DATA LINK LAYER

1
Access Networks Management by V5 Protocol DB
Seminar 14/12/2003 by Yuval Levi
2
Access Networks types Overview

• Cables TV
• ADSL ( Asymmetric Digital Subscriber Line )
• WLL ( Wireless Local Loop )

3
Cable Modem Architecture
CM
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C M T S
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Cable Modem specifications and Evolution

• DOCSIS 1.0
• DOCSIS 1.1
• DOCSIS 2.0
• Cable Home

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ADSL Architecture
Telephony Switch
ADSL Head End
ADSL modem
ADSL modem
ADSL modem
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WLL ( Wireless Local Loop )SYSTEM FH every
2mili/sec
FAU
RPU
RPCU
SWITCH
up to 10 km
E1s
DSL
Up to 4 km
8 32k for US 8 32k for DS
V5.2 protocol
ISDN
Control Station Via SNMP
Pay-phone
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WLL ( Wireless Local Loop ) Appoints

• Developed countries
• Undeveloped countries

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Wireless Local Loopcomes to solve thelast mile
problem

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Rationale for New standard

• COs have grown to serve more lines.
• Remotes used to decrease the cost of providing
  access to end customer.
• These solution remain proprietary and expensive.
• A need to create a flexible and scaleable
  solutions on an open interface.
• Various digital loop carrier solutions have
  evolved
• - Bellcore TR008 / SLC96
• - Bellcore GR303
• - ETSI V5.1/V5.2

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Wireline Access Network
V5
Switch
HFC Access Network
Fixed Radio Access Network
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A network with non-proprietary interface
V5.1/V5.2
Local Exchange
Access Network
PCM-30 (E1)
AN
LE
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Bearer channel
bearer channel
protocols
protocols
E1 link
Communication Channel
Access Network Interface
Local Exchange
Access Network
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SWITCHES NETWORKconnected byE1S TRUNKS
CCS Common Channel Signaling
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V5.1 vs V5.2

• V5.2
• consists of 1 to 16 E1 I/f
• supports concentration, dynamic time slot
  assignment
• Supports PSTN and ISDN BRI PRI
• protection for signaling and control channels
• Maximum 3 TS for signaling / control per link

• V5.1
• Single E1 interface
• No concentration, fixed time slot assignment
• Supports PSTN and ISDN BRI
• No protection
• Maximum 3 TS for signaling / control

LE
AN
LE
AN
V5.1
V5.2
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WLL Systems Operators Requirements

• Transparent
• Robust
• Flexible
• Efficient

Performance
Cost
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WLL main challenges

• Maximum utilization of the shared channel
• Concentration
• Compression
• QoS policy
• System Control

17
Air Interface Frequency Hopping ( FH )
RPU_2
12
21
5
17
RPU_1
17
21
5
12
FAU
12
21
17
5
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WLL - Frame Structure (2 mili/sec)
Broadcast Transmission
Rx

RPU
A B C D E F G H a b c d
e f g h
US ( Up Stream )
DS ( Down Stream )


FAU
a b c d e f g h A B C D
E F G H
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WLL - Slot Structure
DS ( Down Stream )
US ( Up Stream )
FAU


a b c d e f g h
IB Voice / Data
OOB
Guard Time
CRC
Control
8
12
64
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WLL ( Wireless Local Loop )Shared Channel Tasks

• First synchronization ( span )
• Range
• Channel allocation
• Packets transmission
• Traffic statistics
• Clock recovery

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WLL FAU States

• Spectrum Analysis
• Tracking
• Active

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WLL - FAU ( partial ) Tasks
Trigger by Interrupt
App. Layer
Medium Layer
1.5 Layer
Call Processing
DMA Int.
Tx
MAC
Off-Hook detection
S/W Download
Rx
DLL
2m/s Int.
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RPUs Synchronized
RPU_2
5
17
12
21
RPU_1
12
21
17
5
24
Spectrum Analysis Algorithm
Stay for n1 hops
FAU
17
X
Y
Identify RPU n
Identify RPU k
Stay for n1 hops
FAU
21
X
Y
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Spectrum AnalysisWhite Noise Probability
12
Number of options for 12 CRC bits 0.5
875,000 bits sampling / sec
Pr ( CRC ok for white noise per second )
875,000 1 / 4096
213 means a white noise per about
5 mili / sec in average Due to over sampling
its about 1.25 mili to 2.5 mili in average
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Range Correlation
A B C D E F G H
RPU
A B C D E F G H
FAU_1
A B C D E F G H
FAU_2
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FAU Tracking State Tasks

• Clock recovery
• Battery save
• Check for others RPU status
• Channel Allocation ( Slotted Aloha )

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Alert Cycle Channel AllocationDistributed
Slotted Aloha
16 Alerts zone Each one 6 m/sec
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FAU - Active state Tx / Rx Protocol for OOB
channel
Tx
Rx
N1
ACK WEI ok
CRC ok
CRC ok
N2
CRC ok
ACK WEI ok
CRC not ok
N2
CRC not ok
ACK WEI not ok
CRC ok
N2
WEI Work Error Indication
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Bibliography

• Cable Labs site www.cablelabs.com
• Bellcore, TA-NWT-001313, Generic Criteria for
  Wireless Access Communication Systems ( WACS )
• ETSI, EN 300 347-1, V5.2 interface specification
  
• Alex Gillespie, Access Networks, Technology and
  V5 Interfacing

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THANK YOU