About

Software radio decoding written in Java. The idea of this project is to get blocks from the gnuradio and implement them in Java. This gives the following:

• No need for tooling. You could use gnuradio-companion to build a working pipeline, then use the same blocks to build the pipeline in Java.
• All Java benefits: run same binaries on multiple platforms without compilation. Single programming language instead of Python and C++. Better tooling like IDE, profilers and memory analyzers.

Demodulators

jradio supports high-level generic demodulators. They convert I/Q signal into the stream of soft bits (0-255).

• FSK
• AFSK
• BPSK
• QPSK

Modulators

Some generic modulators. They take hard bits and produce I/Q signal.

• GFSK
• BPSK/QPSK
• FSK

De-framers

De-framer is a component that converts soft stream of bits into the frames of specific protocol.

• AX.25 - Ax25BeaconSource
• AX.25 with G3ruh scrambler - Ax25G3ruhBeaconSource
• AX100 - Ax100BeaconSource
• cc11xx - Cc11xxReceiver
• NGHam - Support for NGHam radio protocol
• Generic syncword correlator - CorrelateSyncword
• USP - UspDecoder
• Mobitex - MobitexBeaconSource
  • TUBiX20 - Generic de-framer for TUB-based satellites. TUBiX20BeaconSource
• CCSDS Concatenated - CCSDS 131.0-B-4 implementation for concatenated framing (Convolutional + Reed-Solomon). CcsdsBeaconSource

Auxiliary tools

Quite often decoding require some additional tooling. jradio has some.

Forward error correction:

• Viterbi hard and soft decoders
• CCSDS ReedSolomon
• BCH ReedSolomon
• BCH(15,x,x)
• Repeat Accumulate decoder
• Golay
• PLS

Randomization

• xoroshiro128+
• mt19937
• RayleighRandom

CRC

Most likely the algorithm name can't say you much, so it is better to check corresponding test case. Here is list of supported implementations:

• CRC-8
• CRC-16/XMODEM & CRC-16/X-25
• CRC-16/CCITT-FALSE/CRC-16-IBM
• CRC-16/ARC
• CRC-16-NAIVE. Just sum of bytes.
• CRC-32C

Satellite protocols

• CSP - Full support
• CCSDS - Basic support
• PACSAT - Good support

Low-level blocks

All blocks meant to be binary compatible with gnuradio versions. This will ensure you got the same results when moving from gnuradio-companion to Java.

• Add
• AdditiveScrambler
• AGC
• AX100Decoder. Out-of-tree block. Support ASM + Golay mode.
• BinarySlicer
• Cc11xxReceiver. Out-of-tree block. Decodes frames produced by cc11xx. Based on gr-cc11xx
• ChannelModel
• ChunksToSymbols and ChunksToSymbolsComplex
• ClockRecoveryMM and ClockRecoveryMMComplex
• ComplexConjugate
• ComplexToReal
• ConstellationSoftDecoder
• ConvolutionalDeinterleaver
• CorrelateSynchronizationMarker. Extract data from continuous stream of synchronization markers. Work with soft stream.
• CorrelateSyncword
• CostasLoop
• DcBlocker
• DelayOne. jradio doesn't support split and merge of streams. This block incapsulates delay 1 for imag complex stream
• Descrambler
• DifferentialEncoder/DifferentialDecoder
• DifferentialSoftDecoder. Support qpsk only
• Divide
• FastNoiseSource
• FIRFilterBlock
• File Source (InputStreamSource)
• File Sink (OutputStreamSink)
• FLL Band Edge
• FloatToChar
• FloatToComplex
• FractionalResampler
• FrequencyModulator
• FrequencyXlatingFIRFilter
• GUI Histogram Sink (Spectogram)
• HardToSoft. Convert hard decision stream to soft stream.
• HdlcReceiver. Out-of-tree block. Extracts HDLC frame from the unpacked stream of bytes
• HdlcTransmitter. Take the byte array and create hdlc frame
• InterpFIRFilter
• LowPassFilter and LowPassFilterComplex
• LMSDDEqualizer
• MapBlock
• Multiply
• MultiplyConst
• NrziDecode/NrziEncode. Performs nrzi decoding/encoding over unpacked stream of bytes
• osmocom source (RtlTcp)
• PackedToUnpacked
• PolyphaseArbResamplerComplex
• PolyphaseClockSyncComplex
• PeakDetection. Detect peaks in the FFT. Not a gnuradio block.
• QuadratureDemodulation
• Rail
• Rms
• RmsAgc and RmsAgcComplex. Out-of-tree block. For more details see this blog post
• RootRaisedCosineFilter
• Scrambler
• SigSource
• SequentialSource. Produce time-multiplexed outputs from several sources. Useful in simulations.
• TimeConstraintedSource. Can be used in simulations to time-limit noise source.
• UnpackedToPacked
• WavFileSource
• WavFileSink

Coding:

• NRZI
• Bit stuffing

Supported satellites

jradio has lots of built-in satellite decoders. Some of them have non standard de-framers, some beacon decoders, some both:

Doppler correction

Doppler correction could be made using SigSource and Multiply blocks. Here is the sample code:

PassPredictor predictor = new PassPredictor(tle, currentLocation);
SigSource source2 = new SigSource(Waveform.COMPLEX, sampleRate, new DopplerValueSource(sampleRate, satelliteFrequency, correctPeriodMillis, startTimeMillis) {

	@Override
	public long getDopplerFrequency(long satelliteFrequency, long currentTimeMillis) {
		return predictor.getDownlinkFreq(satelliteFrequency, new Date(currentTimeMillis));
	}
}, 1.0f);
Multiply mul = new Multiply(source, source2, true);

Where "getDopplerFrequency" can be calculated using orekit or predict4java.

Usage

Configure maven:

<dependency>
        <groupId>ru.r2cloud</groupId>
        <artifactId>jradio</artifactId>
        <version>1.57</version>
</dependency>

Contributing

Contributing to the project is super easy:

• Raise an issue with description and use case. Skip this step for small bug fixes or minor features
• Raise pull request
• Make sure pull request contains unit tests for new functionality or bug fix