QoE for IPTV end users
Apr 1, 2008 12:00 PM, BY GERARD O'DRISCOLL
Apply a QoS mechanism
Given the sheer variety in factors that can generate various types of video quality degradation, it is critical that a QoS system is applied to the networking infrastructure to improve end users' viewing experience. Methods called differentiated services (DiffServ) architecture and Multi-Protocol Label Switching (MPLS) DiffServ are becoming increasingly common as a means of improving the delivery performance of both time-sensitive unicast and multicast IPTV streams.
Some IPTV providers use the DiffServ architecture to manage and guarantee a particular level of QoS for subscribers. Implementing this architecture basically means that IPTV traffic is given higher priority over other types of IP-based traffic. The specification for DiffServ was published in 1998 by the IETF and can be found in RFC 2475.
MPLS is a traffic engineering system that boosts the efficiency of IP routing networks. By combining the many benefits of MPLS with the QoS guarantees of DiffServ, network operators can deploy services that require strict performance guarantees such as IPTV. The mechanisms used by MPLS-DiffServ QoS systems are defined in RFC 3270.
IPTV network operators who combine adequate network resources with an enforcement of QoS techniques such as DiffServ architecture and MPLS-DiffServ will help to ensure that end users enjoy a high QoE.
Keep an eye on QoE
Although a properly implemented QoS system will help to ensure that IPTV streams travel from source server to the destination IPTV consumer device in an unhindered manner, service providers still need to monitor how end users perceive the quality of the IPTV experience. A set of QoE measurement models are typically used to measure the satisfaction levels of IPTV end users. There are three primary models used by IPTV quality measurement systems to identify the presence of IPTV stream impairments, namely full reference, zero reference and partial reference.
Full reference
Figure 3.
Click image to enlarge
This system makes a copy of the stream at the IPTV consumer device and compares it with a reference signal obtained from source video content. The signal size varies between measurement equipment but is typically uncompressed and quite large. This measurement will determine distortion levels and degradation that occurred during the encoding and transfer of the original video content across the network. Figure 3 illustrates a basic reference topology used to compare the original signal with a signal post transmission across the IP distribution network.
Zero reference
There are also systems available that do not require a reference video signal to score the video quality of an IPTV stream. Instead, a sample compressed signal is obtained from the IPTV consumer device in real time but not from the source. Zero reference systems are particularly suited to measuring real-time IPTV streams because they analyze fewer factors compared with full reference systems.
Partial reference
Similar to the approach used by full reference systems, partial reference measurement equipment is designed to take a sample at the source and also at the destination IPTV consumer device, compare the signals and output a metric. Partial reference systems require less computational complexities when compared with full reference systems and use a smaller reference IPTV stream sample when comparing both signals.
Conclusion
An increased understanding by network administrators of QoE is critical to ensuring that an end-to-end IPTV system operates effectively. Only when this occurs will companies start to truly unlock the potential of IPTV technologies.
Gerard O'Driscoll is an international telecommunications expert, entrepreneur and author of “Next Generation IPTV Services and Technologies.”
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