6.978/ESD.68
Competition in Access
Networks
Sharon E. Gillett, MIT
The past: Silos
POTS
Copper
Cable TV
Coax
TV
radio
Broadcast
Figur e 1: Past industry struc ture of resid ential ac cess.
From (Clark, 1999)
The present:
“Convergence”
IAP
POTS
Internet
ADSL
HFC
radio
TV
VDSL
CLEC
Copper
Coax
Wireless
Satelli te
Broadc ast
Figur e 2: Emerging indus try structure of residen tial acc ess
From (Clark, 1999)
The Future(?):
Internet as Platform
E-mail
Web
Phone
TV
radio
Internet
IAP
POTS
ADSL
Copper
HFC
Coax
Wireless
Satelli te
Figur e 4: Poten tial indus try struc ture surround ing the Internet.
From (Clark, 1999)
200,000,000
200,000,000
180,000,000
180,000,000
160,000,000
160,000,000
140,000,000
140,000,000
120,000,000
120,000,000
100,000,000
100,000,000
80,000,000
80,000,000
60,000,000
60,000,000
40,000,000
40,000,000
20,000,000
20,000,000
Number of Subscribers
Access Lines
Wireless Telephony Competing With Fixed Lines, 2002
3 mil
0
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Fixed Lines(1)
Wireless(2)
Broadband(3)
Cable Telephony(4)
(1) 1990-1998 data from “FCC Trends in Telephone Service May 2002”; 1999-2002 data from “FCC, Local Telephone
Competition: Status as of Dec 31 2002”; (2) CTIA Semi-Annual Wireless Industry Survey, published 2003; (3) 992001:FCC.COM: Trends in Telephone Service May 2002 (High Speed Lines with 200Kbps in at least one direction;
Legg Mason Wood Walker, Inc. "Coming Down the Pipe - Interim Report 4Q 2002/1Q 2003 Industry Update - March
13, 2003“; (4) NCTA, "Residential Cable Telephony Subscribers”
Source: OECD
Cable
Ita
l
Po y
rtu
N
ew
ga
l
Ze
C
al
ze
a
ch
nd
R
ep
ub
li c
Ire
la
nd
H
un
ga
ry
Po
la
nd
Sl
T
ur
ov
ke
ak
y
R
ep
ub
lic
M
ex
ic
o
G
re
ec
e
DSL
Sp
ai
n
D
en
m
N
ar
et
k
he
rl a
nd
s
Ic
el
an
d
Ko
Sw
re
a
i tz
er
la
nd
Fi
nl
an
d
N
or
w
ay
Sw
ed
en
C
U
a
ni
na
te
da
d
Ki
ng
do
m
Be
lg
U
iu
ni
m
te
d
St
at
es
Ja
Lu
pa
xe
n
m
bo
ur
g
Au
st
ria
Fr
an
ce
Au
st
ra
li a
G
er
m
an
y
30
OECD Broadband subscribers per 100 inhabitants, by technology, June 2006
Other
25
20
OECD average
15
10
5
0
Courtesy of OECD. Source: OECD Broadband Statistics, http://www.oecd.org/sti/ict/broadband. © OECD, 2006.
3. Broadband
Technologies
7
Courtesy of CSTB. Used with permission.
Network Architecture
• Generic model of a broadband access network
• system architecture common across technology alternatives
• important differences in cost-performance and business models
IP packets
technology-specific
part of the system
may be shared
or switched
Web Servers,
etc.
Access Router/
Headend/Cache
Multiplexed
broadband pipe
w/ aggregated data
INTERNET
INTERNET
Subscriber
Interface Access
Medium
(copper, coax,
fiber, wireless)
IP packets
Consumer Equipment
(wired & wireless)
8
Courtesy of CSTB. Used with permission.
