Embed Size (px)
Citation preview
1
xDSL
2
Network reference model
Corenetwork
Accessnetwork
Transportexchange
TPcablefiberWLL
Network provider
Access provider
Serviceprovider
CustomerPremisesNetwork
3
Evolution of Access Network
Evolution based on Twisted Pairs(TP) Evolution based on optical fiber Evolution based on wireless network
4
국내 초고속 가입자 현황 xDSL HFC APT LAN 위성 합계KT 4,625,841 498,306 5,632 5,129,782하나로 통신 1,184,629 1,359,675 386,951 2,931,255두루넷 1,284,963 8,543 1,293,506온세통신 482,172 6,967 489,139드림라인 73,075 87,554 3,663 164,192데이콤 69,630 74,653 144,283부가통신사업자 4,836 363,632 4,388 372,856별정통신사업자 49,205 124,854 174,059합계 5,937,586 3,647,626 1,108,328 5,632 10,699,172점유율 (%) 55.50 34.09 10.36 0.05 100
2003 년 2 월말 자료 : 한국전산원
5
DSL 기술의 배경 One way to avoid enormous investment for
installing optical fiber local loop is to use the traditional copper local loop.
The twisted local loop is actually capable of handling bandwidths up to 1.1 MHz, but the filter installed at the end of the line by the telephone company limits the bandwidth to 4KHz. If the filter is removed, however, the entire 1.1 MHz is available for data and voice communications.
Thus, DSL technology provides higher data rate in addition to support POTS at the same time.
6
Various xDSL(1)
ISDN 2B+D 23B+D
HDSL(High data rate Digital Subscriber Line) ADSL(Asymmetric Digital Subscriber Line) SDSL(Symmetric Digital Subscriber Line) VDSL(Very high data rate Digital Subscriber
Line) RADSL, MDSL, IDSL, UADSL
7
Various xDSL(2)
ADSL2 ADSL2+ VDSL2
8
Characteristics of major xDSL
CentralOffice
(PSTN)
CentralOffice
(PSTN)CO
RepeaterCO
RepeaterLine
RepeaterLine
RepeaterLine
RepeaterLine
Repeater
EndUser
(POTS)
CentralOffice
(PSTN)
CentralOffice
(PSTN)HDSL
CO UnitHDSL
CO UnitHDSL
RT UnitHDSL
RT Unit
EndUser
(POTS)
Headend(Video)
Headend(Video) ADSL
CO UnitADSL
CO UnitADSL
RT UnitADSL
RT Unit
EndUser
(Video)
PSTN POTS
Headend(Video)
Headend(Video)
OpticalNetwork
Unit
OpticalNetwork
Unit VDSLRT UnitVDSL
RT Unit
EndUser
(Video)
POTS
VDSLCO UnitVDSL
CO Unit
PSTN
T1/E1
HDSL
ADSL/SDSL
VDSL
0.3~1km
TP(2 pairs)
1~1.8km 0.3~1km
TP(2 pairs)
TP(1 pair)
TP(1 pair)
9
HDSL
T1/E1 rate with 2 TP pairs Internet access, LAN service
Mainly used for leased line service for business customers
Covers 3.5km(12kf) using 196KHz bandwidth without any repeaterLess expensive than the standard T1/E1
leased line service dual duplex: two transceiver 2B1Q Modulation
10
SDSL
T1/E1 rate with single pair Data rate; 160kbps-
2.048Mbps(symmetrical) Distance: less than 3km 2B1Q
11
ADSL
Asymmetric bi-directional digital subscriber line Data rate:1.5- 8 Mbps (downstream), 16-640
kbps (upstream) depending on distance and line quality
Distance is up to 5.5km(18kft) DMT(G.992.1, G.992.2)
ADSLRT UnitADSL
RT Unit
EndUser
PSTNPOTS
TP 1pair
1.5 ~ 8 Mbps
16 ~ 640kbps
HeadendADSL
COUnit
12
Frequency Bandwidth
Since data transmission is done on the frequency between 30KHz and 1MHz, ADSL provides data services as well as POTS at the same time.
