01- atm basic overview
DESCRIPTION
hiTRANSCRIPT
1 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM BasicsATM Basics
ByBy
Kittipong ThamapaKittipong Thamapa
2 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Network Transfer ModesNetwork Transfer Modes
•Synchronous Transfer Mode
•Packet Transfer Mode
•Asynchronous Transfer Mode
3 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Synchronous Transfer ModeSynchronous Transfer Mode
• Derived from TDM technology
• Divides the physical bandwidth into logical timeslots
• Circuit switched networks (voice and leased lines)
4 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Synchronous Transfer ModeSynchronous Transfer Mode
• Benefits:+ Fixed and guaranteed bandwidth+ Low and fixed delay+ Less delay variation (jitter)
• Drawbacks:– Waste of physical bandwidth in data networks– No over-subscription in the service provider network– Inflexible bandwidth, not ideal for bursty traffic
• Maximum number of connection equals maximum number of timeslots
• Ideal for uncompressed voice networks
5 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Packet Transfer ModePacket Transfer Mode
• X.25 or Frame Relay technology• A DLCI identifies each virtual connection
( DLCI : Destination Link Control ID)
6 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Packet Transfer ModePacket Transfer Mode
• Benefits:+ Less waste of physical bandwidth in data networks+ Over-subscription in the service provider network is possible+ Guaranteed bandwidth is possible (CIR) Committed Information Rate.
• Drawbacks:– No guarantees for delay and jitter
• Ideal for data networks with less demand of the quality of service
• Variable length and delivery of packets
• Flexible bandwidth
7 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Asynchronous Transfer ModeAsynchronous Transfer Mode
• A compromise for voice, data, and video • QoS defined/negotiated when the initial connection is
made• Asynchronous on layer 2 of the OSI reference model• Compromise of STM and PTM
Voice Video Data
ATM cells
48-octet Payload
ATM 53-octet cells areswitched in hardware
8 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Asynchronous Transfer ModeAsynchronous Transfer Mode
• Benefits:+ Over-subscription in the service provider network possible+ Guaranteed bandwidth, delay and jitter are possible+ Proven technology
• Drawbacks:– Most applications are based on IP instead of ATM– A lot of overhead for IP over ATM– Complicated protocol architecture
• Implemented in voice and data networks
• Transport layer in 3G networks
9 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
New world packet networks New world packet networks • Layer 1 to layer 3 in the OSI reference model• Layer 1:
– PDH or (Plesiochronous Digital Hierarch)– SDH/SONET (Synchronous Digital Hierarchy)
(Synchronous Optical Network, SONET)– DWDM optical (Dense Wave Division Multiplexing)
• Layer 2:– ATM – Frame Relay– PPP (Point to Point Protocol)– Ethernet
• Layer 3:– IP (Internet Protocol)
10 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
What is ATM?What is ATM?• ATM = Asynchronous Transfer Mode
• Fast packet switching and multiplexing technology (cell-based )
• Support the universe of services • voice, video and data traffic
• Provides quality of service guarantee and reliability
• Offers "bandwidth on demand"
• Connection-oriented, no error correction for user traffic• error correction for user traffic is handled by the end user• the advantages are increased speed of switching and elimination of associated delay
• Utilises statistical multiplexing• less bandwidth can be reserved than if bandwidth reservation would be based on the
peak rate of the connections.• transmission cost saving is achieved
11 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Why ATM is a transport network in 3G?Why ATM is a transport network in 3G?
