pdh & sdh presentation
TRANSCRIPT
WELCOME TO TRAINING ON PDH &SDH TECHNOLOGY
USEDIN OPTICAL TRANSMISSION
Presented By: A.K. RAI
DM (OPT)
TOPIC COVERED ON SDH
• PDH INTRODUCTION• SDH FUNDAMENTAL• NEXT GEN SDH
Position of Transmission Eqpt. in Telecom NW
Transmission Eqpt.Switching Equpt Switching Equpt
Access NW Access NW
SubscribersSubscribers
TELECOM NETWORK
Different Transmission Media• Twisted pair• Coaxial cable• Wireless transmission.• Optical fiber
Why optical fiber transmission ?
• Large transmission capacity, • Good quality • Small attenuation.• Strict security.• Large trunk distance.
Advantages of Optical Transmission
– Large bandwidth permits high data transmission, which also supports the aggregation of voice, video, and data
– Technological improvements are occurring rapidly, often permitting increased capacity over existing optical fiber
Advantages of Optical Transmission
– Immunity to electromagnetic interference reduces bit error rate and eliminates the need for shielding within or outside a building
– Glass fiber has low attenuation, which permits extended cable transmission distance
Advantages of Optical Transmission
– Light as a transmission medium provides the ability for the use of optical fiber in dangerous environments
– Optical fiber is difficult to tap, thus providing a higher degree of security than possible with copper wire
– Light weight and small diameter of fiber permit high capacity through existing conduits
History of Digital Transmission• ’’70s - introduction of PCM into Telecom 70s - introduction of PCM into Telecom
networksnetworks• 32 PCM streams are Synchronously 32 PCM streams are Synchronously
Multiplexed to Multiplexed to 2.048 Mbit/s (E1)2.048 Mbit/s (E1)• Multiplexing to higher rates via PDHMultiplexing to higher rates via PDH• 1985 Bellcore proposes SONET1985 Bellcore proposes SONET• 1988 SDH standard introduced1988 SDH standard introduced• 1990’s DWDM introduced1990’s DWDM introduced
PULSE CODE MODULATION• The input signal is sampled prior to digitisation and an approximation to
the input is reconstructed by the digital-to-analogue converter:
Sampling Digitisation code, modulate
Transmission•Wire/optical fibre•Aerial/free-space
input
FilteringDigital-to-analogue
conversionDemodulate, Decode
output
Nyquist’s Sampling theorem
For a signal of bandwidth B Hz, the minimum sampling rate is 2B samples/s
• In the telephone system the speech signal has a bandwidth up to 3.4 kHz and a sampling rate of 8 kHz,
The 32-channel PCM Transmission system• 30 speech signals plus two control channels
for signalling and synchronising: – Signal bandwidth 3.4 kHz– Sampling rate 8 kHz (8000samples/sec)
• Hence frame length 1/8000 sec or 125s– Sample size 8 bits/sample
• Hence bit rate from each signal 8*8000=64 kbit/s– 32 channels
• Hence each time slot 3.906 s– 1/(8000*32)
– Overall data rate 2.048 Mbit/s• 32*64 kbit/s =2048 kbit/s or 2.048 Mbit/s
E1 format for 32 CH PCM
• TS 0 is used for synchronization & alarm transport• TS 16 is used for channel associated signalling( CAS)
information & multi frame alignment word (MFA) • 30 Channel for voice
ITU-T G.704 (32 Time Slots)
10 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1716 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Omniplexer - 30 Channel Assignments
1- 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16- 17 18 19 20 21 22 23 24 25 26 27 28 29 30
HIGHER ORDER DIGITAL MULTIPLEXING TECHNOLOGY
• Plesiochronous Digital Hierarchy (PDH) • Synchronous Digital Hierarchy (SDH)
PDH MULTIPLEXING
• Plesiochronous means non synchronous.• Multiplexing of 2 Mbit/s to 140 Mbit/s requires two intermediate multiplexing stages of 8 Mbit/s and 34
Mbit/s.• The multiplexing of several tributaries can be achieved by Bit by bit multiplexing (bit interleaving)• There are four bit streams to be multiplexed. One bit is
sequentially taken from each tributary so that the resulting multiplexed bit stream has every fifth bit coming from the same tributary.
PDH features
• Bit interleaving is used for North American and European PDH system. A typical 8.448 Mb/s plesichronous multiplexer has four primary (E1) MUX, each having an out put of 2.048 Mb/s, bit interleaved to form the next level in hierarchy.
