Operators discover IPTV demands additional testing

TV is fun to watch. But for most of us, it often can be a highly emotional experience, too. We eagerly anticipate watching sporting events or seeing story lines unfold as we indulge in our favorite dramatic series or reality shows. The anticipation of a TV event can last for days, weeks or even entire seasons. So, when it's time to watch 'our' show, we expect a flawless experience, which simply means a great picture and good sound.  What's more, we are demanding the same of IPTV as it makes its debut.

But service providers are finding themselves in a bind.  There is a lot more to consider because of IPTV's expanded capabilities - more parameters that determine the quality of our viewing experience (QoE).  If not dealt with, problems will result.

Case in point: there have been a number of publicized IPTV trials that failed.  They either failed to turn into deployments or resulted in delays of over 12 months.  These have been costly lessons, both in loss of face and in financial terms.  Service providers must pay more attention to the testing and management of their IPTV networks - more than is required of VoIP networks - to deliver acceptable QoE.

In general, IPTV is delivered in much the same way as high-speed data services are. One major difference, however, is the addition of a video head-end to the network with the resulting IPTV data streams traveling from the head-end through the core and access networks to the customers' homes or businesses. 

John J. Jones, IV, regional general manager of JDSU Asia Pacific, said, 'Because service providers are encountering an entirely new set of service delivery challenges, and to address these challenges, operators need to implement the following IPTV service assurance elements:

  • Ensure the content and services' QoS as launched from the head-end 
  • Deliver the video services error free across the optical network, delivering the required QoE
  • Manage the performance of the xDSL loop and FTTx infrastructures
  • Monitor and test the video services from the head-end through into the home to control the TV signal's end-to-end quality'

Furthermore, Jones continued, 'because of IPTV's service complexity and its sensitivity to packet loss and excessive jitter, IPTV's signal quality cannot be assured through traditional data or VoIP test and measurement methodologies.'

For example, impairments - including poor channel changes, blocking, tiling or freezing - can result from packets lost in any portion of the network. Only by properly testing and monitoring the IPTV service from end to end, will service providers to able to deliver a high service level and control costs, both of which are necessary to acquire and keep customers.

From the start

Thus, to ensure that their customers enjoy the QoE they expect, service providers must implement a proactive test and measurement system with enhanced transport and access testing capabilities.

Service providers must overcome several challenges to ensure that the content is good when launched from the video head-end. Some of the challenges include poor video quality handoff, improper packet ID (PID) mapping or MPEG metadata on feeds, as well as issues involving transcoding or transrating.  In addition, service capacity, admission control, and the capacity and performance of application servers can also impact service quality.

To overcome these challenges, service providers should properly outfit their MPEG active locations with digital video testing capabilities that are suited for use with a multitude of digital video interfaces.


In addition, they need to continuously monitor 100% of the digital video services on an active and passive basis at the egress of the head-end as well as implement a wall of monitors (virtual or real) and automated video quality assessment in a post-set-top-box location, monitoring the head-end egress quality.

System providers will need to monitor their networks for continuous service availability, service transaction performance, the quality of the decoded video, and the error-free nature of the metadata and stream data. The test and the management systems must work together so service providers can ensure that services viewed by the customers are as good as launched from the head-end, plus providing operators with the tools they need to quickly isolate problems when service faults do occur.

Error-free delivery through the core

Once service providers ensure that the content launched from the IPTV network's video head-ends is good, they are faced with the challenge of ensuring the error-free delivery of that content across the core to the edge of the optical network. The sensitivity to packet loss and jitter, combined with the multicast nature of the broadcast service, means that even the smallest impairments can have dramatic, system-wide impacts on service quality. Service providers, therefore, need to constantly monitor their networks at key handoff points.

Monitoring should include thresholding and alerts, real-time tests, as well as performance monitoring and analysis of the gathered data that allows them to quickly detect and isolate faults. Their monitoring systems should allow trending and proactive monitoring, which can help them to avoid issues before customers are affected.

As services reach the edge of the network, service providers can gain service visibility by using portable test gear to probe and monitor.  This is a valuable and necessary step to help control costs.

However, clean content to the edge of the network does not automatically mean that customers will see a great picture. Due to the complexity of home networks and the tremendous service impacts that even intermittent errors can have on QoE, service providers need to implement continuous service visibility across the entire network - including the access loop, the residential gateway and home networks into the set-top boxes. 

By continuously monitoring service performance at the set-top box and residential gateway, service providers are able to quickly isolate faults that are causing even intermittent errors. This improves the quality of the customer experience while lowering mean time to repair and thus controlling costs.

Test before you offer

Service providers, especially telcos, are rolling out IPTV because it enables them to offer triple-play services on bandwidth limited xDSL access loops. However, managing the performance and capacity of those loops is paramount to the success of IPTV as a service.

Therefore, service providers using xDSL networks to support IPTV must first ensure that only good copper lines are used to provide service. Providers must manage their prequalification processes and procedures to ensure that areas where concentrations of bad lines are located are excluded from their marketing campaigns. Otherwise, they run the risk of severely damaging their return on investment and reputation by trying to provide IPTV to customers using marginal lines. 


Service providers can avoid this kind of problem by using a combination of software, records-based prequalification, portable- and systems-based loop copper testing, and intelligent 'neighborhood' monitoring of the existing xDSL plant to identify common cable issues. When all these capabilities are used together, service providers will be able  to correctly identify lines that are capable of supporting IPTV service. The alternative is implementing conservative loop length reach limits that are likely to damage their IPTV business cases by unnecessarily restricting service.

Additionally, service providers can optimize xDSL provisioning in ways that optimize the service experience all the way down to the user level. By continuously monitoring for service impacting errors and signal performance on the xDSL loop, service providers can control error control mechanisms such as interleaving to depths that are necessary to eliminate errors and maximize served bandwidth. This preserves the 'low latency' experience for users on error-free lines. Users served by lines with impairments can trade-off lower maximum bandwidth for better video experience.

- Chris Everett