VFS-24, VFS-30, VFS-48, VFS-60 - Single/Dual Digital Voice Compression Server Modules
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OPERATION MANUAL
INSTALLATION AND
VFS-24, VFS-30,
VFS-48, VFS-60
Single/Dual Digital Voice Compression Server
Modules
Megaplex-2100/2104 Version 12
Innovative Access Solutions
VFS-24, VFS-30, VFS-48, VFS-60
Single/Dual Digital Voice Compression Server Modules
Megaplex-2100/2104 Version 12
Installation and Operation Manual
Notice
This manual contains information that is proprietary to RAD Data Communications Ltd. ("RAD").
No part of this publication may be reproduced in any form whatsoever without prior written
approval by RAD Data Communications.
Right, title and interest, all information, copyrights, patents, know-how, trade secrets and other
intellectual property or other proprietary rights relating to this manual and to the
VFS-24, VFS-30, VFS-48, VFS-60 and any software components contained therein are proprietary
products of RAD protected under international copyright law and shall be and remain solely with
RAD.
VFS-24, VFS-30, VFS-48, VFS-60 is a registered trademark of RAD. No right, license, or interest to
such trademark is granted hereunder, and you agree that no such right, license, or interest shall
be asserted by you with respect to such trademark.
You shall not copy, reverse compile or reverse assemble all or any portion of the Manual or the
VFS-24, VFS-30, VFS-48, VFS-60. You are prohibited from, and shall not, directly or indirectly,
develop, market, distribute, license, or sell any product that supports substantially similar
functionality as the VFS-24, VFS-30, VFS-48, VFS-60, based on or derived in any way from the
VFS-24, VFS-30, VFS-48, VFS-60. Your undertaking in this paragraph shall survive the termination
of this Agreement.
This Agreement is effective upon your opening of the VFS-24, VFS-30, VFS-48, VFS-60 package
and shall continue until terminated. RAD may terminate this Agreement upon the breach by you
of any term hereof. Upon such termination by RAD, you agree to return to RAD the
VFS-24, VFS-30, VFS-48, VFS-60 and all copies and portions thereof.
For further information contact RAD at the address below or contact your local distributor.
International Headquarters North America Headquarters
RAD Data Communications Ltd. RAD Data Communications Inc.
24 Raoul Wallenberg Street 900 Corporate Drive
Tel Aviv 69719, Israel Mahwah, NJ 07430, USA
Tel: 972-3-6458181 Tel: (201) 5291100, Toll free: 1-800-4447234
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E-mail: market@rad.com E-mail: market@radusa.com
© 1988–2007 RAD Data Communications Ltd. Publication No. 764-262-10/07Quick Start Guide
If you are familiar with the VF modules, use this guide to prepare the module for
operation.
1. Installing the VFS Modules
Insert the module in the assigned I/O slot.
Setting the Internal Jumpers
VFS-60 Internal Settings
Refer to the figure below and set the module jumpers as required.
VFS-30 Internal Settings
For VFS-30 modules, ignore the jumpers serving link 2.
VFS MP-2100/2104 Ver. 12 Installing the VFS Modules 1Quick Start Guide Installation and Operation Manual
Link 1 Interface Link 1 Jumper JP5
JP7, JP8, JP9, JP10
JP9
NO Pins 3,6 of RJ-45
Connector of Link 1
120 Ω not Connected to
JP7 JP8
Balanced Frame Ground
JP10
JP9 Pins 3,6 of RJ-45
YES Connector of Link 1
JP7 JP8
75Ω Connected to
Unbalanced Frame Ground
JP10
JP5
Link 1 Jumpers JP9
JP7 JP8
JP10
JP13
Link 2 Jumpers JP14 JP15
(VFS-60 only) JP11 JP12
Link 2 Interface Link 2 Jumper JP15
JP11, JP12, JP13, JP14
NO Pins 3,6 of RJ-45
JP13
Connector of Link 2
120Ω not Connected to
JP11 JP12
Balanced Frame Ground
JP14
JP13 Pins 3,6 of RJ-45
YES Connector of Link 2
JP11 JP12
75Ω Connected to
Unbalanced Frame Ground
JP14
VFS-48 Internal Settings
Refer to the figure below and set the module jumpers as required.
VFS-24 Internal Settings
For VFS-24 modules, ignore the jumpers serving link 2.
2 Installing the VFS Modules VFS MP-2100/2104 Ver. 12Installation and Operation Manual Quick Start Guide
Link 1 Jumper JP5
NO Pins 3,6 of RJ-45
Connector of Link 1
not Connected to
Frame Ground
Pins 3,6 of RJ-45
YES Connector of Link 1
Connected to
Frame Ground
JP24
Link 1 Jumper
Link 2 Jumper
(VFS-48 only)
JP25
Link 2 Jumper JP15
NO Pins 3,6 of RJ-45
Connector of Link 2
not Connected to
Frame Ground
Pins 3,6 of RJ-45
YES Connector of Link 2
Connected to
Frame Ground
2. Connecting the Cables
Before starting, refer to the installation plan to determine the cables intended for
connection to this VFS module.
Connecting the Balanced E1 or T1 Interface
To connect the user’s equipment to the balanced E1 or T1 link:
• Connect the user’s equipment to the prescribed VFS RJ-45 connectors marked
LINK1 and LINK2.
Connecting the E1 Unbalanced Interface
To connect the unbalanced interface:
1. Connect the RJ-45 connector of the adapter cable CBL-RJ45/2BNC/E1 to the
prescribed LINK connector.
2. Connect the coaxial cables from the user’s equipment to the two BNC
connectors at the other end of the adapter cable. Pay attention to correct
connection:
VFS MP-2100/2104 Ver. 12 Connecting the Cables 3Quick Start Guide Installation and Operation Manual
Connect the cable from the user’s equipment transmit output to the
green BNC connector (VFS link receive input)
Connect the cable from the user’s equipment receive input to the red BNC
connector (VFS link transmit output).
3. Configuration Procedure
You can sequentially configure all the VFS parameters using the command
DEF CH SS *, where SS is the VFS slot number.
Configuring the Internal Port Parameters
Configure each internal port using the command DEF CH SS CC, where SS is the
VFS slot number, and CC is the internal port number (IN1 to IN8).