• ATM provides efficient support for transmission of voice, data, and video
• ATM provides QoS guarantee and reliability
• ATM utilises statistical multiplexing, so• less bandwidth can be reserved• transmission cost saving are considerable
• ATM supports the soft handover functionality
12 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
• For a group of bursty connections, less bandwidth can be reserved than if bandwidth reservation would be based on the peak rate of the connections
• Most of the traffic sources send bursty traffic and with a high probability all the sources do not simultaneously transmit at their peak rate
• One of the proposed advantages of ATM is that statistical multiplexing gain can be utilized
Statistical multiplexing gain
Statistical multiplexing Deterministic multiplexing
Requiredbandwidth Peak cell rate of
traffic type 1
Peak cell rate oftraffic type 2
Peak cell rate oftraffic type 3
Statistical Multiplexing GainStatistical Multiplexing Gain
13 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM interfaces in 3G networkATM interfaces in 3G network
UNI User Network InterfaceNNI Network Node Interface
PSTNMGW MSCBSUE
A BIu-CSIubUu
UNI NNI
IP networkGGSN
Iu-PS
NNI
RNC
SGSN
RNCBS
BS
Iur
NNI
UNI
UNI
ATM is employed
Gn Gi
14 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM Essential for 3GATM Essential for 3G• ATM Cell
• ATM Virtual Path (VP) and Virtual Channel (VC)
• ATM Adaptation Layer (AAL) (AAL2 and AAL5)
• ATM Layer Service Class (CBR,UBR)
• ATM Cross Connect
• Inverse Multiplexing for ATM (IMA)
• ATM over PDH and SDH
• Fractional E1 and Circuit Emulation Service (CES)
15 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM cellATM cell
• Header contains routing and error control information
• Payload carries the actual user information, either voice, data or video
Header5 bytes
Payload48 bytes
53 bytes
16 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM cellATM cell
GFC Generic Flow ControlVPI Virtual Path IdentifierVCI Virtual Channel Identifier
PT Payload TypeCLP Cell Loss PriorityHEC Header Error Control
User Network Interface (UNI) Network Node Interface (NNI)
VCI
GFC VPI
VPI
VCI
VCI PT CLP
HEC
123457 68
VCI
VPI
VPI
VCI
VCI PT CLP
HEC
123457 68
Payload Payload
Header(5 bytes)
Payload(48 bytes)
Provides local functions, such as identifying multiple stations that share a single ATM interface
The 1st bit - indicates whether the cell contains user data or control dataThe 2nd bit - indicates congestion
Indicates two levels of priority for ATM cells, CLP=1 should be discarded in preference to cells with the CLP=0
17 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM cell headerATM cell header
• GFC provides local functions.
• VPI indicates the virtual path over which the cell should be routed.
• VCI identifies a virtual channel over which the cell is to travel.
• PT discriminates between a cell carrying management information or one, which is carrying user information.
• CLP indicates two levels of priority for ATM cells.
• HEC checks for an error and corrects the contents of the header by using a CRC algorithm.
18 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Access ProfileAccess Profile
• VPI Length
• VCI Length
• total Bandwidth
How many VP and VC bit should be set ?
Note: VC = 0 not used and VC = 1- 31 are reserved for internal used
19 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM in VP and VCATM in VP and VC
48 bytes
5 bytes
HEADER PAYLOAD
ATM cell (53 bytes)
Transmission path
Virtual Path (VP)
Virtual Channel (VC)ATM Cell
ATM Layer
HEADER
PAYLOAD
20 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Advantages of Virtual Path ConnectionsAdvantages of Virtual Path Connections• Simplified network architecture
• Increased network performance and reliability• The network deals with fewer, aggregated entities
• Segregation of traffic• A form of priority control can be implemented by segregating traffic types
requiring different quality of service (QoS)
• Reduced processing and short connection setup time• New VCCs can be established by executing simple control functions at the
end points of the VPC; no call processing is required at transit nodes
– it can decrease the connection setup delay
• Enhanced network services• The user may define closed user groups or closed networks of VC bundles.
21 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM Adaptation LayerATM Adaptation Layer
TypicalUse
FixedConnection
Video&
Audio
FrameRelay
IPServices
AAL AAL1 AAL2 AAL3/4 AAL5
Connection Oriented Connection oriented orconnectionless
Synchronised Not Synchronised
Constant VariableBit Rate
Source & Dest.
