as tough competition has forced price cuts. That puts lots of pressure on engineers such as Sawahashi. His team has managed to get transmission speeds up to 300 megabits per second. That's 20 times as fast as the speediest 3G links, and about 150 times as fast as a typical wired broadband connection to a U.S. home. The system uses a technology called orthogonal frequency and code division multiplexing, which uses the radio spectrum efficiently by chopping signals into many small chunks and sending them across a range of frequencies rather than transmitting them on a single frequency as current cellular networks do. Inside the white van, traveling at up to 40 kilometers per hour, Sawahashi's engineers have simultaneously received two nearly flawless high-definition TV signals from the base station using the system, and in the laboratory they can manage four such transmissions -- which they proudly display on a quartet of flat-panel TVs. Today's speediest wired links in the U.S. can't even handle the transmission of one HDTV signal. Make no mistake: This technology isn't ready for prime time. DoCoMo doesn't expect to introduce 4G service before 2010, in part because the radio spectrum such systems will use likely won't be decided before 2007. There are plenty of technical hurdles, too. For instance, the signal rapidly degrades when the van gets more than 1 km from the base station. And forget about putting a 4G phone in your pocket. The receiver is the size of a refrigerator and consumes about as much power. The size is partially because DoCoMo has used off-the-shelf parts, which could be shrunk if real production were to begin. But the system's power consumption will be harder to trim.WHO NEEDS THESE SPEEDS?Some wonder whether it's worth the trouble. Technologies such as Wi-Fi and Wi-Max use free pieces of the radio spectrum and will likely be acceptable and cheaper -- if not quite as fast -- alternatives for many uses. And few see the need for watching four TV shows while driving, or doing anything else that might require that much mobile bandwidth. ``There just aren't applications today or anytime soon that would use up the kind of bandwidth they're envisioning,'' says Shiv Putcha, an analyst with Yankee Group, a telecommunications research firm. DoCoMo is confident that if they build it, applications will come. The company this year plans to devote $91 million to 4G, and 175 engineers -- 15% of its research staff -- are working on the project. One potential use is simply as a replacement for today's wired links into homes and offices, letting users access a single network whether they're in the bedroom, on the bus, or in the boardroom. DoCoMo execs also note that while there were plenty of 3G skeptics, the company has created a solid business by offering data-rich content such as video on phones. ``As we provide higher transmission speeds, the services will follow,'' says Seizo Onoe, the managing director who oversees the 4G effort. And once those services arrive and subscribers start to clog the airwaves using them, fear not: DoCoMo already has teams working on 5G and 6G. By David Rocks in Kanagawa, Japan