Press-to-Talk

Press-to-Talk (PTT) service is a real-time, point-to-point and point-to-multipoint,
voice-based instant messaging application. This has proved a popular service in the
United States on the Nextel network, based on Motorola’s iDEN architecture. Many
of the features are the same as text-based IM, with buddy lists and chat rooms, etc.
Once again, the biggest potential problem affecting the widespread adoption of the
service will be compatibility between handsets and across networks.

There are, at present, four PTT solutions on the market.

1. Motorola iDEN. This is a well-established system that has a proven track
record in the United States with good performance. Motorola also supplies
a wide range of handsets to support the service. However, only Motorola
manufactures handsets for this service. iDEN does not support a presence
service.

2. Kodiak. This system uses circuit-switched connections, which results in good
performance but misses out on the efficiency of packet-based delivery. The
system is also technology-agnostic. It has been deployed on GSM, CDMA,
and analog networks. However, there is a limited range of handsets available
for this service. Kodiak has a thin-client available to allow vendors to implement
the service.

3. Qualcom Qchat. This service is proprietary to Qualcom and is only supported
on cdmaOne 1X only. In this case, the performance of the 1X network may
not be sufficient to ensure adequate performance. The QChat service is implemented
on Qualcomm’s BREW platform.

4. PTT over Cellular (PoC). The final method is a proposed standard mechanism
from Ericsson, Nokia, Motorola, and Siemens for a PTT over Cellular
(PoC) system. This has been presented to the Open Mobile Alliance (OMA),
which is developing this proposal as a standard in line with the 3G UMTS
and IMS specification from the 3GPP. It is based, generally, on existing protocols
and methods: IP and SIP. This system has the advantage that it will
run over any network. There will be products available in GSM and GPRS,
UMTS, and cdma2000. It is anticipated that it will be possible to interoperate
a PTT service across network boundaries.