Open-Source SDR on Embedded Platforms

Open-Source SDR on Embedded Platforms June 1, 2016 Dr. Rajib Bhattacharjea Georgia Tech Research Institute Information and Communications Lab Atlanta, GA 30318, USA 1

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Part 1 Overview • Prereqs • Topics to be covered • SDR background • SDR uses and users • SDR components • Demo 1

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Prerequisites • Radio/Comms Fundamentals - Analog and Digital Modulation - Mixers, filters, LNA, PA

• Circuit analysis concepts - Transistors - Filters

• Software concepts - High level language source code - Assembly language

• Digital and analog signal processing concepts - Convolution - FFT - Dot products

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What We’re Going to Learn About (and play with)

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Single Board Computers!

http://hackerboards.com/ringing-in-2016-with-64-open-spec-hacker-friendly-sbcs/ 5

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Embedded Computers from the Living Room!

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Signal Processing with Open Source Tools!

http://wiki.opendigitalradio.org/FM_RDS_Stereo_transmitter_using_gnuradio 7

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Software Defined Radio Hardware!

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What We’re Going to Learn About • Overview of available open-source software and embedded hardware tools for SDR development • Signal processing • RF signals • How to get started with SDR on popular embedded platforms - ARM or x86 embedded CPU - Linux

• Commercial SDR hardware • Optimized signal processing capabilities available on embedded platforms

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What We’re Not Going to Learn About • OpenEmbedded, yocto, poky, bitbake…although those would help you with devices that don’t have packages in the distros, or for developing reproducible builds for distribution. • Embedded CPU Hardware without available Linux kernel • IBM Power ISA, µC(Linux), MIPS, SPARC, etc. - Although the open source SDR ecosystem could be made to run on these kinds of platforms with various degrees of effort - MIPS is especially low hanging fruit and much of this talk applies to those devices too - Dedicated DSP chips

• “IoT” but only because we’re not talking directly about what data goes over the radio links we’re talking about. If it was some kind of sensor data, this would be an IoT talk. • OSSIE (is it dead?) 10

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Background (who, what, when, where, why, how?)

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What is a Software-Defined Radio? • A communication system where the capabilities are largely determined by the software running on the system instead of by the radio hardware. • Consists of radio hardware and something to do the signal processing. • The term “SDR” can mean the whole system, or just the radio hardware. • Let’s consider a series of examples

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Conventional Radio Example: Super Regenerative FM Receiver

Design from: http://electronics-diy.com/simple-fm-radio.php 13

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Conventional Radio Example: Super Regenerative FM Receiver • It’s purpose built for a specific task • Designed to tune over 88 MHz – 108 MHz

• It isn’t easily reconfigurable and can perform no other task - The hardware defines the functionality - Many functional stages are collapsed into one; the one JFET is the: • Oscillator

• Mixer • Amplifier • Filter

• Uses VERY few components, only enough to achieve the function it is designed for

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Conventional Radio Example: Superheterodyne FM Receiver

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Conventional Radio Example: Superheterodyne FM Receiver

Superheterodyne receiver schematic by Appaloosa released under CC-BY-SA 3.0 license. https://commons.wikimedia.org/wiki/File:Tuner1.svg 16

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Conventional Radio Example: Superheterodyne FM Receiver

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Conventional Radio Example: Superheterodyne FM Receiver

Design from: http://www.daenotes.com/electronics/communication-system/superheterodyne-fm-receiver 18

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Conventional Radio Example: Superheterodyne FM Receiver

Design from: http://www.radio-electronics.com/info/rf-technology-design/fm-reception/foster-seeley-fm-detector-discriminator.php 19

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Conventional Radio Example: Superheterodyne FM Receiver • It’s purpose-built for a specific task • Designed to tune over 88 MHz – 108 MHz

• Design is more modular than the super regenerative design - Amplification, frequency synthesis, frequency mixing, and a multistage demodulator

• Hardware defines the functionality - Could change out the limiter and discriminator for a simple envelope detector and get an AM radio receiver - Or a PLL and detect FSK

• Design is more complicated and uses about 7 times the number of overall components and 5 times the number of transistors

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Software Defined Radio: Superheterodyne w/ an ADC

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Software Defined Radio: Superheterodyne w/ an ADC • Not purpose-built for a specific task! • Tuning range can be large

• Signal processing is not done by a circuit designed for demodulation or discrimination of a specific type of waveform • Software signal processing defines the functionality - Hardware determines characteristics (tuning range, max instantaneous bandwidth, noise performance)

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Who Uses SDR and Why? • Engineers in R&D • Academics

