ECEN4533 Data Communications
Lecture #42
22 April 2013
Dr. George Scheets


Problems: 2012 Final Exam
Final Exam
– 0950, Friday, 3 May (Live)
 On or before Friday, 10 May (DL)
 0800

Wireshark Project due by midnight 4 May (All)
 Late
turn in NOT accepted
 15 points + 20 points extra credit

Quiz 2 Results
 Hi
= 18.7, Low = 12.2, Ave = 16.82, σ = 2.70
ECEN4533 Data Communications
Lecture #43
24 April 2013
Dr. George Scheets


Problems: 17-12, 17, & 18
Final Exam
– 0950, Friday, 3 May (Live)
 On or before Friday, 10 May (DL)
 0800

Wireshark Project due by midnight 4 May (All)
 Late
turn in NOT accepted
 15 points + 20 points extra credit
Video Delivery Systems
Cable TV
Headend
AMP
...
configuration
 Distribution systems originally all coax
 Originally Analog NTSC
 BW ≈ 700 MHz
AMP
...
 Tree
AMP
...

Initially Simplex Copper Coax
Video Delivery Systems
Cable TV
Headend
AMP
...
configuration
 Distribution systems originally all coax
 Fiber deployed from Head End side moving
out
AMP
...
 Tree
AMP
2nd Generation
Hybrid Fiber Coax
a.k.a. FTTx
Fiber
...

Copper Coax
Video Delivery Systems
Cable TV
 Now
mostly digital ATSC, MPEG2/4
 Analog
 Cable
NTSC now uncommon
Modems require 2-way commo
6 MHz channels pulled from TV pool
AMP
Headend
AMP
...
 Some
Fiber
AMP
...
2nd Generation
Hybrid Fiber Coax
FTT curb
...

Copper Coax
Video Delivery Systems
Cable TV
 Ultimate
Goal: Fiber to the Home (FTTH)
 Passive Optical Network
Splitter
Headend
...
active electronics in access network
Splitter
3rd Generation
FTT home
Splitter
Fiber
...
 No
...

Cable Networks
Have a Lot of BW (XXX MHz)
 Allocate 6 MHz channels for various services

 FDM

6 MHz Channel can carry
2
MPEG4 HDTV signals
 2-6 MPEG2/4 SDTV signals
 30-40 Mbps Cable Modem Traffic (Shared)
DOCSIS (Data over Cable Service Interface Specification)
 Internet
 VoIP
Last Mile Options
Digital Subscriber Line (xDSL)
 Rides
on top of Telco access network
 Runs over twisted pair cabling (BW X to XX MHz)
 Various flavors exist
CO
...

ADSL

Plain Vanilla ADSL
 384
Kbps - 8 Mbps downstream
 16 Kbps - 640 Kbps upstream

Uses FDM
 POTS
analog voice stays in 0 - 4 KHz band
 Upstream and Downstream signals mapped
to higher frequency bands
 Uses
 ATM
OFDM
or Ethernet frame formats
FDM
FDMA
WDM
1
Different channels use some
of the bandwidth all of the time.
frequency
2
3
4
5
Orthogonal FDM
Channel 1
frequency
Channels split into sub-channels
Bits parceled out to sub-channels
Advantage:
Sub-channel bit rates can be
modified to cope with
interference
Less susceptible to multipath
802.11 & Cellular Systems
Ways to decrease P(Bit Error)

Crank up power out
 As
a last resort (cellular)
Reduce noise in system
 Slow down transmitted bit rate
 Use directional antennas
 Use Forward Error Correcting codes
 Use Orthogonal Frequency Division
Multiplexing

FDM with Multi-path
T3
bounce path
time
XMTR
direct path pulses
direct path
RCVR
bounce path pulses
delay
Signal sum seen by Receiver
T1
T2 T3
Symbol decision intervals at Receiver.
The third bit is obliterated by multi-path.
OFDM with Multi-path
Slower symbol rate over
each subchannel.
delay
bounce
direct
bounce
direct
direct
bounce
Matched filter detector will work OK.
T1
T2
T3
Some of the Flavored Versions

