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Access gateway integrates UMTS, WiMAX services

Posted: 01 May 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Loring Wirbel? Airvana? EV-DO? CDMA? Advanced Telecom Computing Architecture?

Airvana Inc., known for the last three years as an EV-DO radio-access specialist for CDMA networks, is moving into the IP core with an aggregation system based on the Advanced Telecom Computing Architecture (ATCA). The company makes no bones about admitting that its Universal Access Gateway (UAG) represents a way to enter UMTS cellular markets, as well as take part in advanced broadband data services based on Wi-Fi and WiMAX.

"We needed IP expertise for EV-DO backbones, so the company always had a strong engineering presence in IP," said Leigh Chinitz, director of marketing and business development at Airvana. "The issue was to define what IP aggregation functions were necessary in most carrier environments going forward."

What the UAG is not, Chinitz said, is an IP multimedia subsystem (IMS) that performs voice gateway functions for Session Initiation Protocol clients. The UAG can complement IMS functions, he said, but Airvana did not want to develop one more voice soft switch for a market rapidly moving to all-packet backbones. Instead, the system uses IP to offer fixed/mobile convergence in the short term, including integration of VoIP, moving to all-IP aggregation as networks phase out circuit-switched voice services. The feature set Airvana will emphasize for IP aggregation will be security, mobility and advanced QoS prioritization.

Airvana designers figured an ATCA chassis was necessary, given central-office carrier trends, but the company customized its ATCA design to avoid complete hardware commoditization, adding a special midplane for redundancy and failover services. Working prototypes of the system were shown at last month's Wireless 2006 show in Nevada.

The UAG may expand Airvana's market from incumbent providers that own full-switched cellular networks with cell towers, to mobile virtual network operators that offer enhanced services on leased networks. Even the latter must maintain overlay equipment to handle specific traffic carried on another's wireless network, Chinitz said, so the UAG can be sold to a variety of service providers.

The gateway meets two emerging 3GPP interworking standards: For the UMTS-based 3GPP 1 standard, it functions as a packet data gateway, while in the CDMA-based 3GPP 2, it serves the defined packet gateway interworking function.

"The gateway is not air-interface-dependent," Chinitz said. "In fact, we want it to meet emerging standards such as Long Term Evolution and 802.20."

Two mobility levels
To secure traffic for virtual private networks, Airvana opted for Internet Protocol Secure and the Internet Key Exchange (IKE) version 2, rather than any Secure Sockets Layer alternative. Authentication is supported with a range of protocols, from Wi-Fi-specific worlds such as EAP to standards from wireline enterprise worlds such as Radius.

The gateway had to support mobility on two levels. When traffic roams within one network topology, such as between Wi-Fi access points, the gateway uses a new multihoming extension of IKEv2, called Mobike. When packets cross multiple network types, the gateway supports the Mobile IP protocol, including foreign-agent modes.

QoS is handled on a per-flow and per-session basis, but what Airvana emphasizes is not the mere ability to prioritize traffic, but the full ingress and egress port management combined with full accounting, including per-flow statistics. The fine-grained flow analysis meets the newest IMS standards for policy and charging rules function (formerly known as a policy decision function).

Chinitz hopes that existing OEM partners of Airvana's radio-access solutions, such as Nortel Networks, will be interested in the UAG for IP backbones. The system does not compete with most backbone equipment OEMs' IMS or aggregation-switch systems, Chinitz said, so the ability to partner may be significant.

- Loring Wirbel
EE Times

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