Broadcast Engineering - April 2008 - (Page 41)

FEATURE QOE FOR IPTV END USERS quickly. Thus, the IPTV consumer device buffer overﬂows, and packets are lost. Once this starts to occur, jitter effects, such as ﬂicker on the TV screen and lockouts to the IPTV consumer device, become obvious to the end user. This effect can be minimized or offset by using large memory buffers in the IPTV consumer device or by increasing the bandwidth capacity on the broadband network. Although the use of larger buffers helps to minimize jitter, it does, however, introduce delays because it takes extra time to ﬁll the buffer full of packets. The size of the buffer varies between different types of IPTV consumer devices. For example, the buffer sizes of IP set-top boxes can store between ﬁve and 40 seconds of video before forwarding to the decoder. The jitter on an efﬁcient IPTV network is generally measured in terms of milliseconds. Other factors such as poor qual- ity source content, encoding mechanisms, IP packet issues, latency, incorrect conﬁguration parameters and server congestion all contribute to a decrease in QoE levels and a corresponding increase in customer complaints. 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. April 2008 | broadcastengineeringworld.com 41 http://broadcastengineeringworld.com

Table of Contents Feed for the Digital Edition of Broadcast Engineering - April 2008

Broadcast Engineering - April 2008 Contents Editorial HD Newsrooms Wavelet Compression Mobile TV Audio Processing for HDTV, Part 1 QoE for IPTV End Users NAB Update Asset Management Advertisers Index

Broadcast Engineering - April 2008

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