Introduction to Wi-Fi radios

BBC should provide high quality via the Internet

The BBC won't be able to switch its DAB stations over to using DAB+ for a few years, so it's important that the BBC should provide its radio stations at high quality on at least one of the digital platforms in the meantime. The Internet is the most suitable platform for this purpose, for the following reasons:

• It is inherently easy to provide radio streams at high quality via the Internet
• The phenomenal success of the BBC iPlayer TV streams has demonstrated the public's appetite for accessing broadcast content via the Internet
• There are a range of Wi-Fi Internet radios and Wi-Fi media adaptors available that allow radio to be listened to on portable devices and on hi-fi systems respectively

Internet bandwidth for broadcasters is now very cheap and plentiful

The best example of how cheap Internet bandwidth has become for broadcasters is the BBC iPlayer TV catch-up service. The iPlayer simply wouldn't have been economically feasible a few years ago due to the amount of bandwidth required, but as the graph below shows, the BBC is now able to devote a large amount of bandwidth to the service:

Data for the above graph was obtained from the BBC under the Freedom of Information Act

Within just one month of the iPlayer TV streams being launched last December, they were already using more bandwidth than the BBC's Internet radio streams (live and on-demand combined), and by May they were using over four times as much. But the bandwidth that the iPlayer TV streams are using at the moment is actually small-fry compared to what they'll be consuming in a few years' time.

People in the TV industry are predicting that on-demand TV viewing will account for 40% of all TV viewing by 2013, and using that figure I've estimated how much bandwidth the iPlayer TV streams might be using in 2013. The figure I've come to, which assumes that the iPlayer will account for a fifth of all on-demand TV viewing (or 8% of all TV viewing), is that the bandwidth for the iPlayer TV streams in 2013 could be 120 times higher than it is today. This equates to the bandwidth increasing by a factor of 2.6 each year between now and 2013, and the following table shows what the bandwidth would be if it grew at this constant rate (in reality it wouldn't grow at a constant rate, because it would grow more quickly early on and less quickly later, but it makes the analysis far simpler). The table also shows how many times higher the iPlayer TV streams bandwidth would be than the approximately 416 TB/month bandwidth currently being used for the BBC's Internet radio streams.

When you look at how many times higher the bandwidth for the iPlayer TV streams will be compared to the radio streams, it's obvious that the BBC could use far higher bit rates for the radio streams than they are doing. To be fair, the on-demand (ex-Listen Again) streams are now using higher bit rates -- e.g. 128 kbps MP3 instead of 64 kbps Real. However, the BBC is considering using lower bit rates for the live streams than the on-demand streams, but considering the enormous amount of bandwidth that the iPlayer TV streams will be using in future, there's obviously absolutely no justification for them doing this, and it would simply show how biased the BBC is against the live Internet streams — which is because the BBC wants everybody to listen to digital radio via DAB, so they don't want the Internet streams to be at far higher quality than the stations are at on DAB.

The following pie chart shows the proportion of live listening hours each of the BBC's national stations accounts for:

And the following table shows how much extra bandwidth the BBC would need in order to provide its stations at very good audio quality once the streams have switched over to using AAC/AAC+ later this year:

The live Internet streams are currently consuming around 416 TB/month, so an increase of 88.4% equates to an additional 367 TB/month of bandwidth. That's less than a fifth of the bandwidth the iPlayer TV streams were using in May this year, and it wouldn't surprise me if the bandwidth for the iPlayer TV streams will be double what it was in May by the end of the year, because the BBC has just launched higher quality iPlayer TV streams that are using 800 kbps as opposed to the standard quality streams that are using 500 kbps.

Basically, bandwidth has become very cheap and plentiful for broadcasters, so there is absolutely no reason why the BBC couldn't provide 128 kbps AAC for the live stereo station streams, and considering the enormous bandwidth that the iPlayer TV streams will be using in the future, you'd hope (if they weren't so biased against them) they'd increase the bit rates of the live streams to 192 or 256 kbps AAC within the next couple of years as well.

The cost of Internet bandwidth halves every 18 months due to Moore's Law

The reason why Internet bandwidth for broadcasters has become so cheap is due to Moore's Law. The speed of fibre-optics technologies accelerates more quickly than Moore's Law, so the "limiting factor" for the cost of Internet bandwidth is due to the speed of Internet routers, which use microprocessors to process the IP packets, so their speed is governed by Moore's Law.

