Page 841 - 5G Basics - Core Network Aspects

Transport aspects 2

A vector block read command shall be used to retrieve a single test parameter over a range of subcarrier
groups. Support of this read command is mandatory. The ID of the test parameter to retrieve shall be
indicated in the third byte of the read command as specified in Table 11-37. In response to a vector block
read command, the FTU shall send information for the test parameter associated with the specified block
of subcarrier groups. All values for subcarrier groups with indices from start subcarrier group index to stop
subcarrier index are transferred in a single response.
If the stop subcarrier group index in the test parameter read command exceeds the round-up of the index
of the highest subcarrier in the MEDLEY set divided by the group size G, the response shall be a NACK. The
format of the bytes for each parameter value shall be as described in clause 11.4.1. Values formatted as
multiple bytes shall be mapped to the response in order of most significant to least significant byte.

The response to a vector block read command for SNR shall include the measurement time in symbol
periods (2 bytes) followed by the SNR test parameter value (see clause 11.4.1.2.2).

The response to a vector block read command for ALN shall include the measurement time in symbol
periods (2 bytes), followed by the group size (1 byte), followed by the ALN test parameter value (see clause
11.4.1.2.4).

Responses to a vector block read command may be segmented.
The values of some test parameters are represented using fewer bits than contained in the corresponding
field defined for the response in Table 11-39. In the case that the field has more than one byte, the bits
shall be mapped to the LSBs of the multibyte field in the response. Unused MSBs in the multibyte field shall
be set to ZERO for unsigned quantities and to the value of the sign bit for signed quantities.

11.2.2.14 Vectoring feedback command and responses
The FTU-O shall use the vectoring feedback command and responses for configuration of the vectoring
report parameters and obtaining VF samples, i.e., clipped error samples or DFT output samples, from the
FTU-R. The command (containing a request for VF samples) may be initiated only by the FTU-O and shall
use the format shown in Table 11-40. The FTU-R shall respond with VF samples for the requested
subcarriers in the requested format, or with NACK. The NACK provides a rejection code describing the
reason of the request denial. Prior to sending the NACK, the FTU-R shall suspend sending VF samples until it
receives a new vectoring feedback command with a valid set of the vectoring feedback report control
parameters.
The first byte of the command and the response shall be the assigned value of the vectoring feedback
command type, as shown in Table 11-4 (near-high priority command). The second and subsequent bytes
shall be as shown in Table 11-40 for the command and in Table 11-43 for responses. The rejection codes
shall be as defined in Table 11-44. The data bytes shall be mapped using the generic format described in
clause 11.2.2.1.
The FTU-O sends in the vectoring feedback command a set of parameters of the requested vectoring
feedback report. The first FTU-R vectoring feedback response data sent in reply serves as an ACK for the
vectoring feedback command. More vectoring feedback data may be transmitted, if necessary, in
subsequent eoc messages. Transmissions of the following vectoring feedback responses shall be triggered
by every VF sample update at superframe counts requested in the vectoring feedback command (update
period and shift period). If the update period q is greater than 1, the FTU-R shall update VF samples only at
the exact superframe counts indicated by the FTU-O (see clause 10.3.2.5.2).
Vectoring feedback responses shall not be acknowledged. If the vectoring feedback data message exceeds
P-4 bytes (see clause 11.2.1.1), it shall be segmented as defined in clause 11.2.2.3 with the maximum
number of segments not to exceed 16. The FTU-R shall not retransmit vectoring feedback data messages or
their segments. If the FTU-O does not receive a response (ACK), it may send another vectoring feedback
command, possibly with different control parameters. The FTU-R shall continue sending vectoring feedback
responses until stopped by the FTU-O, including while waiting for a reply to SRA request RMC command. If
in the time period allocated to send a particular vectoring feedback response the eoc channel is busy with a

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