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(C) 2010-2016 by Harald Weltelaforge@gnumonks.org and contributors

This code aims to implement the sending and receiving part of theTETRA MAC/PHY layer.

If you read the ETSI EN 300 392-2 (TETRA V+D Air Interface), you willfind this code implementing the parts between the MAC-blocks (calledtype-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 conjunctionwith this program.

You will needlibosmocoreto build this softwar

The official homepage of the project ishttps://osmocom.org/projects/tetra/wiki/OsmocomTETRA

You can clone from the official osmo-tetra.git repository using

git clone https://gitea.osmocom.org/tetra/osmo-tetra

There is a web interface athttps://gitea.osmocom.org/tetra/osmo-tetra

Discussions related to osmo-tetra are happening on thetetra@lists.osmocom.org mailing list, please seehttps://lists.osmocom.org/mailman/listinfo/tetra for subscriptionoptions and the list archive.

Please observe theOsmocom Mailing ListRuleswhen posting.

Our coding standards are described athttps://osmocom.org/projects/cellular-infrastructure/wiki/Coding_standards

We us a gerrit based patch submission/review process for managingcontributions. Please seehttps://osmocom.org/projects/cellular-infrastructure/wiki/Gerrit formore details

The current patch queue for osmo-tetra can be seen athttps://gerrit.osmocom.org/#/q/project:osmo-tetra+status:open

src/demod/python/cpsk.py

• contains a gnuradio based pi4/DQPSK demodulator, courtesy of KA1RBI

src/demod/python/osmosdr-tetra_demod_fft.py

• call demodulator on any source supported by gr-osmosdr(uhd, fcd, hackrf, blaerf, etc.)

src/demod/python/simdemod2.py

• call demodulator on a 'cfile' containing complex baseband samples

src/demod/python/{uhd,fcdp}-tetra_demod.py

• use demodulator directly with UHd or FCDP hadware (no gr-osmosdr)

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 unpackedbits, i.e. 1-bit-per-byte

Specifically, it implements:lower_mac/crc_simple.[ch]

• CRC16-CCITT (currently defunct/broken as we need it fornon-octet-aligned bitfields)lower_mac/tetra_conv_enc.[ch]
• 16-state Rate-Compatible Punctured Convolutional (RCPC) coderlower_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 ofeach downlink burst)lower_mac/tetra_scramb.[ch]
• Scramblinglower_mac/viterbi*.[ch]
• Convolutional decoder for signalling and voice channelsphy/tetra_burst.[ch]
• Routines to encode continuous normal and sync burstsphy/tetra_burst_sync.[ch]

The main receiver program 'tetra-rx' expects an input file containing astream of unpacked bits, i.e. 1-bit-per-byte.

The main program conv_enc_test.c generates a single continuous downlinc syncburst (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.

# 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 0src/float_to_bits /tmp/out.float /tmp/out.bitssrc/tetra-rx /tmp/out.bits