• Note that this output rate of 8.448 Mb/s is not exactly four times the tributary bit rate of 2.048Mb/s. This is a result of the non-sychronous nature of the system.
PDH Features
• Every tributary has its own clock. Every tributary is timed with plesiochronous frequency, that is a nominal frequency about which the shifts around it within prefixed limits. For example, the primary multiplexer output is 2.048 Mb/s +- 50ppm.
• To account for the small variations of the tributaries frequencies about the nominal value when multiplexing four tributaries to the next hierarchy level, a process known as positive stuffing (also known as positive justification) is used.
Positive Pulse stuffing or justification
• Pulse stuffing involves intentionally making the output bit rate of a channel higher than the input rate. The output channel therefore contains all the input data plus a variable number of “stuffed bits’ that are not part of the incoming subscriber information.
• The stuffed bits are inserted at the specific locations, to pad the input bit stream to the higher output bit rate. This stuffed bits must be identified at the receiving end so that “de-stuffing” can be done to recover the original bit stream.
Positive Pulse stuffing or justification
• Pulse stuffing is used for higher order multiplexing when each of the incoming lower order tributary signal is unsynchronized, and therefore bears no prefix phase relationship to any of the other.
PDH Multiplexers
Notation Data Rate No. of ch.
E4 139264 Kbps 1920
E3 34368 Kbps 480
E2 8448 Kbps 120
E1 2048 Kbps 30
E0 64 Kbps 1
PDH Bit Rates (European Standard)
Notation Data Rate
T4/DS4 139264 Kbps
T3/DS3 44736 Kbps
T2/DS2 6312 Kbps
T1/DS1 1544 Kbps
T0/DS0 64 Kbps
PDH Bit Rates (American Standard)
PDH Multiplexers
Multiplexer Stages
30 ch2.048 Mb/s
120 ch8.44Mb/s
480 ch34.368
Mb/s
1920 ch139.264
Mb/s
7680 ch564.992Mbit/s
64 kbits/s
x30x4
x4x4
x4
Europe
A typical Plesiochronous Drop and Insert
PDH Equipments in Telecom. Network
2/140 OPTIMUXPDH Equip.
B
2/140 OPTIMUXPDH Equip.
A
2/140 OPTIMUXPDH Equip
B’.
2/140 OPTIMUXPDH Equip.
C
SwitchingEquip.
A
SwitchingEquip.
B
SwitchingEquip.
C
2Mb/s Trib. 1- 64 Add
2Mb/s
1 – 32
Drop
34Mb/s
2Mb/s 1’-32’ Add
2Mb/s 33-64 & 1’-32’ Drop
Tel. Subscribers
Tel. Subscribers Tel. Subscribers
SDH Equipments in Telecom. Network
STM-1/ 4/16Equip. B
STM-1/ 4/16Equip. A
STM-1/ 4/16Equip. C
SwitchingEquip.
A
SwitchingEquip.
B
SwitchingEquip.
C
Tel. Subscribers
Tel. Subscribers
2Mb/s Tribs ADD/DROP
2Mb/s Tribs ADD/DROP 2Mb/s Tribs ADD/DROP
Tel. Subscribers
SDH Equip. in Ring
NMS
Master Clock (2MHz.)
Comparison Of SDH & PDH Technology
For SDH, tributaries & data are mapped/de mapped to VC-4 container directly and have its own identity.
• For PDH , tributaries are mux. /de-mux. in steps and have no identity.
• Synchronous Digital Multiplexers have tributaries with the same clock frequency, and they are all synchronized to a master clock.
• Plesiochronous Digital Multiplexers (non synchronous) have tributaries that have the same nominal frequency (that means there can be small difference from one to another), but they are not synchronized to each other.
• For synchronous case, the pulses in each tributary all rise and fall during the same time interval.
• For the PDH, the rise and fall time of the pulses in each tributaries do not coincide with each other.
