OsmocomBB MS-side GSM Protocol stack (L1, L2, L3) including firmware https://osmocom.org/projects/baseband
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osmocom-bb/src/target/trx_toolkit/gsm_shared.py

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5.8 KiB

# -*- coding: utf-8 -*-
# TRX Toolkit
# Common GSM constants and helpers
#
# (C) 2018-2020 by Vadim Yanitskiy <axilirator@gmail.com>
# Contributions by sysmocom - s.f.m.c. GmbH
#
# 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.
from enum import Enum
# TDMA definitions
GSM_SUPERFRAME = 26 * 51
GSM_HYPERFRAME = 2048 * GSM_SUPERFRAME
# Burst length
GMSK_BURST_LEN = 148
EDGE_BURST_LEN = GMSK_BURST_LEN * 3
class BurstType(Enum):
""" Burst types defined in 3GPP TS 45.002 """
DUMMY = ("DB") # Dummy burst (5.2.6)
SYNC = ("SB") # Synchronization Burst (5.2.5)
FREQ = ("FB") # Frequency correction Burst (5.2.4)
ACCESS = ("AB") # Access Burst (5.2.7)
NORMAL = ("NB") # Normal Burst (5.2.3)
# HSR = ("HB") # Higher symbol rate burst (5.2.3a)
class TrainingSeqGMSK(Enum):
""" Training Sequences defined in 3GPP TS 45.002 """
# Training Sequences for Access Burst (table 5.2.7-3)
AB_TS0 = (0, BurstType.ACCESS, "01001011011111111001100110101010001111000")
AB_TS1 = (1, BurstType.ACCESS, "01010100111110001000011000101111001001101")
AB_TS2 = (2, BurstType.ACCESS, "11101111001001110101011000001101101110111")
AB_TS4 = (4, BurstType.ACCESS, "11001001110001001110000000001101010110010")
# Training Sequences for Access Burst (table 5.2.7-4)
AB_TS3 = (3, BurstType.ACCESS, "10001000111010111011010000010000101100010")
AB_TS5 = (5, BurstType.ACCESS, "01010000111111110101110101101100110010100")
AB_TS6 = (6, BurstType.ACCESS, "01011110011101011110110100010011000010111")
AB_TS7 = (7, BurstType.ACCESS, "01000010110000011101001010111011100010000")
# Training Sequences for Synchronization Burst (table 5.2.5-3)
SB_TS0 = (0, BurstType.SYNC, "1011100101100010000001000000111100101101010001010111011000011011")
SB_TS1 = (1, BurstType.SYNC, "1110111001101011001010000011111011110100011111101100101100010101")
SB_TS2 = (2, BurstType.SYNC, "1110110000110111010100010101101001111000000100000010001101001110")
SB_TS3 = (3, BurstType.SYNC, "1011101000111101110101101111010010001011010000001000111010011000")
# Training Sequences for Normal Burst (table 5.2.3a, TSC set 1)
NB_TS0 = (0, BurstType.NORMAL, "00100101110000100010010111")
NB_TS1 = (1, BurstType.NORMAL, "00101101110111100010110111")
NB_TS2 = (2, BurstType.NORMAL, "01000011101110100100001110")
NB_TS3 = (3, BurstType.NORMAL, "01000111101101000100011110")
NB_TS4 = (4, BurstType.NORMAL, "00011010111001000001101011")
NB_TS5 = (5, BurstType.NORMAL, "01001110101100000100111010")
NB_TS6 = (6, BurstType.NORMAL, "10100111110110001010011111")
NB_TS7 = (7, BurstType.NORMAL, "11101111000100101110111100")
# TODO: more TSC sets from tables 5.2.3b-d
def __init__(self, tsc, bt, seq_str, tsc_set = 0):
# Training Sequence Code
self.tsc = tsc
# Burst type
self.bt = bt
# Training Sequence Code set
# NOTE: unlike the specs. we count from zero
self.tsc_set = tsc_set
# Generate Training Sequence bits
self.seq = [int(x) for x in seq_str]
@classmethod
def pick(self, burst):
# Normal burst TS (26 bits)
nb_seq = burst[3 + 57 + 1:][:26]
# Access burst TS (41 bits)
ab_seq = burst[8:][:41]
# Sync Burst TS (64 bits)
sb_seq = burst[3 + 39:][:64]
for ts in list(self):
# Ugly Python way of writing 'switch' statement
if ts.bt is BurstType.NORMAL and ts.seq == nb_seq:
return ts
elif ts.bt is BurstType.ACCESS and ts.seq == ab_seq:
return ts
elif ts.bt is BurstType.SYNC and ts.seq == sb_seq:
return ts
return None
class HoppingParams:
""" Hopping sequence generation as per 3GPP TS 45.002, section 6.2.3.
Based on firmware/layer1/rfch.c:rfch_hop_seq_gen() by Sylvain Munaut.
"""
# Magic numbers for pseudo-random hopping sequence generation
RNTABLE = [
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,
]
def __init__(self, hsn, maio, ma):
# Make sure MA is not empty
ma_len = len(ma)
if ma_len == 0: # TODO: or rather > 1?
raise ValueError("Mobile Allocation is empty")
self.hsn = hsn
self.maio = maio
self.ma = ma
# Pre-calculate 2 ** NBIN in advance
self._pnm = (ma_len >> 0) | (ma_len >> 1) \
| (ma_len >> 2) | (ma_len >> 3) \
| (ma_len >> 4) | (ma_len >> 5) \
| (ma_len >> 6)
def __str__(self):
fmt = "hsn=%u, maio=%u, ma_len=%u"
return fmt % (self.hsn, self.maio, len(self.ma))
@staticmethod
def fn2gsm_time(fn):
t1 = fn // (26 * 51)
t2 = fn % 26
t3 = fn % 51
tc = (fn // 51) % 8
return (t1, t2, t3, tc)
# Resolve current ARFCN using the given TDMA frame number
def resolve(self, fn):
# Cyclic hopping
if self.hsn == 0:
mai = (fn + self.maio) % len(self.ma)
return self.ma[mai]
# Pseudo random hopping
(t1, t2, t3, tc) = self.fn2gsm_time(fn)
ma_len = len(self.ma)
rn_idx = (self.hsn ^ (t1 & 63)) + t3
m = t2 + self.RNTABLE[rn_idx]
mp = m & self._pnm
s = mp if mp < ma_len else (mp + t3 & self._pnm) % ma_len
mai = (s + self.maio) % ma_len
return self.ma[mai]