DoCoMo sounds 3G spectrum alarm

A senior manager of NTT DoCoMo Inc. has raised a warning flag regarding network capacity for third-generation (3G) mobile services, saying company simulations show the spectrum allocated to the company won't be enough for rich mobile multimedia services within five to six years. The comments come just over two months before NTT DoCoMo is expected to launch the world's first 3G service in Tokyo.

Such 3G services are expected to include a large number of mobile multimedia services offering audio and video services to users in addition to the voice telephony and basic Web browsing available today on second generation (2G) systems. A potential problem exists in that multimedia services such as video require a larger chunk of bandwidth than voice, so serving large numbers of people in a densely populated area may prove difficult.

Just how difficult this will be will not be clear until services are launched and the company gets an idea of usage patterns and how many times and where the average user accesses such services.

"We need to monitor the trend of traffic to determine whether we have sufficient capacity or not," said Kyoji Murakami, senior manager of the IMT-2000 network office at NTT DoCoMo, speaking to IDG News Service at the CeBIT trade show in Hanover. "But we have done simulations and according to simulation, I have to say, the currently allocated spectrum, 15MHz, is not sufficient." He said the projections showed the bandwidth given to the carrier by the government might prove too little in five or six years.

The carrier was actually allocated 20MHz of spectrum but a quarter of it overlaps with the PHS (Personal Handyphone System) service, making it unusable at present. In addition to looking at ways of minimizing interference with PHS, DoCoMo has also been petitioning the Japanese Ministry of Public Management, Home Affairs, Posts and Telecommunications (MPHPT) for at least an additional 5MHz of spectrum. Murakami said adding extra space was the easiest way to solve the problem.

"For the PDC (the current 2G network) system, we are allocated 30MHz and with this spectrum we are now serving 35 million. If we can get an additional 5MHz for FOMA," he said, referring to DoCoMo's 3G brand name, "total spectrum is around 20MHz." This means the company will still have to work on other solutions, such as improved efficiency of frequency usage but, he said, "it will be difficult to accommodate all 35 million subscribers on FOMA."

The problem won't be isolated to DoCoMo either, he predicted.

"It's going to be a universal problem," he said. In Japan, the problem will be greatest in the highly populated Tokyo metropolitan area. "If we can overcome this problem in the Tokyo metropolitan area, the others areas will be OK, so I think the same thing can be said about the U.S.," he said, adding Los Angeles and New York might prove headaches for wireless network operators.