By Jon Mechling, Director of Product Management
Introduction to Mobile Video Applications
With the deployment of 3G wireless networks, carriers worldwide are finally able to offer a broad spectrum of mobile services that transcend voice. Specifically, 3G-324M networks support a range of video capabilities, leveraging the dedicated 64 kbps data connection between the network and the subscriber’s handset.
Emerging video services include music videos, sports shorts, information services, video messaging, and subscriber-to-subscriber video calls. The added value associated with these video capabilities results in higher average revenue per user (ARPU) and decreased subscriber churn.
Essential to the success of these new services is the total quality of the user’s experience. One critical factor in the user experience is the perceived responsiveness of the system, including something as basic as the time it takes to set up a video call—the time it takes from the moment the “Send” button is pressed to the moment the desired video starts to display on the subscriber’s handset.
Customers are accustomed to voice calls setting up in a matter of a couple of seconds—press the “Send” button, and by the time you raise the handset to your ear, you often already hear ringing. Video call setup needs to be perceived as just as fast as voice call setup, or subscribers will think video services are “slow.” That perception will, in turn, damage the potential penetration of these services, and reduce the returns service providers receive for their network investments.
The bottom line—fast call setup is critical to the success of mobile video services.
Improving Call Setup in 3G Mobile Networks
Call setup in 3G networks involves a complex process of messaging, “hand shaking,” and negotiations between 3G-324M terminals. 3G-324M, the umbrella standard for multimedia communication over circuit-switched networks, specifies using the H.245 protocol for much of the call setup negotiation. H.245 can require as many as 10 messages to establish a call (see Figure 1), each of which can introduce about 800 milliseconds of round trip delay. In an unaccelerated form, this signaling results in a video call setup time that can run up to 10 seconds and beyond—unacceptable to subscribers used to call setup times of one second or less.
Figure 1: Standard H.245 Handshaking During Call Setup
As one approach to speeding up the call setup process, accelerated H.245 signaling involves opening the logical channels and allowing audio and video to be transmitted before the MES and MSD messages are exchanged. However, the receiving terminal may reject that incoming media, in which case the sending terminal must try again with a different media type, negating much of the potential time savings of accelerating the signaling in the first place.
WNSRP for Faster Video Call Setup
A key reason the standard H.245 process is slow is that the messages are sent serially—the next message is not sent until its predecessor has been processed and acknowledged. In 2005, the ITU approved WNSRP (Windowed Numbered Simple Retransmission Protocol) as a way to significantly reduce call setup time. With WNSRP, H.245 messages can be sent rapidly, without waiting for confirmation. Missed messages are immediately detected by the receiving handset, and retransmission requests are automatically generated. WNSRP can reduce call setup time to closer to three seconds—significantly better than unaccelerated H.245, but still long enough to negatively affect the customer experience.
MONA Meets Subscribers’ Call Setup Time Requirements
In light of the progress made by WNSRP, but recognizing that further improvements were needed, in 2006 the ITU released the Media Oriented Negotiation Acceleration (MONA) standard, H.324 Annex K. MONA builds on H.245, but adds the concepts of “preference messages,” which are short messages that include signaling to accelerate the establishment of multimedia sessions.
Two key MONA messages include:
- Media Preconfigured Channels (MPCs) that describe which Media Preconfigured Channel configurations the MONA terminal is capable of using. This message is used to set up audio and video sessions using the most common codecs and configurations.
- Signaling Preconfigured Channels (SPCs) that designate whether the MONA terminal prefers negotiation of logical channels using the Signaling Preconfigured Channel, and, if Media Oriented Setup is used, the terminal’s multiplexer level preference. This is used to negotiate a wider range of possible session types (codecs and configurations).
A MONA-capable terminal begins establishing a session by transmitting the Preference Messages, which contain information about its channel establishment capabilities and preferences. Upon receiving each other’s Preference Messages, the two terminals execute a handshaking process that quickly establishes a video and audio channel between them. As a lower complexity fallback from this negotiation, accelerated H.245 signaling is also supported. And finally, for compatibility with legacy terminals, all MONA-compliant terminals can also quickly fall back to using standard, unaccelerated H.245 setup procedures.
The benefit of MONA is that call setup time is typically under one second. The customer experience is much improved, an outcome that could significantly reduce subscriber churn while increasing ARPU.
Summary
Mobile video services offer the possibility of significant new revenue streams to service providers, but only if the customer’s experience with the service is compelling. Key to that positive experience is fast call setup times, comparable to what subscribers are used to on voice calls. Defined by the ITU, MONA builds on traditional H.245 signaling to bring video call setup times under one second. Mobile handsets with MONA support will be coming to market soon. NMS will be supporting MONA in release 3.0 of Video Access (available on July 6), a technology platform for rapidly developing and deploying video applications in 3G mobile networks.
For more information on Video Access 3.0, contact your NMS sales representative .