Required Hardware

To capture signals in real time, you need ADALM-PLUTO radio and the corresponding support package add-on:

For a full list of communications toolboxes supported by SDR platforms, refer to the Supported Hardware section of theSoftware Defined Radio (SDR) discovery page.

Bluetooth BR/EDR Radio Specifications

Bluetooth is a short-range Wireless Personal Area Network (WPAN) technology, operating in the globally unlicensed industrial, scientific, and medical (ISM) band in the frequency range of 2.4 GHz to 2.485 GHz. In Bluetooth technology, data is divided into packets and each packet is transmitted on one of the 79 designated Bluetooth channels. Each channel has a bandwidth of 1 MHz. As there are different types of wireless networks operating in the same unlicensed frequency band, it is possible for two different networks to interfere with each other. To mitigate the interference, Bluetooth implements the frequency-hopping spread spectrum (FHSS) scheme to switch a carrier between multiple frequency channels by using a pseudorandom sequence known to both transmitter and receiver.

The Bluetooth standard specifies these physical layer (PHY) modes:

Basic rate (BR)- Mandatory mode, uses gaussian frequency shift keying (GFSK) modulation with a data rate of 1 Mbps

Enhanced data rate (EDR)- Optional mode, uses phase shift keying (PSK) modulation with these two variants:

Bluetooth BR/EDR Packet Formats

The air interface packet formats for PHY modes include these fields:

Access Code: Each packet starts with an access code. If a packet header follows, the access code is 72 bits long. Otherwise, the length of the access code is 68 bits and referred to as a shortened access code. The access code consists of these fields:

Access Code Format

Packet Header: The header includes link control information and consists of these fields:

Header Format

Payload: Payload includes an optional payload header, a payload body, and an optional CRC.

Payload Format

Guard: For EDR packets, guard time allows the Bluetooth BR/EDR radio to prepare for the change in modulation from GFSK to DPSK. The guard time must be between 4.75 to 5.25 microseconds.

Sync: For EDR packets, the synchronization sequence contains one reference symbol and ten DPSK symbols.

Trailer: For EDR packets, the trailer bits must be all zero pattern of two symbols, {00,00} for pi/4-DQPSK and {000,000} for 8DPSK.

Packet format for BR mode is shown in this figure.

Basic Rate Packet Format

Packet format for EDR mode is shown in this figure.

Enhanced Data Rate Packet Format

Check for Support Package Installation

Check if the Communications Toolbox Library for the Bluetooth Protocol support package is installed.

commSupportPackageCheck('BLUETOOTH');

Decode Bluetooth BR/EDR Waveforms

This example shows how to decode Bluetooth BR/EDR waveforms either captured by using ADALM-PLUTO or by reading IQ samples from a baseband file.

Bluetooth BR/EDR Receiver

The general structure of the Bluetooth receiver example is:

Initialize the Receiver Parameters

To configure Bluetooth BR/EDR parameters, usebluetoothPhyConfigobject.

cfg = bluetoothPhyConfig; cfg.Mode ='BR';% Mode of transmission as one of BR, EDR2M and EDR3Mcfg.WhitenInitialization = [0;0;0;0;0;1;1];% Whiten initialization

Specify the Signal Source

Specify the signal source as File or ADALM-PLUTO.

If you assignADALM-PLUTOas the signal source, the example searches your computer for theADALM-PLUTOradio at radio address 'usb:0' and uses it as the signal source.

% The default signal source is 'File'signalSource ='File'; bbSymbolRate = 1e6;% 1 MSpsifstrcmp(signalSource,'File')switchcfg.Modecase'BR'bbFileName ='bluetoothCapturesBR.bb';case'EDR2M'bbFileName ='bluetoothCapturesEDR2M.bb';case'EDR3M'bbFileName ='bluetoothCapturesEDR3M.bb';endsigSrc = comm.BasebandFileReader(bbFileName); sigSrcInfo = info(sigSrc); bbSampleRate = sigSrc.SampleRate; sigSrc.SamplesPerFrame = sigSrcInfo.NumSamplesInData; cfg.SamplesPerSymbol = bbSampleRate/bbSymbolRate;else% Check if the pluto Hardware Support Package (HSP) is installedifisempty(which('plutoradio.internal.getRootDir')) error(message('comm_demos:common:NoSupportPackage',...'Communications Toolbox Support Package for ADALM-PLUTO Radio',...['...'adalm-pluto-radio.html">ADALM-PLUTO Radio Support From Communications Toolbox']));endconnectedRadios = findPlutoRadio;% Discover ADALM-PLUTO radio(s) connected to your computerradioID = connectedRadios(1).RadioID; rxCenterFrequency =2445000000;% In Hz, choose between 2.402e9 to 2.480e9 with 1e6 spacingbbSampleRate = bbSymbolRate * cfg.SamplesPerSymbol; sigSrc = sdrrx('Pluto',...'RadioID', radioID,...'CenterFrequency', rxCenterFrequency,...'BasebandSampleRate', bbSampleRate,...'SamplesPerFrame', 1e7,...'GainSource','Manual',...“获得”, 25,...'OutputDataType','double');end

