Sprint reveals CDMA push-to-talk plans

Sprint yesterday laid its plans for its next-generation push-to-talk to service, which will bring fully functioning “walkie-talkie” service to its CDMA network as well as link up with Nextel’s successful PTT service.

Sprint plans to use Qualcomm’s QChat solution over its EV-DO revision A advanced data network. Rev. A is the first 3G technology that has the downlink capacity, low latency and built-in QoS necessary to support end-to-end VoIP over a cellular network. While Sprint’s VoIP plans beyond push-to-talk are unclear as its CDMA network fills its voice needs admirably, the carrier has committed to using VoIP over Rev. A in 2008 as the only way to deploy to robust push voice service that can match that of standard-bearer Nextel’s.

Nextel’s PTT specification is based on older mobile radio technologies originally developed by Motorola and built directly into the iDEN specifications of the network. Consequently both Sprint and Verizon Wireless opted for a Motorola solution, developed by softswitch-maker Winphoria, but performance of the technology was poor with long delay times in initiating a talk session. For the new deployment, Sprint seems to be eschewing Motorola, selecting instead Lucent Technologies to develop software and infrastructure necessary to power the new VoIP application, while Qualcomm provides the core technology powering the PTT clients on the handset.

Though Qualcomm developed the technology, Lucent has been working closely with the chipset maker, having recently conducted trials of the QChat technology over Lucent equipment Rev. A in the Sprint network using pre-production handsets and commercial-grade lab infrastructure. Sprint said the technology overcame the long latency issues, setting up sessions in less than a second and, and used far less network capacity than other 2G PTT solutions.

Motorola may not be out of the loop completely though. It and Nortel Networks are all part of Sprint’s EV-DO 3G rollout and will presumably upgrade those networks to Rev. A, which in turn will need to be optimized for QChat. In addition, Motorola is the sole provider and developer of iDEN technology and any integration with its legacy PTT architecture will likely involve the vendor.