• Enables cutting edge research • Speeds prototyping of new radio designs and signal processing algorithms • Allows one radio to support different waveforms • Permits radio designs to be upgraded without buying new hardware • Facilitates detailed offline signal analysis

• US Military - JTRS - SCA

• US Intelligence Community • Amateur radio enthusiasts (hams) • Others

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Who uses SDR and Why? Video • https://youtu.be/Lv-vkBNzZwE

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SDR Users / Developers in the DoD and IC • The Army, Navy, Air Force, and Marine Corps • “No Such Agency” in Fort Meade, MD - https://www.google.com/#q=nsa+redhawk

• Defense Contractors - Harris

http://rf.harris.com/media/RF-7800V-HH_Enlarged_26-12108.jpg 25

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Components of an SDR • Analog front end - Quadrature demodulator - Wide or narrow tuning range - Wide or narrow bandwidths - RX Only, TX/RX half duplex, TX/RX full duplex, TX/RX MIMO configurations typical

• ADC - Direct sampling ADC is a possibility, limits “tuning” range to (0,fs/2)

• Baseband processor w/ high speed interface - FPGA

- CPU - µC

• Signal processing software 26

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Components of an SDR: Front-end

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Components of an SDR: Baseband Processor • Embedded device with a CPU or µC • FPGA

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Demo 1 - CPU Frequency Demodulation

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Questions?

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Part 2 Overview • Embedded platforms • Consumer electronics embedded • Capabilities • Types • Will it SDR? Demos 2 – 4 • Embedded ARM landscape • SDR hardware options

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Embedded Processors (low power brains)

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Ubiquity of Embedded Platforms • Embedded processors or µCs are in - Car - Television - Speakers - Sound system - Wifi router - GPS receiver - Cable modem - Camera

- Vacuum cleaner - Refrigerator - Watch 33

- Calculator, etc.

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Consumer Electronics Embedded Platforms • Largest consumer electronics companies all sell embedded devices - Connected TV devices - Tablets - more than 250 million projected to sell globally in 2016[1] - Smartphones – 1.4 billion units sold in 2015[2]

• Android and iOS devices drive this market - Google - Apple - Samsung - Amazon

[1] http://www.gartner.com/newsroom/id/2954317 [2] http://www.statista.com/topics/840/smartphones/ 34

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Consumer Electronics Embedded Platforms • These embedded CPUS go by the name “applications processors” • Hardware manufacturers amortize investment into a technology; technology trickles laterally into the maker/hacker, educational, and industrial, and commercial communities - Broadcom markets the BCM2820 as “optimized for high volume markets including mobile phones, mobile TVs, and portable audio/video/game devices”[1]

- Sells the almost identical BCM2835 as a learning platform to the Pi Foundation - R&D companies ship Raspberry Pi’s to their customers in other products

• This is the class of embedded hardware we are talking about today

[1] https://www.broadcom.com/press/release.php?id=929312

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What Drives the Capabilities? • Often, the killer app: streaming, decoding, and playback of media - Special CPU instructions - Media processor / GPU hardware - Some of this capability might help in radio signal processing, more on this later

• This talk focuses exclusively on ARM and Intel - Linux runs effortlessly, entire open-source ecosystem is available - Can be extended to anything that runs a full, modern Linux kernel (MIPS24K in particular)

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Types of Consumer Electronics Embedded Platforms

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Set Top Boxes • Class of devices used for consumption of media on TV screens • Options: - Roku devices - Apple TV - Amazon Fire TV - WDTV - NVIDIA Shield - Many, many lesser known brands (check online retailers for “Android TV” or “set top box”)

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Set Top Boxes: Will it SDR? Yes it will!

http://www.cnx-software.com/2015/12/06/how-to-run-headless-linux-on-amlogic-s905-devices-such-as-mini-mx-or-k1-plus/ 39

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Stick Computers • New class of small form-factor computers for vending signs, kiosks, TV streaming, etc. • Options: - Intel Compute Stick - Amazon Fire Stick

- Lenovo IdeaCentre - Asus Chromebit - Azulle Quantum Access - MeeGoPad devices - And others…

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Stick Computers: Will it SDR? • Demo 2: Dongles on dongles • Yes it will!

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Mini PCs • Like a stick computer but slightly larger and the HDMI port goes the other way • Generally more ports and/or storage • Options: - Kangaroo MD2B - Vensmile iPC002 - Compulab MintBox Mini

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Mini PCs: Will it SDR? • Demo 3: Vensmile Mini PC SDR • Yes it will!