Connection
ATM LayerPhysical Layer
A B C DATM Service Classes
PBX
Video Voice Data
AAL
22 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM layer functionsATM layer functions
Convergence Sublayer (CS)
PayloadPayload HeaderHeader
48 bytes5 bytes
User data
AAL
Segmentation and Reassembly Sublayer (SAR)
ATM Layer
Transmission Convergence (TC)
48 bytes
Physical Medium Dependent(PMD)
SD
H O
/H
PayloadHeader
Scramble frame and adapts the signals to the optical or electrical transmission medium
STM-1 Frame
Physical Layer
23 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
AAL2 (ATM Adaptation Layer 2)AAL2 (ATM Adaptation Layer 2)
String of AAL2 Packet Data Units String of AAL2 Packet Data Units
1 2 3 4 5 6
AAL2header
AAL2 is suitable for delay critical applications
ATM CELLHEADER
ATM CELLHEADER
HEADER = 5 BYTES
PAYLOAD = 48 BYTES
1 2 3 4 4 5 6
ATM cell
OFFSET FIELD, 1 byte (indicates where the next AAL2 PDU starts)
AAL2 PACKET, fixed header, variable length payload (max. 48 bytes)
ATM CELL, 5-byte header + 48-byte payload
PADDING
24 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
AAL5 (ATM Adaptation Layer 5)AAL5 (ATM Adaptation Layer 5)
PADDING FIELD, variable length to fill the 48-byte ATM cell
AAL5 PACKET, fixed trailer, variable length payload (max. 64 Kbytes)
ATM CELL, 5-byte header + 48-byte payload
AAL5 Packet Data Unit
USER DATA - Variable length 1 - 65 535 bytes
PAYLOAD = N x 48 BYTES
AAL5trailer
ATM cell 1 ATM cell 2………... ………..ATM cell n
AAL5 is suitable fo
r packet data
AAL5 Packet Data Unit
USER DATA - Variable length 1 - 65 535 bytes
25 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM Layer Service ClassesATM Layer Service Classes
• CBR (Constant Bit Rate)
• VBR (Variable Bit Rate)
• ABR (Available Bit Rate)
• UBR (Unspecified Bit Rate)
Time
Bandwidth
Time
Bandwidth
26 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM ATM SettingsSettings -- Traffic Descriptor (TRDE)Traffic Descriptor (TRDE)
In AXCLCI:11,VC:2,100; //INTERROGATE TERMINATION POINT
SEGMENT TRAFFIC SHAPINGI/F ID VPI VCI USAGE END POINT VP LEVEL----- ----- ----- ------ --------- --------
11 2 100 FREE NO NO
IN IN EG EGCDVT_PCR CDVT_SCR CDVT_PCR CDVT_SCR----------- ----------- ----------- -----------
334 USEC 334 USEC
IN SERV IN CONFOR IN IN IN QOSCATEGORY DEF EPD PPD CLASS-------- --------- --------- --------- ------CBR CBR1 DISABLED DISABLED C1
EG SERV EG CONFOR EG EG EG QOSCATEGORY DEF EPD PPD CLASS-------- --------- --------- --------- -----CBR CBR1 DISABLED DISABLED C1
IN IN IN IN IN INPCR_01 PCR_0 SCR_01 SCR_0 BURST_01 BURST_0----------- ----------- ----------- ----------- ----------- -----------
3000 CPS 1272 KBPS
EG EG EG EG EG EGPCR_01 PCR_0 SCR_01 SCR_0 BURST_01 BURST_0----------- ----------- ----------- ----------- ----------- -----------
3000 CPS 1272 KBPS
ADMIN EFF ADMIN EFF OPERSTATE STATE STATE-------- --------- --------UNLOCKED LOCKED
In RNC & MGW
27 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
VPI 1
VPI 2
VPI 3
VPI 4
VPI 5
VPI 6
VCI 1VCI 2
VCI 1VCI 2
VCI 3VCI 4
VCI 3VCI 4
VCI 5VCI 6
VCI 5VCI 6
Virtual Path SwitchingVirtual Path Switching
VPI 1
VPI 2
VCI 1VCI 2
VCI 1VCI 2
VPI 1
VPI 4
VCI 4
VCI 5VCI 6
VCI 3
VPI 5Port 1
Port 2
Port 3
Virtual Channel SwitchingVirtual Channel Switching
ATM Cross ConnectATM Cross Connect
28 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM crossATM cross--connect (AXC)connect (AXC)
VC2 / VP2
VC1 / VP1
RNC
ATMswitch
VC1 / VP1
BTS 1
AXC
VC3 / VP3VC3, VC4 / VP4
VC3, VC4, VC5, VC6 / VP7VC5 / VP5
VC6 / VP6
VC1/VP1 THROUGH-CONNECTED IN AXC2
VC/VP CROSS-CONNECTION TABLEVC3/VP4 <-> VC3/VP 7VC4/VP4 <-> VC4/VP 7VC5/VP5 <-> VC5/VP 7VC6/VP6 <-> VC6/VP 7
AXC / ATM switch
BTS 2
AXC
BTS 3
AXC
BTS 4
AXC
BTS 5
AXC
BTS 6
AXC
StandaloneAXC
