| Personal Handy-phone System |
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The Personal Handy-phone System ('''PHS'''), also marketed as the '''Personal Access System''' ('''PAS''') and known as '''''Xiaolingtong''''' (小灵通) in China , is a Mobile Network system operating in the 1880-1930 MHz frequency band, used mainly in Japan , China , Taiwan and some other Asia n countries. OUTLINE Technology PHS is, essentially, a Cordless Telephone like DECT , with the capability to Handover from one Cell to another. PHS cells are small, with transmission power of Base Station a maximum of 500 mW and range typically measures in tens or at most hundreds of meters (some can range up to about 2 kilometres in line-of-sight), 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. - NTT DoCoMo - ASTEL )]] PHS uses TDMA / TDD for its radio Channel Access Method , and 32 kbit/s ADPCM for its voice Codec . Modern PHS phone can also support many Value-added Service s such as high speed wireless Data / Internet connection (64 kbit/s and higher), WWW access, E-mail ing, 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 network and the subscriber's home. Actually, it was developed under the concept that it makes up a wireless Front-end of ISDN network. So a base station of PHS has a compatibility with, and is often connected directly to ISDN Telephone Exchange equipments(aka digital switch). As for its low-price Cellular Telephone systems. It makes possible the flat-rate wireless service such as AIR-EDGE all over Japan. The speed of AIR-EDGE data connection is accelerated by combining lines, each of which basically is 32 kbit/s. AIR-EDGE 1x or first version introduced in 2001 provide only 32 kbit/s service. In 2002, 128 kbit/s service (AIR-EDGE 4x) started. In 2005, 256 kbit/s (AIR-EDGE 8x) service started. In 2006, the speed of each line was also up-graded to 1.6 times with the introduction of "W-OAM" technology. The speed of AIR-EDGE 8x is up to 402 kbit/s with the latest "W-OAM" capable instrument. In April 2007, "W-OAM typeG" was introduced allowing data speeds of 512 kbit/s for AIR-EDGE 8x users. Furthermore, the "W-OAM typeG" AIR-EDGE 8x service is planned to be upgraded to a maximum throughput of 800 kbit/s, when the upgrading for access points (mainly switching lines from ISDN to fibre optic) in its system are completed. And it may exceeds the speeds of popular W-CDMA 3G service like NTT DoCoMo 's FOMA in Japan. Implementation Originally developed by 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. Market share in Japan has been declining and NTT DoCoMo, which has absorbed NTT Personal, and ASTEL is going to terminate the PHS service. Some of other countries have already terminated offering PHS services and migrated to GSM. But PHS has seen a resurgence in markets like has announced a rollout of a PHS network in 2007 {Link without Title} China Telecom operates a PAS system in China, even though technically it was not regarded as allowed to provide mobile services, because of some particularities of the Chinese governance. China Netcom , the other fixed-line operator in China, also provides Xiaolingtong service. The system has been a runaway hit, with over 80 million subscribers signed up As Of 2005 . The largest vendors of the system are UTStarcom and ZTE . A PHS global roaming service is available between Japan (WILLCOM) and Taiwan, and Japan and Thailand. INTERNATIONAL DEVELOPMENT
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