TV Network Monitoring

By Paul Dubery

Review contents:
MPEG-2 and measurements TV Network Monitoring Equipment of the the IMOS Company Going digital with program insertion — challenges and solutions Innovative T&M system for MPEG-2 monitoring and analysis Systems from Snell & Wilcox for testing, estimation and checking of MPEG streams Video test and measurement equipment

Although it might feel like an eternity has passed since then, it was less than 20 years ago when viewers around the world began to be offered multichannel television. When in the early 1980s those first, rudimentary cable networks suddenly started to tell people that the TV viewing experience could be significantly richer than what their handful of public broadcasters had been catering so far, one of the most radical revolutions in the history of broadcasting had begun.

And although at that time nobody really knew what the implications might be, the industry as a whole soon realised there was nothing to be afraid of. On the contrary, the new scenario brought about by the emergence of multichannel TV was soon benefiting practically every player in the broadcasting chain. Whereas subscribers could not believe their luck at having a 24-hour channel just for watching football, content production houses saw a multiplicity of new outlets hungry for content; traditional broadcasters saw an opportunity to leverage their experience in content creation; TV equipment manufacturers couldn’t cope with the new levels of demand; and, crucially, a completely untapped business opportunity had suddenly materialised — the network operator, or the one who was needed to “carry the goods”.

It wasn’t long until those primitive CATV family businesses gave place to multinational corporations with hundreds of thousands of subscribers. And it wasn’t long either before cable stopped being the only platform via which multichannel TV could be transmitted, with first satellite and then digital terrestrial television (DTT) systems all fighting for a share of the booming pay-TV market.

For a number of years during initial deployment stages, all that network operators needed to care about was that the pace of their rollouts was enough to keep up with subscriber demand. However, as soon as operators sensed that the market was reaching maturity levels and that they faced increasing competition from rival service providers, they realised that basing their business proposition entirely on “more content” was not going to be enough. In order to guarantee customer loyalty, they needed to offer “better content”, not only just in terms of more attractive programming, but crucially in terms of providing a comprehensively satisfactory viewing experience that included reception and picture quality issues.

Today, as the rollout of digital TV gathers pace, Quality of Service (QoS) is increasingly becoming a vital requirement for network operators. Viewers have become more and more used to high-quality pictures, and can get very quickly dissatisfied when quality is compromised.

It only takes one bit

The need for QoS parameters is accentuated by the fact that today’s transmission architectures are so radically different to the analogue days when, very often, the content producer was the same organisation as the distribution and the transmission provider. In today’s digital environment — where the number of players and organisations directly involved in the handling of content has multiplied to the nth degree — rarely a single TV programme reaches a viewer without before having been formatted, copied, contributed, compressed, decompressed, modulated, demodulated, multiplexed, de-multiplexed, uplinked and downlinked dozens of times after it was initially captured by the camera. And it only takes one or two bits of data to be dropped at any of those digital transactions to get thousands of subscribers asking where the picture has gone. Timing and system information errors in the MPEG stream can fatally affect picture quality and cause re-multiplexing errors in the downstream.

In order for network operators to be able to guarantee a transparent content reception, they need to start negotiating varying levels of service contracts with the various players involved in the transmission chain. And this is not an issue affecting only operators. Steady rising costs in content production is also leading broadcasters to demand the establishment of guaranteed QoS parameters throughout the transmission chain.

It is these demands that are putting in the spotlight the importance of network monitoring. Because the only way that both broadcasters and service providers have of implementing QoS is through the deployment of network monitoring equipment at every layer of the content distribution and transmission chain.

Different content delivery platforms will have an impact on the level of sophistication that these network monitoring activities will require. Digital content delivery platforms will have an impact on the level of sophistication that these network monitoring activities will require. Digital satellite TV uplinks, for example, may have fewer points that need monitoring compared to a digital terrestrial network.

Current market trends

The rollout of digital TV in Europe is yet to reach the scale that the industry has long envisioned. DTT — the platform that is expected to play a vital role in European countries planning to switch off analogue signals at some point in the next decade — has been particularly slow to take off, with only the UK, Finland, Sweden, Spain and now Germany on the air, while all of the other countries have plans roll out similar services in the next few years.

And because these are still early days in terms of DTV infrastructure, the main focus of today’s network monitoring activity is placed on the MPEG transport stream. Probers such as the MTM400 real-time MPEG transport stream monitor from Tektronix, which can measure data rates of up to 155 Mbit/s, can be deployed at each node of a DTT network, cable headend or DTH satellite uplink facility to isolate faults and perform a series of diagnostics on the health of the MPEG stream.

One particular trend that is currently shaping the world of network monitoring is that operators are demanding from their equipment the capability to monitor a number of parameters that are specific to their own services. This has resulted in the emergence of a new concept — template testing. What products incorporating this feature do is to check a number of key parameters to ensure that the transport stream is constructed as the broadcaster intended it to be. These parameters include the transport stream ID, network ID and the number of programmes in the multiplex. And another key feature of template testing is its ability to monitor conditional access status and that each programme has all of its components (video, audio, data, Teletext and subtitles).

As digital networks start to experience increasing subscriber numbers, they will need to start monitoring new elements of their networks, such as the RF transmission to ensure compliance with the specific parameters set out by the DVB standard. And another major network monitoring environment likely to evolve in the near future is that related with the interactive TV software element, where specific MHP testing equipment will need to be brought in.

As soon as Europe’s network operators begin to reach that advanced stage of digital TV deployment, this type of monitoring equipment will form an integral part of the QoS mechanisms that will help them ensure that their most precious asset gets transparently through to the most important part of the network, the TV screen at home.