The internal port configuration parameters and the allowed range of values are
listed below.
Parameter Values
Connect YES
NO
Rate 1 to 31
Max Bytes in 100 to 1472
Multiplex Frame Default: 450
MF Relay Enable
Disable
Min Pulse Width 45 to 300 msec, 60 msec
Min Power Level 0 to –35 dBm, -12 dBm
Frame Interval 10, 20, 30, …, 90 msec
Voice Coding G7231 6.4 kbps
G7231/5.3 kbps
G729A8
G711 A-law
G711 U-law
Type PTP
AAL2oMPLS
Volume NONE
–6 dB to +6 dB
Coding Law A-Law
U-Law
4 Configuration Procedure VFS MP-2100/2104 Ver. 12Installation and Operation Manual Quick Start Guide
Parameter Values
Echo Canceller Enable
Disable
Modem Enable
Disable
S Tandem Disable
Fax Rate N/A
4.8 kbps
9.6 kbps
14.4 kbps
Inband OFF
Management ON
Routing Protocol NONE
PROPRIETARY RIP
RIP2
Dst IP When operating opposite a Vmux device (Type must
be set to AAL2oMPLS), set the IP address in the
format xxx.xxx.xxx.xxx.
When operating opposite a VFS module (Type set to
PTP), N/A is displayed
Src/Dst Bundle ID The allowed range is 1 to 30 when operating
opposite a Vmux device (Type must be set to
AAL2oMPLS)
When operating opposite a VFS module (Type set to
PTP), N/A is displayed
Src IP xxx.xxx.xxx.xxx
N/A
Default: CL module IP address
IP Mask xxx.xxx.xxx.xxx
N/A
Default: 255.255.255.0
Default Gateway xxx.xxx.xxx.xxx
N/A
Default: 0.0.0.0
ML Slot Megaplex-2100: 1 to 12
Megaplex-2104: 1 to 5
ML Channel The allowed range is 1 to 8, in accordance with the
number of external ports on the main link module.
Default: 1
VFS MP-2100/2104 Ver. 12 Configuration Procedure 5Quick Start Guide Installation and Operation Manual
Configuring the Link Parameters
To define the parameters of the desired VFS link, type:
DEF CH SS CC
where SS is the VFS slot number, and CC is the desired link number, 1 or 2 (you
may also use EX1 and EX2).
The link parameters include two types of parameters:
• External E1/T1 port parameters
• Timeslot utilization parameters, displayed immediately after the external
E1/T1 port parameters.
The E1 and T1 parameters are described below followed by timeslot utilization
parameters.
External E1 Port Parameters (VFS-30, VFS-60)
Parameter Values
Connect YES
NO
Frame G.732N
G.732N-CRC4
G.732S
G.732S-CRC4
Sig. Profile 1 to 5
Idle Code 00 to FF (hexa)
Rx Gain LONG HAUL
SHORT HAUL
OOS Signaling FORCED BUSY
FORCED IDLE
Restoration CCITT
Time 10 SECONDS (62411)
1 SECOND (FAST)
Inband OFF
Management DEDICATE PPP
DEDICATE FR
Inband N/A
Management 64kbps (for DEDICATE FR and DEDICATE PPP)
Rate
Routing NONE
Protocol PROPRIETARY RIP
RIP2
6 Configuration Procedure VFS MP-2100/2104 Ver. 12Installation and Operation Manual Quick Start Guide
External T1 Port Parameters (VFS-24, VFS-48)
Parameter Values
Connect YES
NO
Frame SF (D4)
ESF
Sig. Profile 1 through 5
Idle Code 00 to FF (hexa)
FDL Type RESPONSE
COMMAND
Line Code TRANSPARENT
B7
B8ZS
Interface CSU
DSU
Tx Gain CSU Mode – Attenuation
0 dB
7.5 dB
15 dB
22.5 dB
DSU Mode – Length
000 to 133 FEET
133 to 266 FEET
266 to 399 FEET
399 to 533 FEET
533 to 655 FEET
Rx Gain LONG HAUL
SHORT HAUL
OOS Signaling FORCED BUSY
FORCED IDLE
RBMF Sig. YES
NO
Restoration 10 SECONDS (62411)
Time 1 SECOND (FAST)
Inband OFF
Management DEDICATE PPP
DEDICATE FR
Inband N/A
Management 64kbps (for DEDICATE FR and DEDICATE PPP)
Rate
VFS MP-2100/2104 Ver. 12 Configuration Procedure 7Quick Start Guide Installation and Operation Manual
Parameter Values
Routing NONE
Protocol PROPRIETARY RIP
RIP2
Timeslot Utilization Parameters
Parameter Values
Local N/A
Destination INT01 to INT08
SS:CC:TT
Timeslot Type VOICE
TRANS
MNG
CCS
SS7
Connection Id N/A
1 (EX1:1), …, 31 (EX1:31), 32 (EX2:1), …, 62 (EX2:31)
(the first number indicates the VFS destination, the
number in parentheses indicates Vmux destination)
4. Configuring the Module for Server Operation
In the server applications, use the following commands to assign timeslots:
• For the VFS-30 and VFS-24 modules: DEF TS SS IN9
• For the VFS-48 and VFS-60 modules: DEF TS SS IN9 and DEF TS SS IN10.
The internal IN9 and IN10 port timeslot utilization parameters and the allowed
range of values are listed below.
