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PHS Technology (1)
System Overview and Features
PHS is one of the most advanced personal communications system that makes
use of sophisticated wireless technology. It is founded upon digital cordless
technology and a micro-cell architecture, and has a maximum capacity of
up to several million subscribers in an urban setting. PHS has been quite
successful in Japan since its commercial service was launched in July 1995.
The total number of PHS subscribers in Japan had reached 482,000 by the
end of November 1995.
PHS supports inter- and intra-cell handover functions, and achieves an economical
yet advanced system compared with existing cellular systems. Customers are
satisfied with its handover function, including its momentary interruptions.
Moreover, commercial service has proven that PHS works in town centers at
driving speed, 60 to 70 km/hour in most cases.
Key features behind the successful launch of PHS and its promising future
are as follows.
First, PHS handsets are extremely small and lightweight, almost half the
size and weight of cellular handsets, due to its system parameters such
as the very small output power (at both average and peak). Meanwhile, the
standby and talking times are far longer than those for cellulars. Many
kinds of handsets are now on the market. Several types of "home stations"
(cell stations for digital cordless use at homes) are also available. In
addition, network services such as call transfer and voice mail services
are available.
Secondly, the 32 kb/s data transmission capability for PHS will enable the
realization of multimedia applications such as high speed Internet access,
picture and video transmission, database access and mobile computing.
Third, a multi-vendor environment has been established for PHS, which includes
some overseas vendors such as AT&T and Motorola. Currently, the number
of vendors for handsets, cell stations, PBX cordless systems, and home cordless
phones are 15, 11, nine, and eight respectively.
Finally, PHS supports other attractive uses such as home cordless, PBX cordless,
transceiver (walkie-talkie) and WLL (Wireless Local Loop) applications.
The table 3. shows the technical features of PHS.
Table 3. Technical Features of PHS
| | CS Coverage |
(radius)
output power |
20
mW |
100 mW |
500
mW |
| typical |
300m
|
500m |
1
km |
| in good condition |
500m |
800m
|
1.5km |
| Connection
to CS |
Metallic cable
or optical fiber cable |
| Frequency
|
1.9 GHz band (23.1 MHz
bandwidth currently in Japan) |
| Radio
access method |
TDMA/TDD
|
| Radio transmission
rate |
384 kb/s |
| Voice CODEC |
32
kb/s ADPCM |
| Mobility |
Automobile speed in downtown
(up to 60 ~ 70 km/h) |
| Available
mode | Public cordless
/ PBX cordless /
Home cordless / Transceiver / WLL
|
| Frequency
planning |
Dynamic channel
allocation |
| Subscriber capacity
|
Millions |
| Commercial
personal station (handset) |
Output
power |
10 mW (80 mW peak)
|
| Talking time
|
5 hours |
| Standby
waiting time |
400 hours
|
| Weight |
95 g* |
| Volume |
98 cc* |
| Interface
|
Air interface |
Specified
in RCR STD-28 |
| Cell
station to network |
Based
on ISDN |
| Network
to network** |
CCS No.
7 ISUP
CCS No. 7 TUP |
*
R&D has already accomplished prototype handset of 85 g, 60 cc.
** Analog interface to be consifered |
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