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Single Board Computers (SBCs) • Options:

• Like a mini PC without the case

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Raspberry Pi BeagelBone Black Banana Pi Banana Pro M2 Lemaker Guitar Adapteva Parallella 16 CubieBoard4 CC-A80 DragonBoard 410c Odroid XU4 Odroid C1+ MinnowBoard Tubot Intel Edison Nvidia Jetson TK1 Nvidia Jetson TX1 And others…

Single Board Computers

http://hackerboards.com/ringing-in-2016-with-64-open-spec-hacker-friendly-sbcs/ 45

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Single Board Computers: Will it SDR? • Demo 4 – single board computer SDRs - Raspberry Pi 2 - BeagleBone Black - LeMaker Guitar - NVIDIA Jetson TK1 - ODROID XU4+ - ODROID C1+

• Yes it will!

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Plug Computers • A computer with AC mains prongs hanging off the case - Like a wall-wart, but a computer

• The guts are similar ARM processors • A few vendors on the market sell this form-factor

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Plug Computers

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Plug Computers: Will it SDR?

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Embedded ARM Landscape Manufacturer Texas Instruments Broadcom Allwinner Rockchip MediaTek Qualcomm Marvell Amlogic Samsung NVIDIA Apple Actions Semiconductor NXP HiSilicon Atmel Renesas 50

Brand Name OMAP

Snapdragon ARMADA Exynos Tegra AX i.MX, QorIQ SMART SAMA5

End Devices Kindle Fire HD, Droid X, Droid 2 Raspberry Pi Tablets ASUS Chromebook, TV Boxes/Sticks Tablets, Phones Google Nexus One, HTC Incredible Panasonic Toughpad A1, Google Chromecast TV Boxes HP Chromebook, Samsung Galaxy S6 NVIDIA Shield iPhone, iPad, Apple TV, Apple Watch Tablets, TV Boxes Amazon Kindle Huawei Devices Dev Boards Samsung Galaxy Core LTE GTRI

SDR Hardware • • • • • • • • • • • • • •

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Ettus USRP Great Scott Gadgets HackRF Nuand bladeRF LimeSDR Realtek RTL2832U-based devices Afedri SDR Airspy R820t RFSpace RedPitaya Nutaq PicoSDR, ZeptoSDR PicoZed SDR FunCube Dongle Pro+ SDRPlay RSP And more... GTRI

SDR Hardware: References • https://en.wikipedia.org/wiki/List_of_software-defined_radios • http://sdr-radio.com/Radios

• http://www.rtl-sdr.com/roundup-software-defined-radios/ • http://gnuradio.org/redmine/projects/gnuradio/wiki/Hardware

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Questions?

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Part 3 Overview • Open-source SDR signal processing software • Install guides – Demos 5 and 6

• Non-free tools • Core SDR signal processing operations • Speed and optimization

• Intro to CPU ISA extensions

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SDR Software Options • GNU Radio • Mathworks MATLAB*

• NI LabVIEW* • REDHAWK • Scilab

• Custom signal processing code (C++, Python, etc.)

* Not publicly available on ARM architecture, not free of cost

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Open Source SDR Software: Getting Started • Get a Linux distro - Download and “dd” an image file on to an SD card - Or get it onto the on-board eMMC

• Keyboard, monitor, mouse, etc. - Or setup networking for headless operation

• Install your SDR software - More on this later

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GNU Radio: Getting Started • Install - package manager - Debian derivative - install using apt - Red Hat derivative – install using dnf (yum is deprecated) - Others: zypper, pacman, urpmi, RTM for your distro

• Install – source - Install dependencies from package manager if possible - Then git clone, cmake, make, make install - Cross compilation or other tricks might be necessary Embedded systems are limited in computational power, and GNURadio compilation is CPU intensive • RAM can be an issue • eMMC flash storage can be an issue • Colleague’s GNU Radio compile on a Raspberry Pi took a week •

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GNU Radio Install Demo 5

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REDHAWK • Open source signal processing package largely developed for/by the US government • Supported on RHEL or CentOS Linux distributions; developers implicitly assume x86 • Port of REDHAWK for Ubuntu exists - Old version of RedHawk (1.8.4)

- Old version of Ubuntu (12.04)

• Developer community size is a bit of a mystery - Fewer than 200 questions on the official Q&A site for redhawk software

- Zero questions on the official Q&A site for redhawk-related hardware problems.