Wireline Options
• Hybrid fiber-coax
– DOCSIS
– Role of fiber (toward FTTC)
• Digital subscriber line (DSL)
– Distance, crosstalk
– Role of fiber (toward FTTC)
• Optical fiber
– Flavors of fiber to the home (FTTH)
– Service based on equipment at both ends
• Depends on what “kind of “ FTTH: not all the same
– High-performance endpoint—highest cost
• Powerline
9
Courtesy of CSTB. Used with permission.
DSL/Fiber Architecture
• Same architecture evolves naturally from ADSL to
VDSL to FTTC/FTTH
• switching equipment tends to migrate closer to subscribers
(..remote DSLAM, gigabit Ethernet switches, etc.)
• system deployment cost dominated by physical wiring, due to
rapid improvements in switching & transport cost/performance
Access Switch/
Router w/ caches
DSLAM or
Fiber Switch/
Concentrator
Subscriber
Interface
in-home
or curbside
10
fiber or
copper
pair
may be placed
in remote location
or central office
High-capacity fiber link
(ATM or IP/SONET, etc.)
to multiple
ISP’s
Courtesy of CSTB. Used with permission.
HFC Architecture
• Broadband access over cable based on shared
access (DOCSIS standard) to existing TV coax
• Medium access control (MAC) protocol for coax sharing
• Signal converted to analog fiber at remote node
• System cost dominated by fiber upgrade investments, due to
rapidly falling cost of DOCSIS modems & switching gear
• Also evolves naturally towards FTTC/FTTH
Aggregated
traffic
DOCSIS
protocols
Fiber
Node
IP Router &
cache
HFC Analog Fiber Link
data upstream
data downstream
Cable Modem
in-home
11
at remote
locations
shared
coax cable
TV
DOCSIS
head-end
to Internet
Courtesy of CSTB. Used with permission.
One Architecture for BPL
Tr
Backbone
network/
Internet
O/E
IPL-modem
Point-to-point
Link
Distribution Optical fiber
substation
networks
IPL LAN
LV networks
Customer
Wireless Options
• Mobile/3G
– Future: seamless mobile & portable broadband
– Reality: emerging 3G falling short of hype (capacity, speed..)
• WLAN
– 802.11, unlicensed 2.4 and 5 Ghz bands
– Bottom-up deployment is accelerating... (airports, offices, homes..)
• FWA (Fixed Wireless Access)
– MMDS, LMDS,...
– much potential, but uncertain business conditions ...
• Satellite
– Geo-synchronous (GEOS) & Low-earth orbit (LEOS)
– Viable for certain markets, but with capacity limitations...
13
Courtesy of CSTB. Used with permission.
Wireless Architecture
• Broadband wireless based on shared access of
radio medium (MMDS, LMDS, 3G, WLAN,..)
• MAC protocol for shared use of radio (..similar to cable modems)
• Switching or routing beyond access point (...similar to DSL)
• FWA, satellite, WLAN & 3G/mobile as potential options, each
with different entry cost and system cost/performance trade-offs
Fixed Wireless
or satellite
shared
wireless
medium Wireless
Access Point
Wireless
subscriber
Interface
WLAN
at remote
location
or CO
radio
“cell” for
spatial
reuse
Access Switch/
Router w/ caches
High-capacity fiber link
(ATM or IP/SONET, etc.)
to multiple
ISP’s
Mobile Wireless
(2.5G, 3G)
14
Courtesy of CSTB. Used with permission.
Local Access Techs in Context
• Total cost and performance depends on more than
just local access
• Local access aggregates traffic from multiple
premises at POPs, funnels to higher-capacity links
• “Second mile” connects to upstream aggregation
• Broadband providers pay for Internet transit service
or establish peering arrangements
• Caches, service-supporting servers at POPs
15
Courtesy of CSTB. Used with permission.
Unbundling DSL
To Interoffice Transport
Analog
Lines
IP
Gateway
POTS Customer
Router
Call
Server
...
DSLAM
DSL
Lines
ATM
Switch
DSLAM
IP-based Central Office
DSL Customer
Access to
unbundled
loop (“Full”
unbundling)
Figure by MIT OCW.
