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fix issue 2082 - ensure that sched does not exceeds max coderate while decreasing mcs

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master
Francisco 4 years ago committed by Andre Puschmann
parent 96b75b6433
commit 37ee8bcf46
1 changed files with 30 additions and 13 deletions
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43
srsenb/src/stack/mac/sched_ue.cc
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@ -1247,6 +1247,22 @@ int sched_ue::enb_to_ue_cc_idx(uint32_t enb_cc_idx) const
return enb_ue_cc_idx_map[enb_cc_idx];
}
float diff_coderate_maxcoderate(int mcs,
uint32_t nof_prb,
uint32_t nof_re,
uint32_t max_Qm,
float max_coderate,
bool use_tbs_index_alt,
bool is_ul)
{
uint32_t tbs_idx = srslte_ra_tbs_idx_from_mcs(mcs, use_tbs_index_alt, is_ul);
int tbs = srslte_ra_tbs_from_idx(tbs_idx, nof_prb);
float coderate = srslte_coderate(tbs, nof_re);
srslte_mod_t mod = (is_ul) ? srslte_ra_ul_mod_from_mcs(mcs) : srslte_ra_dl_mod_from_mcs(mcs, use_tbs_index_alt);
uint32_t Qm = std::min(max_Qm, srslte_mod_bits_x_symbol(mod));
return coderate - std::min(max_coderate, 0.930f * Qm);
}
int cc_sched_ue::cqi_to_tbs(uint32_t nof_prb, uint32_t nof_re, bool is_ul, uint32_t* mcs)
{
using ul64qam_cap = sched_interface::ue_cfg_t::ul64qam_cap;
@ -1264,25 +1280,19 @@ int cc_sched_ue::cqi_to_tbs(uint32_t nof_prb, uint32_t nof_re, bool is_ul, uint3
}
// function with sign-flip at solution
auto compute_tbs = [&](int sel_mcs) -> float {
uint32_t tbs_idx = srslte_ra_tbs_idx_from_mcs(sel_mcs, cfg->use_tbs_index_alt, is_ul);
int tbs = srslte_ra_tbs_from_idx(tbs_idx, nof_prb);
float coderate = srslte_coderate(tbs, nof_re);
srslte_mod_t mod =
(is_ul) ? srslte_ra_ul_mod_from_mcs(sel_mcs) : srslte_ra_dl_mod_from_mcs(sel_mcs, cfg->use_tbs_index_alt);
uint32_t Qm = std::min(max_Qm, srslte_mod_bits_x_symbol(mod));
return coderate - std::min(max_coderate, 0.930f * Qm);
auto test_mcs = [&](int sel_mcs) -> float {
return diff_coderate_maxcoderate(sel_mcs, nof_prb, nof_re, max_Qm, max_coderate, cfg->use_tbs_index_alt, is_ul);
};
std::tuple<int, float, int, float> ret;
if (nof_prb > 1) {
// for non-voip case
ret = false_position_method(0, max_mcs, 0.0f, compute_tbs);
ret = false_position_method(0, max_mcs, 0.0f, test_mcs);
} else {
// avoid 6 prbs (voip case), where function is not monotonic
ret = false_position_method(7, max_mcs, 0.0f, compute_tbs);
ret = false_position_method(7, max_mcs, 0.0f, test_mcs);
if (std::get<1>(ret) > 0) {
ret = false_position_method(0, 5, 0.0f, compute_tbs);
ret = false_position_method(0, 5, 0.0f, test_mcs);
}
}
int chosen_mcs = std::get<0>(ret);
@ -1452,8 +1462,15 @@ int cc_sched_ue::alloc_tbs(uint32_t nof_prb, uint32_t nof_re, uint32_t req_bytes
}
if (req_mcs >= 0 and req_mcs < (int)sel_mcs) {
sel_mcs = req_mcs;
tbs_bytes = srslte_ra_tbs_from_idx(req_tbs_idx, nof_prb) / 8;
uint32_t max_Qm = (is_ul) ? (cfg->support_ul64qam == sched_interface::ue_cfg_t::ul64qam_cap::enabled ? 6 : 4)
: (cfg->use_tbs_index_alt ? 8 : 6);
float max_coderate = (is_ul) ? srslte_cqi_to_coderate(std::min(ul_cqi + 1u, 15u), false)
: srslte_cqi_to_coderate(std::min(dl_cqi + 1u, 15u), cfg->use_tbs_index_alt);
if (diff_coderate_maxcoderate(req_mcs, nof_prb, nof_re, max_Qm, max_coderate, cfg->use_tbs_index_alt, is_ul) <
0) {
sel_mcs = req_mcs;
tbs_bytes = srslte_ra_tbs_from_idx(req_tbs_idx, nof_prb) / 8;
}
}
}
// Avoid the unusual case n_prb=1, mcs=6 tbs=328 (used in voip)

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