High-speed data transmission is one of the greatest features of PHS. The following is an excerpt from the February 2, 1999 issue of the Nikkei Communication magazine on the new 64kbit/s mobile data transmission service.

Mobile data transmission will play an increasingly important role in the age of multimedia communications. Currently, the most common speed is 9.6kbit/s for cellular and 32kbit/s for PHS. These speeds are much slower than wire data transmission speeds. However, the launch of the revolutionary new PHS 64kbit/s wireless commercial services will spur a big leap forward in the mobile data transmission and computing industry.

ASTEL Tokyo (reorganized into Tokyo Telecommunication Network Co., Inc. on April 1, 1999) launched their 64kbit/s PHS data transmission service that uses two sets of Personal Stations (PSs) in December 1998 (see Figure 2). NTT DoCoMo launched their PIAFS based 64kbit/s service on April 1, 1999, and DDI plans to launch their service this summer (see Figure 1).
The 64kbit/s service by ASTEL is transmitted by two sets of PSs and is based on the PIAFS version 1.0 technical standard. To access the service, the user connects a personal computer and a designated 64kbit/s data adapter to the two PSs. The 32kbit/s data transmitted by each of the two PSs is then combined in the center server, and transmitted to the ISDN network as 64kbit/s data. Though a separate monthly basic fee is required for each of the two PSs, the transmission cost is the call rate to the nearest center server; which comes out to only 10 yen per minute.

Figure 1.

The 64kbit/s service by DDI-P and NTT DoCoMo is based on the PIAFS version 2.0 technical standard. To access the service, the user must use a new 64kbit/s PS and/or a 64kbit/s PHS adapter based on PIAFS 2.0. In a PHS base station, each Cell Station (CS) has three radio channels where voice communication and/or 32kbit/s data transmission occupies one channel. For 64kbit/s data transmission, two channels are used simultaneously providing double the transmission speed. The data signal, based on PIAFS 2.0, is transmitted to the other party without going through protocol conversion. However, in order for this to take place, the other party must also have either a PHS terminal or an ISDN terminal adapter based on PIAFS 2.0. Internet Service Providers (ISPs) will play an important role in the demand for this service as they will have to add 64kbit/s dialup connections to their existing systems.

NTT DoCoMo will first launch the service in the metropolitan area and then gradually expand their coverage area. DDI-P, on the other hand, will launch the service nationwide from the outset.
NTT has announced that they will offer their 64kbit/s service at the same cost as their current 32kbit/s data transmission call charge. DDI-Pocket has not yet announced their charge plans, however they are studying a charge scheme that is 10 yen fixed call initiation charge + 10 yen per 70 seconds’ for each call.

DDI-P will include switch hand-over capabilities and automatic 32kbit/s downshifting functions in addition to the protocol conversion in its 64kbit/s service. Here also, two channels are used for the 64kbit/s.
If the CS does not have two channels available when a 64kbit/s data transmission is requested by the user, the transmission will automatically transparently shift down to the 32kbit/s service mode. Likewise, when two channels become available on the CS during a downshifted 32kbit/s transmission, the handset is able to resume the 64kbit/s transmission, again, without interruptions. Using the protocol conversion service, DDI-P PHS terminals and data adapters based on the PIAFS 1.0 can also access the service for 64kbit/s data transmission.
On the cellular operators side, cdmaOne will launch their 64kbit/s packet data transmission service, and other operators will also be improving their coverage and data transmission service menu.

Cellular is superior in service coverage, however, PHS has more flexibility in the availability of applications. A wider variety of PHS data terminals will be introduced as the manufacturers prepare to launch new data devices.
From the users’ point of view, it is an important capability for the mobile device to be able to access the office LAN and Internet systems. These users most commonly access applications such as e-mail, file transfer, data search, group-ware, etc.

It is expected that the mobile data communication industry will take a big leap forward through the introduction of the 64kbit/s service as well as from the availability of a wider variety of terminal equipment.