0.3 3.3 30 138 1104
POTS upstream downstream
frequency (KHz)
13
ADSL Modem and DSLAM
14
Line coding Discrete Multitone(DMT)
ITU standard(G.992.1, G.992.2) Combines QAM and FDM. The whole bandwidth is divided into 256 channels. For upstream data and control the channel 6 to 30
are used, each using 4KHz. With QAM modulation, available bandwidth is 24x4
000x15 = 1.44Mbps. For down stream, channels 31 to 255 are used, an
d we can achieve up to 224x4000x15=13.4Mbps
15
DMT
16
Bandwidth Division
17
ADSL2
Data rate: 8Mbps(down), 800kb/s(up) Improve ADSL for stability rather than
speed. Improved initialization On-line reconfiguration Framing
DMT(G.992.3, G.992.4)
18
ADSL2+
Improve the downstream data rate of ADSL. Bandwidth for downstream data transmission:
2MHz downstream data rate
16Mb/s, 1.2km 10Mb/s, 1.8km 7Mb/s, 2.5km
Upstream, 1.5Mb/s DMT(G.992.5) However, there is little or no improvement of
speed for loops beyond 2.5km.
19
VDSL
Very high data rate digital subscriber line Because of distance limitation, fiber cable should be installed
up to the curb, and from there twisted pair lines are used up to subscribers.
Depending on distances, up to 13-52Mbps(down), 1.5-2.3Mbps(up)
Bandwidth: 10MHz VDSL line coding standards
ANSI: DMT IEEE: DMT (EFM-Cu for short-reach) ETSI: DMT/QAM ITU-T G.993.1
Because VDSL is used for short distance, there are many technical issued such as crosstalk to be solved.
20
xDSL ComparisonData rate types
TP POTS
IDSL 128kbps ~5.5km 1 X
SDSL 768kbps ~3.5km 1 X
MDSL 64~2,048kbps ~6km 1 X
HDSL 1.544Mbps(T1)2.048Mbps(E1) ~3.5km 2 X
RADSL 128k~1Mbps 128k~8Mbps ~5.5km 1 O
UADSL 128~512kbps 128k~1.5Mbps ~6km 1 O
VDSL 640~2.3Mbps 13~52Mbps ~1.4km 1 O
up downdistance
21
New ADSL
0.5 2 3 4 5 6 71 km거리
50Mb/s
10Mb/s
6Mb/s
1Mb/s
VDSL
ADSL2+
ADSL
ADSL2+
VDSL2
22
VDSL2
Adopts ADSL ‘s new features Backward compatibility to ADSL family Possible new features
Frequency beyond 12MHz 100Mb/s at 1km Etc.
23
Migration Strategy
Copper Loop
DLC
FTTC
FTTH
Wire Plant Neighborhood Curb Premises
DSLAM DSLAM
up to 8Mbps
up to 8Mbps
up to 52Mbps
155Mbps and beyond
DLCDLC
ONUONU
DSL TerminologyDSL Terminology
xDSL = Physical layer technologies allowing transport of digital information over the copper loop.
xDSL = Physical layer technologies allowing transport of digital information over the copper loop.
xDSL = x Digital Subscriber Line
ADSL = Asymmetric Digital Subscriber Line
RADSL = Rate-Adaptive Digital Subscriber Line
UAWG = Universal ADSL Working Group (universal ADSL, ADSL Lite,
G.Lite, splitterless ADSL)
SDSL = Symmetric Digital Subscriber Line
HDSL = High Bit-Rate Digital Subscriber Line
HDSL2 = High Bit-Rate Digital Subscriber Line, 2nd generation
SHDSL = Single-pair High Bit-Rate Digital Subscriber Line
IDSL = ISDN Digital Subscriber Line
VDSL = Very High-Speed Digital Subscriber Line
DSLAM = Digital Subscriber Line Access Multiplexer
25
HFC(Hybrid fiber-coaxial)
26
HFC Overview HFC networks use a hybrid of fiber optic and coaxial cable to
make the cable network bidirectional (two-way). The use of fiber-optic cable reduces the need for amplifiers down to 8 or less.
Coaxial network has a tree & branch structure. An area served by a SO is divided into several cells. The size of a cell is decided by the number of subscribers.
