ARIB Standard "RCR STD-28" has been revised
ARIB's "Working Group 28" for standardization of the PHS air interface ("Personal Handy Phone System") has been investigating the introduction of (1) half-rate system and (2) RF output power control technology.
The result of this investigation has been officially approved at 53rd standardization meeting of ARIB held on May 25, 2004 and released as "RCR STD-28 V4.1". An English version of this V4.1 is to be issued in around summer 2004.
1. Main Revisions
(1) An introduction of the half-rate system
The half-rate system for voice and unrestricted digital communications has been regulated as the public standard.
And the 16Kbps ADPCM has also been regulated as the voice codec.
With those, the number of simultaneously accessible channels per Cell Station (CS) can be doubled and as a result, network cost reduction can also be realized.
As for the half-rate voice coding system, 16Kbps ADPCM stipulated in "ITU-T Recommendation G.726" is to be adopted.
The following table shows all available bearer service items including this time's revision.
| 32kbit/s
speech |
Provides
bearer capability suited for voice communication with terminal;
32kbit/s or 16kbit/s ADPCM CODEC is inserted.
|
| 32kbit/s
3.1kHz audio |
Provides
bearer capability suited for 3.1kHz bandwidths communication
with terminal; 32kbit/s or 16kbit/s ADPCM CODEC is inserted.
|
| 32kbit/s
unrestricted digital |
Provides
bearer capability suited for digital data communication
with terminal; information is transmitted transparently.
|
| 64kbit/s
unrestricted digital |
Using max
2 channels on Um point, provides bearer capability suited for
digital data communication with terminal; information is transmitted
transparently.
|
(2) An introduction of the RF output power control technology
The RF output power control technology which can control PS's output power fixed before within the range of below 10mW according to its receiving signal strength from CS has been regulated.
With an optimization of the PS's output power, both interference tolerance and frequency utilization efficiency can be improved.
Further, originally low PHS's SAR (Specific Absorption Rate : An amount of the energy absorbed by unit mass tissue of the human body exposed to the radio waves) can be reduced more.
