Transcript Document

5. Convergence of fixed networks –
Convergence of TV and Internet (TV over IP)
5.1. IPTV Introduction
5.2. IPTV over DSL
5.3. Video coding standards
5.4. IPTV main building blocks
5.5. QoS issues for multimedia traffic
5.1. IPTV Introduction
The rollout of digital networking infrastructure is opening the door
for Telcos and operators to offer converged services comprising
broadband Internet access and IP based TV and entertainment.
TV (or video) over IP is a broad streaming solution that includes
several applications, all of which can be implemented on digital
broadband networks such as ADSL, VDSL, fiber, LMDS and
Wireless LANs.
TV over IP is being utilized in the following applications:
• TV to the living room (instead of cable TV)
• Time-shifted TV or Personal Video Recorder (PVR)
• Interactive TV
• TV to the desktop
Interactive Television (ITV)
Definition
Interactive Television is TV with interactive content
Combining traditional TV with the interactivity (Internet)
Links to Web sites
On-line communications
•Entertainment
•Home shopping
•Home banking
•Video conferencing
•Video on Demand
•Distance learning
•Instant messaging
•E-mail
IPTV (Internet Protocol television)
• IPTV - IPTV (Internet protocol television) is a method
of distributing television content over IP that enables a
more customized and interactive user experience.
Among other things, IPTV could allow people who
were separated geographically to watch a movie
together, while chatting and exchanging files
simultaneously.
IPTV (Internet Protocol television) – Cntd.
• How does IPTV work?
IPTV uses a two-way broadcast signal sent
through the provider's backbone network
(PSTN) and servers, allowing viewers to select
content on demand, time-shift, and take
advantage of other interactive TV options. The
viewer must have a broadband connection and
a set-top box (STB) programmed with software
that can handle viewer requests to access to
many available media sources
IPTV (Internet Protocol television) – Cntd.
• Traditional cable digital TV has the
capacity to deliver hundreds of channels
simultaneously to each subscriber. IPTV,
by contrast, sends only one program at a
time. When a viewer changes the channel
or selects a program, a new stream of
content is transmitted from the provider's
server directly to the viewer's set-top box.
IPTV (Internet Protocol television) – Cntd.
• IPTV primarily uses multicasting with Internet Group
Management Protocol (IGMP) version 2 for live
television broadcasts and Real Time Streaming
Protocol for on-demand programs. Compatible video
compression standards include H.264, MPEG-2 and 4.
• IPTV has been deployed by telephone companies in
Europe but is still in development stages in the U.S.
Similar services including video on demand are
delivered by cable companies over their proprietary
networks using Digital Video Broadcasting, which is
not used for IPTV.
IP video services market
IP video, viewable on TVs, STBs, and PCs, is expected
to become a major part of any home’s entertainment
line-up.
According to Multimedia Research Group, Inc. (MRG,
Inc.), worldwide IP video services subscriptions are
expected to more than quadruple, from under 2 million
subscribers in 2004 to over 8 million users in 2006 - just
two years.
Global IP video subscriber forecast
IP video services market (Cntd.)
The Telcos face a significant challenge.
In an effort to continue to produce revenue-generating services
that boost ARPU and retain their market share, Telcos are
focusing their efforts on a new video codec, H.264/MPEG-4
Advanced Video Coding (or just H.264/AVC).
This new video encoding/decoding scheme enables a compelling
solution through IPTV-DVD-quality video services over DSL and
the Internet.
IPTV main protocols - H.264
H.264, also known as MPEG-4 AVC (Advanced Video Coding), is
a video compression standard that offers significantly greater
compression than its predecessors. The standard is expected to
offer up to twice the compression of the current MPEG-4 ASP
(Advanced Simple Profile), in addition to improvements in
perceptual quality.
The H.264 standard can provide DVD-quality video at
under 1 Mbps, and is considered promising for full-motion video
over wireless, satellite, and ADSL Internet connections.
H.264 (Cntd.)
