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Achieving Optimal IPTV Quality of Experience: Key Challenges and Opportunities



Not long ago, I authored a whitepaper on the importance of delivering subscriber quality of experience (QoE) for IPTV success, a project that was commissioned by Spirent Communications (News - Alert). I�ve been getting a lot of emails and calls lately about that paper � it seems to have touched on a number of important considerations service providers must take into account as they go down the path of IPTV service delivery.

The gist of the paper is this: As telcos rush to deploy new IP-based network infrastructures and launch new video services, they are faced with a unique set of challenges. First and foremost, they must deliver optimal QoE to their new and existing subscribers � if they don�t, they risk mass defection to their competition. It�s essential, then, that telcos employ a comprehensive video and IPTV testing solution that ensures quality of service (QoS), not only at each element in the network, but end-to-end in the network as well. Such service assurance initiatives must effectively deal with transport and signaling issues, employ the most relevant and accurate methods of measuring customer QoE, and provide ongoing monitoring and management of the live network.

A lot of IPTV discussion has focused on QoS considerations � making sure that the quality of the service delivered to the subscriber is as optimal. However, focusing solely on IPTV QoS is potentially shortsighted, since many impairments in video service can sneak under the thresholds established to detect problems. You need to be able to assess the quality of the subscriber experience � the actual quality of the delivered video signal and performance of the service at the network endpoint � and not just rely on gathering metrics from the network core or edge. What�s more, video is far more problematic than voice, and using the same VoIP service testing and monitoring methodologies for IPTV simply won�t do the trick.

The ability of a telco to deliver high quality IPTV service over its network can be broken down into a number of key, basic areas. Let�s take a look at each one:

Ensuring the effective transport of the service � Regardless of the medium used for the transport of the data (copper, fiber, or coax), it is important to realize that an IP-based network is basically designed for the transport of data from Point A to Point B, and not for real-time services, such as IPTV. In order to enable real-time transport on an IP network, a protocol such as MPLS must be used in order to provide the ability to conduct traffic engineering.

In addition, a variety of QoS metrics must be added to the mix. With these capabilities, it becomes possible to test for and measure a number of service impairments that can negatively impact video service quality, including packet loss and jitter. Another factor that can affect video quality is insufficient available bandwidth on the network to ensure that video packets arrive in the correct order and within the allocated jitter-buffer time. Since the transport of MPEG-4 video signals requires bandwidth of approximately 2 Mbps for standard definition channels and 9 Mbps for high definition channels, it is critical that the required bandwidth be available at the time the IP video stream is viewed. In order to guarantee this, it is vital that the telco be able to measure the bandwidth utilization on the network as well as at the subscriber level.

Verification and monitoring of IPTV service-related signaling � In an IPTV deployment, there are three primary types of signaling used: subscriber to provider, provider to subscriber, and internal network to provider. For example, the most common signaling function from subscriber to provider is the request to change the channel.

Another important subscriber to provider signaling function involves a request for a specific video on demand. Provider to subscriber signaling is primarily confined to the delivery of the actual video content to the set top box. Other such signal functions include the delivery of the channel guide. Internal provider signaling involves various authorization and authentication functions, such as whether a subscriber is allowed to access requested premium channels or order videos on demand. Other signals control the flow of the data, such as from a unicast to a multicast stream (for some of the IPTV transport technologies), and provide information about where video content is being transmitted.

The signaling-related challenges for the telco surround the need of the provider to be able to verify the signals sent over the network in order to ensure the proper operation of the service. Such a system must monitor signals for channel changes or VoD content and verify that the transition between a unicast and multicast transmission is made. If such signals are not passed properly, the user either will not see his show or too much network bandwidth will be consumed.

From a competitive standpoint, the channel change time must be as quick as it is with today�s digital cable service. Actual performance, however, will depend on the ability of the telco to effectively develop, manage, and maintain the network elements for optimal performance during periods of a large number of concurrent channel requests (such as during the Super Bowl or the final episode of American Idol).

Measuring the quality of the video signal received � In practical terms, the quality of the video signal delivered to a subscriber�s shiny new HDTV is really where �the rubber meets the road,� and will determine whether the user will become a loyal, lifetime customer or bolt to the nearest competitor. Indeed, the quality of the video signal received in large part determines the overall QoE IPTV customers will have.

Video quality impairments can be grouped into three major categories:

1. Perceptual � These impairments can manifest as block distortions, image blurring and jerkiness.

2. Spatiotemporal � These impairments occur as repeated frames and energy differences.

3. Fidelity � These impairments consist of color problems and signal-to-noise issues.

As with Voice over IP (VoIP), it is vital for a telco to be able to measure the quality of the video signal � and the presence of impairments � in order to ensure optimal QoE. The standards for measuring video quality fall into three primary models: Full Reference, Reduced Reference, and No Reference.

Ensuring adequate scalability in the network infrastructure � The reality of IP networks is that they are extremely dynamic environments, meaning that, as more people come on the network to use a variety of applications, service is inevitably affected. As video services, and especially IPTV, are added to the network, the dynamic nature of the network is increased exponentially. Just consider the effects of the Super Bowl or a current event that captures the attention of an entire nation�s population, and the strain this can cause a network. Therefore, it is essential that service providers fully understand how the network infrastructure � and especially various switching and routing equipment � will perform under a full service load. If the network infrastructure is not up to snuff, then not only will service suffer, but deployment costs will mushroom as additional equipment must be purchased and installed.

Maintaining security while ensuring service quality � The security issues associated with packet telephony networks are numerous and can be quite complicated. The deployment of an IP-centric network infrastructure for IPTV and triple play service provision may also require that service providers overhaul their network security measures. Service providers must consider the impact of new security apparatus on their network and with their new video services. In fact, many security measures can seriously affect the quality of video traffic by introducing additional jitter and other impairments to the network, and in some cases can cause total service failure.

Effectively delivering IPTV as an integral part of the triple play service bundle � With IPTV, the centerpiece of a telco�s triple play strategy, it is important to remember that there are other services that make up the triple play bundle, such as voice, video telephony, and broadband Internet access. These services all have to contend for network bandwidth. Since multiple protocols and QoS processes may run on the same control and QoS planes, services will often interact with each other, oftentimes in unforeseen and unintended ways. Therefore, it is essential that telcos gain actionable, real-world QoS experience about how the triple play network infrastructure, services, and applications will perform as an integrated solution. In this way, service providers can ensure that, not only will IPTV service perform optimally under heavy load, but that the other services will also perform as expected. IT

Marc Robins is Chief Evangelism Officer of Robins Consulting Group, which offers an array of services to the IP telephony industry. He has been involved in the telecommunications industry as a reporter and analyst, trade show producer and publisher, and marketing executive and consultant for more than 24 years. For more information, call RCG at 718-548-7245 or e-mail

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