PRACH preamble validation

[improperaffo]

I found myself playing with the preamble options, and I feel that the logs in du_high_config_validator.cpp do not always represent the right issue.

  // See TS 38.331, ssb-perRACH-OccasionAndCB-PreamblesPerSSB and totalNumberOfRA-Preambles.
  // totalNumberOfRA-Preambles should be a multiple of the number of SSBs per RACH occasion.
  if (config.total_nof_ra_preambles.has_value()) {
    bool is_total_nof_ra_preambles_valid = true;
    if (config.nof_ssb_per_ro >= 1) {
      if (config.total_nof_ra_preambles.value() % static_cast<uint8_t>(config.nof_ssb_per_ro) != 0) {
        is_total_nof_ra_preambles_valid = false;
      }
      // Ensure \c config.total_nof_ra_preambles can accommodate contention based RA preambles.
      // NOTE: \c config.total_nof_ra_preambles nof. RA preambles are shared among \c config.nof_ssb_per_ro nof. SSB
      // beams.
      if ((config.nof_cb_preambles_per_ssb * config.nof_ssb_per_ro) > config.total_nof_ra_preambles.value()) {
        is_total_nof_ra_preambles_valid = false;
      }
    } else {
      // Number of SSBs per RACH occasion is 1/8 or 1/4 or 1/2.
      const auto product = config.total_nof_ra_preambles.value() * config.nof_ssb_per_ro;
      if ((product - static_cast<uint8_t>(product)) > 0) {
        is_total_nof_ra_preambles_valid = false;
      }
      // Ensure \c config.total_nof_ra_preambles can accommodate contention based RA preambles.
      // NOTE: Each SSB beam has multiple RACH occasions and each occasion has \c config.total_nof_ra_preambles RA
      // preambles.
      if (config.nof_cb_preambles_per_ssb > config.total_nof_ra_preambles.value()) {
        is_total_nof_ra_preambles_valid = false;
      }
    }

    if (not is_total_nof_ra_preambles_valid) {
      fmt::print("Total nof. RA preambles ({}) should be a multiple of the number of SSBs per RACH occasion ({}).\n",
                 config.total_nof_ra_preambles.value(),
                 config.nof_ssb_per_ro);
      return false;
    }
  }

For example, if we set a RA preamble count lower than the number of contention based RA preambles, we get:

Total nof. RA preambles (2) should be a multiple of the number of SSBs per RACH occasion (1.0).

which does not help.

I suggest more expressive logs like:

  // See TS 38.331, ssb-perRACH-OccasionAndCB-PreamblesPerSSB and totalNumberOfRA-Preambles.
  // totalNumberOfRA-Preambles should be a multiple of the number of SSBs per RACH occasion.
  if (config.total_nof_ra_preambles.has_value()) {
    bool is_total_nof_ra_preambles_valid = true;
    if (config.nof_ssb_per_ro >= 1) {
      if (config.total_nof_ra_preambles.value() % static_cast<uint8_t>(config.nof_ssb_per_ro) != 0) {
        is_total_nof_ra_preambles_valid = false;
        fmt::print("Total nof. RA preambles ({}) should be a multiple of the number of SSBs per RACH occasion ({}).\n",
                   config.total_nof_ra_preambles.value(),
                   config.nof_ssb_per_ro);
      }
      // Ensure \c config.total_nof_ra_preambles can accommodate contention based RA preambles.
      // NOTE: \c config.total_nof_ra_preambles nof. RA preambles are shared among \c config.nof_ssb_per_ro nof. SSB
      // beams.
      if ((config.nof_cb_preambles_per_ssb * config.nof_ssb_per_ro) > config.total_nof_ra_preambles.value()) {
        is_total_nof_ra_preambles_valid = false;
        fmt::print("Total nof. RA preambles ({}) should be greater than or equal to the number of contention based "
                   "RA preambles ({}) for all SSBs per RACH occasion ({}).\n",
                   config.total_nof_ra_preambles.value(),
                   config.nof_cb_preambles_per_ssb * config.nof_ssb_per_ro,
                   config.nof_ssb_per_ro);
      }
    } else {
      // Number of SSBs per RACH occasion is 1/8 or 1/4 or 1/2.
      const auto product = config.total_nof_ra_preambles.value() * config.nof_ssb_per_ro;
      if ((product - static_cast<uint8_t>(product)) > 0) {
        is_total_nof_ra_preambles_valid = false;
        fmt::print("Total nof. RA preambles ({}) should be a multiple of the number of SSBs per RACH occasion ({}).\n",
                   config.total_nof_ra_preambles.value(),
                   config.nof_ssb_per_ro);
      }
      // Ensure \c config.total_nof_ra_preambles can accommodate contention based RA preambles.
      // NOTE: Each SSB beam has multiple RACH occasions and each occasion has \c config.total_nof_ra_preambles RA
      // preambles.
      if (config.nof_cb_preambles_per_ssb > config.total_nof_ra_preambles.value()) {
        is_total_nof_ra_preambles_valid = false;
        fmt::print("Total nof. RA preambles ({}) should be greater than or equal to the number of contention based "
                   "RA preambles ({}) for all SSBs per RACH occasion ({}).\n",
                   config.total_nof_ra_preambles.value(),
                   config.nof_cb_preambles_per_ssb,
                   config.nof_ssb_per_ro);
      }
    }

    if (not is_total_nof_ra_preambles_valid) {
      return false;
    }

Which would output:

Total nof. RA preambles (2) should be greater than or equal to the number of contention based RA preambles (4.0) for all SSBs per RACH occasion (1.0).