29 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Iub NBAP SignallingIub NBAP Signalling• Common NBAP:
– Procedures to create new user equipment contexts
– Setup of first radio link of one UE– Selection of the traffic termination point– Cell configuration– Handling of RACH/FACH and PCH channels– Initialisation and reporting of cell or
NodeB measurement– Fault management
• Dedicated NBAP:– Addition, release and reconfiguration of
radio links for one UE context– Handling of dedicated and shared
channels– Handling of softer combining– Initialisation and reporting of radio link
specific measurements– Radio link fault management
RNCBS
Physical Layer Physical Layer
ATM ATM
AAL5
NBAP NBAP
Convergence Protocol(s) Convergence Protocol(s)
AAL5
Iub
30 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM resource management IubATM resource management Iub
Phy
TTPATM
logical interface
VPLtpVPLtp
VCLtp
ATM logical interface
VPLtpVPLtp,
O&M traffic (UBR)
Signalling and user traffic (CBR)
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
Common NBAP link (C-NBAP)
Dedicated NBAP link (D-NBAP)
Dedicated NBAP link (D-NBAP)
AAL2 signalling link (AAL2SL)
AAL2 signalling link (AAL2SL)
AAL2 user plane link (AAL2UD)
AAL2 user plane link (AAL2UD)
AAL2 user plane link (AAL2UD)
VCLtp
VPLtp
AAL2 user plane link (AAL2UD)
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
VCLtp
RNC
WAM
WAM
Phy
TTP
O&M / Usage IPOAM
31 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM connection TableHW VPI VCI
x x x
VCI
x
VPI
x
HW
x
CIF1CIF1CIF1CIF1
Term-1Term-1Term-1
0000
36333435
120567240
1111
IFUAIFUAIFUAIFUA
Term-2Term-2Term-2
VCI 36
VCI 30
AXU
Private IP addresses
LMP
IFUA
PDH, IMA or SDH
CIF 1 VCI 56 CNBAP
VPI 1(CBR)
VPI 0 (UBR)VCI 32 O&M
Transmission Convergence Adaptor
VPI 4
VPI 0
BTS_ID =1
C-NBAP
O&M
D-NBAP
AAL2 UP
AAL2 sig
WAM 2
O&M Master WAM
VCI 33
VCI 34
VCI 35
VCI 120 AAL2UP
VCI 72 DNBAP
VCI 40 AAL2SIG
IP router
C-NBAP only forTelecom Master WAM
Iub ATM Transport Layer (Example)Iub ATM Transport Layer (Example)
32 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Iub cIub crossross connections in connections in AXCAXC
AXUIFUCslot 2if 1
STM-1CIF 1
VCI 120
VPI 1
VCI 56
BTS
WAM 2
VCI 72
VCI 40
AXC
VCI 36
VPI 0
CNBAP
AAL2UP
VCI 33
VCI 34
VCI 35
Name VPI VP PCR [cells/s]
VCI VC PCR [cells/s]
VPI VP PCR [cells/s]
VCI VC PCR [cells/s]
Service Category
CNBAP 0 58726 33 300 1 4528 56 300 CBRDNBAP 0 58726 34 150 1 4528 72 150 CBR
AAL2SIG 0 58726 35 150 1 4528 40 150 CBRAAL2UP 0 58726 36 3618 1 4528 120 3618 CBR
DNBAP
AAL2SIG
33 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Views inside AXCViews inside AXC--ManagerManager
34 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Creating Creating Cross Cross ConnectionsConnections
35 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
• Problem ?: More bandwidth than 2 Mbit/s is needed, but only T1/E1 services are offered by the carrier
PBX PBX
ATM E1 based
Inverse Multiplexing for ATM (IMA)Inverse Multiplexing for ATM (IMA)
PBX PBX
ATM
E1 based
Multiple T1/E1s are bundled for more bandwidth
Solution IMASolution IMA
36 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Tx direction: cells distributed across links in round robin sequence
Rx direction: cells recombined into single ATM stream
Physical Link #0
Single ATM Cell Streamfrom ATM Layer
IMA Virtual Link
IMA Group
PHY
PHY
PHYPhysical Link #1
Physical Link #2
IMA Group
PHY
PHY
PHY
Original ATM CellStream to ATM Layer
Concept of IMAConcept of IMA• Low bit rate transmission lines can be combined into a group that seen
as a single virtual link by ATM• IMA sublayer is part of the physical layer.• It is located between the traditional Transmission Convergence sublayer and the ATM
layer.
