Dpbo; Upbo/Dpbo Electrical Length - ZyXEL Communications MSC1024G Series User Manual

Chapter 11 Subscriber Port Setup Screens

11.2.8 DPBO

VDSL signals may interfere with other services (such as ISDN, ADSL or ADSL2 provided by
other devices) on the same bundle of lines due to downstream far-end crosstalk. DPBO
(Downstream Power Back Off) can reduce performance degradation by changing the PSD
level on the VDSL switch(es) at street cabinet level.
ISDN in Europe uses a frequency range of up to 80 kHz, while ISDN in Japan uses a
frequency range of up to 640 kHz. ADSL utilizes the 1.1 MHz band. Both ADSL2 and ADSL
2+ utilize the 2.2 MHz band.
An example is shown next. VDSL Line 1 and ADSL Line 2 are in the same binder. Crosstalk
occurs when the ADSL signal flows from CO (B) and is near to CO (A)'s ONU (Optical
Network Unit) location. Besides, higher Line 1 PSD causes higher interference to the Line 2.
CPE (B) receives signal with higher attenuation. With DPBO enabled on the CO (A), it
decreases the PSD level and reduces the crosstalk impact on other service lines.
Figure 125 DPBO Resolves Downstream Far-End Crosstalk
ADSL
CO (B)

11.2.9 UPBO/DPBO Electrical Length

The distance between a cabinet and the central office is an important parameter of DPBO
settings as mentioned in
the real physical distance according to G.997.1 format. Depending on the cable type, the line
used and physical line length, you can calculate the electrical length (in dB). For example, if
the distance is 1 kilometer and you use 24 AWG cable type, the electrical length 20.5 dB is
recommended.
212
VDSL
CO (A)
No-DPBO
DPBO
Section 11.2.8 on page
ADSL
Line2 (600m)
CPE (B)
Line1 (150m)
212. The electrical length is used instead of
MSC1000G/1024G/1224G Series User's Guide
VDSL
CPE (A)