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-rw-r--r--Src/osmolib/src/target/firmware/layer1/rfch.c152
1 files changed, 152 insertions, 0 deletions
diff --git a/Src/osmolib/src/target/firmware/layer1/rfch.c b/Src/osmolib/src/target/firmware/layer1/rfch.c
new file mode 100644
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+++ b/Src/osmolib/src/target/firmware/layer1/rfch.c
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+/* RF Channel utilities */
+
+/* (C) 2010 by Sylvain Munaut <tnt@246tNt.com>
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include <stdint.h>
+
+#include <osmocom/gsm/gsm_utils.h>
+
+#include <layer1/sync.h>
+
+
+/*
+ * Hopping sequence generation
+ *
+ * The algorithm is explained in GSM 05.02 Section 6.2.3
+ *
+ * if HSN = 0 (cyclic hopping) then:
+ * MAI, integer (0 .. N-1) :
+ * MAI = (FN + MAIO) modulo N
+ *
+ * else:
+ * M, integer (0 .. 152) :
+ * M = T2 + RNTABLE((HSN xor T1R) + T3)
+ *
+ * S, integer (0 .. N-1) :
+ * M' = M modulo (2 ^ NBIN)
+ * T' = T3 modulo (2 ^ NBIN)
+ *
+ * if M' < N then:
+ * S = M'
+ * else:
+ * S = (M'+T') modulo N
+ *
+ * MAI, integer (0 .. N-1) :
+ * MAI = (S + MAIO) modulo N
+ */
+
+static uint8_t rn_table[114] = {
+ 48, 98, 63, 1, 36, 95, 78, 102, 94, 73,
+ 0, 64, 25, 81, 76, 59, 124, 23, 104, 100,
+ 101, 47, 118, 85, 18, 56, 96, 86, 54, 2,
+ 80, 34, 127, 13, 6, 89, 57, 103, 12, 74,
+ 55, 111, 75, 38, 109, 71, 112, 29, 11, 88,
+ 87, 19, 3, 68, 110, 26, 33, 31, 8, 45,
+ 82, 58, 40, 107, 32, 5, 106, 92, 62, 67,
+ 77, 108, 122, 37, 60, 66, 121, 42, 51, 126,
+ 117, 114, 4, 90, 43, 52, 53, 113, 120, 72,
+ 16, 49, 7, 79, 119, 61, 22, 84, 9, 97,
+ 91, 15, 21, 24, 46, 39, 93, 105, 65, 70,
+ 125, 99, 17, 123,
+};
+
+
+static int pow_nbin_mask(int n)
+{
+ int x;
+ x = (n ) |
+ (n >> 1) |
+ (n >> 2) |
+ (n >> 3) |
+ (n >> 4) |
+ (n >> 5) |
+ (n >> 6);
+ return x;
+}
+
+static int16_t rfch_hop_seq_gen(struct gsm_time *t,
+ uint8_t hsn, uint8_t maio,
+ uint8_t n, uint16_t *arfcn_tbl)
+{
+ int mai;
+
+ if (!hsn) {
+ /* cyclic hopping */
+ mai = (t->fn + maio) % n;
+ } else {
+ /* pseudo random hopping */
+ int m, mp, tp, s, pnm;
+
+ pnm = pow_nbin_mask(n);
+
+ m = t->t2 + rn_table[(hsn ^ (t->t1 & 63)) + t->t3];
+ mp = m & pnm;
+
+ if (mp < n)
+ s = mp;
+ else {
+ tp = t->t3 & pnm;
+ s = (mp + tp) % n;
+ }
+
+ mai = (s + maio) % n;
+ }
+
+ return arfcn_tbl ? arfcn_tbl[mai] : mai;
+}
+
+
+/* RF Channel parameters */
+void rfch_get_params(struct gsm_time *t,
+ uint16_t *arfcn_p, uint8_t *tsc_p, uint8_t *tn_p)
+{
+ if (l1s.dedicated.type == GSM_DCHAN_NONE) {
+ /* Serving cell only */
+ if (arfcn_p)
+ *arfcn_p = l1s.serving_cell.arfcn;
+
+ if (tsc_p)
+ *tsc_p = l1s.serving_cell.bsic & 0x7;
+
+ if (tn_p)
+ *tn_p = 0;
+ } else {
+ /* Dedicated channel */
+ if (arfcn_p) {
+ if (l1s.dedicated.h) {
+ *arfcn_p = rfch_hop_seq_gen(t,
+ l1s.dedicated.h1.hsn,
+ l1s.dedicated.h1.maio,
+ l1s.dedicated.h1.n,
+ l1s.dedicated.h1.ma);
+ } else {
+ *arfcn_p = l1s.dedicated.h0.arfcn;
+ }
+ }
+
+ if (tsc_p)
+ *tsc_p = l1s.dedicated.tsc;
+
+ if (tn_p)
+ *tn_p = l1s.dedicated.tn;
+ }
+}
+