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Wireless Curriculum Development Section
ISSUE ORI000008 ATM Principle
4.2
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Course Outline
Overview
Basic Concepts of ATM
ATM Protocol & Service Type
Basic Concepts of IPOA
ATM in CDMA2000 BSS
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To provide a high-speed , low delay
multiplexing and switching network to any type of
user traffic , such as voice support , data,or videoapplications.
Why do we need a new technology?
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What is ATM?
ATM for Telecommunications is Async hrono us Trans fe r Mode , (not Automatic Teller Machine!).
ATM is a technology that has transport, swi tch ing , ne twork
management , and customer services built into it right from the start.
In general, ATM means that traffic is carried in small, fixed-lengthpackets called cells.
A technology that integrates advantages of circuit switch and packet
switch .
ATM can support any type of user services, such as voice, data , or
video service .
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ATM Overview
53byte fixed length cell= 5Bytes cellheader+48Bytes payload.
ATM must set up virtual connection beforecommunication.
ATM network will confer with terminal onparameter of QoS before the connection isset up.
Contract
5-BytesHeader
48-BytesPayload
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Connectionless & Connection-oriented
Connectionless: Every packet istransferred from different routes, sothe receiving order of packetsdoesnt possibly depend on thesending order.
Connection-oriented : All packetsare transferred from the sameroute , so the receiving order ofpackets depends on the sendingorder. Time delay is fixed.
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Traditional Switch Models Characteristic
Circuit Switching Data is sent from the same route, so time delay is fixed High-speed switching Fixed rate
Packet Switching Support multi-rate switching
Take full advantage of bandwidth/waste of bandwidth Time delay is not fixed
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ATM Switch Models Characteristic
Bandwidth will be shared and statisticallymultiplexed, any users cell will not be sendperiodically.
Many types of service can be transferred in thesame time with high QoS.
Fixed length cell, so switch can be controlled byhardware and high-speed switching is easy to be
realized.
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Course Outline
Overview
Basic Concepts of ATM
ATM Protocol & Service Type
Basic Concepts of IPOA
ATM in CDMA2000 BSS
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ATM Cell
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ATM Cell
GFC ( Generic Flow Control): It is intended for control of a possible bus
system at the user interface and is not used at the moment.
VPI ( Virtual Path Identifier): The VPI contains the second part of the
addressing instructions and is of higher priority than the VCI.
VCI ( Virtual Channel Identifier): VCI in each case indicates a path section
between switching centers or between the switching center and the subscriber.
PTI ( Payload Type Identifier): Indicates the type of data in the information
field.
CLP ( Cell Loss Priority): Determines whether a cell can be preferentially
deleted or not in the case of a transmission bottleneck.HEC ( Header Error Control): Provided in order to control and, to some
extent, correct errors in the header data that may occur. The HEC is used to
synchronize the receiver to the start of the cell.
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VP and VC
Why two fields?
Consider VPI as a bundle of virtual
channels. (256 VPI on one link)
The individual virtual channels have
unique VCIs. The VCI values may
be reused in each virtual path.
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Port 1 VPI=2 VCI=37
VPI=3 VCI=39
NNI
UNI
UNI
ATM Cell Switching
ATM Switch
Port VPI VCI1 2 37
2 1 51Port 2
Port 1 ATM Switch
Port VPI VCI1 1 512 3 39
Port 2
ATM TerminalUser B
User A
ATM Network Node
Cell and usersdata changeeach other
VPI=1 VCI=51
ATM Network Node
ATM TerminalCell and usersdata changeeach other
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ATM Connections
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ATM Virtual Connection
UNI cellVPI =1VCI =1
UNI cellVPI =20VCI =30
NNI cellVPI =26VCI =44
NNI cellVPI =6
VCI =44 NNI cellVPI =2VCI =44
1
2
3
1
2
3
1
3 2
2
3 1
ATM Virtual ConnectionPort VPI VCI
1 26 442 2 44
Port VPI VCI
1 2 44
2 6 44
Port VPI VCI2 6 44
3 20 30
Port VPI VCI
1 1 12 26 44
A B
In order to exchange cells between A and B, several tables must be set up innetwork node where the cells passed. After these tables have been set up, all the
cells will be transferred along this route. This route is called Virtual Connection.
