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TETRA MAC/PHY layer experimentation code (C) 2010-2011 by Harald Welte <firstname.lastname@example.org> ====================================================================== This code aims to implement the sending and receiving part of the TETRA MAC/PHY layer. If you read the ETSI EN 300 392-2 (TETRA V+D Air Interface), you will find this code implementing the parts between the MAC-blocks (called type-1 bits) and the bits that go to the DQPSK-modulator (type-5 bits). It is most useful to look at Figure 8.5, 8.6, 9.3 and 19.12 in conjunction with this program. You will need libosmocore (http://bb.osmocom.org/trac/wiki/libosmocore) to link. == Demodulator == src/demod/python/cpsk.py * contains a gnuradio based pi4/DQPSK demodulator, courtesy of KA1RBI src/demod/python/tetra-demod.py * call demodulator on a 'cfile' containing complex baseband samples src/demod/python/usrp1-tetra_demod.py * use demodulator in realtime with a USRP1 SDR src/demod/python/usrp2-tetra_demod.py * use demodulator in realtime with a USRP2 SDR The output of the demodulator is a file containing one float value for each symbol, containing the phase shift (in units of pi/4) relative to the previous symbol. You can use the "float_to_bits" program to convert the float values to unpacked bits, i.e. 1-bit-per-byte == PHY/MAC layer == === library code === Specifically, it implements: lower_mac/crc_simple.[ch] * CRC16-CCITT (currently defunct/broken as we need it for non-octet-aligned bitfields) lower_mac/tetra_conv_enc.[ch] * 16-state Rate-Compatible Punctured Convolutional (RCPC) coder lower_mac/tetra_interleave.[ch] * Block interleaving (over a single block only) lower_mac/tetra_rm3014.[ch] * (30, 14) Reed-Muller code for the ACCH (broadcast block of each downlink burst) lower_mac/tetra_scramb.[ch] * Scrambling lower_mac/viterbi*.[ch] * Convolutional decoder for signalling and voice channels phy/tetra_burst.[ch] * Routines to encode continuous normal and sync bursts phy/tetra_burst_sync.[ch] === Receiver Program === The main receiver program 'tetra-rx' expects an input file containing a stream of unpacked bits, i.e. 1-bit-per-byte. === Transmitter Program === The main program conv_enc_test.c generates a single continuous downlinc sync burst (SB), contining: * a SYNC-PDU as block 1 * a ACCESS-ASSIGN PDU as broadcast block * a SYSINFO-PDU as block 2 Scrambling is set to 0 (no scrambling) for all elements of the burst. It does not actually modulate and/or transmit yet. == Quick example == # assuming you have generated a file samples.cfile at a sample rate of # 195.312kHz (100MHz/512 == USRP2 at decimation 512) src/demod/python/tetra-demod.py -i /tmp/samples.cfile -o /tmp/out.float -s 195312 -c 0 src/float_to_bits /tmp/out.float /tmp/out.bits src/tetra-rx /tmp/out.bits