CDN Tech for Multiscreen in Mobile Networks

April 15, 2015
In today’s multiscreen world, consumers have extremely high expectations when it comes to the quality of video services. Whether they're ...

By Nivedita Novel, Broadpeak

In today's multiscreen world, consumers have extremely high expectations when it comes to the quality of video services. Whether they're viewing VOD or live content, at home or on the go, the quality must be exceptional. End-users don’t like to wait for video to buffer when they switch to a new channel. Latency during a live event must be minimal, and video content should be crystal-clear on every screen, without any visible encoding artifacts.

Yet based on the type of video application that mobile operators want to address and the end-user environment, the best technical solution for delivering a high quality of experience (QoE) is not necessarily the same. The density, in terms of viewers in the coverage area, is a relevant factor when deciding what video delivery optimization architecture to deploy. This article outlines the most effective strategies for utilizing content delivery network (CDN) technologies in various areas of mobile networks.

Low-density areas

In locations where the number of smartphone users is not an issue (i.e., there are only a few tens of users per cell), bandwidth savings can be realized in the backbone network by deploying a standard CDN.

By design, CDNs rely on cache servers distributed throughout the network to deliver popular content from a location closer to end-users. The popularity of content is calculated at each regional point of presence (PoP), based on the number of times it is requested in a given timeframe. When a threshold is reached, the content is kept in the PoP and streamed from there to the end-users requesting it. Operators can keep only the traffic for non-popular content in the backbone network, greatly optimizing network usage by reducing the costs related to the deployment of the equipment.

High-density areas

While small cell technology has helped operators deal with the increasing traffic and bandwidth limitations of the radio spectrum in the access network, traffic still has to be managed by the evolved packet core (EPC), otherwise known as the backhaul network. Much like the backbone network, EPC also faces bandwidth limitations, making it difficult for operators to guarantee a good QoE to subscribers.

Through a CDN, popular content can be streamed to end-users from a location as close as possible to them. Operators can get closer by using the base station as a component of the CDN capable of hosting some processing mechanisms as well as caching capacity. This traffic offload or local breakout reroutes the U-plane directly to a local gateway, or more generally to the Internet.

To make the solution truly scalable for live content, operators can use a CDN technology to convert the unicast signal into multicast in the headend, down to the base station where the channel is converted back into unicast. This same technology can also be applied to VOD content, by pre-caching popular videos in base stations utilizing multicast.

Very high-density areas

In a very crowded area, small cells can again be used to increase the capabilities of a network; however, this solution has limits. For example, in a crowded stadium environment, operators have to deal with thousands of simultaneous users in a zone covered by a limited number of base stations. In these types of situations, the best solution is to use a broadcast technology, such as LTE eMBMS (evolved multimedia broadcast/multicast service), to share bandwidth among all of the users watching the same content in a given area.

For this approach to work, two pieces of equipment must be installed in the network:

  • A Broadcast Multicast - Service Center (BM-SC), which serves as the entry point for content providers or any other broadcast/multicast source external to the network
  • A Multicast Broadcast Multimedia Service Gateway (MBMS-GW), which broadcasts the packets to the base stations within a service area.

Leveraging multicast technology, a small CDN deployed within a service area enables operators to deliver live TV and reach millions of subscribers with only a few Mbps consumed in the access network. It works by detecting peaks in live TV content consumption and informing the BM-SC gateway to deliver the corresponding live channel in multicast. The access network is then dynamically reallocated based on the content popularity.


4G LTE networks have opened up new video content consumption models that are not just limited to single mobile devices. The development of LTE home gateways now allows users to watch videos on their TV screens, switching to broadband ADSL or cable networks in zones where fixed lines have not yet been deployed. By optimizing their network for video, operators can generate new revenue streams.

Nivedita Novel is the VP of marketing at Broadpeak. Reach her at [email protected].