Timeslot Utilization Parameters
Parameter Values
Local N/A
Destination INT01 to INT08
Timeslot Type VOICE
Connection Id N/A
1 (EX1:1), …, 31 (EX1:31), 32 (EX2:1), …, 62 (EX2:31)
(the first number indicates the VFS destination, the
number in parentheses indicates Vmux destination)
8 Configuring the Module for Server Operation VFS MP-2100/2104 Ver. 12Contents
Chapter 1. Introduction
1.1 Overview....................................................................................................................1-1
Product Options......................................................................................................1-1
Main Features.........................................................................................................1-1
Voice Transmission.............................................................................................1-1
Automatic Fax and Modem Transmission ............................................................1-2
Transparent Transfer of Timeslots ......................................................................1-2
Traffic Carrying Capacity .....................................................................................1-2
1.2 Typical Applications....................................................................................................1-4
Point-to-Point Applications .....................................................................................1-4
Point-to-Multipoint Applications..............................................................................1-4
Server Application...................................................................................................1-5
1.3 Physical Description ...................................................................................................1-6
1.4 Functional Description................................................................................................1-8
Functional Block Diagram ........................................................................................1-8
TDM Bus Interfaces.................................................................................................1-9
Routing Matrix on TDM Buses Side ..........................................................................1-9
Overview of Internal Routing Method .................................................................1-9
Routing Matrix Functions ..................................................................................1-10
CPU ......................................................................................................................1-10
DSP Subsystem .....................................................................................................1-10
Signaling RAM .......................................................................................................1-11
Link Interfaces ......................................................................................................1-11
E1 Link Interfaces (VFS-30, VFS-60)..................................................................1-11
T1 Link Interfaces (VFS-24, VFS-48)..................................................................1-11
Clock Generator and Timing Subsystem .................................................................1-12
Link Timing.......................................................................................................1-12
System Timing..................................................................................................1-12
Local Management Subsystem ..............................................................................1-12
E1 Interface Characteristics (VFS-30, VFS-60) ........................................................1-13
T1 Interface Characteristics (VFS-24, VFS-48) ........................................................1-13
Handling of Signaling Information .........................................................................1-14
Handling of CAS Signaling.................................................................................1-14
Handling of CCS Signaling .................................................................................1-14
Handling of SS7 Signaling .................................................................................1-14
Audio Signal Processing Capabilities ......................................................................1-14
Handling of Voice Signals .................................................................................1-15
DTMF Processing ..............................................................................................1-15
Automatic Fax Processing .................................................................................1-16
Handling of Voiceband Modem Signals..............................................................1-16
Test and Diagnostic Capabilities ............................................................................1-17
1.5 Technical Characteristics ..........................................................................................1-18
Chapter 2. Installation and Operation
2.1 Introduction...............................................................................................................2-1
2.2 Setting the Internal Jumpers .......................................................................................2-1
VFS-60 Internal Settings..........................................................................................2-1
VFS-30 Internal Settings..........................................................................................2-2
VFS-48 Internal Settings..........................................................................................2-3
VFS MP-2100/2104 Ver. 12 iTable of Contents Installation and Operation Manual
VFS-24 Internal Settings..........................................................................................2-4
2.3 Installing the Module in the Chassis............................................................................2-4
2.4 Connecting the Cables................................................................................................2-5
Connecting the Balanced Interface ..........................................................................2-5
Connecting the Unbalanced Interface ......................................................................2-5
2.5 Normal Indications .....................................................................................................2-6
Module Status Indication.........................................................................................2-6
Link Status Indications ............................................................................................2-6
Chapter 3. Configuration
3.1 Overview....................................................................................................................3-1
3.2 Outline of Configuration Procedure ............................................................................3-1
Outline of Configuration Procedure .........................................................................3-1
3.3 Configuration Instructions ..........................................................................................3-2
Configuring Internal Port Parameters.......................................................................3-2
Configuring Link Parameters....................................................................................3-5
External E1 Port Parameters (VFS-30, VFS-60) ....................................................3-6
E1 Timeslot Utilization Parameters .....................................................................3-8
External T1 Port Parameters .............................................................................3-10
T1 Timeslot Utilization Parameters ...................................................................3-14
3.4 Configuring the Module for Server Operation............................................................3-15
3.5 System Timing Considerations ..................................................................................3-16
3.6 Displaying VFS Information.......................................................................................3-16
Displaying Status and Configuration Information ...................................................3-17
Displaying Signaling Information............................................................................3-17
Chapter 4. Troubleshooting and Diagnostics
4.1 Introduction...............................................................................................................4-1
4.2 Performance Monitoring.............................................................................................4-1
Overview ................................................................................................................4-1
Internal Port Performance Parameters.....................................................................4-2
4.3 Test and Diagnostic Functions....................................................................................4-3
Loopbacks and Tests on External E1/T1 Ports..........................................................4-3
Remote Loopback on External E1/T1 Interface ..................................................4-3
Local Loopback on External E1/T1 Interface ........................................................4-4
Loopbacks on Internal Ports....................................................................................4-5
4.4 Troubleshooting the Modules .....................................................................................4-6
Troubleshooting New Installations ..........................................................................4-6
General Troubleshooting Procedure.........................................................................4-7
4.5 Frequently Asked Questions .......................................................................................4-7
4.6 Technical Support ......................................................................................................4-8
ii VFS MP-2100/2104 Ver. 12Chapter 1
Introduction
1.1 Overview
VFS-24, VFS-48, VFS-30 and VFS-60 are digital voice/fax compression server
modules for the Megaplex-2100 and Megaplex-2104 Modular Integrating Access
Nodes.
Product Options
The voice/fax compression modules are available in the following versions that
differ with respect to the interface type (E1 or T1) and the number of external
links installed on the module:
• VFS-30: module with one E1 link, supports 30 channels
• VFS-60: module with two independent E1 links, supports 30 channels per link
for a total of 60 channels per module.
• VFS-24: module with one T1 link, supports 24 channels
• VFS-48: module with two independent T1 links, supports 24 channels per link
for a total of 48 channels per module.
Note
In this manual, the generic term Megaplex is used when the information is
applicable to both the Megaplex-2100 and Megaplex-2104 chassis types, and the
term VFS is used when the information is applicable to all the four modules. The
complete designation is used only for information applicable to a specific version.
Main Features
Voice Transmission
The VFS modules connect and compress E1/T1 voice trunks for efficient
transmission over TDM or IP networks. The timeslots received from the external
E1/T1 trunks or from the VC-4/8/16/4A/8A voice compression modules via the
backplane are compressed by the module DSP using one of the following
standard algorithms:
• ITU-T Rec. G.723.1 at 6.4 kbps per channel. This enables transmitting up to
10 voice channels in one timeslot.
• ITU-T Rec. G.723.1 at 5.3 kbps per channel. This enables transmitting up to
12 voice channels in one timeslot.
• ITU-T Rec G.729.A at 8.0 kbps per channel. This enables transmitting up to
8 voice channels in one timeslot.
VFS MP-2100/2104 Ver. 12 Overview 1-1Chapter 1 Introduction Installation and Operation Manual
Compression methods are user-selectable per bundle.