37 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Inverse multiplexing for ATMInverse multiplexing for ATM
ATM Layer
Physical Medium Sublayer
Transmission Convergence Sublayer (TC)Physical Layer TC
IMA
• Iub IMA max 8 E1• Iur IMA max 16 E1• All E1 in IMA have to belong to same NIP or IFU• Only one ATM interface/ IMA group• Only one ATM interface per exchange terminal• NIP1 can have up to 16 ATM Interfaces
38 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM over SDHATM over SDH
VC-4
OVERHEAD
STM-1 (155,52 Mbps) can fit 44.15 cells per frame -> 353 207 cells per second.
VP1
VP2
VP3
.
.
.
39 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM cell mapping into PDH 2048 kbps
• PDH frame structure for 2048 kbps is describedin ITU-T Recommendation G.704
• ATM cell is mapped into bits 9 to 128 and bits 137 to 256(i.e. time slots 1 to 15 and time slots 17 to 31)
• Time slots 0 and 16 are not used for ATM cell
•Nokia AXC supports however only contiguousmapping starting from time slot 1!
<- Bits 1 to 8 ->
<-Tim
e slots (TSs) 0 to 31 ->
Bit 1 Bit 8Bit 9 Bit 16
Bit 121 Bit 128Bit 129 Bit 136Bit 137 Bit 144
Bit 249 Bit 256
Available for ATM cell
Available for ATM cell
TS 1TS 0
TS 30TS 31
ATM over PDH
40 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM over E1ATM over E1
Header Payload
0 1 2 16 1817 3115
TS0TS1-15
TS16TS17-31
. . . . . . 0 1 2 16 1817 3115
TS0TS1-15
TS16TS17-31
. . . . . .
E1 frameE1 frame
41 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM cell mapping into PDH 2048 kbps
Example Bit 1 Bit 8Bit 9 Bit 16
Bit 121 Bit 128Bit 129 Bit 136Bit 137 Bit 144
Bit 249 Bit 256
Bit 121 Bit 128Bit 129 Bit 136Bit 137 Bit 144
Bit 249 Bit 256
42 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
•• 3G 3G ATM ATM Traffic SharingTraffic Sharing GSM 2M GSM 2M FrameFrame
MetroHubMetroHub
GSMBTS
GSMBTS
WCDMABS
WCDMABS RNCRNC
BSCBSCTDM
Fractional E1
Fractional E1
43 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Fractional and non fractional E1's Fractional and non fractional E1's
RNC
BSC
ET
COMMONTRANSPORTON MICROWAVE
E1's for 3G BTS
WSP WSP WSP
3G BTS AXC
...
WAM
WSP WSP WSP...
WAM
IFU E
ATMSWITCH
•••
•••
• One or several, fractional or non fractional E1's
Non fractional E1Fractional E1 shared with 2G BTS
MetroHub
FXCRRI
FXCE1/T1 NIU
FB1
2G BTSTRX
TRX
TRX
TRX
TRX
TRX
TRUA
RRIC
D-bus
FB2
LIF2
LIF3
FB1
RAN1Phase 1.5
44 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Fractional E1Fractional E1
- Fractional E1 means that some timeslots are not used for ATM traffic (configurable by management), TS0 and TS16 are not allowed by default
- using only three timeslots provides a 192 kbit/s transmission path for ATM traffic- long transmission delays for ATM traffic!