• ARM ports will take some work 59

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REDHAWK • Demo 6: REDHAWK on embedded ARM

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SciLab • Some efforts exist to use a combination of SciLab and GNU Radio • Not developed for SDR work, but for interfacing with data acquisition hardware https://www.researchgate.net/publication/266009629_GNURadio_Scilab_Xcos_and_COMEDI_for_Data_Acquisition_and_Control_An_Open_Source_Alternative_to_LabVIEW

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Non-Free Tools (MATLAB and LabVIEW) • Title of the tutorial contains “Open-Source SDR…” • You can open source the code you write but development tools are not free (neither “freedom” nor “beer”) • Mentioned here for completeness

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Custom Signal Processing / Vendor APIs • Most SDR manufacturers have written C/C++ libraries interfacing to the hardware • These can be variously used directly or through wrapper/binding layers to other languages

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Signal Processing on Embedded Platforms (make it go faster)

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Embedded Processing: Operations and Speed SDR Operations • Modulation

• The modern CPU is optimized for managing the flow of instructions, not quickly executing a small group of instructions

• Entropy and error coding • Encryption • Computationally heavy DSP operations

• CPU manufacturers see this gap, have created special CPU instructions for common DSP or multimedia computations

- Convolutions - FFTs

• Potentially high data rates

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Embedded Processing: Operations and Speed Dot product 𝑀−1

𝑥 𝑛 ∙𝑦 𝑛 =

𝑥 𝑚 𝑦[𝑚] 𝑚=0

#define M (1L dispatch - Empirically fastest implementation - Similar to the FFTW library (“wisdom”)

• ARM NEON and Intel SSE/AVX • If no SIMD acceleration, plain C implementation is used http://libvolk.org/ Image © Marcus Müller

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How to Leverage CPU Extensions: OpenCL • Open Computing Language • C-based language designed for optimizing math heavy operations

• Some constructs are designed to map to SIMD structures on particular hardware - “float4” is a type with four single precision floating point numbers - Can map directly to Intel SSE XMM0-XMM7

• OpenCL code can be compiled for - CPU: uses SIMD / other extensions - GPU: uses massively parallel shader architecture

- Special OpenCL coprocessors: Intel Xeon Phi, Adapteva Epiphany

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How to Leverage CPU Extensions: OpenCL Hardware must have OpenCL implementation available • Intel ships OpenCL implementation for their CPUs

• Official ARM CPU OpenCL using NEON was announced but unavailable? • ARM Mali GPU design does have an OpenCL implementation, more on this later • POCL - Portable Compute Language - OpenCL implementation for ARMv7, x86, MIPS32

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How to Leverage CPU Extensions: OpenCL • Demo 8: OpenCL Acceleration demo with gr-fosphor on Vensmile iPC002 (Intel Atom) • Formerly had to do this on some distros: - https://bitbucket.org/snippets/rajb245/epGzn

• But latest Intel OpenCL Runtime 16.1 supports RHEL, SLES, and Ubuntu - https://software.intel.com/en-us/articles/opencl-drivers

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How to Leverage CPU Extensions: Performance Tuned Libraries Background – BLAS • Basic Linear Algebra Subprograms • API definition of common numerical operations • Level 1: Scalar/vector and vector/vector operations - Rotating 2-vectors, dot products, scalar times vector, vector norms

• Level 2: Matrix/vector operations - Matrix/vector multiplication, triangular matrix system solver, vector outer product

• Level 3: Matrix/matrix operations - Matrix multiplication - Sums of products of matrices

• Do they map directly to signal processing? 85

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How to Leverage CPU Extensions: Performance-Tuned Libraries • CPU vendors make performance-tuned BLAS (and the related LAPACK) implementations - AMD ACML – open sourced, BLIS is what we want for the CPU, runs on ARM and x86, very portable - Intel MKL – Intel and AMD x86, closed source

• ATLAS project automatically tunes itself on the target hardware, works on ARM • OpenBLAS has comprehensive architecture support 86

https://software.intel.com/en-us/intel-mkl

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How to Leverage CPU Extensions: Performance-Tuned Libraries Open questions • Integration of high-performance BLAS into GNU Radio? REDHAWK?

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Optimization Path 2: Embedded GPU

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Embedded GPU Landscape • Consumer electronics embedded processors often have specialized multimedia processing hardware / GPU (recall the killer app) End device list not exhaustive

•

IP Holder

Brand Name

Licensees / Manufacturers

End Devices

Broadcom

VideoCore

Broadcom

Raspberry Pi, Samsung Galaxy (various)

ARM Holdings

Mali

Allwinner, Amlogic, MediaTek, Rockchip, Samsung

Samsung Gear/Galaxy/Chromebook (various), Google Nexus 10, ODROID (various)