The speed of microprocessors doubles every 18 months or so due to Moore's Law (the trend is towards increasing the number of processors on a single chip rather than doubling the clock speed these days, but bandwidth continues going up at the same rate), and this leads to the bandwidth that Internet routers can handle doubling every 18 months as well. But as the price of microprocessors stays the same, the bandwidth doubles for no additional cost (equipment is replaced periodically anyway to cater for the increased demand for bandwidth, which typically grows at around 50 - 100% per year), so the cost per Mbps of Internet bandwidth falls in-line with Moore's Law.

Internet radio streams use modern audio codecs

Internet radio streams can use whichever audio codecs that are widely supported by the media players that people have installed on their computers. And because the media players support modern audio codecs, as well as users typically updating the media players they use on a frequent basis, broadcasters are free to use modern audio codecs for Internet streams. In comparison, DAB uses the MP2 audio codec, which dates back to the 1980s, and the only way to change to a different codec is to switch to using DAB+, which is of course problematic because switching over to DAB+ immediately would render all DAB radios obsolete.

An example of what I've described above happened recently: When the BBC iPlayer TV streams were launched last December, only a small percentage of users had the latest version of Flash Player installed on their computers. However, according to Anthony Rose, the person in charge of the iPlayer at the BBC, around 80% of iPlayer users now have the latest version of Flash installed, and it was this that allowed the BBC to launch the new higher quality iPlayer TV streams recently. These new streams are using the H.264 video codec (at 700 kbps) and the AAC+ audio codec (at 96 kbps), and these are the most efficient video and audio codecs available today (incidentally, AAC+ isn't the "best" codec at all bit rates, but it is the most efficient at very low bit rate levels).

The advantage of using modern audio and video codecs is that for a given bit rate level the audio or picture quality will be higher than it is on older and less efficient codecs.

Superfast broadband

Virgin Media is planning on launching a 50 Mbps broadband package later this year on its cable TV network, and Virgin has said that it's looking at providing 200 Mbps broadband speeds on its network by 2012. BT has also announced that it's going to roll out superfast broadband to 10 million UK homes by 2012, with speeds of 40 - 100 Mbps.

The main application that BT and Virgin say will drive take-up of superfast broadband is HDTV, and it's widely expected that HDTV streams will become commonplace on the Internet over the next few years. When you consider that an HDTV stream would need to use a bit rate level of around 8 Mbps (8,000 kbps), whereas to provide an Internet radio stream at high audio quality using modern audio codecs such as AAC would only require a bit rate of 192 kbps, it's difficult to imagine the BBC not providing its radio streams at high quality once it makes HDTV streams available on the iPlayer.

Multicast

Live Internet broadcasts are distributed using a technology called unicast, which consists of each user receiving their own individual stream. The problem with unicast though is that it doesn't scale to the huge audience levels associated with broadcasting, because the bandwidth required is proportional to the number of users. So even though bandwidth for broadcasters has become cheap and plentiful, it's still unfeasible to deliver high bandwidth applications such as HDTV streams to very large audiences using unicast.

Multicast eliminates unicast's inefficiencies by only requiring one stream of each channel to be distributed on each Internet link, so it allows an unlimited number of users to watch or listen to the same channel whilst the broadcaster only requires the bandwidth needed to send a single channel over the Internet. For example, if there were 1,000 users watching or listening to a live stream, multicast would consume just 0.1% of the bandwidth that unicast requires.

Multicast is the key enabling technology that will allow IPTV systems to carry live TV channels, and as five out of the six biggest UK broadband providers either already provide or plan to provide IPTV services to their customers, multicast should be widely supported within the next few years. The reason why multicast hasn't been supported up to now in spite of its advantages is a long story, but it basically revolves around BT's network not supporting multicast. However, BT demonstrated delivering video streams over its new 21CN network (which is being rolled out nationally between now and 2010/11) to assembled journalists a few months ago, and it's expected that BT's 21CN will support multicast within the next year or two.

Virgin is also going to enable multicast on its cable network when it launches its 50 Mbps broadband package later this year, as it's planning on distributing an HDTV channel that will only be available via multicast.
 
 

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