Nippon Telegraph & Telephone Corp reckons that the 800GHz band used for cellular radio mobile telephones in Japan will reach capacity within five or six years, and is looking to be ready when the airwaves become overloaded. The company has announced that it has completed successful tests of high-quality digital voice telephone communications in the quasi-microwave 1.5GHz band. In the meantime, Nippon Telegraph plans to expand the capacity of the current 800GHz band next spring. The Japanese phone company, in slow process of being privatised, is also doing research into radio channel control, further miniaturisation of mobile telephones – and a reduction in their power consumption, and at new techniques for more bandwidth-efficient coding of digitised speech.
