5G (the fifth-generation mobile network) is finally here, as the first 5G standards were completed in December 2017 and the remaining aspects will be standardized soon in the second half of 2018. Generally speaking, the public perception of 5G is higher download data rate that is enabled by a number of cutting-edge radio technologies, and lower latency that would enable more mission-critical and tactile applications such as remote surgeries. Therefore, it is no wonder that many people take it for granted that the often-advertised >1Gbps download speed is what they will get when they stream ultra-high-quality videos using 5G networks. However, although 5G can indeed offer such speeds over the radio, there are a number of myths that most people are not aware of.

First, the super-high download speed is on a per-cell (i.e., base station) basis, not usually on a per-user basis. What 5G radio has really enabled is the scenario where many users can simultaneously use bandwidth-intensive applications in the same cell without running out of radio bandwidth resources.

Second, and most importantly, the advertised download speed is at physical layer. As you may know, the data delivery in the Internet follows the OSI 7-layer model, where the physical layer represents the raw bit streams and the upper layers (e.g., transport layer) are used by actual applications. For example, TCP (transport control protocol) is used by almost all multimedia applications nowadays as their transport-layer protocol. TCP uses the so-called congestion control mechanism to ensure that every single packet is reliably delivered end-to-end. Sounds great, right? Well, you may have guessed it – this assurance comes at the price of speed. Take video streaming as an example, the greater the distance that a viewer is located from the video source (i.e., higher network latency), the lower data rate TCP will get. In fact, based on our real-world experiments, when we tried to stream a video here from Japan over a 1Gbps link, the data rate we got was less than 2% of the bandwidth. This is irrelevant to whether you are using optical fiber, Wi-Fi, 4G or 5G at home, because once you get past your network operator’s local access network, TCP (which was designed in the 70s) becomes the performance bottleneck.

Now my point is that 5G, despite the super-high radio bandwidth it offers, is not enough to enable the next-generation video applications that often require very-high data rate. Fortunately, there are already a number of well-established technologies to mitigate this issue. The first one, which is probably the most commonly used one nowadays, is called CDN (content delivery networks). This means the video content providers hand over their content to CDN operators, who distribute copies of the content and cache them at servers located worldwide. While this significantly reduces the content access latency, it can be costly and is generally suitable for popular content such as TV episodes or movies. The second approach, which is the one we focus on at the University of Surrey’s 5G Innovation Centre (5GIC), is based on MEC (multi-access edge computing). As advocated by ETSI (European Telecommunications Standards Institute), MEC enables in-network intelligence at the edge of mobile networks (e.g., close to base stations). This means the network operator can now deploy intelligent algorithms and run software directly from within the network edge, which has never been possible in 4G. Based on this principle, the 5GIC has developed an MEC-based solution that effectively guarantees that no matter how far a user is located from a video source, he/she can always enjoy video streamed at consistently 4K quality and above without any rebuffering. Our solution has been recognized worldwide for its significance and we have showcased it at Mobile World Congress 2018.

To summarize:

  • While 5G offers much higher data rate and lower latency over the radio, TCP still becomes the performance bottleneck when it comes to video streaming applications.
  • There are existing technologies that can help mitigate the TCP performance limitation, such as CDN and MEC-based solutions.
  • 5GIC, University of Surrey has developed an MEC-based solution that guarantees a stalling-free 4K video streaming experience regardless of the distance between a video’s source and its viewer.

ABOUT THE AUTHOR

Dr Chang Ge

Senior Research Fellow | University of Surrey 5G Innovation Centre