NVIDIA

Tegra GPU

NVIDIA

NVIDIA Shield, Acer Chromebook, Google Pixel C, HTC Nexus 9

Intel

HD Graphics, GMA, Iris, Iris Pro

Intel

Dell Pro 11 2in1, Lenovo ThinkPad (various), Dell Venue 11 Pro

Qualcomm

Adreno

Qualcomm

Samsung Galaxy (various), Sony Xperia X, HTC 10

Imagination Technologies

PowerVR

Ti, Apple, Intel, Broadcom, Allwinner, Samsung, Rockchip

iPhone (various), iPad (various), Apple Watch, PS Vita, Asus Zenfone 4, ODROID-XU

Vivante Corporation

(None)

Marvell, Freescale, Ingenic Semiconductor, Rockchip

Samsung Galaxy Tab 4, Chuwi V90, Hummingboard (various)

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GPU Processing on Embedded • Mali OpenCL is the only easy option right now - Signal processing with AMD clMath? - Integration into GNU Radio or REDHAWK?

• PowerVR has beta access to OpenCL for developers • NVIDIA has CUDA - Library of functions that turn into highly parallelized code that runs on the GPU - Specific to one vendor

• Some work has been done on Broadcom VideoCore - Assemblers for the VideoCore, including one where you write assembly in python (PyVideoCore) - PyVideoCore has a single example of a single BLAS/LAPACK function

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GPU Processing on Embedded • Demo 9: Mali GPU w/ OpenCL gr-fosphor

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Optimization Path 3: FPGA

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FPGA Processing • Field-programmable gate array - Can be configured to be an arbitrary digital logic circuit (within a size constraint)

• Many of the SDR hardware platforms have an on-board FPGA - Handles interpolation, decimation, fine frequency tuning, digital I/O buses (host and RF front-end)

- HackRF*, Ettus B and N series, bladeRF, and others

• Some embedded processors have an on-die FPGA† - Xilinx Zynq - Altera SoC

*Actually a CPLD, but the difference is in implementation not functionality †Intel Xeon+FPGA is hardly embedded and is vaporware so far 93

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FPGA Processing • Xilinx Zynq powers three popular SDR platforms - Ettus E310 - Red Pitaya - PicoZed SDR

• Do most of the signal processing on the FPGA

http://www.xilinx.com/products/boards-and-kits/1-askjht.html

• Use the ARM for what’s left • Development Tools - LabVIEW FPGA Module* - MATLAB HDL Coder* - RFNoC https://www.ettus.com/product/details/E310-KIT *Not free, no public ARM release 94

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FPGA Processing • Demo 9: RFNoC fosphor on the X310 - (Martin Braun’s demo is much better, so we’ll skip this)

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Optimization Path 4: Other Coprocessors

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Special Coprocessors • Xeon Phi - Not embedded yet; power draw is same as thirty SBCs

• Adapteva Epiphany Coprocessor - Has not really caught-on

- Used in one design, the Adapteva Parallella-16 SBC

*

http://www.adapteva.com/epiphanyiii/

*http://www.intel.com/content/www/us/en/architecture-and-technology/many-integrated-core/intel-many-integrated-core-architecture.html 97

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Conclusions and Summary (what did we learn)

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Conclusions and Summary • Embedded SDR runs the gamut of price and performance - Pi Zero + RTL2832U device - ODroid + Hack RF

- Ettus E310 or PicoZed SDR - NVIDIA Tegra TX1 + Ettus X310

• GNU Radio is the dominant open-source SDR package that is popular for researchers and hobbyists - Others exist but there’s no annual “REDHAWK con”, i.e., the user community and support seems to be best for GNU Radio

• Using available, COTS, embedded hardware and open-source software, any practical radio technology can be implemented - Even experimental technology can be realized - Massive MIMO - Spectrum sensing / cognitive radio 99

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Conclusions and Summary • You can’t pick up an embedded device and get optimal signal processing performance - Software work to be done to leverage the processing power of the GPUs and SIMD technologies - Should the VOLK project support GPU accelerated implementations? - Should everyone use OpenCL?

- Or should there be accelerated BLAS/LAPACK, and other code can call those functions?

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Conclusions and Summary • It’s an exciting time in embedded SDR! • The unprecedented popularity of mobile, wireless, and TV markets has effectively subsidized the SBC and embedded computer market. • You can realistically learn SDR and signal processing with practical, hands-on experience for the price of a drink at a nice restaurant.

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Acknowledgements • Ben Riley of GTRI for funding IRAD

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Thank You

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Copyright Notice • Copyright 2016, Georgia Tech Applied Research Corporation • Portions of this work are under the copyright of their respective, original rights holders. - No copyright claim is made on these portions. - Where possible, attribution has been given to the original rights holders. - Use of these portions has been for the purposes of comment, teaching, scholarship, and research; as such, the authors of this work assert that this usage constitutes a fair use of the copyrighted material.

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