Nippon Telegraph and Telephone Corp. (NTT), telecommunications operator in Japan, has announced that it will incorporate the PHS-WLL system in its telephony service from the autumn of 1998. The new system aims to provide advanced telecommunications services in rather scarcely populated areas, such as farming villages and islands, while reducing phone installation costs in those areas. NTT plans to deploy the PHS-WLL based telephony service nationwide, starting in Obihiro City, Hokkaido Prefecture.

In addition to conventional subscriber telephone service, the PHS-WLL system to be put in place by NTT will handle wireless data transmission functions including access to ISDN. Fiber-optic cables will be laid from switching offices to PHS-WLL cell stations in targeted telephone service areas, and from the cell stations to household subscriber loops will be linked via wireless connection.
This PHS-WLL system will allow subscribers living far from switching offices to have access to ISDN service as well as 64 kbit/se and 128 kbit/s high-speed digital transmission services, which are not readily available with the current telephone service using copper cables due to transmission loss and other difficulties. Also, because this PHS-WLL-based system requires a far fewer cables and utility poles than wired systems, installation costs can be dramatically reduced.
NTT plans to introduce its PHS-WLL system in relatively un-populated areas to replace old copper cables and to prepare for demand for ISDN service. Fig. 1 shows NTT’s PHS-WLL system configuration.

Main features of PHS-WLL are as follows:

1. What is PHS-WLL?

PHS-WLL is a 1.9-GHz band digital wireless system based on PHS technologies. A PHS-WLL cell station with a transmission power of 20 mW (average) can cover a radius of about 2 km (max. 5 km). One cell station can accommodate 120 subscriber telephones.

2. Merits

1) PHS-WLL system will give access to 64 kbit/s and 128 kbit/s high-speed digital transmission services, which enable high-speed access to Internet services. The introduction of PHS-WLL systems will accelerate replacement of copper cables with fiber-optic cables from switching offices to cell stations. Therefore, as demand breaks for high-speed, broadband networks in the near future, fiber-optic subscriber loops to households will be laid more quickly than before.
2) The installation cost per subscriber telephone line has traditionally been much higher in areas sparsely dotted with households than in densely built-up areas. PHS-WLL based system will dramatically reduce installation costs in comparison with metallic cables.
\ Virtually shortening the total cable length in the system can reduce communications faults resulting from cable snapping and other factors. This is anticipated to lead to provision of much improved services in islands and the areas prone to natural disasters including typhoons, which require a lot of time for line persons to arrive.

3. Introduction plans:

NTT plans to introduce its PHS-WLL-based telephony service nationwide, starting with the Hokkaido and Kyushu areas.
The introduction of PHS-WLL system into rural areas in Japan is permitted with the rider that the PHS-WLL system does not interfere with existing PHS systems.