Disadvantage of PDH System
• Inability to identify individual channels in a higher-order bit stream;
• Insufficient capacity for network management; • Non compatibility between different vendors.• No worldwide standard optical interface specification.• Restricted to point-to-point transmission.• Can’t sustain high bit rate multiplexing (Above
140Mb/s)• Impossible to extract base-band signal in between
without complete De multiplexing the aggregate• restoration time is several seconds to minutes
Advantage of SDH System• Simple multiplexing processes• Easy access to various signals in a multiplexed high
bit rate signal• Standardized interface can support multi vendor inter
working, international connection and many different services; i.e. Voice , Ethernet, video, ATM, IP
• Support advance Network Management System (OAM&P) – Overhead bits for Fault, Configuration, Performance Monitoring, Security and Accounting management
Advantage of SDH System
• Service restoration time is less than 50 ms• A flexible and efficient way of networking
– Network Distribution: Add/Drop capability– Network survivability: APS (Automatic Protection
Switching)– Traffic Cross connection: capacity management,
bandwidth management and protection route diversity
SDH Frame Format
STM-N
SectionOverhead
MSOHRSOH
AdministrativeUnit
PathOverhead
PointerVirtual
Container
Container
Mapping Elements
• Container• Virtual Container• Tributary Unit• Tributary Unit Group• Administrative Unit• Administrative Unit Group
Mapping Elements
• The Container (C ) Basic packaging unit for tributary signal ( PDH )
Alignment
Clock
Line Input
PDH Circuit
Mapping Elements
• The Virtual Container ( VC ) Formation of the container by adding of a POH ( Path Overhead )
• The Tributary Unit ( TU ) Is formed via adding a pointer to the VC• The Tributary Unit Group ( TUG ) Combines several TUs to formed a new VC
Mapping Elements
• The Administrative Unit ( AU ) Is shaped if a pointer is allocated to the VC formed at last• The Synchronous Transport Module ( STM-N) Formed by adding a section overhead ( SOH ) TO AUs
SDH Hierarchy
STM-16 AU-4-16c C-4-16cVC-4-16c
E1: 2.048Mb/s
E4: 139.264Mb/s
STM-4
STM-1
AU-4-4c
AU-4
AU-3
VC-4-4c
VC-4
C-4-4c
C-4
C-3
C-2
C-12
C-11
VC-3
VC-2
VC-12
VC-11
TUG-3
TUG-2
DS1:1.544Mb/s
E3: 34.368Mb/sDS3: 44.736Mb/s
DS2:6.312 Mb/s
VC-3
TU-3
TU-11
TU-12
TU-2
x4
x3
x1
x7x7
x3x3
564.992Mb/s
2259.968Mb/s
VC-n
AU-n
AUG
STM-n Synchronous Transport Module
Administrative Unit Group: One or more AU(s)
Administrative Unit: VC + pointers
Virtual Container: payload + path overhead
STM-64 AU-4-64c VC-4-64c C-4-64c
AUG
x16
x4
x4x64
x16
x4
9039.872Mb/s
Containers of Base Signal (Low Order Payloads)
High Order Payloads
Frame Structures
*270 Columns
9 Rows
9 Rows
9 Rows
1,080 (270*4 )Columns
4,320 (270*16) Columns
STM-1
155.52 Mbit/s
STM-4
STM-16
622.08 Mbit/s
2488.32 Mbit/s
270 columns x 9 rows = 2430 bytes2430X8byte=19440bits8000 fps x 19440 bits = 155.52 Mbit/s
4 x 155.52 Mbit/s = 622.08 Mbit/s
International organization defined standardized bit rates :
