1. IPTV Systems, Standards and Architectures: Part II - IPTV Architectures for Cable Systems: An Evolutionary Approach Vasudevan, S.V.   Xiaomei Liu   Kollmansberger, K.   Cisco Syst., San Jose, CA; This paper appears in: Communications Magazine, IEEE Publication Date: May 2008 Volume: 46,  Issue: 5 On page(s):
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2. Outline Introduction Cable Video Architecture Cable IPTV Architecture
Improving Bandwidth Efficiency in the Last Mile
Cable IPTV Admission Control
Scaling for Tomorrow’s Entertainment
Conclusion
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3. Introduction
CATV providers must establish triple-play services (ex. IPTV) with existed infrastructure to make themselves have more competitiveness
CATV history
First-generation
Frequency are divided into subchannel with 6 or 8 MHz.
Transmit single analog signal (program) per subchannel.
New (future)
Use compression technology to transmit multiple digital programs per subchannel.
To use the DOCSIS to support IP services over cable.
Such that, non-RF clients can receive the service.
To compete with telcos. and DBS(Direct broadcast satellite)
CATV=>headend to hub use IP network.
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4. Introduction Direct Distance Devices CATV service companies Two-way
Limited
Coax/RF tuner/receivers
Traditional voice wireline companies
IPTV receivers (STBs) with
broadband modem
Direct broadcast satellite
(DBS)
Uni-directional
No limited
RF receivers
Table: some difference about the three kinds of service provider.
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5. Cable Video Architecture
Video service definition
Broadcast services
Digital broadcast
Encoded/compressed programs send to all subscribers.
Switched digital video (SDV)
Encoded/compressed programs send to the subscriber group which need those programs. (two way communication)
On-demand services
Program is sent to one who request the program.
Video on demand (VOD)
Contents are stored at server.
Network-based personal video recorder (nPVR)
Like home PVR, except that the storage is part of the service provider network.
A subscriber group typically consists of all of the suscribers served by one or more HFC nodes, which can range anywhere form 125 to 2000 subscribers.
VOD: movie
nPVR: 邊看邊錄影
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6. Cable Video Architecture
Video transport architecture
Headend
Equivalent to video headend office (VHO).
Content acquire here.
Back office systems reside.
IP network
Transport IP services from headend to hubs.
Hub
Equivalent to video serving office (VSO).
The control of bandwidth-intensive applications.
HFC-connected components reside.
HFC network
Fiber-coax access network.
Subscriber
Coax receivers (cable modem + STBs)
Personal or business.
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7. Cable Video Architecture
Video system architectures (1/3)
Digital broadcast architecture
Get the source from satellite and terrestrial.
Feed the source to the following functions
Statmux
Performs STDM to multiple sources.
Grommer
“Transrates” content into to a maximum bandwidth.
Splicer
Ads are inserted here.
Then, forward the data to IP-enabled QAM (using scrambler).
Use out-of-band (OOB) channel to send the tuning information, decryption keys, software upgrades … etc.
Transrates => 編成較小的檔案可用來傳輸。
Channel map => tuning informations
Whereas encryption usually refers to operations carried out in the digital domain, scrambling usually refers to operations carried out in the analog domain.
Statmux: statsitical time-division multiplexing of real-time video content from multiple sources.
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8. Cable Video Architecture
satellite and
terrestrial source
Digital broadcast architecture
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9. Cable Video Architecture
Video system architectures (2/3)
On-demand architecture
Get the sources from satellite or terrestrial or VOD assets.
If from 1, go to the groomer and then ingest to VOD server. If from 2, ingest to VOD server directly. (Use FTP)
Then, forward data to IP network, and arrive the session-based encryptor.
After encrypted, forward data to the QAM and then to the STB.
Session is a temporary identifier, and session manager (SM) is the coordinator between the STB and server.
SM replies the tuning and decryption information to the STB, and OOB channel provides the IP-address of the SM and software-upgrades. 1 2
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10. Cable Video Architecture
Video assets
Use FTP
satellite and
terrestrial source
SM’s IP address
On-demand architecture
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11. Cable Video Architecture
Video system architectures (3/3)
Switched digital video architecture
Programming terminates at the headend or hub and does not traverse the access network unless requested.
A receiver signals upstream to request programming, and a hub-based controller receives the request and enables the stream into the HFC network by multiplexing the stream into a pool of allocated frequencies.
※ request, if the program is currently watched in the same group (a HFC network), reused the existing session frequency information.
Cost-effective
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12. Cable Video Architecture
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13. Cable IPTV Architecture
IPTV can be enabled with three newly added components:
Cable modems (CM).