Note
Every six voice timeslots are handled by a single DSP. Each DSP supports one
compression method at any time.
The module includes adaptive echo canceling for near-end hybrid echo, for delays
of up to 16 msec. The echo canceller enables acceptable voice quality on voice
lines with long delay, such as long-distance calls or calls over non-terrestrial
(satellite) links.
To ensure reliable transmission of DTMF signals, they are always transmitted
through the link as digital signals (this is called DTMF relaying), and clean
representations are synthesized at the receiving end. The same process is used
for the call progress tones that are detected within the T1 trunk timeslots.
Automatic Fax and Modem Transmission
In addition to voice transmission, the VFS modules also support automatic fax
relaying, which allows the transmission of Group III fax (ITU-T Rec. V.17 and V.29)
at rates of 2.4 to 14.4 kbps, irrespective of the digitizing rate selected for voice.
The modules have automatic rate fallback capability, to automatically switch to
the next lower data rate supported by both communicating faxes.
Voiceband modem transmissions at all the standard rates up to 14.4 kbps (per
ITU-T Rec. V.22bis and V.32bis) are also supported, and are handled in the same
way as fax transmissions.
Transparent Transfer of Timeslots
In addition to timeslots being processed to support voice and fax, it is also
possible to transparently transfer selected timeslots of the external trunks,
through the Megaplex links, to a remote location, thereby providing support for
fractional T1 services together with compressed voice through the same T1 trunk.
Another application for transparent transfer of timeslots is support for CCS
signaling in any desired protocol or flavor: the timeslot carrying the CCS
information can be transferred transparently together with the timeslots carrying
the voice channels to the remote Megaplex equipment. This permits restoring the
original E1/T1 trunk structure, including the signaling channel, at the external link
interface of the remote VFS module.
Inband management through dedicated timeslots is also supported. Among other
options, this enables extending the inband management links, through the E1/T1
interfaces of the module, to the other equipment connected to these interfaces.
Traffic Carrying Capacity
The advanced digital signal processing (DSP) techniques used by the
VFS modules provide voice compression options that meet a wide range of user
requirements and enable the transmission of high-quality compressed voice
signals while requiring low bandwidth.
The number of channels that can be transmitted depends on the percentage of
silence the number of simultaneously active calls, and the packet parameters. The
number of channels and the approximate bandwidth can be estimated using the
following formula:
1-2 Overview VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
[(H e a d e r size x p a cke ts p e r se co n d ) + (# tim e slo ts x size o f
{ co m p re sse d G .7 3 2 p a cke t x 1 0 0 0 /3 0 x a ctu a l tra n sm issio n tim e (%
n o n -sile n ce ) )] x 8 b yte s p e r b it
1 0 0 0 b its p e r kilo b it
} + ra te
co n ve rte d
to kb p s
You can also use for this purpose the Vmux-110/2100 Bandwidth calculator
supplied on the Megaplex Technical Documentation CD.
Two companding laws are supported, µ-law and A-law. In accordance with ITU-T
Rec. G.711, the A-law should be used on E1 trunks and the µ-law should be used
on T1 trunks. However, the user can select the desired companding law, µ-law or
A-law, in accordance with the specific system requirements.
Since the VFS modules can compress and transmit multiple E1/T1 trunks using
minimal bandwidth, the Megaplex units can utilize the remaining bandwidth to
provide other required services such as data, Ethernet LANs, ISDN and/or
management, all in one platform.
With regular voice encoding methods, much bandwidth is wasted during the
normal periods of silence in a call. To further reduce the actual bandwidth
required for voice transmission, the VFS modules support voice activity detection
(VAD) techniques with silence detection and suppression:
• When a silence interval is detected in a channel (timeslot), an indication is
sent to the far end, and the transmitting side releases most of the bandwidth
normally occupied by the channel traffic.
• The far end fills the interval with noise having characteristics similar to normal
background noise (this capability is called comfort noise generation), and
therefore the subjective quality of the call is not noticeably affected.
This method enables using less bandwidth to transmit the same amount of voice
traffic, without degrading the quality of the call.
The low-rate digitized voice data packets that are the result of digital signal
processing of the payload carried by the external port timeslots are routed to
internal ports. The VFS modules support up to 8 internal ports; each internal port
can be routed to a different destination through any desired main link port,
thereby supporting both point-to-point and point-to-multipoint applications.
The user can therefore select the bandwidth (number of timeslots on the main
link) that will be allocated per internal port in accordance with the selected
compression rate. By considering the statistical distribution of speech and call
traffic loads, even higher compression ratios are possible.
VFS MP-2100/2104 Ver. 12 Overview 1-3Chapter 1 Introduction Installation and Operation Manual
1.2 Typical Applications
Point-to-Point Applications
Figure 1-1 shows a typical point-to-point application for VFS modules. In this
application, a single PBX trunk is connected to a VFS module, and the resulting
data stream is routed by means of a single internal port, allocated the desired
number of timeslots, to a main link port.
The compressed voice data stream is transported through the TDM network to
the far end, where it is restored and connected to another PBX. The PBX trunks
can use any desired signaling protocol:
• For CAS (robbed-bit signaling), no special arrangements are needed, as this
signaling protocol is processed and transferred by the VFS module within the
compressed voice data stream.
• For other signaling protocols, for example, protocols using CCS, the timeslots
carrying the signaling information can be transparently transferred to the far
end in other main link timeslots, and made available to the equipment
connected to the far end module.
A single Megaplex-2100 unit can be equipped with up to 10 VFS-60/VFS-48
modules, and therefore can support up to 20 E1/T1 trunks (600/480 digital voice
channels). After compression, this payload can be transmitted using only
two E1/T1 links, enabling very efficient utilization of the E1/T1 links.
Megaplex-2104 units can be equipped with 4 VFS-60/VFS-48 modules to support
up to 8 E1/T1 trunks.
Figure 1-1. Transport of Compressed Digital Trunks in Point-to-Point Topology
Point-to-Multipoint Applications
Point-to-multipoint applications use the multiple internal ports (up to 8)
supported by the VFS modules. Each internal port can operate at a different voice
encoding rate and/or fax rate. Each internal port can be routed to a different
destination by routing it to a different main link port or IP destination.
