Push to talk
Encyclopedia
Push-to-talk also known as Press-to-Transmit, is a method of conversing on half-duplex
communication lines, including two-way radio
, using a momentary button to switch from voice reception mode to transmit mode.
For example, an air traffic controller
usually talks on one radio frequency to all aircraft under his supervision. All can hear each other's transmissions and those of the controller, and take turns speaking, using procedure word
s such as "over" and "out".
Thus they are aware of each other's actions and intentions, and do not hear any noise from the ones who are not speaking. Similar considerations apply to police radio
, the use of business band
radios on construction
sites, and other situations requiring coordination of several parties. Citizens Band is another example of classic push to talk operation.
Where a user may be too busy to handle a talk switch, for example in combat aircraft, voice operated switch
es are sometimes employed. Some systems use PTT ID
to identify the speaker.
Push to Talk over Cellular (PoC) is a service option for a cellular phone network which permits subscribers to use their phone as a walkie-talkie
with unlimited range. A typical Push to Talk connection connects almost instantly. One significant advantage of PoC / PTT is that it allows a single person to reach an active talk group with a single button press; users need not make several calls
to coordinate with a group.
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, the telephone communication protocol does not allow for casual and immediate transmissions to be sent to other parties on the network. While 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.
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. 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.
In addition to mobile handsets, the Push-to-Talk service may be complemented with fixed PC
applications acting as PTT clients connected to the mobile operator via secured Internet links. A dispatcher
is a specialized type of PC Client but designed for heavy load dispatching, i.e. 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.
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.
Verizon Wireless
enabled push-to-talk communication on its BlackBerry
devices in March 2010, requiring download and a monthly fee.
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 .
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.
As of June 2010 no tier-1 operator worldwide launched OMA. Availability of OMA handsets and fully inter-operable solutions remain to be seen.
OMA solution missed the most important factor for such a niche market which is performance. In addition, standard was mainly adopted by NSN, Nokia, Ericsson and others who all never had major success or background on PTT. OMA PoC also assumed it is a service for consumers which is not true. PTT/PoC is an enterprise service. On the bottom line, it is more of a North American phenomenon due to existence of iDEN and other networks. Other parts of the world do not know the service and operators are having a hard time identifying who needs this service.
Duplex (telecommunications)
A duplex communication system is a system composed of two connected parties or devices that can communicate with one another in both directions. The term multiplexing is used when describing communication between more than two parties or devices....
communication lines, including two-way radio
Two-way radio
A two-way radio is a radio that can both transmit and receive , unlike a broadcast receiver which only receives content. The term refers to a personal radio transceiver that allows the operator to have a two-way conversation with other similar radios operating on the same radio frequency...
, using a momentary button to switch from voice reception mode to transmit mode.
Air traffic controller
Air traffic controllers are the people who expedite and maintain a safe and orderly flow of air traffic in the global air traffic control system. The position of the air traffic controller is one that requires highly specialized skills...
usually talks on one radio frequency to all aircraft under his supervision. All can hear each other's transmissions and those of the controller, and take turns speaking, using procedure word
Procedure word
Procedure words or prowords are words or phrases limited to radio telephone procedure used to facilitate communication by conveying information in a condensed standard form. - OUT :...
s such as "over" and "out".
Thus they are aware of each other's actions and intentions, and do not hear any noise from the ones who are not speaking. Similar considerations apply to police radio
Police radio
Police radio is a communications radio system used by law enforcement agencies all over the world.Many such systems are encrypted to prevent eavesdroppers from listening in.-Portable radios:...
, the use of business band
Business band
The business band is the name used by US radio users and scanner hobbyists who listen to Federal Communications Commission licensees using Industrial/Business pool frequencies...
radios on construction
Construction
In the fields of architecture and civil engineering, construction is a process that consists of the building or assembling of infrastructure. Far from being a single activity, large scale construction is a feat of human multitasking...
sites, and other situations requiring coordination of several parties. Citizens Band is another example of classic push to talk operation.
Where a user may be too busy to handle a talk switch, for example in combat aircraft, voice operated switch
Voice operated switch
In telecommunications, a voice operated switch, also known as VOX or Voice Operated eXchange, is a switch that operates when sound over a certain threshold is detected. It is usually used to turn on a transmitter or recorder when someone speaks and turn it off when they stop speaking...
es are sometimes employed. Some systems use PTT ID
PTT ID
PTT ID, or Push-To-Talk ID, is a generic term for an ANI-like system used in Two-way radio systems. It provides identification of the transmitting radio over the air, and is commonly used in Selective calling/signaling systems, usually in commercial and public safety radio systems.PTT ID features...
to identify the speaker.
Push to Talk over Cellular (PoC) is a service option for a cellular phone network which permits subscribers to use their phone as a walkie-talkie
Walkie-talkie
A walkie-talkie is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola...
with unlimited range. A typical Push to Talk connection connects almost instantly. One significant advantage of PoC / PTT is that it allows a single person to reach an active talk group with a single button press; users need not make several calls
Telephone call
A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...
to coordinate with a group.
Mobile phone
Push-to-talk cellular calls similarly provide half-duplex communications — while one person transmits, the other(s) receive. This combines the operational advantages of PTT with the interference resistance and other virtues of mobile phones.Traditional mobile phone
Mobile phone
A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...
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, the telephone communication protocol does not allow for casual and immediate transmissions to be sent to other parties on the network. While 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.
Later versions of PTT are based on 2.5G or 3G
3G
3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 specifications by the International Telecommunication Union...
packet-switched networks and use SIP
Session Initiation Protocol
The Session Initiation Protocol is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol . The protocol can be used for creating, modifying and terminating two-party or multiparty sessions...
and RTP
Real-time Transport Protocol
The Real-time Transport Protocol defines a standardized packet format for delivering audio and video over IP networks. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications, television services and...
protocols. These particular versions of PTT are called Push to Talk over Cellular, which is abbreviated PoC. 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.