• The need for an advanced video coding standard that evolves
MPEG-2 and H.263 to the next level has been addressed over the
last several years through a combined working group of the ITU-T
and ISO/IEC organizations, who have previously produced the
H.26x and MPEG-x standards, respectively.
• The new standard has emerged as H.264. It is also called
MPEG- 4, Part 10, or MPEG-4 Advanced Video Coding (AVC).
• H.264/AVC cuts in half the bandwidth required to deliver fullscreen DVD-quality digital video to consumers, and it reduces
standard television quality digital transmission bandwidth
requirements to 700 kbps—both well within the capabilities of a
1.5 Mbps DSL loop.
H.264 (Cntd.)
The enhanced compression and perceptual quality of
H.264 are obtained by:
• Motion estimation, which minimizes temporal
redundancies
• Intra estimation, which minimizes spatial redundancies
• Transformation of motion estimation and intra
estimation into the frequency domain
• Entropy coding, which assigns a smaller number of
bits to frequently encountered symbols and a larger
number of bits to infrequently encountered symbols.
IPTV main protocols - IGMP
• The Internet Group Management Protocol (IGMP) is the
Internet protocol, part of the Network Layer. IGMP is formally
described in the Internet Engineering Task Force (IETF)
Request for Comments (RFC) 2236.
• IGMP provides a way for an Internet computer to report its
multicast group membership to adjacent routers. Multicasting
allows one computer on the Internet to send content to multiple
other computers that have identified themselves as interested
in receiving the originating computer's content.
Multicasting applications:
• updating the address books of mobile computer users in the field
• sending out company newsletters to a distribution list
• "broadcasting" high-bandwidth programs of streaming video to an audience
5.2. IPTV over DSL
Using new H.264/AVC delivery platforms and standard PCs or
STBs, Telcos can offer exciting IP video services - Video-onDemand (VOD), television programming, gaming, music, and,
even interactive television - to their home and business customers
using their existing copper infrastructure.
With DSL technology, the Telcos hold a significant advantage
by delivering IPTV to more of the masses than cable operators.
While cable and satellite Internet access is encroaching on the
Telcos long-held dominance, DSL is still the leading broadband
technology that users subscribe to around the world.
Global DSL connections forecast
According to the DSL Forum (www.dslforum.org), 55 million
Internet users worldwide use DSL in September of 2003; 25
million new subscribers alone were added from September 2002
to September 2003.
The growth trend is expected to continue, with subscriptions
reaching nearly 100 million users worldwide by 2006.
H.264/AVC reduces the barriers to entry for Telcos, who can offer
more services than cable operators.
Global DSL connections forecast
Delivering video services over DSL
Similar to MPEG-2, H.264/AVC requires encoding and decoding
technology to prepare the video signal for transmission and then
read it at the customer’s receiver (STB and TV set, or PC).
In fact, H.264/AVC can use transport technologies compatible with
MPEG-2, simplifying an upgrade from MPEG-2 to H.264/AVC
to help protect the investments in MPEG-2 some companies have
already made, while enabling transport over TCP/IP and wireless.
This also allows service providers to deliver content to devices
for which MPEG-2 cannot be used, such as PDA and digital cell
phones.
Delivering video services over DSL (Cntd.)
The H.264/AVC encoder system in the main office turns the raw
video signals received from content providers into H.264/AVC
video streams. The streams can be captured and stored on a
video server at the head-end, or sent to a video server at a
regional or central office (CO), for video-on-demand services.
The video data can also be sent as live programming over the
network. Standard networking and switching equipment routes
the video stream, encapsulating the stream in standard network
transport protocols, such as ATM.
Delivering video services over DSL (Cntd.)
A special part of H.264/AVC, called the Network Abstraction
Layer (NAL), enables encapsulation of the stream for transmission
over the Telco’s DSL Internet access services network.
When the video data reaches the customer’s site, it is routed to
the client through a DSL modem and the customer’s local network
(wired or wireless). An STB client decodes the stream for display
on a TV set, while a PC client decodes the data using a plug-in
for the client’s video player (Real Player*, Windows* Media
Player*, etc.).
