Transcript Broadcast on Demand Concept

Broadcast on Demand in BFWA
networks (IST-1999-11571 EMBRACE)
John R Norbury
Broadcast on Demand Concept
 Many digital TV channels are now available
 The number of available programmes will exceeds
the number of “active” TV viewers in any particular
BFWA cell
 better spectral efficiency and use of RF systems can
be achieved by broadcasting only required content
 TV transmissions should become a broadcast on
demand (BoD) service for all but the most popular
channels
Do viewing statistics support the BoD concept
• BARB (www.barb.co.uk.) provides TV viewing
figures for the most popular programmes
 30 most popular terrestrial TV programmes
 10 most popular satellite (& cable) TV
programmes
• TV viewing statistics generated with help of
programme schedules
Statistics of TV viewing as a
function of channel number
• Distributions have been reconstructed for
peak viewing values and average value over
the five evening hours (1800 to 2300)
• logarithmic and cumulative distributions
(two different weeks) are shown
10000
average
1000
peak
170,000
100
50,000
10
channel number
45
41
37
33
29
25
21
17
13
9
5
1
1
number of view ers
(thousands)
100000
channel number
45
41
37
33
29
25
21
17
13
9
5
1
cumulative % number by channel
120
100
80
60
27-May
15-Apr
40
20
0
Interpretation of statistics
• If BFWA cell has 500 TV viewers, then one
viewer represents 0.2% of the population
(or 50,000 TV viewers in all UK).
• only 37 channels need to be broadcast to
satisfy all users
• The cumulative curve indicates that 90% of
viewers watch the 10 most popular channels
Other evidence for BoD concept
• Current CATV experience in UK suggests
that:
 about 75% of customers will only pay for basic
service
 only ~25 % of viewers select pay TV option
Proposed BoD Solution
• Transmit 20 to 30 TV channels as
conventional MPEG multiplexes
• All other channels are provided through
BoD services
Main issues for BoD
• Should the BoD transmissions be:
 a stand alone service similar to a time varying
conventional broadcast TV
 combined with VoD, as BoD is similar to fixed
schedule near video-on-demand
 an IP based service
DVB broadcast
channels
BoD channels VoD channels
DVB format
Internet traffic
DVB broadcast
channels
BoD and VoD channels
Internet traff ic
DVB broadcast
channels
combined BoD, VoD as IP streams, with Internet, data, etc
IP based service is best option
 Live TV combined with other IP streams should
facilitate efficient packaging of data
 IP implementation uses fairly standard equipment –
modified set top box technology and routers
 The other methods require time dependant remultiplexing – very expensive to implement
 The first two options are less efficient in terms of
spectrum and hardware
 General tendency towards IP based services
 IP based services requires the set top box to display
IP video streams on a conventional TV
Central office functions
input services
DV B
broadcast
services
BoD
services
V oD
services
v oice, Internet
and data
serv ices
control links to
interactive
services
output
services
return path
and control
of netw ork
combiner,
multiplexer
& sw itcher/
router
dow n link to
local netw ork
& user
up link
f rom local
services &
user
DVB
bouquet of
several 34
Mbps
multiplexes
selected
programmes
(cy an)
BoD, VoD, Internet and
data streams, in 34
Mbps base band
channels
programmes
selection
f rom f irst
channel
down
converter/
demod.
modulator
and
combiner
multiplex 1
(base band)
programmes
selection f rom
second
channel
down
converter/
demod.
VoD,
Internet
and data
traff ic
streams
b
multiplex 2
(base band)
modulator
and
combiner
combination
of selected
BoD , VoD,
Internet and
data traf f ic
streams and
routing to
particular
cells
programmes
selection
f rom
k th channel
down
converter/
demod.
modulator
and
combiner
multiplex k
(base band)
programmes requests
routed to
selection stack
cell
1
cell
2
cell
n
requests
f rom cells
RF
to
cell
1
RF
to
cell
2
RF
to
cell
n
BoD
cell 1
requests
f or
cell 2
particular
cell n programmes
Implementation of BoD in network
 either Central office
 or Local base station
• Central office solution combines all hardware in
one location but imposes a large requirement for
bandwidth on the backbone connecting the base
station
• Local base station implementation require
significant hardware at each base station
Some other issues
 Does BoD make economic sense? How does the
cost of implementation compare with conventional
broadcast TV
 What is the effect of personal video recorders on
BoD
 How will customers react to BoD
 Is BoD a solution for CATV when the total number
of programmes available exceeds the bandwidth of
the coax connection to the user?
Multicast Push and Proxy Services with Support for
Broadcast on Demand
• H. Linder1, John Norbury2, J. Schmidbauer1
1Institute
for Computer Sciences, University of Salzburg,
Austria, 2Eurobell (Telewest Broadband), UK
•
•
EMBRACE Workshop 30 September to 1 October 2002
IST-1999-11571
• http://www.telenor.no/fou/prosjekter/embrace/