Correction: Telephony on Monday incorrectly stated that Motorola’s 3G PTT platform incorporated the Open Mobile Alliance’s Push-to-Talk over Cellular (PoC) standard. Rather, the platform is still a proprietary solution but incorporates OMA protocols that allow it to communicate with other PTT networks. The corrections are reflected below.

Motorola is answering Qualcomm’s QChat push-to-talk challenge with its own push-to-talk solution optimized for the unique capabilities of CDMA EV-DO Revision A networks. In addition, Motorola has tweaked its solution to bridge push sessions to other operators’ networks.

Like QChat, Motorola’s PoC solution utilizes the low-latency and high-capacity return channel of EV-DO Revision A to achieve near-one-second response times and call clarity. Verizon Wireless confirmed that it is using the Motorola platform in its newly revamped PTT service, which went nationwide this month.

Though still a proprietary solution, Moto’s platform has gone one step further, incorporating protocols from the Open Mobile Alliance’s PTT over cellular (PoC) standard that will allow cross-carrier PTT, even with operators using other proprietary solutions. Software based on the OMA’s Network-to-Network Interface (NNI) standard sits in the PTT server, which can then mediate sessions between another operator so long as that operator’s PTT server also uses the NNI protocols, said Jacqueline Majka, Motorola senior product marketing manager for LTE and PTT over cellular solutions.

Motorola originally pioneered PTT on iDEN networks, creating the benchmark to which all other PTT solutions are measured. Outside of iDEN, however, PTT’s success has been limited, hampered by slow session initiation speeds. The advent of Revision A systems, however, not only provided greater data capacity on the upstream and downstream and supported a higher-quality VoIP connection but also had lower latency and quality of service (QoS) controls unavailable in CDMA 1X or plain EV-DO revision 0 networks. “PoC did work on CDMA 1X networks, but we optimized the latest PoC release to take full advantage of Revision A,” Majka said, adding that the upgraded platform provides walkie-talkie services competitive with alternative PTT products on the market -- both proprietary and standardized, including its own iDEN implementation.

Motorola was able to take advantage of features natively supported by the Rev. A network such as binary session initiation protocol, which can be integrated into a next-generation network framework such as IP Multimedia Subsystem (IMS). Motorola was also able to add support for some advanced features such as incorporating push messaging and multimedia into a unified buddy list and linking the PTT network back to other vertical applications like PC-based dispatching.

The cross-network connectivity allowed by NNI also raises the possibility of creating the first fully interoperable PTT networks. Sprint’s new QChat service allows it to bridge PTT between its CDMA and iDEN systems, but doesn’t yet permit PTT sessions outside of the Sprint Nextel network. In addition, Alltel and several regional CDMA operators use Kodiak Networks’ PTT solution. If those vendors incorporated NII into their PTT servers, they could support sessions with the Verizon network as well one another’s. Supporting interconnectivity between CDMA and UMTS networks, however, would require additional transcoding, which is in the pipeline but not yet commercially available, Majka said.