NR UE scan for SSB within current bandwidth
Till this commit, the UE gets the position of SSB in frequency from command line and does the syncronization by locating the SSB in time. It does this by generating a PSS time signal during initialization with the SSB offset given via command line. Then PSS detection is done by correlation. In this commit, the UE computes a list of GSCN in the current NR band that falls within the current bandwidth for the set center frequency. For each GSCN in the list, the UE starts a thread and performs the following: 1. Generate PSS time signal with SSB offset for current GSCN. 2. Detect PSS, SSS and decode PBCH (this step remains the same). After all threads finishes, the results are collected. For now, only the first detected PBCH is used to proceed further. So this PBCH is indicated to MAC and UE exits initial sync. Future work: The cell search can be standalone feature where the UE could scan for SSB in the entire NR band. This would require changing radio's frequency on the fly as the UE's bandwidth would not cover an entire NR band. The cell detection can futher be imporved by looking for SIB1 for each decoded PBCH.
This commit is contained in:
Sakthivel Velumani
@@ -97,71 +97,6 @@
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extern uint16_t sf_ahead;
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// synchronization raster per band tables (Rel.15)
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// (38.101-1 Table 5.4.3.3-1 and 38.101-2 Table 5.4.3.3-1)
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// band nb, sub-carrier spacing index, Range of gscn (First, Step size, Last)
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const sync_raster_t sync_raster[] = {
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{1, 0, 5279, 1, 5419},
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{2, 0, 4829, 1, 4969},
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{3, 0, 4517, 1, 4693},
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{5, 0, 2177, 1, 2230},
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{5, 1, 2183, 1, 2224},
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{7, 0, 6554, 1, 6718},
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{8, 0, 2318, 1, 2395},
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{12, 0, 1828, 1, 1858},
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{13, 0, 1871, 1, 1885},
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{14, 0, 1901, 1, 1915},
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{18, 0, 2156, 1, 2182},
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{20, 0, 1982, 1, 2047},
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{24, 0, 3818, 1, 3892},
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{24, 1, 3824, 1, 3886},
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{25, 0, 4829, 1, 4981},
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{26, 0, 2153, 1, 2230},
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{28, 0, 1901, 1, 2002},
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{29, 0, 1798, 1, 1813},
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{30, 0, 5879, 1, 5893},
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{34, 0, 5030, 1, 5056},
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{34, 1, 5036, 1, 5050},
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{38, 0, 6431, 1, 6544},
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{38, 1, 6437, 1, 6538},
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{39, 0, 4706, 1, 4795},
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{39, 1, 4712, 1, 4789},
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{40, 1, 5762, 1, 5989},
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{41, 0, 6246, 3, 6717},
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{41, 1, 6252, 3, 6714},
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{48, 1, 7884, 1, 7982},
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{50, 0, 3584, 1, 3787},
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{51, 0, 3572, 1, 3574},
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{53, 0, 6215, 1, 6232},
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{53, 1, 6221, 1, 6226},
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{65, 0, 5279, 1, 5494},
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{66, 0, 5279, 1, 5494},
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{66, 1, 5285, 1, 5488},
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{67, 0, 1850, 1, 1888},
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{70, 0, 4993, 1, 5044},
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{71, 0, 1547, 1, 1624},
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{74, 0, 3692, 1, 3790},
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{75, 0, 3584, 1, 3787},
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{76, 0, 3572, 1, 3574},
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{77, 1, 7711, 1, 8329},
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{78, 1, 7711, 1, 8051},
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{79, 1, 8480, 16, 8880},
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{85, 0, 1826, 1, 1858},
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{90, 1, 6252, 1, 6714},
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{91, 0, 3572, 1, 3574},
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{92, 0, 3584, 1, 3787},
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{93, 0, 3572, 1, 3574},
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{94, 0, 3584, 1, 3587},
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{257, 3, 22388, 1, 22558},
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{257, 4, 22390, 2, 22556},
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{258, 3, 22257, 1, 22443},
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{258, 4, 22258, 2, 22442},
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{260, 3, 22995, 1, 23166},
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{260, 4, 22996, 2, 23164},
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{261, 3, 22446, 1, 22492},
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{261, 4, 22446, 2, 22490},
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};
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extern int config_check_band_frequencies(int ind, int16_t band, uint64_t downlink_frequency,
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int32_t uplink_frequency_offset, uint32_t frame_type);
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@@ -960,8 +895,6 @@ void RCconfig_NR_L1(void)
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}
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}
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static void check_ssb_raster(uint64_t freq, int band, int scs);
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static NR_ServingCellConfigCommon_t *get_scc_config(configmodule_interface_t *cfg, int minRXTXTIME)
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{
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NR_ServingCellConfigCommon_t *scc = calloc(1,sizeof(*scc));
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@@ -1536,56 +1469,6 @@ void config_security(gNB_RRC_INST *rrc)
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}
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}
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// Section 5.4.3 of 38.101-1 and -2
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static void check_ssb_raster(uint64_t freq, int band, int scs)
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{
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int start_gscn = 0, step_gscn = 0, end_gscn = 0;
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for (int i = 0; i < sizeof(sync_raster) / sizeof(sync_raster_t); i++) {
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if (sync_raster[i].band == band &&
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sync_raster[i].scs_index == scs) {
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start_gscn = sync_raster[i].first_gscn;
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step_gscn = sync_raster[i].step_gscn;
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end_gscn = sync_raster[i].last_gscn;
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break;
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}
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}
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AssertFatal(start_gscn != 0, "Couldn't find band %d with SCS %d\n", band, scs);
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int gscn;
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if (freq < 3000000000) {
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int N = 0;
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int M = 0;
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for (int k = 0; k < 3; k++) {
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M = (k << 1) + 1;
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if ((freq - M * 50000) % 1200000 == 0) {
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N = (freq - M * 50000) / 1200000;
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break;
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}
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}
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AssertFatal(N != 0, "SSB frequency %lu Hz not on the synchronization raster (N * 1200kHz + M * 50 kHz)\n",
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freq);
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gscn = (3 * N) + (M - 3) / 2;
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}
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else if (freq < 24250000000) {
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AssertFatal((freq - 3000000000) % 1440000 == 0,
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"SSB frequency %lu Hz not on the synchronization raster (3000 MHz + N * 1.44 MHz)\n",
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freq);
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gscn = ((freq - 3000000000) / 1440000) + 7499;
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}
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else {
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AssertFatal((freq - 24250080000) % 17280000 == 0,
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"SSB frequency %lu Hz not on the synchronization raster (24250.08 MHz + N * 17.28 MHz)\n",
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freq);
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gscn = ((freq - 24250080000) / 17280000) + 22256;
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}
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AssertFatal(gscn >= start_gscn && gscn <= end_gscn,
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"GSCN %d corresponding to SSB frequency %lu does not belong to GSCN range for band %d\n",
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gscn, freq, band);
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int rel_gscn = gscn - start_gscn;
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AssertFatal(rel_gscn % step_gscn == 0,
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"GSCN %d corresponding to SSB frequency %lu not in accordance with GSCN step for band %d\n",
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gscn, freq, band);
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}
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void RCconfig_NRRRC(gNB_RRC_INST *rrc)
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{
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