Delivering video services over DSL (Cntd.)
Switch
TV over IP using ADSL
ADSL can support last-mile bandwidths between 512 Kbps and 6 Mbps. The actual bandwidth
available depends on the distance between the end-point and the ADSL DSLAM. Depending on
the last mile bandwidth available, users can receive 2 channels of video. In this case, two IP STBs
will reside at the end point (one STB for each channel).
Streaming Server
TV over IP using VDSL
VDSL configuration rests on fiber connectivity over the backbone at bit rates of 155
Mbps and up. Transmission from the last mile network node to the end point is at bit
rates of between 10 and 40 Mbps. The high bandwidths supported by VDSL enable
consumers to receive multiple channels for playback on multiple TV sets. With VDSL,
the backbone infrastructure is based on fiber to the curb/basement while the last mile
solution uses VDSL over the telephone copper line.
Streaming Server
TV over IP using FTTH (Fibre to the Home)
FTTH configuration rests on fibre connectivity from the head-end to the end-point. In this
configuration video is transmitted over a fibre backbone at more than 155 Mbps. Last
mile configuration consists of a 100BaseT network. Such wide bandwidths allow users to
receive multiple channels, which are played back by IP/STB.
Streaming Server
5.3. Video coding standards
H.264 Features
• H.264 compresses video more efficiently, cutting
transmission costs over satellite or terrestrial links.
• Density of services over existing DSL loops is high:
two standard-quality video streams can be transmitted
over a single 1.5 Mbps loop.
Customers can watch (and Telcos can bill for)
two video-on-demand streams at the same time.
H.264 Features
• More content can be transmitted on longer loops - to more
customers. Where MPEG-2 could only reach customers in a 9,000
sq. ft service area per CO, H.264/AVC video streams can reach
customers in a 16,000 sq. ft service area per CO.
• H.264/AVC is also part of the upcoming 3GPPv6 specifications.
With the use of joint technologies, UDP or TCP/IP and H.264,
there is a common ground for greater interaction between the
home and mobile devices.
H.264/AVC enables reaching greater
distances over DSL with more content
H.264/MPEG-4 AVC: The IPTV enabling
technology standard
The following table summarizes the development of
different H.26x/MPEG standards and their intended
applications.
Video coding standards (Cntd.)
• MPEG-2 (hardware technology) has been the industry-standard digital
video broadcast codec for many years for high bit rate applications. MPEG-2
requires 2 Mbps of bandwidth, which is available over coaxial lines and satellite
lines, to deliver broadcast-quality, jitter-free, digital video.
• MPEG-4 Simple Profile (SP) and Advanced Simple Profile
(ASP) were developed for streaming video over Internet connections. MPEG-4
offers a software method to compress and decompress video over a network
that provides only a best-possible connection with a wide range of data rates.
The result is not what viewers have come to expect from their televisions,
but enough to offer interesting services and enhance the richness of the
Internet experience.
Video coding standards (Cntd.)
• H.264/MPEG-4 AVC addresses the needs for greater compression,
leading to lower data rates, while maintaining broadcast quality for
video-on-demand (VOD) and high-definition television (HDTV) needs.
H.264 meets the needs of both broadcast and the Internet by cutting the
MPEG-2 bit rates in about half for digital video transmission-without a loss in
video quality.
This advance has followed the evolution of video compression science toward
higher quality and lower bandwidth, and it opens new doors for service
providers operating over the local copper loop infrastructure.
Using H.264/MPEG-4 AVC and new H.264-enabling technology platforms
for encoding, transport, and decoding, Telcos and ISPs can boost their
average revenue per user (ARPU) with exciting and compelling new
video-on-demand, HDTV distribution, and interactive TV services. The age of
IPTV over DSL has arrived.