Capture the Bluetooth BR/EDR Waveforms

Capture the IQ samples corresponding to Bluetooth BR/EDR waveforms either by using ADALM-PLUTO or baseband file as signal source. Visualize the spectrum of the received Bluetooth waveforms by using a spectrum analyzer.

% The transmitted waveforms are captured as a burstdataCaptures = sigSrc();% Setup spectrum viewerspectrumScope = dsp.SpectrumAnalyzer(...'SampleRate', bbSampleRate,...'SpectrumType','Power density',...'SpectralAverages', 10,...'YLimits', [-130 -30],...'Title','Received Baseband Bluetooth Signal Spectrum',...'YLabel','Power spectral density');% Show power spectral density of the received waveformspectrumScope(dataCaptures);

Process Bluetooth BR/EDR Waveforms at Receiver

To decode the packet header, payload header information, and raw message bits, the receiver processess the baseband samples received from the signal source. This figure shows the receiver processing.

Bluetooth Practical Receiver

The Bluetooth practical receiver performs these functions:

% p蓝牙ractical receiver[decBits,decodedInfo,pktStatus] = helperBluetoothPracticalReceiver(dataCaptures,cfg);% Get the number of detected packetspktCount = length(pktStatus); disp(['Number of Bluetooth packets detected: 'num2str(pktCount)])

Number of Bluetooth packets detected: 2

% Get the decoded packet statisticsdisplayFlag =true;% set true, to display the decoded packet statisticsif(displayFlag && (pktCount~=0)) decodedInfoPrint = decodedInfo;forii = 1:pktCountif(pktStatus(ii)) decodedInfoPrint(ii).PacketStatus ='Success';elsedecodedInfoPrint(ii).PacketStatus ='Fail';endendpacketInfo = struct2table(decodedInfoPrint,'AsArray',1); fprintf('Decoded Bluetooth packet(s) information: \n \n') disp(packetInfo);end

Decoded Bluetooth packet(s) information:

LAP PacketType LogicalTransportAddress HeaderControlBits PayloadLength LLID FlowIndicator PacketStatus _____________ __________ _______________________ _________________ _____________ ____________ _____________ ____________ {24x1 double} {'FHS'} {3x1 double} {3x1 double} 18 {2x1 double} 0 {'Success'} {24x1 double} {'FHS'} {3x1 double} {3x1 double} 18 {2x1 double} 0 {'Success'}

% Get the packet error rate performance metricsif(pktCount) pktErrCount = sum(~pktStatus); pktErrRate = pktErrCount/pktCount; disp([的模拟模式:cfg.Mode', '...'Packet error rate: ',num2str(pktErrRate)])end

Simulated Mode: BR, Packet error rate: 0

% Release the signal sourcerelease(sigSrc);

This example enables you to decode Bluetooth BR/EDR waveforms either captured by using ADALM-PLUTO or by reading IQ samples from a baseband file. Visualize the spectrum of the received Bluetooth waveforms by using a spectrum analyzer. The packet error rate is computed based on the decoded packet information.

Further Exploration

You can use this example to receive EDR packets by changing the PHY transmission mode. To generate the Bluetooth waveforms in this example, refer toBluetooth BR/EDR Waveform Generation and Transmission using SDR.

Troubleshooting

General tips for troubleshooting SDR hardware and the Communications Toolbox Support Package for ADALM-PLUTO Radio can be found inCommon Problems and Fixes(Communications Toolbox Support Package for Analog Devices ADALM-Pluto Radio).

Appendix

This example uses this helper function:

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