Cross-Layer Optimization: The Impact on Today’s Wireless World

The transition from a wired information and communication society to one that is wireless and always on the move is well under way. 3G mobile networks enable consumers to access their favorite Internet and business applications on the go. But while the potential is enormous, the reality of high-speed wireless Internet services often falls short of consumer expectations.

3G services (video/audio streaming, video conferencing, VoIP and multiplayer gaming) are potential sources of significant new service revenue for mobile service providers. The success of these services is dependent upon factors such as service quality, availability and pricing. Yet technical and environmental challenges, the nature of wireless networks, and the data transport requirements of video and audio Internet streaming, can slow adoption, create customer retention challenges and produce suboptimal ROI.

A cross-layer optimization approach that adapts Internet and multimedia content for wireless transport under all RF conditions enables mobile service providers to deliver a variety of 3G services that meet or exceed subscriber performance and reliability expectations. In turn, this increases customer satisfaction and improves ROI for mobile service providers.

Offering a wide range of compelling mobile services at an attractive price point is critical for consumer adoption of 3G services. Overall application performance is another critical issue. Consumers expect fast, uninterrupted access to their applications and content anywhere, anytime.

• Service Consistency – Stable, consistent service quality is a basic requirement. If the consumer’s experience is inconsistent, he or she will be less likely to continue subscribing to the service.
• Connection Reliability – Reliable connections are extremely important to build consumer confidence in 3G services. A dropped connection during a wireless data session is more disruptive than a dropped voice call.
• Consistent Multimedia Streaming – Streaming video and audio are the key services that differentiate 3G from 2G/2.5G networks. In a wireless WAN, RF variations can lead to long, initial buffering times and additional interruptions during viewing.

Internet protocols, specifically Transport Control Protocol (TCP), were designed for wireline environments where the biggest challenges are determining how to route data between two points and how to handle network congestion. Because of the way in which TCP applies congestion control algorithms in a wireless environment, network efficiency problems occur:

• Redundant data is transmitted – Congestion control algorithms induce retransmissions resulting in redundant data transmissions and multiple acknowledgements of data already received.
• Less bandwidth is utilized – When congestion control kicks in, the rate at which packets are sent is reduced, thereby failing to exploit valuable bandwidth.
• Sessions are terminated – When the protocol inaccurately determines that a connection has timed out, the session will terminate. Due to this response, some applications, like e-commerce, may be impossible to use.

Other challenges are tied to the RF environment which can cause busy tones and dropped calls in a crowded cell as well as aborted mobile data transactions and slow speeds. For revenue-generating services such as mobile video, Internet streaming can suffer unacceptable interruptions due to delay swings and available bandwidth.

Cross-layer optimization addresses many of the challenges mobile operators face when deploying consumer and business applications on wireless networks. Subscribers can enjoy the best possible user experience with improved speed and reliability independent of network or RF conditions.

With consumers expecting the same consistent and reliable experience every time they connect, the key to consumer satisfaction is consistent application and network performance.

• Improved Coverage – Transport optimization can increase effective cell coverage so that in areas where a user previously could not download a Web page due to poor signal quality, a user now can do so quickly. Carriers are able to deliver consistent service quality over a larger area without having to increase base station density.
• More Capacity, Higher Returns – Wireless networks have limited capacity due to limited spectrum. With a cross-layer optimization approach, mobile service providers increase network and spectrum utilization, freeing up usable bandwidth and available capacity. Operators then can serve more customers with their existing network resources, achieving greater consumer reach and cost savings.
• Increased Throughput and Improved Multimedia Performance – Cross-layer optimization can increase application throughput up to nine times, improving the user experience and resulting in faster browsing, shorter buffering times for multimedia, and fewer interruptions in all cell areas.

For multimedia, higher frame rates, fewer frame drops and fewer interruptions during streaming means video and audio streams start two to three times faster, eliminating freezes during streaming, and delivering superior image quality –necessary improvements for the success of 3G data services.

In today’s wireless world, consumers are demanding secure, high-quality wireless data services to access their most important business, news and entertainment content while they are mobile.

Carriers ultimately will benefit from the combination of a better user experience, competitive service pricing and faster 3G wireless data service adoption. By employing a cross-layer optimization solution that works transparently at the transport and application layer, the Web, streaming multimedia, e-mail and other applications perform at a level users expect.

Bret Sewell is the CEO of Venturi Wireless, a global provider of 3G mobile optimization solutions. He can be reached at bsewell@venturiwireless.com.

Venturi Wireless www.venturiwireless.com

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