Figure 1-2 shows a typical point-to-multipoint application for VFS modules. In this
application, two PBX trunks are connected to a VFS-48 module, and the resulting
data stream is routed by means of three internal ports, allocated the desired
number of timeslots, to a ML-IP module.
The ML-IP module provides independent links to the desired destinations through
the IP network.
1-4 Typical Applications VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
Figure 1-2. Combining Compressed Digital Voice, Analog Voice and Data in Point-to-Multipoint
Topology
Server Application
Figure 1-3 shows a typical server application for VFS-24 modules. In this
application, the VFS module is used to compress the PCM data for sending it
towards the network. The VC-16 module is sending PCM data and signaling
towards the backplane. The VFS server takes this information from the backplane,
compresses it and sends it via the bundles back to the backplane. At this stage,
the main link takes the bundle and sends it towards the remote VFS.
Figure 1-3. Transport of Compressed Digital and Analog Channels over TDM Network (VFS as
Compression Server)
VFS MP-2100/2104 Ver. 12 Typical Applications 1-5Chapter 1 Introduction Installation and Operation Manual
1.3 Physical Description
The VFS modules are 4U-high and occupy one slot in the Megaplex chassis. All the
module parameters are configurable by software, except for the selection of the
link interface type (balanced or unbalanced) in VFS-30 and VFS-60 modules.
The module panels are shown in Figure 1-4. The panels include an RJ-45
connector and a group of status indicators for each link, and a module alarm
indicator.
Table 1-1 explains the functions of the components located on the module
panels.
VFS-24 VFS-48 VFS-30 VFS-60
T1 2T1 E1 2E1
ALARM ALARM ALARM ALARM
ON ON ON ON
TST LINE TST LINE TST LINE TST LINE
RED YEL RED YELL LOC REM LOC REM
I
S. LOSS S. LOSS N S. LOSS S. LOSS
K L
L 1 I
I N
K
N 1
K
L
I
L N
I
N K
ON K
TST LINE 2
RED YEL
S. LOSS
L
I
N
K
2
ON
TST LINE
LOC REM
S. LOSS
VFS-24 VFS-48 VFS-30 VFS-60
Figure 1-4. VFS Module Panels
1-6 Physical Description VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
Table 1-1. VFS Panel Components
Component Description
ALARM indicator Lights when a fault has been detected in the module
ON LINE indicator Lights steadily when the corresponding link is operating properly and is
active (i.e., some of its timeslots are connected to an internal port or
bypassed).
Off when the corresponding link is defective, or none of its timeslots is
connected to an internal port or bypassed
RED S. LOSS (VFS-24/48) Lights when the corresponding local link has lost frame synchronization
LOC S. LOSS (VFS-30/60)
indicator
YEL S. LOSS (VFS-24/48) Lights when a loss-of-frame synchronization indication is received by the
REM S. LOSS (VFS-30/60) corresponding link from the equipment connected to that link
indicator
TST indicator Lights when a test is being performed on the corresponding link
LINK connector RJ-45 connector for connection to the corresponding link interface
VFS MP-2100/2104 Ver. 12 Physical Description 1-7Chapter 1 Introduction Installation and Operation Manual
1.4 Functional Description
Functional Block Diagram
Figure 1-5 shows the functional block diagram of the VFS modules.
Internal VFS
Ports
1 Voice
Processing
DSP 1
2
Link
3 Interface Link 1
(Port EX1)
4
Routing
Matrix
and 5 CPU
TDM Bus VFS-48, VFS-60 Only
Interfaces
6
Link
Interface Link 2
TDM Bus A
TDM Bus B
TDM Bus C
TDM Bus D
7 (Port EX2)
Voice
Processing
8 DSP 2
ABCD
Signaling RAM
Control To Link Interfaces
Management
Channel
Local
Management
To CL Module
Nodal Timing Internal Clock
& Timing Signals
Main Clock Clock
Generator Receive Clock from
Fallback Clock
Link Interfaces
Clock
Selection
Figure 1-5. Functional Block Diagram
1-8 Functional Description VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
The VFS modules include the following subsystems:
• Routing matrix and TDM bus interfaces
• CPU (including internal ports)
• DSP subsystem
• Link interfaces
• Clock generator and timing subsystem
• Local management subsystem
• ABCD Signaling RAM.
TDM Bus Interfaces
The VFS module has four independent TDM bus interfaces, one for each Megaplex
TDM bus. Each TDM bus interface is used to connect timeslots from the
corresponding bus to the routing matrix of the VFS module, in accordance with
the commands received from the CL module.
Routing Matrix on TDM Buses Side
Overview of Internal Routing Method
To understand the payload routing method used within the VFS module, it is
necessary to consider three entities:
• Chassis TDM buses. The flow of payload on these buses is organized in
timeslots (31 timeslots per bus). The CL module automatically assigns
timeslots on the TDM buses to each connected I/O channel or internal port of
the modules installed in the chassis.
• External ports. The external port, which has an E1 or T1 interface, provides
the connection to the local user’s equipment. VFS-60 and VFS-48 modules
have two independent external E1 and T1 ports, respectively.
An external E1 port has a capacity of 31 timeslots. However, since signaling
information must always be transmitted, only 30 timeslots can carry voice
(one timeslot is always assigned either to CAS or CCS signaling).
An external T1 port has a capacity of 24 timeslots. When using CCS signaling,
only 23 timeslots can carry voice (one timeslot is then assigned to CCS
information).
• Internal ports IN1 to IN8. On the TDM buses side, the timeslots that carry
voice and fax payload directed for transmission through the VFS module are
formally connected to entities designated internal ports. The
VFS modules can be configured to use up to 8 internal ports of this type.
Internal ports IN9, IN10. These internal ports are logical ports used to specify
the Connection ID and the destination bundle for each analog voice channel.
An internal port provides a convenient way to indicate which payload is to be
routed to a certain destination, and enables the user to specify associated
parameters. For flexibility in routing, the internal ports are located between
VFS MP-2100/2104 Ver. 12 Functional Description 1-9Chapter 1 Introduction Installation and Operation Manual
two routing matrices: the TDM bus side routing matrix, and the internal ports
routing matrix.