Head end ONU
splitter
Cablemodem PC
Set topbox TV
27
HFC 망
Distribution center(SO)PP
ISP
Outdoor optical RTX(ONU)
TBAsplitter
Tap-off
Cell 1
Cell N
Coaxial cable
CMTS CM
broadcastH/E
CM: cable modemCMTS: cable model termination systemTBA: trunk bridge amplifier
Optical R
TX
Power supply
PP: program providerSO: system operator
28
Components
ONU(Optical Network Unit) Transforms between optical signals and RF signals in a cell.
TBA Guarantee the loss of line signal of coaxial cables.
Splitter Split one RF signal into more than two RF signals.
Tap-off It distributes equally RF signal into subscriber terminals.
29
Frequency bandwidth
The downstream data occupies 450-552MHz band. This band is divided into 6MHz.
The upstream data occupies 5-42MHz band, which is also divided into 6MHz channels. The 5-42MHz frequency band for upstream is very susceptible to
noises by consumer electronics devices and signals caused by HAM, CB radios.
For this reason, The low bit rate modulation technique such as QPSK is used for stability.
upstreamAnalog
broadcastInternet
Digital broadcastValue added services
5 42 54 450 552 750 MHz
30
Data rates
Data rates depending on modulation techniques of DOCSIS modems
upstream Downstream
bandwidth 1.5MHz 6MHz
modulation
Data rate
QPSK 16QAM 64QAM 256QAM
2.5Mbps 5Mbps 27Mbps 40Mbps
31
Characteristics
One cell serves up to 500-2500 subscribers. Bidirectional transmission Limitation of data rate
When 100 subscribers use at the same time, data rate is reduced to less than 300kbps(downstream).
Because of tree & branch structure, the transmission quality is deteriorated by signal interruption.
32
국내 HFC 망 연혁 1995 년 종합유선방송 ( 케이블 TV) 사업 개시
PP(Program provider): 프로그램 공급자 SO(System operator): 지역 방송국
• 광역시 , 대도시 1 차 53 개 지역• 지역 중소 도시 2 차 24 개 지역• 중계유선 3 차
NO(Network operator):• 케이블 TV 분배망 (PP-SO): 파워콤 , KT( 위성 )• 케이블 TV 전송망 (SO- 가입자 ): 파워콤 , SO 의 HFC 망
케이블 모뎀을 통한 인터넷 사업 시작 1997 년 KEPCO 양방향 시버 서비스 성공 1998 년말 두루넷 (KEPCO 의 HFC 망 사용 ) 사업 시작 1999 년 하나로 , 2000 년 온세 통신 등 다수 사업자 참여
• HFC 망 : KEPCO 1 차 지역 , 데이터 HFC 망 구축 2000-2002 년 초고속 가입자 사업 활성화
KT 시설분 SO 매각 , 중계유선의 SO 전환 파워콤 분리 인터넷 가입자 증가로 데이터 HFC 망 시설 폭증 ( 하나로 , 두루넷 , SO 등 HFC 자가망
구축 ) 2003 년 디지털 케이블 TV 도입 개시
자료 : 파워콤㈜ KRNET2004 발표자료
33
국내 인터넷 가입자 현황 전체 가입자 증가와 마찬가지로 현재 완만한 증가 추세로
인터넷 가입자의 포화 상태에 이르렀음을 알 수 있다 .
전체가입자
HFC 망가입자
2000.12 2001.2 2002.12 2003.12 2004.4
자료 : 파워콤㈜ KRNET2004 발표자료
398 만
139 만780 만
262 만
1,040 만 1,118 만 1,143 만
355 만 383 만 402 만
34
Standards CableLabs, DAVIC, IEEE 802.14, ATM Forum, IETF 의 IP over Cabl
e Data Network CableLabs(Cable Television Laboratories Inc.)
Non profit organization composed of cable modem manufacturers. CableLabs standards are adapted by ANSI, ITU-T Also performs certificates. DOCSIS(Data Over Cable Service Interface Spec.)
