Putting quality and performance at the heart of broadband experience with QED
Putting quality and performance at the heart of broadband experience with QED
Gavin Young, Head of Fixed Access Centre of Excellence at Vodafone
Having reached more than half of the homes on earth with broadband, operators are faced with managing the experience of these users to further monetize their broadband experience. The industry has already achieved remarkable results when it comes to delivering high bit rates to the premises, so operators are now turning their attention to broadband performance and quality.
What end-users want is seamless broadband connectivity, so that their applications can work optimally, together. Broadband Forum’s Broadband Quality Experience Delivered (Broadband QED), is an initiative which helps to do just that, looking beyond conventional measurements to improve overall broadband experience and improve management of network latency, consistency, predictability and reliability. The initiative is gathering momentum and is providing operators with the tools they need to meet current user requirements.
Ensuring the highest quality
The work of Broadband Forum comes at a critical time, as new applications place tremendous strain on networks. In an ideal world, the IP packets carrying the end user’s application, for example during a video conference, would traverse the network with zero delay and zero packet loss. However, no real network is perfect and so all packets will at some point get delayed or may even get dropped or ‘lost’. But help is at hand, as the Forum’s QED project uses Quality Attenuation methods to deliver greater insight into Quality of Experience (QoE) and application outcomes, by measuring the statistical distribution of delay and loss.
There is also synergy between Quality Attenuation and the way engineers traditionally think about electrical and optical communication transmission systems, through the concept of signal attenuation. For metallic bearers such as twisted copper pair phone lines or coaxial cable for DOCSIS cable networks, the transmitted electrical signal becomes weaker as it traverses the bearer en route to the receiver. Quality Attenuation works at the IP (or Ethernet) packet layer. Hence there is a similarity between the attenuation of signal strength and the attenuation of IP packet layer quality due to latency.
A benefit of Quality Attenuation performance analysis is that it can specifically isolate the component and degree of quality degradation due to any inadequate scheduling operation when the network is under load. Therefore, it enables network operators to optimise broadband performance more cost-effectively via configuration changes rather than just increasing link speeds, which could be counter-productive and involve significant costs.
Dealing with packet networks
So, what is the situation in packet networks? Surprisingly, a much higher speed link in just one part of the end-end broadband connection could make performance much worse. IP network engineers use packet buffers in the equipment at the node where ingress and egress transmission rates are mismatched. It is mainly a problem when the egress transmission system is at a much lower speed than the ingress link speed.
Modern IP networks are essentially a cascaded tree of IP packet multiplexors so such a mismatch can occur at multiple locations such as the Access Node or the customer’s broadband router. With a significant speed mismatch, even a small “microburst” of packets from the Broadband Network Gateway (BNG) could overrun the Access Node ingress buffer, causing some packets to be dropped.
Once this happens, higher layer protocols like Transmission Control Protocol (or adaptive video encoding) will sense the packet loss and will “back-off” to reduce the sending rate. The outcome can be a lower speed-test result, a reduction in video resolution quality or similar degradation to application outcome and customer experience. Hence the analogy to impedance matching in electrical and optical transmission systems. To mitigate the problem, a common technique is for the BNG to have access to the knowledge of the customer’s downstream access speed. This then allows the BNG’s downstream packet transmission scheduler to ‘shape’ the speed at which it sends packets down to the Access Node so that it won’t overflow that node’s ingress buffers.
Evolution continues
As with many branches of engineering, the fundamental principles from one domain can help frame the way we think about problems and solutions in other domains. Solutions developed for improving manufacturing processes and also for optimising electrical, optical and RF transmission systems may also assist us as we seek to apply the newly standardized technique of Quality Attenuation to IP packet networks.
Until now, the broadband industry’s emphasis has been placed on achieving ever-higher speeds but as our ‘always on’, ultra-connected lifestyle now demands so much more, QoE can no longer be ignored. Consumers expect impeccable QoE – in all applications, all the time.
As the evolution continues, speed will no longer be a main priority but rather one of the goals being sought in the quest for a more holistic network performance, based upon depths in quality and service.
Join the latest Broadband Forum ‘Quality of Experience: Why Just Broadband Speed is not Enough’ webinar on Wednesday February 17 at 10AM EST (4PM CET). Register here.
For Press and Analyst inquiries, contact Proactive PR at broadbandforum@proactive-pr.com
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