A situation may arise in Hong Kong in which both DECT and PHS telecommunications technologies may be required to co-exist. Both technologies occupy radio spectrum in the region of 1.9 GHz: DECT from 1880-1900 MHz and PHS from 1895-1918.1 MHz. Unfortunately, these two bands overlap by 5 MHz which suggested that difficulties could arise. In order to determine the exact extent of such difficulties, OFTA decided to conduct coexistence tests.

The tests have been organized by OFTA in Hong Kong and took place from 6 to 10 November 1995, involving the Japanese ARIB and the DECT Forum to carry out the tests. The tests have been successfully concluded on schedule. Two series of tests were undertaken.

The first series restricted the spectrum used to the 5 MHz overlap to determine the actual interactions in this band between the two systems. The procedure was to establish a call between two handsets in one system followed by two in the other followed by a further two in the first and so on.

The second series allowed both systems to use their standard working spectrum to determine performance in a eal-life?situation. Here, a level of traffic was established in one system following which the other made an increasing number of calls.

Based on the test results the following is concluded:

• Coexistence is possible between DECT and PHS systems working alongside each other, as currently defined by their respective standards and unmodified in frequency assignments.

• In the overlapping 5 MHz band, 1895-1900 MHz, the success rate of call setups for each system is slightly reduced by coexistence. However, the two systems can coexist with more than 24 air links even under the worst case coexistence scenario.

• When the two systems work alongside each other and are restricted to use the 5 MHz overlapping band only, the test results show an overall average call success rate and drop rate of :

  95% and 7% for DECT (air links)

  63.7% and 13.7% for PHS (air links)

  95% and 12.3% for DECT (call connections)

  63.7% and 13.7% for PHS (call connections).

When applying the conclusions in Hong Kong the DECT Forum recommends:

• OFTA sanctions the use of DECT and PHS as specified in Europe and Japan respectively, with their respective standards and frequency assignments (DECT 1880-1900 MHz for private and public use; PHS 1895-1906.1 MHz for private and public use and 1906.1-1918.1 MHz for public use).

• OFTA follows the spectrum implementation strategy adopted by the Japanese MPT in which the 1895-1906.1 MHz band is initially limited to private use only.

• There is no need for RF Coordination rules for coexisting DECT and private PHS systems.

The full DECT Forum report consists of two files

Click (i) to download zipped DECTtext.doc (in MSWord 6.0 Format) and

Click (ii) to download zipped DECTdata.xls (in MSExcel 5.0 Format and contains the test data sheets; readers are advised to print the worksheets separately instead of the entire workbook in order to avoid printing format mismatch)