New push-to-talk mobile phone systems being developed for packet-based GSM networks could prove to be a disruptive technology in more ways than one.

Equipment manufacturers are split over different interpretations and implementations of the draft push-to-talk over cellular (POC) standard from the Open Mobile Alliance (OMA) standardization body. Their differences threaten to fragment the market for a service that both excites and worries GSM operators. While many view the walkie-talkie-like service as a huge opportunity to expand their voice offerings, others fear it could cannibalize their highly lucrative phone business.

Push-to-talk technology can be a relatively inexpensive, simple way to use mobile phones for immediate voice communications. In its simplest form, the technology allows customers to use their mobile phones as walkie-talkies. By pressing and holding down a button, they can talk instantly to one or more participants without having to make a dial-up call.

Moving quickly to capture a slice of what they expect to be a huge market, equipment makers have developed pre-standard POC handsets and network servers ahead of the OMA standard, which is expected by year-end.

In the one camp is Nokia together with Samsung, which has agreed to license POC technology from the Espoo, Finland, mobile phone and infrastructure manufacturer. In the other is Motorola, Siemens AG, Sony Ericsson Mobile Communications AB and Telefonaktiebolaget LM Ericsson.

All six companies are OMA members and are participating in the standardization work on POC. The problem, according to Tapio Heikkilä, director of business development at Nokia's network division, is that their pre-standardized systems aren't fully interoperable. And differences remain on the final drafting of the OMA push-to-talk standard.

On March 16, two days before the official start of the Cebit trade show in Hanover, Germany, Ericsson, Motorola, Siemens and Sony Ericsson announced the first joint interoperability tests of their POC systems and plans to introduce the first pre-standard, interoperable products in the second quarter of 2004.

On the same day, Nokia announced an "initiative" to enable operators to use its POC technology, which isn't interoperable with the other group's. Reaching out, the company said it plans to introduce a protocol converter in its server software, allowing its POC systems to be interoperable with those of the other four vendors. Nokia added it expects these companies to make their systems interoperable with its system.

The IDG News Service is a Network World affiliate.