Current use in mobile telephony (PoC)
Full-duplex operation on mobile phone networks is made possible by 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. 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 his 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 may be complemented with fixed PC
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
applications acting as PTT clients connected to the mobile operator via secured Internet links. A dispatcher
Dispatcher
Dispatchers are communications personnel responsible for receiving and transmitting pure and reliable messages, tracking vehicles and equipment, and recording other important information...
is a specialized type of PC Client but designed for heavy load dispatching, i.e. coordinating many issues typically caused when managing large fleets from a dispatch center. In Spain, Telefonica
Telefónica
Telefónica, S.A. is a Spanish broadband and telecommunications provider in Europe and Latin America. Operating globally, it is the third largest provider in the world...
has launched PTT offering with focus on dispatch orientated group communications.
Nextel Communications
Nextel Communications
Nextel Communications, commonly styled NEXTEL and formerly traded on the NASDAQ as NXTL, now a part of the Sprint Nextel Corporation, was a United States telecommunications firm operating a nationwide push to talk mobile communications system. Unlike other mobile networks, the Nextel network...
introduced mobile push-to-talk in August 1993 using iDEN
Iden
For other uses of the word, see Iden The Iden was an English automobile manufactured from 1904 until 1907. Designed by George Iden, formerly of Daimler, they were four-cylinder 10/17 hp and 25/35 hp shaft-driven cars; each came with "Idens's frictionless radial gearbox"....
. The first system was turned on in Los Angeles
Los Ángeles
Los Ángeles is the capital of the province of Biobío, in the commune of the same name, in Region VIII , in the center-south of Chile. It is located between the Laja and Biobío rivers. The population is 123,445 inhabitants...
with 134 sites and a capacity for 50,000 dispatch subscribers. The "MOTO Talk
MOTO Talk
MOTO Talk is a feature on some Motorola iDEN cellular phone handsets which allows users to make short-range 'push-to-talk' calls to other such handsets without being on the iDEN network. This feature goes by different names on iDEN service providers. In the US, Nextel calls it 'DirectTalk' and...
" feature by Nextel includes both on- and off-iDEN network walkie-talkie
Walkie-talkie
A walkie-talkie is a hand-held, portable, two-way radio transceiver. Its development during the Second World War has been variously credited to Donald L. Hings, radio engineer Alfred J. Gross, and engineering teams at Motorola...
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.
Verizon Wireless
Verizon Wireless
Cellco Partnership, doing business as Verizon Wireless, is one of the largest mobile network operators in the United States. The network has 107.7 million subscribers as of 2011, making it the largest wireless service provider in America....
enabled push-to-talk communication on its BlackBerry
BlackBerry
BlackBerry is a line of mobile email and smartphone devices developed and designed by Canadian company Research In Motion since 1999.BlackBerry devices are smartphones, designed to function as personal digital assistants, portable media players, internet browsers, gaming devices, and much more...
devices in March 2010, requiring download and a monthly fee.
The Open Mobile Alliance
Open Mobile Alliance
The Open Mobile Alliance is a standards body which develops open standards for the mobile phone industry.- Principles :Mission: To provide interoperable service enablers working across countries, operators and mobile terminals....
is defining PoC as part of the IP Multimedia Subsystem
IP Multimedia Subsystem
The IP Multimedia Subsystem or IP Multimedia Core Network Subsystem is an architectural framework for delivering Internet Protocol multimedia services. It was originally designed by the wireless standards body 3rd Generation Partnership Project , as a part of the vision for evolving mobile...
, 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 .
A pre-standard version of PoC is also defined by the industry consortium made up of Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
, Nokia
Nokia
Nokia Corporation is a Finnish multinational communications corporation that is headquartered in Keilaniemi, Espoo, a city neighbouring Finland's capital Helsinki...
, Ericsson
Ericsson
Ericsson , one of Sweden's largest companies, is a provider of telecommunication and data communication systems, and related services, covering a range of technologies, including especially mobile networks...
, Siemens AG
Siemens AG
Siemens AG is a German multinational conglomerate company headquartered in Munich, Germany. It is the largest Europe-based electronics and electrical engineering company....
and AT&T Mobility with the aim of creating a commercial offering enabling interoperability between vendors.
As of June 2010 no tier-1 operator worldwide launched OMA. Availability of OMA handsets and fully inter-operable solutions remain to be seen.
OMA solution missed the most important factor for such a niche market which is performance. In addition, standard was mainly adopted by NSN, Nokia, Ericsson and others who all never had major success or background on PTT. OMA PoC also assumed it is a service for consumers which is not true. PTT/PoC is an enterprise service. On the bottom line, it is more of a North American phenomenon due to existence of iDEN and other networks. Other parts of the world do not know the service and operators are having a hard time identifying who needs this service.
See also
- IP Multimedia SubsystemIP Multimedia SubsystemThe IP Multimedia Subsystem or IP Multimedia Core Network Subsystem is an architectural framework for delivering Internet Protocol multimedia services. It was originally designed by the wireless standards body 3rd Generation Partnership Project , as a part of the vision for evolving mobile...
- IMPS
- Push-to-type operationPush-to-type operationPush-to-type operation: In telegraph or data transmission systems, that method of communication in which the operator at a station must keep a switch operated in order to send messages....
- Click-to-callClick-to-callClick-to-call, also known as click-to-talk, click-to-chat and click-to-text, is a form of Web-based communication in which a person clicks an object to request an immediate connection with another person in real-time either by phone call, Voice-over-Internet-Protocol , or text...