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How to optimise bandwidth efficiency and improve QoE in the Covid-era

As England and Scotland return to lockdown, Xavier Leclercq, VP of Business Development at Broadpeak looks at key technologies that can help meet the ever-growing demand for connectivity being driven by video services.

Throughout the Covid-19 global pandemic, broadband and video streaming consumption has risen dramatically. At one point in the U.K., BT reported a 35-60 per cent increase in daytime weekday fixed broadband usage. During the first lockdown in Europe, the demand on broadband networks created such extreme network congestion that some video services had to reduce their top quality to avoid overloading networks. Disney Plus launched in France without UHD, and Netflix reduced video bit rates for 30 days in Europe in order to decrease the amount of bandwidth consumed by subscribers during the crisis.

Covid-19 has also impacted viewing habits. The traditional evening peak is now more spread out as people spend more time at home. There has been an increase in time-shifted viewing, including restart TV and catch-up TV. Live video consumption is also higher than normal as people around the world rely on the news and government briefings for information about the pandemic. Audiences for live sports broadcasts over IP are also ramping up; therefore, we expect this trend to continue to accelerate.

As the pandemic continues into 2021, there are several strategies that service providers can adopt to ensure a continuous high quality of experience (QoE) for subscribers on every screen. 

Next-Gen Technologies for Enhancing Bandwidth Efficiency and Video Quality

The key benefit of ABR video technology is that it offers an extensive reach, allowing service providers to stream to any screen in the home. Furthermore, ABR technology opens up additional advertising and content personalisation opportunities for service providers. However, video service providers have little to no control over streaming quality and bandwidth usage with ABR. When there is an audience peak, if the network becomes congested or if the CDN is overloaded, then viewers will likely experience quality problems such as rebuffering, freezes, and low resolution.

Modern CDNs can mitigate these issues by either using multicast technology for live content, or becoming context aware, allowing the introduction of advanced policies to choose how the resources should be shared.

To avoid congestion in their network, a growing number of ISPs are using multicast ABR (mABR) solutions on their managed networks. Now endorsed by DVB, mABR combines the scalability and robustness of multicast with the versatility of ABR to serve any screen in the home with a single stream from the network. This results in a scalable system capable of serving a pristine quality of experience to consumers, equivalent to what is achieved with broadcast technologies.

Another avenue to avoid quality problems when delivering ABR streams is to introduce policies in a context -aware CDN. We know that with traditional ABR streaming the client holds the power over performing quality selection. It’s not uncommon for each client to greedily use as much bandwidth as possible, often at the expense of other clients. So, some modern CDNs have embraced initiatives that allow service providers to choose how the resources are shared.

An option is for the resources to be shared equitably across all the users (similar to how Netflix stopped its UHD content delivery to allow everyone to access the HD versions). When the CDN or the network gets too busy, the top-layer video profile is removed from the offering. An alternative option is to prioritise streams (i.e., allocate more bandwidth to them), based on a set of rules defined by the service providers in a way that is as transparent as possible for end-users. Stream prioritisation may be according to the size of the screens or to the type of video (pretty still or with many movements). The same bandwidth is not required to achieve an equivalent QoE, and this can be taken into account by the video delivery system to optimise delivery costs.

In the end, we believe that all the streams should not be treated equally by the CDN, but rather based on their value to the service provider. For example, a live sports stream delivered as part of a premium subscription to an Apple TV to a 4K screen will likely be more valuable to service providers than a children’s cartoon delivered as part of a free catch-up TV package to an iPhone. Modern CDNs have become context aware and allow service providers to prioritise some streams based on the content, user subscription, and device type. This is done on the server side by implementing rules that rank the streams and choose how/where the congestion will be felt while protecting the most valuable streams.

Going forward service providers are considering new ways to alleviate bandwidth problems with mobile edge caching, where CDN caches are deployed very close to the consumer, resulting in an even better video experience. Initiatives like Google Cloud or AWS Wavelength are the first opportunities to deploy CDN caching in Mobile Edge Computing (MEC). With caching embedded in the mobile edge infrastructure, service providers can deliver more throughput to the consumers and virtually eliminate network congestion. The drawback of this approach is that it is a more costly infrastructure, requiring hundreds of CDN points of presence (PoPs) vs. the tens of CDN PoPs used today. Therefore, mobile edge caching will naturally be better suited to live premium streams to meet the expectations of low-latency delivery and to avoid rebuffering events. More than likely, the CDN delivery capacity will be instantiated temporarily where needed and when needed.

We are heading toward a delivery world where multiple options for CDN will be in play for every stream: on-net CDN as a starting point, mobile edge CDN for premium experiences, CDN aaS for overflow capacity.  The CDN selection becomes a critical tool to ensure the best possible CDN is used at the beginning of a video streaming session, but it’s not enough. Similar to the way Netflix uses multiple connections for a single session,  video service providers may soon be deploying multi-CDN technology solutions that allow them to fetch content from multiple CDNs in parallel. They can then decide in real time which CDNs to use based on costs and quality metrics, achieving the best possible video quality at the lowest possible cost.

Finally, analytics are the key to optimising the CDN and improving QoE over time. With data and analytics service providers can perform A/B testing to validate which changes should be made to their content delivery platform. Analytics are particularly needed when introducing new features like low-latency live delivery, new delivery protocols like HTTP/2 or HTTP/3, or new TCP congestion control algorithms like BBR from Google or PCC from Compira Labs in the CDN.

The explosion in broadband usage caused by people spending more time at home during the Covid-19 pandemic has led service providers to look for new ways to improve QoE and bandwidth efficiency. By investing in next-generation technologies such as multicast ABR, context-aware CDNs, dynamic multi-CDN selection, mobile edge caching, and video analytics, service providers can meet the ever-growing demand for connectivity driven by video services.