move openbsc/* to repos root

This is the first step in creating this repository from the legacy openbsc.git.

Like all other Osmocom repositories, keep the autoconf and automake files in
the repository root. openbsc.git has been the sole exception, which ends now.

Change-Id: I9c6f2a448d9cb1cc088cf1cf6918b69d7e69b4e7

1 files changed, 54 insertions, 0 deletions

diff --git a/doc/gsm-hopping.txt b/doc/gsm-hopping.txt
new file mode 100644
index 000000000..c964963c0
--- /dev/null
+++ b/doc/gsm-hopping.txt
@@ -0,0 +1,54 @@
+according to GSM 05.02:
+
+general parameters from CCCH:
+* CA cell allocation of ARFCN's (System Information / BCCH)
+* FN: TDMA frame number (t1,t2,t3') in SCH
+
+specific parameters from channel assignment:
+* MA: mobile allocation, defines set of ARFCN's, up to 64
+* MAIO: index
+* HSN: hopping sequence generator number (0..64)
+
+
+hopping sequence generation (6.2.3):
+
+uint8_t rntable[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,
+	125,  99,  17, 123
+};
+
+/* mai=0 represents lowest ARFCN in the MA */
+
+
+uint8_t hopping_mai(uint8_t hsn, uint32_t fn, uint8_t maio,
+		     uint8_t t1, uint8_t t2, uint8_t t3_)
+{
+	uint8_t mai;
+
+	if (hsn == 0) /* cyclic hopping */
+		mai = (fn + maio) % n;
+	else {
+		uint32_t m, m_, t_, s;
+
+		m = t2 + rntable[(hsn xor (t1 % 64)) + t3];
+		m_ = m % (2^NBIN);
+		t_ = t3 % (2^NBIN);
+		if (m_ < n then)
+			s = m_;
+		else
+			s = (m_ + t_) % n;
+		mai = (s + maio) % n;
+	}
+
+	return mai;
+}
+