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Types of ATM Virtual Connection
According to the switching mode, ATMVirtual Connection can be classified :
VPC (Virtual Path Connection)
VCC (Virtual Channel Connection)
According to connection establishment,ATM Virtual Connection can be classified:
SVC(Switching Virtual Connection)
PVC(Permanent Virtual Connection)
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UNI cell
VPC and VCC
ATM terminal A C
ATM network node G UNI cell
NNI cell NNI cell VCswitching
VCC
VPC
VCC
UNI cell UNI cell
B D
For example: When E receives cells from A or B, which would betransferred to C or D, the VPI of these cells would be set touniform value in E. These cells would be received by G andswitched to F by VP switching. Then the cells will be delivered toC or D at F. It means that VPC has been set up between E and F,
whi l e VCC has been se t up among A, B , C and D.
E F
VPswitching
VCswitching
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Course Outline
Overview
Basic Concepts of ATM
ATM Protocol & Service Type
Basic Concepts of IPOA
ATM in CDMA2000 BSS
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ATM Sublayer Model
ATM Protocol Stack Model OSI Reference Model
User
PMD
TC
PHY
ATM
AALCS
SAR
Interfacemanage
ment
7 Application
6 Presentation
5 Session
4 Transport
3 Network2 Data link
1 Physical
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Two sublayers:
Transmission Convergence Sublayer (TC)transmission frame generation/recoveryProcessing HEC
cell delimitingtransmission frame adaptation
Physical Medium Dependent Sublayer(PMD)
Link codingNetwork physical medium
Function of ATM Physical Layer
AAL
ATM
PHY
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Cell switch
Quality of Service
Processing the cell header
Types of payload
Multiplexing /Demultiplexing ofdifferent connection cell
Function of ATM Layer
AAL
ATM
PHY
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Support services for user
Segment and reassemble
Complete the change betweenUser-PDU and ATM payload
Function of AAL layer
AAL
ATM
PHY
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Function of ATM AAL Overview
Function of ATM AAL:
Provide a high-speed,
low delay multiplexingand switching network
to support any type of
user service, such as
voice, data,or video
applications.
ATM Payload
ConstantBit Rate
DataBursts
VariableBit Rate
ATM Cell
Multiplexing
AAL SDU
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Types of AAL
In order to support different types of user services, there arefive types of AAL.
In Huaweis BSS, voice is transferred over AAL2 and restsignals are transferred over AAL5.
Service type A B C DBit rate constant variable variable variable
Real time YES YES NO NO
Connection mode Connection oriented connectionless
AAL AAL1 AAL2 AAL3/4 AAL5
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Service Types of ATM layer
CBR (Constant bit rate)
VBR-RT (Variable bit rate-real time)
VBR-NRT (VBR-non real time)
UBR (Unspecified bit rate)
ABR (Available bit rate)
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Service type in CDMA2000 BSS System
Variable bit rate real time( VBR-RT), such as voice
service in CDMA2000 BSS System. It is realized by
AAL2.
Variable bit rate non real time (VBR-NRT), such as
signaling and other service in CDMA2000 BSS System.
It is realized by AAL5.
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Course Outline
Overview
Basic Concepts of ATM
ATM Protocol & Service Type
Basic Concepts of IPOA
ATM in CDMA2000 BSS
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IPOA Protocal Stack
ATM network Physical layer
IP address is mapped to PVCor SVC
User application
ATM
AAL
IP
TCP/UDP
ATM
AAL
IP
TCP/UDP
IP packet is transferred toATM Payload
User application
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INARP in IPOA PVC Mode
Terminal A IP:192 .168 .1 .1
ATM Network
Terminal B IP:192 .168 .1 .2
PVC
Any IPOA terminal that wants to communicate with other terminalmust know the destination IP address. But how to know the IP address?PVC connecting the source and destination terminals should be set upfirst. For example: Terminal A must set up a PVC to B in order to knowthe IP address of B.
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ARP in IPOA PVC Mode
Terminal A will send InvATMARP information to request remote IPOA
client s (such as computer B) IP address. So does computer B.
Computer A IP:192 .168 .1 .1
ATM Network
Computer B IP:192 .168 .1 .2
PVC InvATMARP
InvATMARP
VPI VCI IP Address
1 33 . . .
