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terminals, the development of Jacket with separated W-SIM is
carried out. As a result, 9 types of Jacket have been marketed by the end of last year. In order to further expand the
influence of PHS, more terminals adopting various W-SIM devices for different business fields will be developed in future.
2. Advantages and Topics of PHS
To avoid the tight frequency restriction, the development of PHS, which
was started in late 1980, has been targeted at the combination of public circuit with private one. Since a PHS system is
always based on a home telephone system, the construction of a dense network with strong interference is possible. Hence,
as long as area construction is completed, making use of the differentiated network capacity is also possible. The current
big-capacity-network, which covers 99.3% of the population with 160 thousand base stations, has realized flat-rate voice
service. It is ten years' toil to build the current network, but we have much to expect as we look ahead of network that
was completed.
3. Development of PHS
The area topic remains despite of the development on network capacity.
Advanced PHS, which will realize the capacity of 3.5 generation mobile, is being tackled with to overcome the remained
topic. The advanced PHS is expected to meet with four targets including the expansion of single cell coverage, the
improvement of mobility to 120km/hr, the reduction of network cost to ~1/2rate with IP access and the acceleration of data
communication to 1Mbps and above.
ISDN is used as the circuit connecting a cell station to backbone now,
and it is possible to realize an average data communication speed of 800kbps by replacing the circuit with IP access that
corresponds to a base station in a more advanced way. Since backbone itself has realized IP access already,
Next-generation PHS network can be realized with simple replacement of cell stations.
4. Next-generation PHS
The average monthly traffic on fixed-line broadband is around 10GB.
If a wireless broadband is to reach such a flow, the network capacity needs to be expanded by 100 to 1000 times. With
evolvement of technology, it is possible to improve the top speed, but the total transfer capacity is something with
technical limit. Hence, the most important topic for wireless broadband is not top speed, but the expansion of network
capacity. It is believed that PHS system, whose capacity can be expanded easily, is the best choice to optimize wireless
broadband.
Meanwhile, with the development of internet and the undergoing IP conversion of
technologies, various broadband players appeared. This broke the conventional business model of vertical integration
type in the wire and cable business world. The destroy of the vertical integration business model is to happen more in
wireless world as well. WILLCOM‘ open strategy is just being pushed forward in such a background.
The Next-generation PHS is designed to enable the co-existence with
the current PHS system. The development is preceded with both lab and field experiments being carried out. Standardization
process is also undergoing, and Next-generation PHS has already gained recommendation from ITU-R as one of the international
wireless broadband standards since this March.
We all see the fact that PHS has developed over 100,000,000 users led by the Chinese market
. As the presentation is drown to the end, Mr. Chika made a wish to expect to see Next-generation PHS system expanding as a
technology that supports wireless broadband infrastructure worldwide.
(compiled by Mr. Ohya at NEC Infrontia Corporation) | 