Codecs
100000
Kbit/ sec
Alca tel Propr. Codec
M- JPEG
MPEG2
10000
Audio CD
MPEG4
1000
100
MP3
G.711
MP3Pro,
AAC
G.726
G.728
10
G.729
G.723.1
1
1970
1975
1980
voice
1985
1990
HiFi audio
1995
2000
2005
2010
TV qual video
Source: Alcatel
Video compression of 1024x768 pixel, 24-bit color image
H.264/AVC benefits bandwidth demand, storage
requirement, and download times
5.4. IPTV main building blocks
Streaming Server
Streaming server resides at the head- end. It can encode and
stream live streams in real-time and pre-encoded streams that are
stored on the video server. Streaming server transmits the
streams to the switch or router which transfers them over the
backbone to the central/remote offices, and from there to the end
user location.
IPTV main building blocks (Cntd.)
Video Server
Video servers fulfill several purposes. For store and forward
transmissions, video servers store digitally encoded content and
stream it through level III devices via operators’ networking
infrastructure. Video servers receive newly encoded digital
content that is uploaded from the streaming server.
Video servers also enable time shifted TV applications. Viewers
at home can then watch any program at a time convenient to
them.
IPTV main building blocks (Cntd.)
Level III Device
A switch or router that supports multicast transmission. The router
or switch resides at the head-end, interfacing with the network.
Another router or switch receives data at the central office and
transmits either to DSLAMS located there, or into end-user
network.
IPTV main building blocks (Cntd.)
DSLAM
The DSLAM (Digital Subscriber Line Access Multiplexer) resides
at the central office, connecting xDSL subscribers to the backbone
and subsequently to the head-end. When distributing TV over IP,
the DSLAM should support multicast transmission. If it doesn’t,
the switch or router at the central office has to replicate
each channel for each request. This can cause congestion at the
DSLAM input level. If the DSLAM supports multicast, it receives
one stream for each channel and replicates the stream for each
end point.
IPTV main building blocks (Cntd.)
CPE (Customer Premises Equipment)
The equipment located at the end-point that receives the TV/IP
stream. Usually the term CPE refers to the DSL modem. The DSL
modem receives the stream from the DSLAM or Level III device
and transfers it directly to the PC for display on the desktop or to
the IP STB.
IPTV main building blocks (Cntd.)
Set-top Box (STB)
Gateway between TV set/PC-TV and NT (PSTN line, satellite or
cable)
Signal processing – receiving, decoding/decompressing
STB also accepts commands from the user and transmits these
commands back to the network, often through a back channel
Functions - TV signal receiver, modem, game console, Web
browser, e-mail capabilities, video-conferencing, cable telephony
Set-top Box (STB) – Cntd.
• Components - Electronic Program Guide (EPG), CD
ROM, DVD player etc.
• Many STBs are able to communicate in real time with
devices such as camcorders, DVDs, CD players and
music keyboards
•
•
•
•
•
Hardware
Data network interface
Decoder
Buffer
Synchronization hardware
Set-top Box (STB) - Cntd
Types of STB
(1) Broadcast TV Set-top Boxes - (Thin Boxes)
More elementary level set-top box with no return channel (back-end). Some
memory, interface ports and some processing power.
(2) Enhanced TV Set-top Boxes - (Smart TV set-top box, Thick Boxes)
These have a return channel, usually through a phone line. Video on Demand,
Near Video on Demand, e-commerce, Internet browsing, e-mail
communications and chat.
(3) Advanced Set-top Boxes - (Advanced digital Set-top boxes,
Smart TV Set-top box, Thick Boxes)
Like a PC -processors, memory and optional large hard-drives.
(4) All-in-one Set-top Boxes - (Integrated set top box, Super Box)
A fully integrated set-top box. Features could include everything from highspeed Internet access to digital video recording to games and e-mail capacity.
5.5. QoS issues for different types of traffic
• Voice traffic is smooth, benign, drop-sensitive, and delay-sensitive, and
is typically UDP-based. Bandwidth per call depends on the particular codes
adopted, sampling rate, and Layer 2 media employed. Voice quality is
directly affected by all three QoS quality factors (loss, delay, and delay
variation).