Note
In addition to packetized payload, it is also necessary to transparently bypass
timeslots to a main link port. Bypassing of timeslots is needed to support
fractional E1/T1 service through the module links; it may also be used to
transparently transfer the common channel signaling (CCS) information received
from the user’s equipment connected to the external port to the remote end of
the compressed voice link, where the original frame structure and signaling can
be restored.
The timeslot carrying inband management traffic may also have to be bypassed.
Routing Matrix Functions
The routing of the TDM bus side matrix is user-programmable, under the control
of the CL module, and enables connecting any timeslot between of its ports. As a
result, the matrix can be used to perform the following functions:
• Connect timeslots between main link ports of modules installed in the
Megaplex and the internal ports of the VFS module. This is performed by
connecting the desired timeslots from the TDM buses to the prescribed
internal port.
• Bypass timeslots between the external ports of the VFS module and main link
ports (through the internal ports of the VFS module).
CPU
CPU is used to route the packetized voice traffic to timeslots that are then
connected by the TDM side routing matrix to the TDM buses.
The CPU is also used to bypass timeslots between the external ports of the
VFS module and main link ports.
DSP Subsystem
The DSP subsystem consists of two voice processing DSP groups: DSP 1 and
DSP 2.
Each voice processing DSP group includes four DSPs for each external port.
In the VFS-30 and VFS-60 modules, each DSP processes six timeslots out of the
30 payload timeslots that may be carried by an external port. In the VFS-24 and
VFS-48 modules, each DSP processes six timeslots out of the 24 payload
timeslots that may be carried by an external port.
The timeslots processed by each DSP are identified in Table 1-2 for the
VFS-30/60 modules and in Table 1-3 for the VFS-24/48 modules.
Since the DSP performs the same operations on all of the processed timeslots,
the six timeslots must use the same voice coding standard and fax rate. The
resulting voice packets are sent to the internal ports routing matrix.
Note that the rate at which the DSP exchanges data on the external port side
must be locked to the external port timing, whereas the packet data rate on the
TDM buses side must be locked to the Megaplex nodal timing.
1-10 Functional Description VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
These two rates need not be synchronized, because it is not necessary to lock
the packet timing to the external port timing.
Table 1-2. Timeslots Processed by Individual DSPs (E1 Links)
DSP Processed Timeslots
1 1, 2, 3, 4, 5, 6
2 7, 8, 9, 10, 11, 12
3 13, 14, 15, 17, 18, 19
4 20, 21, 22, 23, 24, 25
5 26, 27, 28, 29, 30, 31
Table 1-3. Timeslots Processed by Individual DSPs (T1 Links)
DSP Processed Timeslots
1 1, 2, 3, 4, 5, 6
2 7, 8, 9, 10, 11, 12
3 13, 14, 15, 16, 17, 18
4 19, 20, 21, 22, 23, 24
Signaling RAM
The VFS module can serve voice channels from two sources: either two external
E1/T1 ports or DS0 from the TDM backplane. While the DSP is taking care of the
DS0 compression, the CPU is reading the signaling from the Framer or from the
Signaling RAM, respectively. The CPU combines the compressed voice and its
signaling and sends it to the remote equipment.
Link Interfaces
E1 Link Interfaces (VFS-30, VFS-60)
The VFS-30 module has one link interface, and the VFS-60 module has two
independent link interfaces. Each link interface performs the following functions:
• The transmit path of each interface generates the E1 frames in accordance
with the framing mode selected by the user, and prepares the resulting data
stream for transmission.
• The receive path recovers the receive signal and the associated clock.
In addition, the link interface can collect performance diagnostic data (CRC-4
block error data) in accordance with the applicable standards.
T1 Link Interfaces (VFS-24, VFS-48)
The VFS-24 module has one link interface, and the VFS-48 module has two
independent link interfaces. Each link interface performs the following functions:
VFS MP-2100/2104 Ver. 12 Functional Description 1-11Chapter 1 Introduction Installation and Operation Manual
• The transmit path of each interface generates the T1 frames in accordance
with the framing mode selected by the user (SF (D4) or ESF), and prepares
the resulting data stream for transmission.
• The receive path recovers the receive signal and the associated clock.
In addition, when using ESF framing, the link interface collect performance
diagnostic data (CRC-6 block error data) in accordance with the applicable
standards.
Clock Generator and Timing Subsystem
Link Timing
The link receive path always uses the clock signal recovered from the received line
signal.
The timing of the link transmit path is always derived from the Megaplex nodal
timing.
Therefore, the user’s equipment must operate with loopback timing, i.e., it must
be configured to lock its transmit timing to the clock signal recovered from the
VFS transmit signal.
System Timing
The VFS clock generator and timing subsystem provides the clock signals needed
by the local module circuits.
In addition, this subsystem can also provide Megaplex nodal main and fallback
clock signals, derived from the clock signals recovered from the received line
signals by each link interface.
Therefore, the Megaplex nodal timing can be locked to the clock signal recovered
from the desired E1/T1 receive signal. This mode is used when the E1/T1 link
timing must be determined by the user’s equipment connected to the VFS
interface.
This option is necessary only when timeslots are bypassed from the module links
to main link ports, and the user’s equipment cannot be configured to lock its
transmit timing to the clock signal recovered from the VFS transmit signal.
Local Management Subsystem
The local management subsystem of the VFS module controls the operation of all
the module circuits, under the control of the CL module.
The management subsystem can also provide an interface between the Megaplex
CL module and the external links, to support inband management through a
dedicated timeslot when this option is enabled by the user:
• In the receive-from-link direction, the management traffic is extracted from
the user-specified timeslot and transferred to the CL module via the
Megaplex chassis buses.
• In the transmit to-link direction, the management traffic received from the CL
module is inserted in the user-specified timeslot of the link interface, for
1-12 Functional Description VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
transmission to the user’s equipment (when it can be managed using one of
the protocols supported by Megaplex equipment).
The management traffic can use the PPP or Frame Relay protocols, in addition to
the RAD proprietary routing protocol.
E1 Interface Characteristics (VFS-30, VFS-60)
The E1 interfaces of the VFS-30 and VFS-60 modules meet the requirements of
ITU-T Rec. G.703, G.704, and G.732. The line code is HDB3. Jitter performance
complies with the requirements of ITU-T Rec. G.823.
