The promise of IP-based fixed/mobile convergence is clear: Allow subscribers to maximize wireless and wireline connections, seamlessly moving between networks based on user location and application requirements.

Delivering on that promise for carriers, however, can be challenging. Sonus Networks, which has provided carrier-class voice-over-IP (VoIP) infrastructure products, is now looking to bridge wireless access onto core IP networks. The vendor’s new mobileEdge Wireless Access Node acts as a gateway conversion point, aggregating femtocell and picocell signals carried into the network via in-place broadband connections and converting them onto a session initiation protocol-based core carrier network. Ultimately, the plan is to leverage this mobile edge gateway to “harmonize all devices — phones, handsets, TVs — onto a common IP-services infrastructure,” said Vikram Saksena, chief technical officer for Sonus.

“We see integrated wireline/wireless operators focusing on leveraging the high-speed broadband connection to the home as a fundamental mechanism to deliver both fixed and mobile services,” Saksena said. “When you put a device like a femtocell at the end of the broadband connection, suddenly you’ve opened up a lot of broadband and capacity to that mobile phone at the same time. The power here is driving more and more of that traffic onto and delivering advances services via that IP-based core.”

The mobileEdge node is Sonus’ first major wireless offering, and it is focused clearly on carriers. In addition to facilitating wireless-to-IP protocol and signaling conversion, mobileEdge can aggregate large numbers of femtocell users onto carrier IP networks. The modular mobileEdge9000 version can aggregate up to 640,000 users in a single chassis, while the smaller, fixed-configuration mobileEdge 4010 can handle 25,000 users. The access node supports today’s GSM- and UMTS-based access as well as future 4G networks. The node also takes advantage of switching technology from Zynetix, which Sonus acquired last year. That technology is integrated into Sonus’s IP-based GSX switching platform, which handles IP call routing, TDM-to-IP conversions and secure IP-to-IP border switching.

Sonus admits it is a bit ahead of the market. While full of promise, femtocell deployments are still in their early stages but expected to grow quickly. In-Stat projects femtocell installations to reach 40 million by 2011 and could surpass 100 million uses over the next five years.

Initial carrier customers likely will come in two flavors, Saksena said: operators that want to maximized their mobile and fixed networks, and mobile pure-plays aiming to join the convergence game by leveraging broadband connections delivered by another carrier.