The Importance of the Last Mile to QoE
As we discussed in an earlier post, quality of experience (QoE) is critical for everyone involved in “over the top” (OTT) video streaming. Consumers demand high-resolution video that loads quickly, plays without rebuffering, and, in the case of live streaming like sports events, has no discernable lag behind “real time.”
Viewers who repeatedly find that the movie they’re watching “drops” half-way through, or that they don’t see the winning goal in the World Cup final until 30 seconds after they read about it on Twitter, are understandably frustrated with their providers. OTT video streaming and CDN providers are likely to feel the impact in increased churn and reduced revenue.
Traditional broadcasters that use cable, satellite, and terrestrial TV networks don’t face this problem, because their networks are either self-owned or highly regulated by the government. It’s a challenge that’s unique to OTT video streaming services, which make use of networks and infrastructure that they don’t own and can’t control.
Existing strategies for improving QoE
With so much riding on good QoE, OTT providers invest a great deal of resources into trying to improve it. One of the aspects OTT providers often discuss is encoding algorithms, like HEVC instead of H.264, or applying title-based encoding. These approaches are all focused on achieving high picture quality with lower number of bits. Efficient encoding is always important, but it does not solve delivery problems, which are a major impedance to good QoE. The biggest delivery problem is The Last Mile network, which is explained in more detail below.
But while we’re talking about delivery problems, we should explore Content Delivery Networks (CDNs) which were designed specifically to overcome the challenging Internet environment and ensure that content gets where it’s supposed to go, quickly and efficiently. CDNs are networks of proxy servers and data centers that are located all over the world. They strongly impact streaming video QoE as they make content delivery both faster and more reliable. The closer a CDN server is to the end consumer, the less time it takes for content to reach their device. Providers try to ensure that the CDN end node, where video is cached before it is streamed to the end consumer, is as close as possible to the end consumer. However CDNs alone are not enough to ensure good QoE, as most consumers know instinctively, since we have all endured frustrating video experiences.Again, this is due to the Last Mile network.
As consumers, we have been trained to think that poor streaming video experience is related to the size of the Internet connection, and Internet Service Providers are more than happy to feed into this persistent myth. The humorous ad below communicates this visually.
We’d all like to believe that bigger bandwidth ensures better quality viewing, but research has revealed that it is far from the truth. Together with researchers from Princeton University and the University of Chicago, the Wall Street Journal spent months monitoring the Internet usage of 53 journalists across the country, and the title of the article says all you need to know: “The Truth About Faster Internet: It’s Not Worth It.”
In the lengthy exposé, the article revealed that most households use only a fraction of their bandwidth. The study found that on average, it takes no more than 3.5 Mbps to maintain a Netflix stream, and 6.1 Mbps to maintain an Amazon stream. Journalists who tested the system by running 7 streams at the same time over bandwidths of 100 Mbps or more still only used a maximum of 7.1 Mbps of capacity, without seeing any noticeable improvement in streaming speeds or video quality.
In fact, they found that premium subscribers with Internet bandwidth of 250 Mbps and higher were only able to watch Netflix or Amazon in HD less than 40% of the time. That means that more than 60% of the time they were watching low quality video streams!!!
Unfortunately for Internet providers, bigger bandwidths and faster internet connections don’t necessarily improve video streaming quality, because they fail to address the real problem: the Last Mile network.
What is the Last Mile Network?
When it comes to video streaming, the Last Mile refers to everything that happens after traffic leaves the CDN’s edge node. Data has to navigate a series of transfers, through ISP and mobile networks, wired and wireless networks, and residential WiFi networks. Every network, whether it’s DSL, cable, cellular, or WiFi, has different characteristics regarding bandwidth, stability, delay, and jitter, adding to the difficulties for video traffic that crosses between them.
The result is a chaotic stretch that is full of obstacles for video traffic.
As we discussed in an earlier post, streaming video uses Adaptive Bitrate (ABR) technology, which means the video traffic is broken up into small segments, each just a few seconds long. With ABR, these small segments of video are delivered in succession from the last stop on the CDN, with the media player requesting the new segment as it delivers the previous one. And all these requests and delivery of video segments occur over...you guessed it...the Last Mile.
Let’s take a closer look at network conditions on the Last Mile which affect video streaming quality.
Frequently Changing Network Conditions
The Internet is by nature a shared infrastructure. While many aspects of the Internet are shared (think about a single HTML page shared to whoever wants to see a particular web site), the most important for this discussion of QoE are the “pipes” themselves, that is, the network through which streaming video must pass. Regardless of where in the network you are, it is shared and almost always oversubscribed - the fiber optic and coaxial cables, ADSL lines, everything. And because of this, the network conditions are changing all the time. Traffic patterns are constantly shifting. This creates moments of high congestion when everyone is trying to use the network at the same time, like traffic jams during rush hour.
If you have multiple people all trying to do different, resource-intensive things on the same network - watch video, play games, and so on - it leads to congestion and burstiness (traffic that appears and disappears) that can degrade QoE. Bottom line, if half a dozen of your neighbors are playing an online multiplayer game or watching Youtube, your episode of Game of Thrones might load more slowly, and at a poorer resolution level.
Cellular networks have the added challenges of base stations that may offer poor coverage in a certain area, due to geographical distance, weather conditions, or obstacles between the nearest cell tower and the mobile device. Also, as more or fewer devices connect to a particular base station, the network conditions change which affects QoE. Also, If you are moving, for example, let’s say you are watching a video on your phone during your morning commute, you’ll repeatedly be handed over from one base station to the next as your bus or train moves on. This affects your last mile network conditions and your QoE.
Heavy Traffic at Home
The level of use of your own local network - typically WiFi - also affects video streaming quality. WiFi is frequently unstable vis-a-vis latency and bandwidth, and was certainly not designed for video delivery. Even a nearby microwave can disrupt WiFi! WiFi can also only handle so much traffic. If someone is holding a Skype video call, another person is streaming HD video, and someone else is involved in an online game, all at the same time, that could impact your viewing experience watching the Super Bowl in real time.
These many factors turn the last mile into a very challenging environment, making it extremely hard to deliver a consistent level of quality of experience.
Last Mile is the Key to Video Streaming Quality
Despite the use of efficient encoding formats and CDNs and the hype around getting bigger and bigger bandwidth Internet connections, the key to achieving QoE is the Last Mile. With chaotic, ever-changing network conditions, the Last Mile presents a serious challenge for all video streaming services. Conquering the technical challenges of the last mile is the final frontier in significantly enhancing QoE.