Document 180-0161-001 R04
Summary Diagram of Typical Installation
DSLAM BRX-VDSL2-2
L1
Distance from DSLAM to BRX-VDSL2-2
L2
Distance from BRX-VDSL2-2 to CPE
IMPORTANT NOTE: The BRX-VDSL2 unit is powered from the Sealing
Current found on a standard POTS pair. Each pair of the BRX-VDSL2-2
is powered independently with each pair requiring the presence of the
-48Vdc sealing current for proper operation. The BRX-VDSL2-2 will not
operate on a dry pair (line with no -48Vdc sealing current). You can use
the Positron BRX Power Injector to provide the -48Vdc sealing current
when operating on dry pairs.
Connecting the BRX-VDSL2-2
Step 1: Select the location where the BRX-VDSL2-2 will be inserted as
close as possible to the midpoint of the loop.
Step 2: Connect the grounding lug of the unit to a proper ground
(usually available near a splice point).
Step 3: Connect one of the DSLAM pairs to a pair coming from the
DSLAM. The corresponding DS LED on the faceplate will turn GREEN
to conrm presence of -48Vdc sealing currentand proper operation of
BRX-VDSL2-2 unit.
NOTES: -The US LED currently not used.
-If operating on a dry pair, you should use a BRX Power Injector.
Step 4: Connect the corresponding CPE pair to the pair going to
the subscriber home. Be sure to match the pair color used for the
connection to the DSLAM.
IMPORTANT: Make sure to match DSLAM pair# to CPE pair#.
After step 4, the DSLAM and the CPE will re-train the circuit and bring up
the VDSL2 link with the higher bandwidth. The performance may be limited
(or capped) by a setting in the DSLAM and/or BRAS conguration. During
this process, the optimum amplication gain is automatically determined.
CPE
Placement Guidelines for BRX-VDSL2 Devices
The BRX-VDSL2 amplies VDSL2 loops and supports proles 17a, 8a, 8b and
8d. It is designed to deliver solid amplication of the loops as long as the BRX-
VDSL2 device is installed within 45% to 60% of the total loop distance. It is
recommended to install the BRX-VDSL2 unit at an existing splice point that is
within the recommended placement range. When multiple splice points exist
within that range, you should select the one that is most convenient.
The BRX-VDSL2 installation should follow these simple rules:
1. L1 - Minimum Loop Length from DSLAM to BRX-VDSL2 should be
no less than 2000 feet (0.6 km) for 24 AWG (0.5 mm) gauge or 1600 feet
(0.5km) for 26 AWG (0.4 mm) gauge.
2. L2 - Minimum Loop Length from CPE to BRX-VDSL2 should be no less
than 650 feet (200m) for 24 AWG (0.5mm) gauge or 500 feet (150m) for 26
AWG (0.4 mm) gauge.
For a 25 / 3 Mbps service, the recommended range is as follows (single pair):
• Maximum total loop length: 6250 feet (1.9 km) for 24 AWG (0.5mm)
gauge or 5000 feet (1.5 km) for 26 WG (0.4 mm) gauge.
• Recommended placement range: 3000 to 3600 feet (0.9 to 1.1 km) of
24 AWG (0.5mm) gauge or 2400 to 2900 feet (0.7 to 0.9 km) of 26 AWG
(0.4 mm) gauge.
For a 10 / 1 Mbps service in VDSL2 mode (useful when you want to limit
the use of ADSL2+ loops inside a binder mostly used for VDSL2 loops),
the recommended range is as follows (single pair):
• Maximum total loop length: 10000 feet (3 km) for 24 AWG (0.5mm)
gauge or 8000 feet (2.4 km) for 26 WG (0.4 mm) gauge.
• Recommended placement range: 4500 to 5500 feet (1.4 to 1.7 km) of
24 AWG (0.5mm) gauge or 3600 to 4400 feet (1.1 to 1.3 km) of 26 AWG
(0.4 mm) gauge.
Recommended DSLAM Settings
Parameter Downstream Upstream
Maximum Bitrate 100 Mbps 50 Mbps
Maximum Delay 8 msec 8 msec
Path Latency Interleaved
Impulse Noise Protection (INP) 2 1
Target SNR Margin 8.0 dB 8.0 dB
In order to fully benet from the amplied VDSL2 signal, there are a few DSLAM
settings to be set as per the following recommendation:
You should also make sure that the DSLAM and/or the BRAS settings are not set
at a lower level than the target service offered to the subscriber for this loop.
NOTE: You should always follow your corporate guidelines for the DSLAM
settings if they differ from the Positron recommendation. If in doubt, you
should check with the Engineering or Operation team.
The BRX-VDSL2 Calculator can help determine the optimal installation
location for each specic loop. To download the BRX-VDSL2 Calculator,
sign up on the Positron Access Portal at www.positronaccess.com/
Portal.php. You will get a username and password to access the Portal.
