1. Introduction

On September 30, 1998, the Ministry of Posts and Telecommunications (MPT) revised regulations related to the Radio Law for the introduction of "Fixed Wireless Access (FWA) System Using 1,900 MHz Band Frequencies." These regulations were promulgated and enforced on the same day. In rural areas with a low fixed telephone density, this system allows high-quality subscriber transmission lines, through which high quality services can be provided, to be constructed far more economically and easily than by laying costly fiber-optic cables. With its introduction, the FWA system is expected to rapidly advance regional telecommunications networks in rural areas, including launch of multimedia services via such networks. On November 20, 1998, MPT designated the Telecom Engineering Center (TELEC) as the body in charge of certifying conformity of radio equipment with technical requirements. TELEC began this service on the same day. Outline of technical requirements for the PHS-FWA system is as follows.

2. Technical conditions of the FWA system

1) Main Specifications

The FWA system using the 1,900 MHz band is known as PHS-FWA. This system uses the frequency band allocated for public and private PHS systems, because it has adopted current PHS technology and should meet demand for efficient use of the band frequencies. However, introduction of FWA system is allowed only when it causes no interference with the PHS services being provided in the target areas (see Table 1.).

Table 1 Main specifications

Frequency band	1,900 MHz band (within the frequency band allocated for PHS)
Communications method	TDMA/TDD
Modulation	/4 shift QPSK
Transmission power	Base station: less than 160 mW Subscriber station: less than 80 mW
Antenna	Absolute gain: less than 22 dBi; and detachable from the case
Other requirements	Introduction of PHS-FWA system must not cause any adverse effect (such as interference) to PHS services already in operation.

2) System configuration

The PHS-FWA system consists of base stations which are on telecommunications carriers' side, subscriber stations which are installed in subscribersO premises, and wireless transmission lines that interconnect both stations (see Fig. 1.). The blanket licensing system, introduced in October 1997, is made applicable to subscriber stations. This means that, as stipulated in Article 27-2 of the Radio Law, if the party applying for radio station licenses is to use only radio equipment that has been certified as being in conformity with technical requirements and therefore these radio stations (in this case, subscriber stations) are regarded as specified radio stations, the party needs to obtain just one license for operating all these stations.

3. Items to be tested and technical requirements

In principle, testing methods for certifying conformity of each PHS-FWA system with technical requirements are very similar to those for public and private PHS systems. This is because there are very limited differences in the technical requirements for both. One major difference resides, however, in the definition of aerial RF power by the Radio Law: the Law defines this for PHS-FWA system as average power within a slot. Therefore, it is 160 mW for a base station and 80 mW for a subscriber station (see Table 2).

Table 2 Technical requirements

Test items	Technical standard
Frequency stability	Less than 3x10
Allowed value for ccupied bandwidth	Within 288 kHz
Transmission supurious	In-band: less than 250 nW Out-band: less than 2.5 W
Transmission power	Base station: 160 mW Subscriber station: 80 mW 20% for upper limit and 50% for lower limit
Adjacent channel power	600 kHz detuning: less than 800 nW 900 kHz detuning: less than 250 nW
Off time leakage power	Less than 80 nW
Transmission rate accuracy	5x10 (signal transmission rate: 384 kbps)
Conducted spurious component of receiver, etc.	Less than 4 nW
Carrier sense	Must be in compliance with the technical requirements of MPT Notice No. 463
Operation check	Proper call dispatching and reception (establishment and ending of communication) must be confirmed using external testing devices.