155.520 Mbit/s STM-1 63E1 1890 Ch
622.080 Mbit/s STM-4 252E1 7560 Ch
2.488 Gbit/s STM-16 1008E1 30240Ch
9.953 Gbit/s STM-64 4032E1 120960Ch.
39.81312 Gbit/s STM-256 16128E1 483840Ch
Synchronous Digital Hierarchy (SDH)
Overhead Layer Concepts
path
path termination
pathtermination
service (E1, E4..)mapping demapping
service (E1, E4..)mapping demapping
PTE PTE
multiplex section multiplex section
multipl. section termination
ADMor
DCS
regeneratorsection
regen. section termination
regen. sectiontermination
REG REG
PTE = path terminating elementMUX = terminal multiplexerREG = regeneratorADM = add/drop multiplexerDCS = digital cross-connect system
regen.section
regen.section
regeneratorsection
SDH Frame
SDH Over Head
SDH Overhead
RSOH bytes
• A1, A2 Frame alignment• J0 Reg Trace byte• Z0 Spare byte• B1 Reg Monitoring• E1 Reg EOW• F1 Data Channel• D1-D3 64kbps X 3=192kbps Management
Channel
Regenerator Section– Regeneration section layer is the lowest level of link
components in a SDH network– Deals with the transport of an STM-N frame across
the physical medium– Point-to-point connection between two regeneration
section termination points with direct optical or electrical domain connectivity
– Terminated by Regenerator Section Terminating Equipment (RSTE)
– The Regeneration section is mainly designed to overcome physical limitations of the transport technology
Pointer
• H1, H2, H3 Pointers
– Pointers were included into SDH design to provide tools to compensate for incoming payload phase differences
• It avoids delay and jitter in payload
MSOH
• B2 MSOH error monitoring• K1, K2 APS function• D4-D12 576 data communication channel• S1 syncronization status• M1 MSOH remote monitoring• E2 EOW channel
Multiplex Section– One or more consecutive regenerator sections might
compose a multiplex section• Main element to build different topologies (e.g. ring)
– Deals with the transport of path layer payloads across the physical medium
– Multiplex section is a point-to-point logical link that connects to ADM, MUX, or DCS devices
• These devices might not include a path termination– Overhead is interpreted and modified by Multiplex
Section Terminating Equipment (MSTE)• Multiplex section (MS) overhead is accessed only after the
section overhead has been first terminated
Path Over Head (POH )• J1 trace byte• B3 Error monitoring• C2 Path signal label of container• G1 Higher order alarm status• F2 data channel• H4 pointer indicator• F3 user channel• K3 APS status• N1 TCM byte
Path Over Head (POH )• J1 trace byte• B3 Error monitoring• C2 Path signal label of container• G1 Higher order alarm status• F2 data channel• H4 pointer indicator• F3 user channel• K3 APS status• N1 TCM byte
POH– One or more connected multiplex sections may provide
a transport service for a path• Multiplex section may carry multiple paths by multiplexing
– Deals with the transport of various payloads between SDH terminal multiplexing equipment
– Path layer maps payloads into the format required by the MS Layer
– Communicates end-to-end via the Path Overhead (POH)
– POH is terminated and modified by Path Terminating Equipment (PTE)
• Regenerator and multiplex section overhead must be terminated to access the overhead
SDH TOPOLOGY• Point-to-point
– Used for SDH island trunks in old asynchronous networks, or data services as POS or ATM links
– Linear point-to-multipoint• Adds up ADM in the middle• Max. 16 nodes
– Hub network• A DCS interconnects ADMs
– Ring• ADMs are put into a ring• Redundant, multiple connected rings
– Automatic protection switching (APS)
USHR
Add and Drop Example– STM-4 Ring– 4 x STM-1 channels– Uni-directional routing– Provisioning:
• add 1-3 (drop 3-1)• add 3-4 (drop 4-3)• add 4-2 (drop 2-4)
– 2 channels occupiedADM
2
ADM3
ADM1
ADM4
OC-12
Drop
Add 1-3
Add 3-4
Drop
Add 4-2
Drop
• Network Protection
1:1 protection
– 1:1 protection (special case of 1:n)• Bi- or unidirectional• Revertive• Typically dedicated protection• May transmit traffic on both channels, or use protect for
low priority traffic
Protection facility
Working facility
ADM/Router ADM/Router
1:n protection
– 1:n protection• Bi- or unidirectional• Revertive• Shared protection facility
Protection facilityADM/Router ADM/Router
A
CE
BF
D
Loops
Fiber cut
WorkingTraffic
STM-1#10 into STM-1#4
STM-1#10 into STM-1#4
STM-1#4 into STM-1#10
•No dedicated protection bandwidth - only used when protection required•Only nodes next to the failure know
about the protection switch•No traffic lost
Shared protection
*
Next Generation SDHNext Generation SDHTechnologyTechnology
SDH/SONET/OTN
SDH
MU
X/D
EM
UX
Nat
ive
Inte
rfac
es
New SDH
?VCVirtual
Concatenation
LCASLink
Capacity Adjustment
Scheme
GFPGeneric Frame
Procedure
Ethernet
Ficon
Escon
Fibre Channel
Edge CoreAdaptation
Customer Operator
GFP
GFP - Client Specific Aspects (payload dependent)
GFP - Common Aspects (payload independent)
SDH/SONET VC-n Path
OTN ODUk Path
Others(e.g. Fibre)
Ethernet IP/PPP Fibre Channel OthersClients
GFP
Transport
Frame Mapped Transparent Mapped
ESCON
Making SDH efficient through Virtual Concatenation (VC)
VC- 3VC- 3
VC- 4
VC-4-4cVC-4-4c
VC-4-16cVC-4-16c
SDH
92%98%
100%100%100%100%89%95%
EthernetATM
ESCON
Fibre Channel
Fast Ethernet
Gigabit Ethernet
data
10 Mbit/s25 Mbit/s
200 Mbit/s400 Mbit/s800 Mbit/s
100 Mbit/s
1 Gbit/s
efficiency
100M Ethernet STM-1= 64 x VC-12
VC-12-5v
VC-12-46v
2x 10M Ethernet VC-12-5v
8x E1 Services
Example:
More services integrated- by using VC!