Access to
“bitstream”
After Fryxell, Sirbu, and Wanichkorn, 1999.
Sub-loop Unbundling
Copper wire
pairs
Laser
transmitter
and receiver
Central
Office
Fiber feeder
Remote
electronics
•
•
•
Remote
electronics
•
•
•
•
•
•
ADSL Spectrum Allocation
(Line Sharing)
Up stream channel
Bidirectional
PO TS
Dow nstream channel
10 KHz
50 KHz
1 MHz
Open Access and Layering
Layer:
Municipality provides…
0
Conduit and collocation facilities.
1 (Physical
Layer
Unbundling)
2 (Data Link
Layer
Unbundling)
3 (Network
Layer
Unbundling)
Dark fiber leasing, or perhaps, Optical
Layer unbundling (CWDM or DWDM
in PONs)
Dark fiber and link-layer electronics at
each end. For example, Ethernetbased VLAN, or ATM-based PVCs.
Basic network service provided. For
example, IP Layer 3 service over
cable using policy-based routing to
multiple ISPs
Regulatory Dilemma
Heisenberg’s Uncertainty Principle:
Can’t observe situation without perturbing it
Fundamental
Economics
Regulatory
Outcome
Assumption About
Competition
Competition is
sustainable
(competitive
equilibrium
exists)
Sustainable
Free market
Not sustainable
Regulation stifles
innovation, competition
Competition is
not sustainable
(no competitive
equilibrium)
Sustainable
Government-sanctioned,
unregulated monopoly
Not sustainable
Necessarily regulated
monopoly
Additional Tech Slides
Internet Access via Cable
TV channels
Headend
Data (LAN) channel
IP router
Data (LAN) channel
RF Modem
Translator
Rest of Internet
Converter
RF Modem
Translator
Converter
Local Loop
Telephone
Network
Hierarchy
Twisted-pair copper
loops dedicated to
individual subscribers
• Physical aggregation
at “Central Office” (CO)
via Main Distribution
Frame
• CO Switching: Access
• IXC Switching:
Tandem
• Increasing aggregation
at each level
Local Loop
"CITY"
•
•
•
LEC
switching
office
LEC
switching
office
inter-office transmission
LEC = Local
Exchange
Carrier (local
telephone
company)
•
•
•
IXC = IntereXchange
Carrier (long
distance
company)
Inter-exchange ("long distance") network
IXC
switch
IXC
switch
Local Loop
Local Loop
"CITY"
•
•
•
LEC
switching
office
inter-office transmission
LEC
switching
office
•
•
•
Multiplexing and
Concentration in CO Switch
600
subscriber
lines
••
TDM
600 subscribers
(DS-3)
•
•
•
8:1
concentration
600 trunks
port
(5000 subscribers)
•
•
•
•
20-port
• switch
fabric
•
port
Telephone
Access Network
Splices represented by
Distribution cable
Distribution cable
Drop
Drop
Drop
Drop
• Feeder
• Distribution
• Drop
• Aggregation is physical:
bundles of wire-pairs
Feeder cables
Junction
Box
Drop
Junction
Box
Drop
Drop
Distribution cable
Drop
Distribution cable
toward
Central
Office
Internet over ADSL
(with VoIP)
To Interoffice Transport
Analog
Lines
IP
Gateway
POTS Customer
Router
Call
Server
...
DSLAM
DSL
Lines
ATM
Switch
DSLAM
IP-based Central Office
DSL Customer
Access to
unbundled
loop (“Full”
unbundling)
Access to
“bitstream”
Figure by MIT OCW.
After Fryxell, Sirbu, and Wanichkorn, 1999.
Telco migration to
Fiber-to-the-Neighborhood
Copper wire
pairs
Laser
transmitter
and receiver
Central
Office
Fiber feeder
Remote
electronics
•
•
•
Remote
electronics
•
•
•
•
•
•