• DOCSIS 1.0(1999):• DOCSIS 1.1: • DOCSIS 2.0(2001):
Digital settop box standards: Opencable• Cable Network Interface Standard(SCTE40/DVS313)
35
DOCSIS cable modem
DOCSIS 1.0(1999 년 ) First commercialized standards Bidirectional data transmission
DOCSIS 1.1(2001 년 ) Improve OoS functions DOCSIS 1.0 can be upgraded to DOCSIS by software.
DOCSIS 2.0(2002 년 ) Improve upstream data rate: 30Mbps Symmetrical bidirectional service H/W upgrade
36
HFC MAC
Credit-based MAC For upstream transmission, the headend grants the
right to send data to cable modems. CRA(Collision Resolution Algorithm)
• When cable modems send credit requests collision may happen, When it happens, the headend detects the collision, and notifies cable modems of it. Then the cable modems backoff and retry after random intervals.
37
Future
Speed improvement Frequency bandwidth can be expanded upto 1.5Gb
ps, the speed can be increased upto 100Mb/s. Downsizing of cells
The current distance from ONU to subscribers which is about 1km will be decreased to less than 500m.
Improve network monitoring system.
38
SDH (SONET)
39
Multiplexing of Telephone Lines
40
Multiplexing of Digital Signals
41
Table 6.1 DS and T lines ratesTable 6.1 DS and T lines rates
Service LineRate
(Mbps)Voice Channels
DS-1DS-1 T-1T-1 1.5441.544 2424
DS-2DS-2 T-2T-2 6.3126.312 9696
DS-3DS-3 T-3T-3 44.73644.736 672672
DS-4DS-4 T-4T-4 274.176274.176 40324032
Digital Hierarchy
42
Table 6.2 E line ratesTable 6.2 E line rates
E LineRate
(Mbps)Voice
Channels
E-1E-1 2.0482.048 3030
E-2E-2 8.4488.448 120120
E-3E-3 34.36834.368 480480
E-4E-4 139.264139.264 19201920
Digital Hierarchy (Europe)
43
Synchronous Digital Hierarchy(SDH)
PDH
DS-0 0.064 1DS-1 T-1 1.544 24DS-2 T-2 6.312 96DS-3 T-3 44.736 672DS-4 T-4 274.176 4032
SDH
STM-1 OC-3 155.52STM-4 OC-12 622.08STM-16 OC-48 2488.32STM-48 OC-192 9953.28
44
Synchronous Digital Hierarchy(SONET)
STS OC Rate (Mbps) SPE (Mbps) User (Mbps)
STS-1STS-1 OC-1 51.84 50.12 49.536
STS-3STS-3 OC-3 155.52 150.336 148.608
STS-9STS-9 OC-9 466.56 451.008 445.824
STS-12STS-12 OC-12 622.08 601.344 594.432
STS-18STS-18 OC-18 933.12 902.016 891.648
STS-24STS-24 OC-24 1244.16 1202.688 1188.864
STS-36STS-36 OC-36 1866.23 1804.032 1783.296
STS-48STS-48 OC-48 2488.32 2405.376 2377.728
STS-192STS-192 OC-192 9953.28 9621.604 9510.912
45
SONET transport network
46
2.5Gbps(POS)
GSRGES
동선
FLC STM-4 (2.5G)
EdgeRouter(7500)
ADM DSC(D/MUX)
FLC
DSC(D/MUX)
ADM
CSU
OC3
OC3/OC12
Internet
MTU
STU
ADSL (1.5M~8Mbps)DSLAM
B-RAS
DS3/OC3
DS3/OC3
CO( 수용국 )
POP( 주노드국 )
수용국
수용국
ADM
ADM
LAN C
LAN A
LAN B
SONET/SDH
T1
T1
CSU
LAN D
T1 1.544 Mbps
T1 (1.544Mbps)
64Kbps
28
STS-1(45M)
STS-N…
OC-N
…
24
11
1.544Mbps
…
STS-1
64Kbps
28
STS-1
STS-N …
…
24
11
1.544Mbps
…
STS-1
TDM multiplexing/Circuit switchingNo Statistical multiplexing
T1 1.544 Mbps
T1 1.544 Mbps T1 1.544 Mbps
Home
TDM-based transport network
47
SONET frame