XX YY . . .
VPI VCI IP Address
2 33 . . .
ZZ YY . . .
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ARP in IPOA PVC Mode
Thereby, A and B establish the map table of IP address to PVC. Similarly, allthe IPs of the computers that answered the InvATMARP will be set to themap table.
Computer A IP:192 .168 .1 .1
ATM Network
Computer B IP:192 .168 .1 .2
PVC ACK
ACK
VPI VCI
1 33
XX YY
IP Address
192 .168 .1.2
xxx .xxx .xxx .xxx
VPI VCI
1 33
ZZ YY
IP Address
192 .168 .1.1
xxx .xxx .xxx .xxx
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ARP in IPOA PVC Mode
For example: A will transfer a IP packet to B, and the IP packetwill be changed to AAL-PDUs first. When ATM layer receives AAL-PDU,it can find the PVC by map table and set VPI/VCI of ATM cell.Thereby, cells could be transferred to B by ATM network.
omputer A IP:192.168.1.1
ATM Network
Computer B IP:192.168.1.2
PVC ATM cell stream ATM cell stream
VPI VCI
1 33
XX YY
IP Address
192 .168 .1.2
xxx .xxx .xxx .xxx
VPI VCI
1 33
ZZ YY
IP Address
192 .168 .1.1
xxx .xxx .xxx .xxx
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Course Outline
Overview
Basic Concepts of ATM
ATM Protocol & Service Type
Basic Concepts of IPOA
ATM in CDMA2000 BSS
ATM i CDMA2000 BSS t L
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ATM in CDMA2000 BSS system LargeCapacity Configuration
ResourceManagement &
Packet ProcessingSubrack (CRPS)
IntegratedProcessing
Subrack (CIPS)
Optical fiber orseveral E1cables
BTS
BTS baseband frame
service/ signal-in-band AAL2 maintenance / signal-out-bandAAL5
Abis interface:signal-in-band/service AAL2
signal-out-band /maintenance AAL5 IPOAIf Abis interface is connected with several E1 cables,IMA mode will be adopted to transfer ATM cells.
BSC inside
Voice AAL2signal/data service:AAL5maintenance AAL5 IPOA
Connected to
MSC
Data ServiceProcessing
Subrack (CPMS)
Connected to
PDSN
Opticfiber
Opticfiber
Ethernetcable
cBSC
SwitchSubrack
GPS/Glonassreceiver
Opticfiber
IntegratedManagementSubrack (BAM)
ATM in CDMA2000 BSS System Small
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ATM in CDMA2000 BSS System SmallCapacity Configuration
several E1cables
BTS
BTS baseband frame
service/ signal-in-band AAL2 maintenance / signal-out-bandAAL5
Abis interface:signal-in-band/service AAL2
signal-out-band /maintenance AAL5 IPOAIf Abis interface is connected with several E1 cables,IMA mode will be adopted to transfer ATM cells.
BSC inside
Voice AAL2signal/data service:AAL5maintenance AAL5 IPOA
Connectedto MSC
Resource &PacketSubrack
IntegratedManagement
Subrack(BAM)
Connected to
PDSN
cBSC
GPS/GlonassReceiver
several E1cables or
Optic fiber
IntegratedProcessing
Subrack
Ethernetcable
LAN
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IMA Mode
PHY
IMA Group
PHY
PHY
PHY
IMA Group
PHY
PHY
Physical Link #1
Physical Link #0
Physical Link #2
Virtual ATM Link
If Abis interface is connected with several E1 cables, IMA mode will be
adopted to transfer ATM cells. In this way, cells of high speed ATM linkcould be transferred on several low speed physical links.
ATM Layer ATM Layer
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Summary
ATM Basics
ATM switching is cell switching,it has advantageof circuit switch and packet switch, connectionoriented .
ATM cell:53byte fixed length cell= 5Bytes cellheader+48Bytes payload
ATM switching
ATM switching has two types:VP and VC switch.
As a rule: only VPI has been changed in VPswitch,Both VCI and VPI have been changed inVC switch. VPI and VCI is only of effect betweenthe two ATM physical nodes.
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Questions
State ATM application in CDMA2000 BSSsystem?
What is the difference between SVC and PVC?
What is the difference between VP switchand VC switch?
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