TOKYO-In early February, some 300 telecom experts from 25 nations in the Asia-Pacific region met in Tokyo to compile their proposals for WRC-2000. Based on the five-day meeting, the Asia Pacific Telecommunity Conference Preparatory Group (APG) plans to submit a proposal at WRC-2000 for an additional allocation for IMT-2000 services in the frequency bands of 800 MHz (806 MHz to 906 MHz), 1.7 GHz (1710 MHz to 1885 MHz) or 2.5 GHz (2520 MHz to 2670 MHz).
APT will recommend that each government select the most appropriate band of those three, considering the nation’s environment and circumstances for IMT-2000. Yasuo Tawara, deputy director of Japan’s Ministry of Posts and Telecommunications (MPT) Mobile Communications Division, said Japan will support all three bands.
Regardless of which band is selected for 3G services at WRC-2000, operators will not be able to use the additional allocation until 2010 at the earliest, because most bands are currently used, and it takes time for incumbents to relocate. All three of APG’s recommended bands are used today in Japan.
At WRC-1992, a total of 230 megahertz was allocated for IMT-2000 services. Although Japanese carriers will launch their services as early as May 2001, some users will continue to occupy portions of the IMT-2000 spectrum until October 2002.
The Japanese government plans to allocate 30 megahertz for uplink and downlink (or 15 megahertz for either uplink or downlink) for 3G carriers later this year. The uplink transmission, from the terminal to the base transceiver station (BTS), will be in the 1925 MHz to 1980 MHz band. The downlink transmission, from the BTS to the cellular phone, will be located in the 2115 MHz to 2170 MHz band.
Japan initially planned to allocate 40 megahertz for both uplink and downlink (or 20 megahertz for one way) for each of the three 3G licensees. However, due to possible interference with PHS services, the government shrank the bandwidth for each carrier from the initial 20 megahertz to 15 megahertz to construct a 5-megahertz guard band for each operator.
In reality, only one carrier must have the guard band to prevent interference with PHS systems. But the government decided to shrink the bandwidth of each of the three carriers to be fair.
Because additional bandwidth allocations probably will not be available in the short term, and Japanese carriers think 15 megahertz is too little spectrum to facilitate all their users, carriers must consider the possibility of using the spectrum in the guard bands.
MPT said lifting the guard band is possible if both PHS carriers and 3G carriers apply appropriate measures to prevent interference. However, debt-ridden PHS carriers may not want to spend a lot of money to improve their base station systems to prevent interference with IMT-2000 networks. So 3G carriers may have to bear the cost of applying the preventive measures. Under the current circumstances, however, 3G carriers must deal with the limited bandwidth of 30 megahertz for uplink and downlink for the next few years.
3G carriers do not disclose how many users they will be able to accommodate with the 30 megahertz allocation. But according to the 3G advisory body to MPT, carriers must accommodate at least 170,000 subscribers per 1 megahertz of spectrum.