• Data traffic is much more varied. It can be smooth or bursty, benign or
greedy, or drop- and delay-insensitive, and involves Transmission Control
Protocol (TCP) for send/receive acknowledgment and retransmit. Traffic
patterns vary by application, and data classes must support several different
priorities or application categories.
• Video traffic is bursty, bandwidth-greedy, drop-sensitive, and delaysensitive. IP-based videoconferencing has some of the same sensitivities as
voice traffic.
QoS issues for different types of traffic (Cntd.)
Data traffic is typically handled with multiple classes, where each class can be
defined and given the appropriate support based on the priority requirement of
the application that is generating the traffic. In general, enterprises should
restrict themselves to about five main traffic classes, such as:
•
•
•
•
•
Mission-critical and real-time - Transactional and interactive applications with high
business priority; in some cases, real-time traffic such as voice over IP (VoIP) can be
subdivided into a separate class
Transactional/interactive - Client-server applications, messaging applications
(typically foreground activities that directly affect employee productivity)
Bulk - Large file transfers, e-mail, network backups, database synchronization and
replication, and video content distribution (background activities that do not directly
affect employee productivity and are generally time-insensitive)
Best-effort - Default class for all unassigned traffic; typically at least 25 percent of
bandwidth is reserved for best-effort traffic
Scavenger (optional)—Peer-to-peer media sharing applications, gaming traffic, and
entertainment traffic
QoS issues for different types of traffic (Cntd.)
QoS requirements for video applications
There are two main types of video applications—interactive video
(such as videoconferencing) and streaming video (such as IP/TV
content, which may be either unicast or multicast).
Provisioning for interactive video traffic:
# Packet loss should be no more than 1 percent.
# One-way latency should be no more than 150 ms.
# Jitter should be no more than 30 ms.
# The minimum priority bandwidth guarantee is the size of the
video conferencing session plus 20 percent. (For example, a 384
kbps video conferencing session requires 460 kbps of guaranteed
priority bandwidth.)
QoS issues for different types of traffic (Cntd.)
Streaming video applications
have more tolerant QoS requirements, as they are delay
insensitive and are largely jitter insensitive (due to application
buffering).
However, streaming video may contain valuable content, such as
e-learning applications or multicast company meetings, and
therefore may require service guarantees through QoS.
Provisioning for streaming video traffic:
# Loss should be no more than 2 percent.
# Latency should be no more than 4-5 seconds (depending on
video application's buffering capabilities).
# There are no significant jitter requirements.
# Guaranteed bandwidth requirements depend on the encoding
format and rate of the video stream.
QoS issues for different types of traffic (Cntd.)
Streaming video is typically unidirectional and, therefore,
remote branch routers may not require provisioning for
streaming video traffic on the customer edge (CE) in the
direction of branch to campus.
Non-important streaming video applications (either unicast or
multicast), such as entertainment video, content may be
provisioned in the Scavenger traffic class and assigned a minimal
bandwidth percentage.
Scavenger Class
The Scavenger class is intended to provide deferential services, or “less-than
Best-Effort” services, to certain applications.
Applications assigned to this class have little or no contribution to the
organizational objectives of the enterprise and are typically entertainmentoriented.
These include:
• Peer-to-peer media-sharing applications (KaZaa, Morpheus, Groekster,
Napster, iMesh, etc.)
• Gaming applications (Doom, Quake, Unreal Tournament, etc.), and any
entertainment video applications.
Assigning a minimal bandwidth queue to Scavenger traffic forces it to be
squelched to virtually nothing during periods of congestion, but allows it to
be available if bandwidth is not being used for business purposes, such as
might occur during off-peak hours.
Bandwidth consumption of video over IP traffic in the face of
competing web surfing traffic. No traffic shaping is present.
Additional network latency added by congestion
With QoS From Packet Shaper
(guaranteed bandwidth of 820k for video traffic)