- Mr. Yasunori Akatsuka, Manager of System Business Promotion Dept., SANYO Electric Co., Ltd. -

In the past PHS has been spread as a voice-feature phone. However, recently the need for high-speed mobile data communications is increasing as the Internet spreads. An evolution of PHS, Advanced PHS, that will serve as an mobile information socket is expected. In order to realize the above, an affinity with IP networking, improved communications quality and reduced interference with IMT-2000 are required. Particularly, high-speed data communications and introduction of packet data transmission can support the affinity with IP networks. Realizing these items can lead to Advanced PHS.

Approaches for Advanced PHS in Japan are as follows:

- The ministerial ordinance for Advanced PHS was revised in February 2002 and the technological feasibility of Advanced PHS was verified by SCAT (Support Center Advanced Telecommunication Technology Research).
- For the standardization of Advanced PHS, the technological regulations were standardized and included in RCR STD-28 Version 4.0 in March 2002.
- In the future, the communications protocol for data transmission using Advanced PHS is to be standardized.

In December 1999, SANYO started the basic technological study for realizing Advanced PHS and the development of the evaluation equipment, evaluation of the feasibility of high-speed communications, verification of the feasibility of Advanced PHS using actual equipment were done based on the above and actual application of Advanced PHS is now being developed.

An outline of Advanced PHS technologies is as follows.

- Realization of high-speed data communications, effective use of frequency and co-existence with IMT-2000 are three major themes in Advanced PHS.
- An introduction of multi-valued modulation system and speeding up of the symbol transmission speed are necessary for realization of high-speed data communications.
- The communications quality should be improved to enhance the transmission throughput and this will be realized by introducing adaptive array antenna technology.
- As for effective use of frequency, adaptive array antenna technology is hopeful because it can concentrate the beam only toward the desired direction and reduce the interference. In addition, SDMA (Space Division Multiple Access) technology is effective because it can minimize the frequency reuse distance.
- As for co-existence with IMT-2000, the suppression of spurious emissions is required not to give further interference and at the same time, the performance against the interference should be improved not to receive further interference.

- Advanced PHS can be classified to two types typically, one type (Type I) applies the advanced strategic technology with the same modulation bandwidth as current PHS and another type (Type II) uses the modulation bandwidth three times wider than the current PHS to speed up the symbol transmission and applies more advanced strategic technology.
- There are three techniques as the most basic method of high-speed data communications, multi-valued modulation system, high-speed symbol transmission and expansion of data occupied area for each transmission slot.
- As for a multi-valued modulation system, data transmission speed can be doubled to 4 bits per symbol by introducing 16QAM(Quadrature Amplitude Modulation) modulation method rather than the current Pi/4 DQPSK (Quadrature Phase Shift Keying) modulation method.
- As for high-speed symbol transmission, Advanced PHS can increase the number of symbols in one slot from 120 to 400 by speeding up the symbol transmission, which is 3.3 times higher than the current system.
- As for expansion of data occupied area for each transmission slot, high-speed symbol transmission can also reduce the occupied rate of overhead area and can expand the data area to 80% of the total symbols.

- Especially, as for the technical issue and its solution of the transmitter, receiver and radio communications method, high accuracy modulation system by introducing high-speed digital processing technology, high accuracy linear signal amplification by introducing feed-forward amplification technology or pre-distortion amplification technology and synchronous detection system by accumulation arithmetic processing are effective.
- As for the radio transmission method, adaptive array antenna technology can reduce errors during data transmission and increase interference tolerance. CSs can concentrate the radio signal directivity to the desired PS and minimize it to the interference PS so that this technology can reduce interference to realize high quality data communications.

- Firstly, to realize the compact CS and PS, the lower power consumption, lower cost and communications protocol standardization is essential for this approach.
- In addition, it is important to study the backbone network which needs the affinity with IP network and the network configuration with low cost.
- Lastly, it is essential to develop a new application. This approach will require taking advantage of the PHS such as uplink/downlink high-speed data transmission etc. and can differentiate it from other mobile systems.