VC-12-5vVC-12-12vVC-12-46v
VC-3-2vVC-3-4vVC-3-8vVC-4-6vVC-4-7v
NewSDH
20%50%
66%
33%66%26%42%
efficiency
SDH Line Rates
10 M
Transport 10M Ethernet over SDH?
C-4-4c 0.599 Gbit/sC-4-16c 2.396 Gbit/sC-4-64c 9.584 Gbit/sC-4-256c 38.338 Gbit/s
Contiguous ConcatenationContiguous Concatenationonly large containers!
C-11 1.600 Mbit/sC-12 2.176 Mbit/sC-2 6.784 Mbit/sC-3 48.384 Mbit/sC-4 149.760 Mbit/s
SDH Payload Sizes
Standard Containers are inefficient!
Concatenate 5 x VC-12!
!5x
Contiguous Concatenation
Offers concatenated payloads in fixed, large steps
One towing truck (POH) for all containers
All containers are on one path thru the network
VC-4-4c
C4 C4 C4 C4
Virtual Concatenation
Offers structures in a fine granularity Every container has its own towing truck
(POH) Every container might take a different
path
VC-4-4v
VC-4 #1VC-4 #2VC-4 #3VC-4 #4
AU-4 Pointers
MSOH
RSOH
VC-4-5 VC-4-6 VC-4-7 VC-4-8
VC-4-9 VC-4-10 VC-4-11 VC-4-12
VC-4-13 VC-4-14 VC-4-15 VC-4-16
VC-4-1 VC-4-2 VC-4-3 VC-4-4STM-16
ContiguousConcatenation
VC-4-4c
AU-4 Pointers
MSOH
RSOH VC-4-1 VC-4-2 VC-4-3 VC-4-4
VC-4-5 VC-4-6 VC-4-7 VC-4-8
VC-4-9 VC-4-10 VC-4-11 VC-4-12
VC-4-13 VC-4-14 VC-4-15 VC-4-16
The block has to start at defined positions in the payloadThe block consists of consecutive VC-4-nsThere is only one pointer
STM-16
VirtualConcatenation
VC-4-7v
AU-4 Pointers
MSOH
RSOH
VC-4-5 VC-4-6 VC-4-7 VC-4-8
VC-4-9 VC-4-10 VC-4-11 VC-4-12
VC-4-13 VC-4-14 VC-4-15 VC-4-16
VC-4-1 VC-4-2 VC-4-3 VC-4-4
Pointers
MSOH
RSOH VC-4-1 VC-4-2 VC-4-3 VC-4-4
VC-4-5 VC-4-6 VC-4-7 VC-4-8
VC-4-9 VC-4-10 VC-4-11 VC-4-12
VC-4-13 VC-4-14 VC-4-15 VC-4-16
The blocks can start at any position in the payloadThe block consists of distributed VC-nsEach container has it‘s own pointer
VCG Granularity
VCG Payload Capacity
Maximum
MinimumVCGs:VC-4-1v Payload Size 149,76 Mbit/sVC-4-2v Payload Size 299,52 Mbit/s
VC-4Example High Order VC:VC-4 Container Size 150,3 Mbit/sVC-4 Payload Size 149,76 Mbit/s
VC-4-7v Payload Size 1048,3 Mbit/s
VC-4-256v Payload Size 38338 Mbit/s
Minimum
VCG GranularityVCGs:VC-12-1v Payload Size 2,176 Mbit/sVC-12-2v Payload Size 4,352 Mbit/s
VCG Payload Capacity
Maximum
Example Low Order VC:VC-12 Container Size 2,240 Mbit/sVC-12 Payload Size 2,176 Mbit/s
VC-12-5v Payload Size 10,88 Mbit/s
VC-12-64v Payload Size 139,26 Mbit/s
VC-12
The end