Cable modem termination system (CMTS).
PacketCable Multimedia (PCMM).
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14. Cable IPTV Architecture
CM and CMTS
Provide a two-way IP over DOCSIS transport in the HFC network.
Modular CMTS : separated MAC and PHY layers.
CMTS
Manages the DOCSIS QAM resources.
Provides QoS over the DOCSIS channel.
Manage the CMs.
Optimize traffic distribution in the downstream.
Scalability and economics.
M-CMTS: separated MAC and PHY layers to improve the economics and scalability of DOCSIS transport.
Load-balance.
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15. Cable IPTV Architecture
STB and IPTV-capable devices
IP STBs which is like RF STBs.
Hybrid STBs which can receive program form traditional QAM/RF or DOCSIS IP path.
PacketCable Multimedia (PCMM) policy server
Define the QoS policies, while CMTSs enforce QoS policies.
SM can request and reserve DOCSIS bandwidth through the PCMM policy server.
PacketCable Multimedia
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16. Improving Bandwidth Efficiency in the Last Mile
Some methods
Splitting optical nodes to reduce service group size.
Applying advanced video compression algorithms.
Reclaiming analog channels.
Upgrading the plant to 1 GHz.
Dynamic bandwidth sharing: SDV, VOD, IPTV over DOCSIS.
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17. Improving Bandwidth Efficiency in the Last Mile
QAM and HFC bandwidth sharing
Dynamic QAM sharing
DOCSIS M-CMTS: allows the PHY layer (specifically the QAMs) to be dynamically allocated and de-allocated.
Universal QAM: can be function as either MPEG video QAMs or DOCSIS QAMs.
Standardization in edge QAM resource management.
QAM sharing: 不同service有不同的peak hours
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18. Improving Bandwidth Efficiency in the Last Mile
QAM and HFC bandwidth sharing
ERMI specifications specifies
ERMI-1
Is an interface for edge devices to register QAM channels to the ERM and notify the ERM of any QAM failures or state changes.
ERMI-2
Is an interface for the ERM to bind the QAM resources from an edge device to the resource allocation request.
ERMI-3
Is an interface for the M-CMTS core to allocate QAM-channel bandwidth from the ERM.
The M-CMTS uses the downstream external PHY interface (DEPI) protocol to establish a tunnel to remote QAM channels after obtaining QAM resources from the ERM.
IPTV can use the PCMM framework to obtain session-level bandwidth. (due to channel bounding, load-balance, sharing spectrum)
M-CMTS core obtains resources from the ERM at the granularity of full QAM channels.
IPTV use PCMM due to
1. CMTS can dynamically load-balance CMs among different MAC domains an QAMs.
2. Channel bounding in DOCSIS 3.0 is dynamic, and CMs may change bounding groups per flow. (把較小的組合起來)
3. IPTV shares the same pipe with other applications, and thus is unaware of their bandwidth consumption.
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19. Improving Bandwidth Efficiency in the Last Mile
VOD and SDV QAM
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20. Cable IPTV Admission Control
Focused on the HFC portion.
Centralized (in HFC) vs. distributed (in IP)
Can be categorized as
off-path
Direct signaling to the PCMM policy server.
on-path
Traverses the data path for bandwidth requests that use the commonly selected RSVP.
RSVP: resource reservation protocol
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21. Cable IPTV Admission Control
Off-path signaling
For multicast
On-path signaling
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22. Scaling for Tomorrow’s Entertainment
Scaling VOD servers
Streamers
Video sources.
Which play out stored content in real time.
Optimized for networking throughput.
Vaults
Storage components.
Optimized for storage.
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23. Scaling for Tomorrow’s Entertainment
Scaling VOD servers
Less popular content
-- provided just in time transmission
Popular content is cached here
如果在streamer的cache沒hit中，則由vault提供。
Less popular content is transferred from a vault “just in time” to maintain streaming timing integrity in the case of a cache miss
(the failure to acquire asset data on the first try from a streamer’s local cace.)
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24. Scaling for Tomorrow’s Entertainment
Scaling the IP transport network
M-CMTS architecture
Allow the PHY layer to scale independently of the MAC layer.
Scaling statistical multiplexing
Old
MPEG statistical multiplexing is widely used for VBR.
Too expensive.
New
Better statistical multiplexing
Channel bounding .
Too expensive
1. statemuxes 佈置貴
2. inherently delay 0.5~1 s
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25. Conclusion To enable IPTV in the DOCSIS 3.0.
SDV can provide a stepping stone to cable IPTV.
Standardization of universal QAMs
Allows forward compatible.
Scalability.
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