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March 8, 2014 |
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PHS is, essentially, a cordless telephone with the capability to handover from one cell to another. PHS cells are small, with transmission power a maximum of 500mW and range typically measures in tens or at most hundreds of meters, as opposed to the multi-kilometer ranges of GSM. This makes PHS suitable for dense urban areas, but impractical for rural areas, and the small cell size also makes it difficult if not impossible to make calls from rapidly moving vehicles. PHS uses TDMA/Time division duplex|TDD as its radio interface and 32K ADPCM as its voice codec. Modern PHS phone can also support many value-added services such as high speed wireless Internet connection (32K/64K), Web access, emailing, text messaging and even color image transfer. PHS technology is also a popular option for providing a wireless local loop, where it is used to bridge the "last mile" gap between the POTS wired network and the subscriber's home. Originally developed by Nippon Telegraph and Telephone|NTT Laboratory in Japan in 1989 and far simpler to implement and deploy than competing systems like PDC or GSM, the commercial services has been started by 3 PHS operators (NTT-Personal, DDI-Pocket and ASTEL) in Japan in 1995. However, the service has been pejoratively dubbed as the "poor man's cellular" due to its limited range and roaming abilities in Japan. Market share in Japan has been declining and NTT-Docomo, which merged NTT-Personal, is planning and ASTEL is going to terminate the PHS service. Other countries like Chile, have already terminated offering PHS services and migrated to GSM. But PHS has seen a resurgence in markets like China, Taiwan, Vietnam, Bangladesh, Nigeria, Mali, Tanzania and Honduras where its low deployment costs (estimated as low as 20% of a GSM network) make it attractive to operators. In late years, Willcom|WILLCOM, former DDI-Pocket , is introducing flat-rate wireless network and flat-rate calling in Japan, which has reversed the local fate of PHS up to an extent.
ja:PHS zh:PHS wireless-stub Category:Mobile telephony standards This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Personal Access System".
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