Cellular Ptt

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Current use in mobile telephony (PTT PoC) PTT PoC or Push to Talk over Cellular is a service option for a cellular phone network which permits subscribers to use their phone as a walkie-talkie. A typical Push to Talk connection connects almost instantly. One significant advantage of PoC is that it allows a single person to reach an active talk group with a single button press; users no longer need to make several calls to coordinate with a group. Push-to-talk cellular calls are half duplex communications while one person transmits, the other(s) receive. Traditional Mobile Phone networks and devices utilize full-duplex communications, allowing customers to call other persons on a mobile or land-line network and be able to simultaneously talk and hear the other party. Such communications require a connection to be started by dialing a phone number and the other party answering the call, and the connection remains active until either party ends the call or the connection is dropped due to signal loss or a network outage. Therefore, telephone communication protocol does not allow for casual and immediate transmissions to be sent to other parties on the network. Whereas telephone calls require the lengthy process of dialing, network switching and routing, call setup, and waiting for the other party to answer, a two-way radio has a much quicker protocol because of the immediacy of push to talk communication. Full-duplex operation on mobile phone networks is made possible by using separate frequencies for transmission and reception. Mobile Push-to-Talk service, offered by some mobile carriers, adds functionality for individual half-duplex transmissions to be sent to another party on the system without needing an existing connection to be already established. Since the system is half-duplex, only one user can transmit by PTT at a time; the other party is unable to transmit until the transmitting user unkeys their PTT button. Currently, PTT service is supported only between parties on the same mobile carrier service, and users with different carriers will be unable to transmit to each other by PTT. In addition to mobile handsets, the Push-to-Talk service might be complemented with fixed PC applications acting as PTT clients connected to the mobile operator via secured Internet links. A specialized type of PC Client is a dispatcher, similar to a PC client but designed for heavy load dispatching. That is, coordinating many issues typically caused when managing large fleets from a dispatch center. In Spain, Telefonica has launched PTT offering with focus on dispatch orientated group communications. When used with GSM and CDMA networks, the PTT service commonly does not use up the regular airtime minutes that are available for general voice calls. Nextel Communications introduced mobile push-to-talk in August 1993 using iDEN. The first system was turned on in Los Angeles with 134 sites and a capacity for 50,000 dispatch subscribers. The “MOTO Talk” feature by Nextel includes both on- and off-iDEN network walkie-talkie service for newer Motorola phone models. The off-iDEN-network handset-to-handset Direct-Talk feature works for a radius of up to six miles. Push to Talk over Cellular Later versions of PTT are based on 2.5G or 3G packet-switched networks and use SIP and RTP protocols. These particular versions of PTT are called Push to Talk over Cellular, which is abbreviated PoC. The Open Mobile Alliance is defining PoC as part of the IP Multimedia Subsystem, and a first version of OMA PoC standard was finalized in first half of 2005. There are few full-fledged commercial deployments of OMA PoC. It is very unclear whether OMA PoC will be seriously launched in the European market[citation needed]. A pre-standard version of PoC is also defined by the industry consortium made up of Motorola, Nokia, Ericsson, Siemens AG and AT&T Mobility with the aim of creating a commercial offering enabling interoperability between vendors. See also IP Multimedia Subsystem IMPS Push-to-type operation References ^ Rush, Susan, Wireless Leaders Band For PTT Interoperability, http://www.wirelessweek.com/wireless-leaders-band-for-ptt.aspx, retrieved 2009-03-03 Push-to-Talk over Cellular Consortium Phase 2 Specifications and Documentation Open Mobile Alliance- Push to talk over Cellular (PoC) – Architecture Candidate Version 2.0 26 Feb 2008 v d e Mobile telephony and mobile telecommunications standards 0G (radio telephones) MTS MTA MTB MTC IMTS MTD AMTS OLT Autoradiopuhelin 1G NMT AMPS Hicap Mobitex DataTAC TACS ETACS 2G GSM/3GPP family GSM CSD 3GPP2 family CdmaOne (IS-95) Other D-AMPS (IS-54 and IS-136) CDPD iDEN PDC PHS 2G transitional (2.5G, 2.75G) GSM/3GPP family HSCSD GPRS EDGE/EGPRS 3GPP2 family CDMA2000 1xRTT (IS-2000) Other WiDEN 3G (IMT-2000) 3GPP family UMTS (UTRAN) WCDMA-FDD WCDMA-TDD UTRA-TDD LCR (TD-SCDMA) 3GPP2 family CDMA2000 1xEV-DO (IS-856) 3G transitional (3.5G, 3.9G) 3GPP family HSDPA HSUPA HSPA+ LTE (E-UTRA) 3GPP2 family EV-DO Rev. A EV-DO Rev. B Other Mobile WiMAX (IEEE 802.16e-2005) Flash-OFDM IEEE 802.20 4G (IMT-Advanced) 3GPP family LTE Advanced WiMAX family IEEE 802.16m Related articles History Cellular network theory List of standards Comparison of standards Spectral efficiency comparison table Cellular frequencies GSM frequency bands UMTS frequency bands Mobile broadband v d e Two-way radio Amateur and hobbyist Amateur radio Amateur radio repeater Citizens’ band radio Family Radio Service General Mobile Radio Service Mobile rig Multi-Use Radio Service PMR446 LPD433 UHF CB (Australia) Aviation (aeronautical mobile) Air traffic control Aircraft emergency frequency Airband Mandatory frequency airport Single Frequency Approach UNICOM Land-based commercial and government mobile Business band Base station Mobile radio Professional Mobile Radio Radio repeater Specialized Mobile Radio Trunked radio system Walkie Talkie Marine (shipboard) 2182 kHz 500 kHz Coast radio station Marine VHF radio Maritime mobile amateur radio Signaling / Selective calling CTCSS Dual-tone multi-frequency D-STAR MDC-1200 Push to talk Quik Call I Quik Call II Selcall System elements and principles Antenna Audio level compression Automatic vehicle location APRS Call sign CAD DC remote Dispatch Fade margin Link budget Rayleigh fading Tone remote Voice procedure Voting (diversity combining) Categories: IMS servicesHidden categories: Telecommunications articles needing expert attention | Articles needing expert attention from June 2009 | All articles needing expert attention | All articles with unsourced statements | Articles with unsourced statements from January 2009

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