Japanese national standards concerning the network portion of the Personal Handy-phone System (PHS) were previously formulated by the Telecommunication Technology Committee (TTC). This article outlines the major PHS standards drawn up by TTC from last autumn to this spring.

1. Addition of 3.1 kHz audio communications

Unlike JT-Q931, JT-Q931-b which specifies the interface between PHS cell stations and the digital network previously did not allow a "3.1 kHz audio signal" as a parameter for the "information transfer capability."
A provision was added to JT-Q931-b for the purpose of transmitting data by a modem using PHS. The said standard was changed to allow 3.1 kHz audio communications. This change was adopted by the Technical Assembly on November 28, 1995, and was put effect following a procedural examination at the Councilors' Meeting on December 16, 1995.

2. Realization of 32 kbps digital communications

TTC formulated a standard with an eye toward realizing 32 kbps digital communications over the PHS wireless section which the system has the inherent capability to support.
A rate adaption provision was previously stipulated in JT-Q931 (and ITU-T Recommendation Q.931), which specifies the subscriber line signalling system of ISDN. A Supplement was added this time that clearly specifies this provision is to be applied to 32 kbps and 64 kbps rate adaption by PHS cell stations.
Further, a provision specifying 32 kbps for the layer 1 protocol of the bearer capability information element was newly added to JT-Q931-b. The respective value of the low layer and high layer compatibility information elements was also made the same as that specified in JT-Q931, thereby facilitating rate control between end systems.
These changes were adopted by the Technical Assembly on April 24, 1996, and took effect at the Councilors' Meeting on May 16, 1996.

3. Addition of VLR roaming method

The only roaming system standardized previously for PHS was the HLR method, whereby the service profile is provided only on a subscriber's home network. The standard has now been revised to include the VLR method as well, whereby a portion of the service profile is also redundantly provided on the network serving the area where a PHS subscriber is present. This change expands the selection of roaming methods and makes it possible to achieve an efficient method matching the situation involved.
The standard revised in this connection was JT-Q1218-a, which specifies the roaming procedure between networks for PHS services. The VLR method was newly added as capability set 2 to this standard. The provision incorporates the latest results of the work by ITU-T Study Group 11 on Intelligent Networks (IN) and adopts the SDF-SDF interface.

4. Other changes

4.1 Notification of calling party number

In order to support a wide variety of PHS services, it is desirable to have calling party number information exchanged between PHS cell stations and the digital network via the JT-Q931-b interface. JT-Q931-b has now been revised to allow notification of calling party number information between PHS cell stations and the digital network even in cases where a display of the caller's number to the called party is prohibited.

4.2 Unification of terminology

The term "Second Generation Cordless Telephone System" has also been used in TTC standards to date to indicate PHS. The terminology has now been unified to PHS.