1. Open Source Digital Radio David Rowe

2. Topics ● Digital Radio and VOIP ● Applications ● Open Source Digital Radio – who cares? ● Codec 2 explained ● Digital Versus Analog Radio Demo ● FreeDV

3. Digital Radio and VOIP over Wifi ● Why is two way radio special? ● Why not just use VOIP over a radio channel? ● Lets compare VOIP over Wifi to Digital Radio.......

4. Digital Radio and VOIP over Wifi

5. ● Digital Radio can be about 1000 times more bandwidth and power efficient than VOIP over Wifi ● or 30dB, e.g. 1W is like 1000W of Wifi ● Can operate on HF and VHF rather than microwave ● non Line of Sight (global for HF) ● Real time voice but not broadband data

6. Digital Radio Applications ● Ham Radio (experimental service) ● Police/Fire/Emergency Services ● Humanitarian/Disaster (when the Internet dies) ● Democracy movements (when the Internet is switched off) ● Developing world (ease of set up, low cost, long distance, low infrastructure, local manufacture)

7. Open Digital Radio - Who Cares? ● Two way radio is transitioning from analog to digital ● The last transition was to analog modulation schemes like FM and SSB in the 1950's ● All other digital radio schemes are using proprietary and closed software (Codecs) ● Emergency Services – lives depend on closed source! ● We will be locked in for years – unless we act

8. Open Digital Radio - Who Cares? ● We should be able to innovate and experiment ● Knowing how the codec/modem works = better integration and system performance ● Technical superiority: Our Codec runs at just 1400 bit/s compared to 2400 bit/s for closed competitors. ● (Already) Rapid porting to different platforms, x86 Win32/Linux/BSD/Mac, embedded Raspberry Pi/single chip and even Android ● Software is the new hardware, costs decreasing ● Software can be free, which makes communication free (as in speech and beer)

9. Why this matters to me ● I have some skills in speech coding (and modems and radio) ● I want to use them to improve the world a little bit ● It's a fun problem, and a lot of people want to see it solved ● I really like working with open source and Ham radio people ● I like talking to people about it

10. Digital Voice Radio System codec2 enc mod HF/VHF radio codec2 dec demod mic spk r

11. How Codec 2 Works

12. Octave Demo

13. Bit Allocation ● 56 bits per 40ms frame, or 1400 bit/s

14. Demo: Analog v Digital Voice Radio System codec2 enc mod HF/VHF radio codec2 dec demod mic spk r

15. Demo: Analog v Digital Radio ● Input Speech (300 to 2600 Hz) ● Modem signal at Tx ● Modem signal at Rx (SNR = 5dB, 50Hz offset) ● Decoded Speech using Codec 2 ● SSB over same channel ● Decoded Speech (high SNR)

16. Recent Work ● Over the past 12 months.... ● (re) written a modem for HF radio ● Developed a 3200 bit/s Codec 2 mode ● Developed a post filter to improve quality for all rates ● Co-developed and released a GUI Application called FreeDV

17. Roadmap FDMDV modem Robust HF VHF Mode Embedded Android (next!) FreeDV Codec 2 1400 b/s

18. FreeDV ● GUI Application for Linux/Win32 (Mac/BSD) ● GPL V2.1 (only open source Digital Voice) ● Allows any SSB HF radio to be used for Digital Voice ● Ease of Use ● Fun! ● Demo....

19. Links ● http://rowetel.com/codec2.html http://rowetel.com/codec2.html ● http://freedv.org http://freedv.org