Each link can be configured by means of internal jumpers to use either of the
following types of interfaces:
• 120Ω balanced line interface. The nominal balanced interface transmit level is
±3V.
• 75Ω unbalanced interface. The nominal unbalanced interface transmit level is
±2.37V.
You can select the maximum line attenuation that can be compensated without
degrading the BER performance: 12 dB (similar to a DSU) or 36 dB (as required of
an LTU).
Each link can be configured to use its own framing mode. The following framing
modes are supported:
• G732S (16 frames per multiframe), intended for use with channel-associated
signaling (CAS). In most applications, the required signaling mode is CAS: this
mode is compatible with the signaling mode used by PBXs.
• G732N (2 frames per multiframe), intended for use with common-channel
signaling (CCS) protocols. These protocols exchange the signaling information
through a dedicated timeslot and therefore require transparent transmission
of the CCS timeslot through the link.
You can configure each interface to operate with or without the CRC-4 option.
The use of the CRC-4 option allows monitoring the E1 connection to the user’s
equipment.
T1 Interface Characteristics (VFS-24, VFS-48)
The T1 line interface of the VFS-24 and VFS-48 modules meets the requirements
of AT&T TR-62411, ANSI T1.403, and ITU-T Rec. G.703, G.704. Jitter performance
complies with the requirements of AT&T TR-62411. The interface has a 100Ω
balanced line interface, terminated in an RJ-45 eight-pin connector. The nominal
transmit level is ±3V.
Each T1 line interface has an integral CSU, which enables operation with line
attenuations up to 30 dB. The CSU transmit level can be attenuated by 7.5, 15, or
22.5 dB, for compliance with FCC Rules Part 68A. The line interface can also
emulate a DSU interface. When configured for DSU emulation, the line transmit
signal is user-adjustable for line lengths of 0 to 655 feet in accordance with AT&T
CB-119, and the maximum attenuation is 12 dB.
VFS MP-2100/2104 Ver. 12 Functional Description 1-13Chapter 1 Introduction Installation and Operation Manual
The VFS-24/VFS-48 modules support both the D4 (SF) and ESF framing formats,
in accordance with user's selection. Zero suppression over the line is
user-selectable (transparent (AMI) coding, B7ZS, or B8ZS). Framing and zero
suppression methods are separately selectable for each link interface.
Handling of Signaling Information
Handling of CAS Signaling
In the CAS (robbed-bit signaling) mode, the signaling information of each channel
is processed and transferred in the packets transferred through the internal port
serving the corresponding voice channels.
In case the link to the remote VFS module is out-of-service, the user can select
the state of the signaling information sent in all the channels during the
out-of-service period:
FORCED BUSY The signaling information is forced to the busy state during
out-of-service periods.
FORCED IDLE The signaling information is forced to the idle state during
out-of-service periods.
Handling of CCS Signaling
In addition to CAS signaling, the VFS modules can also support equipment using
common-channel signaling (CCS) protocols. These protocols exchange the
signaling information through a dedicated channel timeslot and therefore require
transparent transmission of the CCS timeslot through the module.
The CCS timeslots can be compressed and transmitted to the destination ports in
up to 8 logical groups, CCS to CCS. Timeslots are assigned to logical
groups manually be the user.
Handling of SS7 Signaling
Handling of SS7 signaling timeslots is similar to that of CCS.
Audio Signal Processing Capabilities
This section explains the audio processing capabilities of VFS modules. The audio
processing capabilities, which are performed by the digital signal processors
(DSPs), include:
• Voice processing
• Processing of DTMF and call progress tones
• Processing of fax and voiceband modem signals.
Each DSP processes its group of timeslots (see Table 1-2, Table 1-3)
independently of the other DSPs, in accordance with the parameters selected by
the user for that group. However, within each group, the DSP detects the signal
type (voice, DTMF, fax, etc.) carried in each timeslot (channel), and automatically
selects the appropriate processing method.
1-14 Functional Description VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
Handling of Voice Signals
Voice is digitized and compressed using one of the processing algorithms
supported by the VFS.
The low bit rate voice compression options and data rates supported by the VFS
modules are as follows:
• Voice compression using multiple-pulse, maximum likelihood code-excited
linear prediction (MP-MLQ) per ITU-T Rec. G.723.1, at a channel data rate of
6.4 kbps. When using this option, up to 10 voice channels can be carried by
each timeslot sent to the Megaplex TDM buses.
• Voice compression using conjugate structure-algebraic-code-excited linear
prediction (CS-ACELP) per Annex A of ITU-T Rec. G.729A, at a channel data
rate of 8 kbps. When using this option, up to 8 voice channels can be carried
by each timeslot sent to the Megaplex TDM buses.
To further reduce the bandwidth needed to transmit the voice, the VFS DSP
recognizes “silence” intervals and replaces them with special “silence” packets,
that require much less bandwidth than regular voice packets. When “silence”
packets are received, the comfort noise generator (CNG) of the remote channel
generates background noise to fill the silence intervals and give the remote
subscriber the impression of a live line.
The resulting channel data stream is packetized for transmission through the
network. The user can select two parameters:
• The maximum number of bytes included in each voice coder frame (100 to
450 bytes). This limits the size of packets sent to the network.
• The maximum interval between consecutive frames: if this interval expires,
the frame is closed and sent, even if the specified maximum number of bytes
has not yet been collected. This parameter ensures that the end-to-end delay
is not excessive, for example, the additional delay needed to collect timeslots
to fill a frame from an internal port that carries a single channel (timeslot),
even for the minimum frame length (100 bytes) is approx. 12.5 msec.
Note
Because the DSP sends only data packets toward the Megaplex TDM buses, and
packets can be read and transmitted independently of the rate of the incoming
E1/T1 stream, in general it is not necessary to lock the timing of the link interface
to the Megaplex timing. The timing must be locked only when the module
transfers (bypasses) timeslots transparently.
To improve the perceived link quality, the DSPs also implement adaptive echo
canceling for near-end reflections (echo delay less than 16 milliseconds). The
echo canceling performance complies with ITU-T Rec. G.168 requirements.
