Page 706 - 5G Basics - Core Network Aspects

2 Transport aspects

The specific frequency bands to be notched are configured in the DPU-MIB by the operator and set during
the ITU-T G.994.1 handshake phase of initialization (see clause 12.3.2).

The configuration parameter RFIBANDS specified in the DPU-MIB specifies the start and stop frequencies of
each notched RFI band. The configuration parameter IARBANDS specified in the DPU-MIB specifies whether
or not a given IAR band is notched. The PSD slopes forming the notch outside of the start and stop
frequencies are vendor discretionary.

7.3.1.3 Subcarrier masking

The ITU-T G.9701 transmitters shall be able to mask one or more subcarriers. Subcarrier masking is defined
in the DPU-MIB by a configuration parameter (CARMASK).

All masked subcarriers shall be turned off (see clause 6.5 of [ITU-T G.9700]), i.e., Zi' = 0 (see Figure 10-16).
The subcarrier masking shall override all other instructions related to the transmit power of the subcarrier.

7.3.1.4 Upstream power back-off (UPBO)
Upstream power back-off (UPBO) shall be performed by the FTU-R to improve spectral compatibility
between the ITU-T G.9701 systems operating on loops of different lengths deployed in the same binder.
This UPBO mechanism does not apply during the ITU-T G.994.1 handshake phase.
7.3.1.4.1 UPBO mechanism

The transmit PSD of the FTU-R shall be established using the following procedure:
• The FTU-O shall communicate to the FTU-R during the channel discovery phase of the initialization
(in the O-SIGNATURE message, see clause 12.3.3.2) the PSDMASKus (see clause 7.3.1.1) defined in
the DPU-MIB.

• The FTU-O shall communicate to the FTU-R during the channel discovery phase of the initialization
the UPBO parameters defined by the operator via the DPU-MIB (in the O-SIGNATURE message).
• The FTU-R shall perform UPBO as described in clause 7.3.1.4.2, using the obtained UPBO
parameters. The UPBO shall be performed autonomously, i.e., without sending any significant
information to the FTU-O until the UPBO is applied. No upstream transmission after the handshake
phase is allowed prior to UPBO being applied.
• After UPBO has been applied, the FTU-O shall be capable of further adjusting the transmit PSD
selected by the FTU-R; the adjusted transmit PSD shall be subject to the limitations above and
those given in clause 7.3.1.4.2.

7.3.1.4.2 UPBO PSD mask
The FTU-R shall explicitly estimate the electrical length of its loop, kl0, and use this value to calculate the
UPBO PSD mask (UPBOMASK) at the beginning of the channel discovery phase of the initialization, prior to
the first upstream transmission. The FTU-R shall then adapt its transmit signal PSD to conform to the
UPBOMASK during the initialization and showtime. Other restrictions to the transmit signal PSD are
detailed in clause 7.3.2.

7.3.1.4.2.1 Electrical length estimation
The FTU-R shall and the FTU-O may estimate the value of kl0 autonomously, using the following equation:
loss(f )
kl  AVERAGE( i dB ) [dB/ MHz ]
0
f i

where the average is taken over the usable part of the ITU-T G.9701 frequency band. The function loss(fi) is
the insertion loss in dB of the loop at the subcarrier frequency fi expressed in MHz and corresponding to a
subcarrier with index i. Only subcarriers within the SUPPORTEDCARRIERSds set shall be accounted. The
AVERAGE function refers to mean average, computed as a sum of terms divided by the number of terms.

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