Activities for Advanced PHS System Development Plan


- An introduction of the summary report "Technologies for Reducing the Interference Between PHS and IMT-2000 as the Enhancement of PHS Performance" by the Advanced PHS Committee.

On March 2002, an investigation committee, headed by Mr. Sanpei, associate professor of Osaka University, compiled a report on "Technologies for reducing the interference between PHS and IMT-2000 as the enhancement of PHS performance". The investigation committee was organized under the "Support Center Advanced Telecommunications Technology Research (SCAT)" by an entrustment of the Ministry of Public Management, Home Affairs, Posts and Telecommunications (MPHPT) in 2001. The committee has been conducting research using "Evaluation equipment for advanced PHS systems" on the above subject and on the possibility of the communications based on the advanced PHS systems development plan. This evaluation equipment was ordered by the MPHPT in 2001 and its procurement specifications and appearance are available in the Table and the Photo, respectively. In order to materialize an advanced PHS system in Japan, it is necessary to introduce "PHS speed enhancement technology" as described in the Telecommunications Council report No.119 (refer to the PHS MoU Group News Nos. 34, 35 and 36 for more details) and to reduce mutual interference between PHS and IMT-2000 in adjacent frequency bands.

Evaluation Equipment

In addition, the committee conducted research on transmitter spurious emission suppression by low-noise wireless technology, the technical trend of receiver interference-resistance improvement possibility by enhanced filter, simulation evaluation, indoor testing and field testing concerning the measures for mutual interference reduction with IMT-2000 system. Further, indoor verification testing, field testing for validating an advanced PHS systems' possibility have also been conducted.Main conclusions as the result of above research are as follows.

Regarding technologies of advanced PHS systems for reducing the interference with IMT-2000 systems;

  • Taking into account technical development trends as well as international standards trends, it is recommended that transmitter spurious emissions from advanced PHS systems be suppressed as much as possible
  • The simulation evaluation result showed that for most cases there is no additional interference on IMT-2000 from PHS if new transmitter spurious emission standards of less than -36 dBm/MHz is satisfied.
  • After an investigation on transmitter spurious suppression level attainable by the PHS Cell Station (CS), it was confirmed by calculation that less than -60 dBm/MHz at 2.25 MHz off carrier frequency is achievable by low-noise transmitter design without filters.
  • Indoor verification testing with the evaluation equipment confirmed that transmitter spurious level obtained by calculation at simulation evaluation has been realized.
  • After field-testing with the evaluation equipment placed next to an actual IMT-2000 base station, it was confirmed that interference from IMT-2000 system does not cause deterioration in the PHS receiver's performance.

    Regarding communication testing of advanced PHS systems;

  • At an indoor verification testing with actual products, two possible measures for advanced PHS systems, multi-value modulation system 8PSK (Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation) and high symbol transmission (640K symbols/sec.) were tested. It was confirmed that BER (Bit Error Rate) of less than 0.001% is realizable.
  • Field-testing under relatively good sight conditions was also conducted. Range of approximately 3,000 meters was achieved with 16QAM at the same symbol rate and twice the data rate as the existing system. Range of approximately 1,000 meters was achieved with 16QAM at higher symbol rate and eight times the data rate (up to 1Mbps with four slot aggregation) compared to the existing system.

    To summarize the results of the research, the possibility of realizing an advanced PHS system, one that satisfies requirements for interference with IMT-2000 systems, has been confirmed by this report.

    Association of Radio Industries and Businesses (ARIB) has also started standardization work for advanced PHS systems and future developments are expected.

    Procurement Specifications for "evaluation equipment for advanced PHS systems"
    Item Specifications
    Wireless Access System TDMA-TDD
    RF Frequency Band 1880 MHz-1919.6 MHz
    Channel Separation 300 KHz/900 KHz
    Occupied Frequency Band Within 288 KHz/884 KHz
    Modulation System 1/4 Shift QPSK, 8PSK, 16QAM
    Roll-off Rate 0.5/0.38
    Data Transmission Speed 384 kbps-2.56 Mbps
    RF Output Power Less than 500 mW
    (Continuously variable)
    Antenna Gain More than 0 dBi
    In-band Spurious Emission to IMT-2000
    (PS to CS)    		 Less than - 46 dBm/MHz
    (Off carrier Frequency > 5 MHz)
    Interference-resistance of IMT-2000
    (CS to PS)    		 More than 0 dBm
    (Receiver Sensitivity Suppression)
    Antenna Type Omni-spectrum & Adaptive Array
    RF Signal Processing Software Defined
    Power Supply AC100 10%