TS0 TS0
fractional E1termination point
fractional E1termination point
3 octets of the ATM cell 3 octets of the ATM cell
53 octets per ATM cell
RAN1Phase 1.5
45 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
TDM links with Fractional E1/JT1TDM links with Fractional E1/JT1• Physical link can be Fibre, Microwave, leased service, ...• BTS site:
•WCDMA BTS connected to GSM Abis•WCDMA BTS supports ATM over Fractional E1
• BSC/RNC site:•TDM traffic (GSM + WCDMA) separated by TDM cross-connect Hub•Possible, not earlier groomed, Fractional E1 traffic is terminated with a standalone AXC
GSM BTS
WCDMA BTS
TDM link (PDH/SDH)HUB BSC
RNC
Combined Abis and Iub
TDM crossconnect function (n x 64 kbits/s)
Fractional E1 (partly filled) (n x 64 kbits/s)
Fractional E1
Fractional E1
Full E1 Full E1
46 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
ATM cell mapping into FRACTIONAL PDH 2048 kbps
• PDH frame structure for 2048 kbps is describedin ITU-T Recommendation G.704
• ATM cell is mapped into bits 9 to 128 and bits 137 to 256 (i.e. time slots 1 to 15 and time slots 17 to 31)IF they are not reserved for 2G traffic
• Time slots 0 and 16 are not used for ATM cell
• In general any mapping for fractionality is allowed i.e. any mapping of "allowed" time slots, both contiguous or non-contiguous
• Nokia AXC supports however only contiguousmapping starting from time slot 1!
<- Bits 1 to 8 ->
<-Tim
e slots (TSs) 0 to 31 ->
Bit 1 Bit 8Bit 9 Bit 16
Bit 121 Bit 128Bit 129 Bit 136Bit 137 Bit 144
Bit 249 Bit 256
Available for ATM cell
Available for ATM cell
TS 1TS 0
TS 30TS 31
Reserved for 2G traffic
47 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
GSM GSM Traffic Over Traffic Over ATM ATM
SAXC orWCDMABTS-AXC
SAXC orWCDMABTS-AXC
GSMBTS
GSMBTS
WCDMABS
WCDMABS RNCRNC
BSCBSC
ATM
CES
Circuit Emulation Service (CES)
48 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Circuit EmulationCircuit Emulation
RNC
BSC
ET
E1 from 2G BTS
ATMSWITCH
Non fractional E1
AXCIFU A
NIU
2G BTSTRX
TRX
TRX
TRX
TRX
TRX
TRUAD-bus
LIF1
WSP WSP
3G BTS AXC
...
WSP WSP...
IFU A
IFU EWAM
WAM
•••
•••
CESIWF
Flexbus connection
••
E1
VCC
VCC
VCC
VPC
AXU
CESIWF
VCC
VCC
VCC
VPC
IFU E
49 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Unstructured Circuit Emulation Service Unstructured Circuit Emulation Service
- Transmitting CES interworking function takes the E1 signal and segments that stream into ATM cells
- ATM cells are transported via a CBR VCC to the receiving CESinterworking function
- receiving CES interworking function recovers E1 signal from the ATMcell stream
- Note: CES works bidirectional
CESInterworking Function (IWF)
CESInterworking Function (IWF)
TS0 TS0 TS0 TS0
G.703 frames
RAN1.5
50 © NOKIA ATM Basic V 4.0 / Kittipong Thamapa
Structured Circuit Emulation ServiceStructured Circuit Emulation Service
- Transmitting CES interworking function takes only some timeslotsfrom the E1 signal puts these into ATM cells
- ATM cells are transported via a CBR VCC with lower bandwidth compared tounstructured CES to the receiving CES interworking function
- receiving CES interworking function recovers TS from the ATM cell stream- Note: CES works bidirectional- Management configures which timeslots are transmitted
CESInterworking
Function (IWF)
CESInterworking Function (IWF)
TS0 TS0 TS0 TS0
TS1-TS3
RAN2