3G Quick Connect Through New Processing of Existing Signaling
The delay in 3G-324M call setup time is caused by multiple H.245 message transmissions in several protocol layers, many of which require an acknowledgement before the transmission of the next message. A single round-trip of a message in a 3G-324M connection typically requires 800 milliseconds or more. Call setup typically requires transmitting ten H.245 messages to establish media transmission resulting in a setup time of up to eight seconds (not including the initial setup time of the 3G call connection itself). This is long even without taking into account errors on the network.

An additional contributing factor to call setup time is the acknowledgment required by SRP (Simple Retransmission Protocol) or NSRP (Numbered Simple Retransmission Protocol) frames. NSRP frames are used to send the H.245 messages. Each NSRP command frame can hold several H.245 messages. An NSRP command frame cannot be sent for an H.245 message before the previously sent NSRP command frame is acknowledged by an NSRP response frame. Sometimes H.245 messages are segmented on top of more than a single NSRP command frame by CCSRL (Control Channel Segmentation and Reassembly Layer).

WNSRP (Windowed NSRP) speeds up the handling of H.245 messages in H.324M by using a windowing mechanism that can send several different messages at the same time. It ensures that all messages are received and are in the correct order. WNSRP works in a similar manner to NSRP. It adds a response window that enables an overlap of the round trips required by H.245 messages, thus reducing call setup time.

The proposed WNSRP solution is a joint contribution of RADVISION and Motorola (with many other vendors committing to support) and is currently being considered by the ITU-T for approval.

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Fast Session Initiation With Non-3G Devices
Because WNSRP is protocol independent, it is not only ideal for point-to-point 3G video calls but is also unique in the market for its support of connectivity between 3G devices and devices running other signaling protocols such as IP.  WNSRP enables session establishment between 3G-324M devices with video telephony end points (H.323 and SIP), video streaming, video portal, and video mail IP servers, and other network devices.

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Future Proof
Unlike competing solutions, which are proprietary communications architectures that are part of a device’s underlying terminal, WNSRP simply provides a different way of handling existing standard signaling without interacting with the underlying codecs.  As such, WNSRP is not part of the underlying device functionality and is immune to future incompatibility issues that could arise through the additions of new codecs, new capabilities, and new call messages. 

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Network Independent Leads to Roaming and High Reliability
On a related issue, because WNSRP is not a new way of signaling but just a different way of processing existing signaling, it is network and MSC (switch) transparent – enabling 3G handsets to roam to countries and networks without interoperability issues.  Additionally, its overlay architecture makes it immune to network errors because it does not introduce new signaling that needs to be network validated but rather handles existing signaling in a new way.

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