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Easiest way to supplement downlink capacity

Twitter: @suSandhu


If you’re anything like me, you have kids who watch a lot of video content – films, YouTube vloggers and streamed shows from the likes of Netflix and Amazon Video. What they don’t do is watch that big TV set in the corner of the room. More attractive to them and their friends is the freedom to watch when and where they want and that means accessing their favourite shows on their mobile devices.

Yet using a small portable device doesn’t mean that these users will accept low performance.

The majority of all videos watched on smartphones are less than 10 minutes long* and viewers are less tolerant of delays in these short clips than for longer formats such as an hour-long drama. It isn’t uncommon for online viewers to ditch a slow-loading video after only a few seconds, we all do it. This also means lost ad views.

Streaming of video and other content has changed the traffic profile of networks with around 10x more traffic on the downlink than on the uplink in LTE networks. It is the ease with which people can stream content that makes traffic on LTE networks more asymmetric than any previous technology.

Obviously this puts operators under pressure to provide enough capacity to ensure fast-loading, smooth playback.

To help achieve this, operators can make use of Supplementary Downlink in which a frequency band is used for downlink-only traffic to support a conventional band running both uplink and downlink. Most LTE networks today use paired spectrum where both uplink and downlink are given a dedicated spectrum block allocated of the same size. Simply put, Supplementary Downlink enhances a network’s downlink capacity as well as the users’ experiences. Essentially, it gives significantly faster downloads and supports a much greater number of users with mobile devices.

For example, the downlink only band can use the L-band (1452-1492 MHz), which was previously used as a broadcast band for terrestrial and satellite DAB in Europe. It could also be considered in other bands.

Using Supplementary Downlink allows operators to avoid the costs of investing in additional base station and backhaul infrastructure - once mobile broadband demand exceeds network capacity, networks can be easily expanded by deploying a 1.4 GHz Supplementary Downlink on existing base station sites.

Supplementary Downlink and carrier aggregation have been enabled in standards from HSPA+ Release 9 and LTE Release 10. Nokia has for some time offered Supplementary Downlink radios for the two most common bands, Band 29 for North America and the 1.4 GHz L-Band standardized as band 32 in 3GPP and harmonized in Europe. The 1.4 GHz Supplementary Downlink L band, when paired with low frequency spectrum such as 800 MHz, offers similar propagation characteristics as sub-1 GHz because the uplink, which is the limiting factor for coverage, is only carried on 800 MHz, while 1400 MHz is only used for the downlink. The Supplementary Downlink radios offer additional downlink link capacity and receivers, resulting in 4RX diversity for the primary band (for example 800 MHz in Europe) to deliver better service quality, in particular better indoor coverage.

The industry is already gearing up for Supplementary Downlink. An example is the recent demonstration to be held by Nokia, Qualcomm and the Finnish Public Broadcast Company Yle, showing Supplementary Downlink operating in a TV broadcast band.

With many people now spending hours a day on their smartphones, the demand for short video clips and instant downloads can surely only continue, meaning that those operators with the most capable solutions in place are more likely to keep subscribers happy and avoid churn.

Curious to find out more? Then make sure to visit our Flexi webpage.

*  Video marketing insight as reported by Tubular Insights

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