ADSL2
 Needs
higher SNR than ADSL
 8 -12 Mbps downstream
 800 Kbps - 3.5 Mbps upstream

ADSL2+
 Doubles
used Bandwidth & Bit Rates
 Can also bond multiple twisted pairs
Inverse Multiplex

VDSL2
4
- 8 MHz BW, Inverse Multiplexing
 100 Mbps over short distances
xDSL

ADSL (< 8 Mbps downstream) can carry
A
handful of 1.5 Mbps SDTV signals
 Internet traffic (in left over BW) & Standard voice call
 0 HDTV signals

ADSL2+ (< Mbps down stream) can carry
 Two
9 Mbps MPEG4
 Internet traffic (in left over BW) & Standard voice call

To Support Triple Play Service
 TelCo's
need to drive fiber down towards homes
 FTTH: Gbps speeds possible
 VDSL2+ can support 100 Mbps on copper out to 0.5 Km
Longer reach if FTTC in place
DSL Speeds
(Copper)
source: www.convergedigest.com/blueprints/ttp03/bp1.asp?ID=232&ctgy=Loop
IPTV & Last Mile Networks

On the Access Network
 Cable
TV/Cable Modem: No Problem
 FTTH : No Problem
 xDSL: Problem
 Unless Next Door to CO
 Or near FTTC termination
 Either way, can't stream 150 HDTV channels
 Solution: Selectively feed a few

On the Home Network
 100
Mbps can handle several HDTV channels
 Leaves significant BW available for data &
yet-to-be-invented apps
Powerline HAN
10/100BaseT Ethernet: PC ↔ Adapter
500 Mbps: Adapter ↔ Adapter
IPTV on the Access Network

ISP Backbone
Regional Caches
 Streamed
All or Most
TV Network Programs
Regional
Cache

...
Local Cache
 House
Apartment Complex
 Streamed > 1 channel,
Access BW permitting.
Local
Cache
...
User
TV
User
User
TV
TV
User
TV

User TV
 Streamed
> 1 channel,
Home BW permitting.
IPTV on the Access Network
Want to change
channel?
 TV Cache Checked

ISP Backbone
Regional
Cache
 Available?
...
< 1/2 second to change
 Not available?
Packet request shipped to
Local Cache
Local
Cache
...
User
TV
User
User
TV
TV
User
TV
IPTV on the Access Network

ISP Backbone
Local Cache Checked
 Available?
Channel streamed to TV
May take > 1/2 second
 Not available?
Packet request shipped to
Regional Cache
Regional
Cache
...
Local
Cache
...
User
TV
User
User
TV
TV
User
TV
IPTV on the Access Network

ISP Backbone
Regional Cache Checked
 Available?
Regional
Cache
...
Local
Cache
...
User
TV
User
User
TV
TV
User
TV
Channel streamed to
Local Cache, then user
TV.
 Not available?
Packet request might
need to be shipped to info
source.
 If these are busy...
IPTV on the Access Network
ISP Backbone
Channel Change May
Take Several Seconds
 Channel Surfers Won't
be Happy
 Ongoing Research

Regional
Cache
...
Local
Cache
 Streaming
...
User
TV
User
User
TV
TV
User
TV
Techniques to
minimize channel change
time.
When they're
awake.
 Predicting
next
channel
HDTV Video On Demand
Roughly 80 TV's per 100 U.S. Population
 Current population about 314,900,000
 About 251.9 million TV's
 Worst Case Traffic Demand
251,900,000 x 9.51 Mbps/user =
2,395,569,000,000,000 bps

 All
aren't HDTV capable
 All won't be on
 Should be some multicasting
 etc.
Video On Demand- Reservations
I want to watch
"Dr. Strangelove"
at 7:12 pm.
Someone else in
vicinity commenced
watching at 6:58 pm?
Reservations 1 hour in
advance required?
System can plan ahead.
6:58 request could be streamed live and forwarded
(multicast) to my location, stored locally, played back
commencing at 7:12.
Unicast
Server
Router
Sink
Sink
3 Separate Streams
Required to service
3 users.
Sink
Multicast
Server
Router
Sink
Sink
For a portion of
the route, 1 stream
suffices.
Sink