DTMF Processing
The waveform of the DTMF signals is very different from speech waveforms,
therefore most compression algorithms distort DTMF signals to the point that
errors occur in the detection of the dialed digits when the DTMF signals are
transmitted as analog signals through a compressed voice channel.
To enable reliable transmission of DTMF signals, the VFS module uses DTMF
relaying. For this purpose, each DSP detects incoming DTMF signals,
VFS MP-2100/2104 Ver. 12 Functional Description 1-15Chapter 1 Introduction Installation and Operation Manual
independently for each timeslot, and identifies the dialed digits. The digits
detected by the receiving end are digitally transmitted through the link to the
remote end, where clean digital representations of DTMF signals are synthesized
and inserted into the data stream sent in the corresponding timeslot.
While DTMF information is received, the voice path is disconnected, to prevent
interference by signals transmitted through the regular processing path.
The method used for DTMF relaying is also used to transfer transparently call
progress tones.
Automatic Fax Processing
The processing of audio signals by low bit rate voice compression methods does
not enable analog transmission of fax signals. Therefore, when it is possible that
fax machines may be connected to a VFS voice channel, it is necessary to enable
the automatic fax relaying function on that channel.
When automatic fax relaying is enabled, a VFS channel will automatically recognize
and transmit fax messages at the standard rates in the range of 2.4 to 14.4 kbps,
complying with ITU-T Rec. V.17 and V.29. The maximum fax rate can be selected
by the user. The VFS supports automatic fallback capability, that is, it will
automatically switch to the next lower data rate supported by both
communicating faxes.
The whole fax transmission process is handled as a data transmission, with the
corresponding DSP providing the fax signal modulation/demodulation functions
and the detection and generation of the fax connection set up tones (in digital
format), to enable the handshaking necessary to implement the standard fax
communication protocol. Fax transmission over the digital network improves
transmission quality, while greatly reducing long distance telephone costs and the
time needed for freeing the fax machine.
To set up a fax connection, the DSP processing the local timeslot (channel)
emulates the remote fax machine toward the local machine, and the remote DSP
emulates the local fax toward the remote machine. After the fax connection is
established, the fax data stream is transmitted as a packetized data stream
through the link. This means that the link must have enough free bandwidth to
enable sustained transmission of a data stream at the fax data rate (and the
additional connection supervision signals).
This process enables any standard Group III fax machine to transmit over the link.
The only limitation is that the round-trip transmission delay through the link
cannot exceed the time-out intervals specified by the fax communication protocol
(about 700 msec); otherwise, the handshaking needed to establish a fax
connection will fail.
Since each VFS channel automatically switches between the fax relay mode and
the voice mode in accordance with the type of signal being detected, the VFS
modules can serve PBX tie lines or channels serving a combined phone/fax
machine.
Handling of Voiceband Modem Signals
The DSPs can also handle voiceband modem signals, in accordance with ITU-T
Rec. V.22bis and V.32bis. The processing method is similar, except that the DSP
emulates a voiceband modem instead of a fax modem.
1-16 Functional Description VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
Test and Diagnostic Capabilities
The VFS modules feature the following user-initiated loopback functions:
• External E1/T1 ports. The loopbacks available at the external E1/T1 port level
include:
Local loopback toward the Megaplex TDM buses
Remote loopback toward the user’s equipment connected to the port.
• Internal ports. The internal ports support the local loopback toward the
Megaplex TDM buses.
VFS MP-2100/2104 Ver. 12 Functional Description 1-17Chapter 1 Introduction Installation and Operation Manual
1.5 Technical Characteristics
General Number of External Ports
VFS-30 One E1 port
VFS-60 Two E1 ports
VFS-24 One T1 port
VFS-48 Two T1 ports
Number of Internal Ports 8 ports for regular operation
2 additional ports for server operation
Voice Encoding Voice Encoding Technique • MP-MLQ per ITU-T Rec. G.723.1, at a channel
data rate of 6.4 kbps or 5.3 kbps
• Conjugate structure-algebraic-code-excited
linear prediction (CS-ACELP) per Annex A of
ITU-T Rec. G.729A, at a channel data rate of
8 kbps
Fax Support Fax Data Rates 4.8, 9.6 and 14.4 kbps, selectable per internal
port
E1 Interface Voice Channels Supported Up to 30 (per port)
Format E1, 2.048 Mbps
Standard Compliance ITU-T Rec. G.703, G.704, G.732
Framing • G.732N
• G.732N with CRC-4
• G.732S
• G.732S with CRC-4
Interface • 120Ω, 4-wire balanced
• 75Ω, coaxial unbalanced
Line Code HDB3
Signal Levels
Transmit • Balanced : ±3V ±10%
• Unbalanced: ±2.73V ±10%
Receive • 0 to -12 dB for short-haul applications (DSU)
• 0 to -36 dB for long-haul applications (LTU)
1-18 Technical Characteristics VFS MP-2100/2104 Ver. 12Installation and Operation Manual Chapter 1 Introduction
Jitter Performance Per ITU-T Rec. G.823
Timing Mode • Transmit clock derived from Megaplex nodal
clock
• Receive clock recovered from the receive
signal, can be selected as timing reference for
Megaplex nodal clock
Connectors • Balanced: 8-pin RJ-45
• Unbalanced: Two BNC coaxial connectors, via
adapter cable
T1 Interface Voice Channels Supported Up to 24 (per port)
Format T1, 1.544 Mbps
Standard Compliance AT&T TR-62411, AT&T Pub. 54016, ANSI T1.403,
and ITU-T Rec. G.703, G.704
Framing • SF (D4)
• ESF
Interface 100Ω, 4-wire balanced
Line Code AMI
Zero Suppression • Transparent (no zero suppression)
• B7ZS
• B8ZS
Signal Levels
Transmit Levels • DSU emulation: ±3V ±10%, software
adjustable, measured at 0 through 655 ft
• CSU mode: 0, -7.5, -15, -22.5 dB
software-selectable
Receive • 0 to -12 dB for short-haul applications (DSU)
• 0 to –36 dB for long-haul applications (CSU)
Jitter Performance Per AT&T TR-62411
Timing Mode • Transmit clock derived from Megaplex nodal
clock
• Receive clock recovered from the receive
signal, can be selected as timing reference for
Megaplex nodal clock
Connectors 8-pin RJ-45
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