Telstra demonstrates Push To Talk

Telstra yesterday performed its first public demonstration of Push To Talk technology at the Media Connect Kickstart Forum at Stradbroke Island in Queensland.

Push To Talk is a technology that allows mobile phones with the feature to be used in a similar manner to walkie talkies. Users connect in predefined or ad hoc groups, and when one member of the group pushes a special button on their phone, they can then speak to all other members of the group.

Push To Talk runs as packetised data over GPRS in a half duplex mode. When the button on the phone is pressed, the voice is digitised, then broken into packets which are sent to a central server and then distributed to all other members of the group simultaneously. This means that only one person can talk at a time.
 
During the demonstration there was a 1 to 2 second latency from speaking into one phone and hearing it back from another.

The phone used for the demonstration was a Nokia 5140 and a "broader range of phones will be available at launch" said Greg.

Telstra will be commencing public trials of Push To Talk in two weeks, with a nationwide launch mid year. Pricing has yet to be announced.

Telstra will begin by targeting the business market before focusing on the consumer market, especially youth.

Other future services are Push To Video and Push To Data, both of which should be launched in around 18 months. Telstra is also currently testing with Push To Talk over CDMA.

The protocol that underlies Push To Talk is SIP-based (Session Initiation Protocol). Each phone will have a unique address and domain, similar to an internet email address, that will be used to route the data. To establish a group, first an SMS invitation must be sent and accepted by the other users. Each phone can hold multiple groups, with one being a default. When a message arrives, the phone will display who the sender is, as well as the group they are a part of. That group then becomes active on the recipient's phone for several seconds before it reverts back to the default group, thus allowing the recipient to reply without having to change groups.

There is no fixed range for Push To Talk as it runs over GPRS. During the demonstration Greg Young spoke to another Telstra representative in the same room as well as with a third individual in Melbourne.