Page 932 - 5G Basics - Core Network Aspects

2 Transport aspects

12.3.3.2.10 R-SNR

The R-SNR message reports the downstream SNR.

Table 12-33 – R-SNR message
Field Field name Format

1 Message descriptor Message code
2 Downstream SNR report NSNR bytes, where NSNR is the number of
subcarriers on which the SNR is requested
in field#2 of the O-SNR message.
3 DS SOC tone repetition rate (pds) One byte
4 BLACKOUTds set Tone descriptor

Field 1 "Message descriptor" is a unique one-byte code (8416) that identifies the message. See Table 12-7
for a complete list of codes.

Field 2 "Downstream SNR report" contains the downstream SNR report requested by the FTU-O in the
format defined for the O-SNR message. The reported value of the SNR for a particular subcarrier shall be
coded as an eight-bit unsigned integer A using the rule SNR = −32 + (A/2) dB. This format supports SNR
range from -32dB to +95dB with the granularity of 0.5 dB. Values of SNR that exceed 95 dB shall be
reported as 95 dB and values of SNR that are lower than -32 dB shall be reported as
–32 dB. The bytes representing SNR(k) values for different subcarriers shall be transmitted in ascending
order of subcarrier index k, for the set as requested in field 2 of the O-SNR message. Subcarriers in the set
for which SNR estimation is not available shall be set to FF16. The values of SNR for the subcarriers that are
not in the set shall not be reported.

Field 3 "DS SOC tone repetition rate (pds)" indicates the tone repetition rate (pds) of SOC normal bit mapping
to be used by the FTU-O in subsequent SOC messages. The field shall contain the downstream value pds
defined in clause 10.2.2.2.1, represented as an unsigned integer.

Field 4 "BLACKOUTds set" indicates the set of downstream blackout subcarriers using a tone descriptor
format presented in Table 12-34.

Table 12-34 – Tone descriptor

Byte Content of field
1 Number of tones

2 to 4 (if applicable) Bits 0-11: index of tone 1
Bits 12-23: index of tone 2
5 to 7 (if applicable) Bits 0-11: index of tone 3
Bits 12-23: index of tone 4
etc. (if applicable) etc.

The first byte of the tone descriptor shall contain the number of tones selected by the FTU-R. If this number
is zero, there shall be no further bytes in the descriptor. If the number of tones is not equal to zero, each
group of three consecutive bytes in the descriptor describes two tones. For example, a field value 400200 16
means tone 20016 = 512 and tone 40016 = 1 024. If the number of tones is odd, the last 12 bits in the last
field shall be set to ZERO. The FTU-O shall support 255 downstream blackout subcarriers.

922