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The Internet Radio Linking Project. Presentation for the Triangle Linux Users Group by Jim Price WW4M April 10, 2003. Portions of this presentation courtesy of KD4RAA, VE3SY, VE7LTD, VK3JED. Overview. What is Amateur Radio? Ham Radio Activities IT and Amateur Radio

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The Internet Radio Linking Project


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    1. The Internet RadioLinking Project Presentation for the Triangle Linux Users Groupby Jim Price WW4M April 10, 2003 Portions of this presentation courtesy of KD4RAA, VE3SY, VE7LTD, VK3JED

    2. Overview • What is Amateur Radio? • Ham Radio Activities • IT and Amateur Radio • Ham Radio Internet Linking • The IRLP Network • IRLP Hardware • IRLP Software • Using IRLP • Listening • For More Info... • Demonstration

    3. What is Amateur Radio? • Licensedas apublic serviceby the Federal Communications Commission • voluntarynon-commercialcommunications, with an emphasis on providingemergency communications • advancementof the radio art • advancing communication and technical skillsand provide trained operators, technicians and electronics experts • promoteinternational goodwill • 680,000 hams in the U.S., 18,000 in NC

    4. Celebrity Hams Entertainers: Chet Atkins WA4CZD, Ronnie Milsap WB4KCG, Marlon Brando FO5GJ, Patty Loveless KD4WUJ, Gary Shandling KD6OY, Burl Ives KA6HVA, Arthur Godfrey K4LIB, Priscilla Presley N6YOS Joe Walsh WB6ACU

    5. .A huge number of politicians and royals including:Gov. George Pataki N2ZCZ, Sen. Barry Goldwater K7UGA, Spain’s King Juan Carlos EA0JC, Jordan's King Hussein JY1 and Queen Noor JY2, Argentina’s Pres. Carlos Menem LU1SM, India’s Rajiv Gandhi VU2RG Famous and infamous hams: most astronauts, Hugh Downs KD6WUS, Art Bell W6OBB, Kevin Mitnick N6NHG, and the author of The Joy of Sex, Dr. Alex Comfort KA6UXR Walter Cronkite KB2GSD

    6. Celebrity non-Hams Forest WhitakerPhenomenon Dennis Quaid

    7. non-Celebrity Hams

    8. TV TV Amateur Radio Activities • “Dxing” (long distance contacts) • Contesting • Amateur Radio Satellites • Digital Modes • HF (shortwave) • VHF/UHF and repeaters • Morse code, analog voice • Public Service/ Emergencies • Home-building equipment

    9. IT and Amateur Radio • Computer-Controlled Modes • Packet Radio • Narrow Band Teletype (e.g. PSK-31) • Amateur Television • IEEE 802.11b WiFi / HSMM • GPS & APRS • Amateur Radio Satellites • Internet Radio Linking • Remote Bases and Web Radio • Digital Signal Processing • Software Defined Radio • Spread Spectrum Technology • Contact Logging Software • Antenna Design

    10. Computer Radio or Repeater Distant Radio or Repeater Internet Radio Link Mobile Station Computer

    11. 441 MHzdown 446 MHzup • Repeater: A station that simultaneously retransmits the transmission of another station over a wider area on another frequency

    12. Coverage from 320-ft in West Raleigh

    13. Ham Radio - Internet Linking Radio-only Access • IRLP (linux) PC -or- Radio Access: • eQSO (Windows) • iLink (Windows) • WIRES (Windows) • EchoLink (Windows or linux)

    14. The Internet Radio Linking Project (IRLP) • Uses the Internet to link distant radio sites • Gives global coverage to normally localized VHF and UHF frequencies • Enables minimally equipped stations to communicate globally • Allows end user control of links via their radio’s DTMF (Touchtone) keypad

    15. The Internet Radio Linking Project (IRLP) Created by Dave Cameron VE7LTD of Vancouver, BC   Dave was frustrated with the unreliable operation of Windows-based Iphone and turned to linux. Iphone and other systems use VOX. IRLP uses COS.IRLP is radio-access only.

    16. Dave VE7LTD and Pete VK2YX

    17. IRLP Growth November 1998 - 2 December 1999 +10= 12June 2000 +20 = 32December 2000 +29 = 61June 2001 +61 = 122December 2001 + 199 = 321June 2002 + 236 = 557December 2002 +263 = 820 database records 1/1/03

    18. IRLP Network 445 United States154 Canada 54 Australia + New Zealand 49 Europe 12 Caribbean + Bermuda 6 Japan 3 Southern Africa 2 Ecuador, Mexico 1 India 1 Antarctica active nodes 4/1/03

    19. Australia and New Zealand

    20. Europe

    21. NorthAmerica

    22. Example:Los Angeles Area Nodes

    23. IRLP is based on Speak Freelyfor Linux. Speak Freely for linux is Open Source, while Speak Freely for Windows is GPL. Linux offered the best in reliability, programmability, efficiency, and functionality.  IRLP currently ships with RH 7.3 and will run on a 486 DX100 or better computer(init=3).

    24. Typical IRLP Node • Standard PC, P100 or better • Linux (Red Hat 7.3) • SB16 ISA soundcard • Custom IRLP computer/radio control interface • Radio • Dedicated internet connection

    25. Custom Red Hat CD-ROM Boot Diskette Custom IRLP Software IRLP Control Board Does COS, PTT & DTMF DB9 IRLP to Radio Interface LPT1 to IRLP Jumper Cable

    26. DB9 for radio inter-face DB25 for Data Control from LPT1 & IRLP +12VDC from PC v.2 IRLP card

    27. Indicators on v.2 Control Board – DTMF Decode Sense – Carrier Operated Squelch Sense – PTT out to Link Radio or Controller

    28. v.3 IRLP card features surface-mount components

    29. 100MB Switch 10MB HubLinksys Router DualBand 2M/440Control Xcvr KD4RAANode 4260 / 4270Configuration 4270 Link Radio 4260 Link Radio Audio Equalizer and Broadcast Leveling

    30. What Happens During a Call? Notes from Dave Cameron, VE7LTD

    31. DTMF Decode • DTMF program monitors COS and DTMF • Once detected DTMF sequence passed to the decode script • Decode script checks custom_decode for matches • Assuming a call is decoded, call script is started with the node number as the argument VE7LTD

    32. Call Script • Best server is determined by using find_best_server script • Best server is asked for latest IP of node being called • If IP received is different from IP in hosts file, a new hosts file is d/l from best server • Irlp_call is started, and a TCP connection is made to the called node on port 15425 VE7LTD

    33. IRLP_CALL / IRLP_ANSWER • Remote node starts irlp_answer in response to TCP call on port 15425 • PGP security performs a dual challenge to ensure calling node is an IRLP node • Codec (GSM/ADPCM) is determined • Irlp_call and irlp_answer start speak freely software on UDP ports 2074 and 2075 VE7LTD

    34. During the Call • Irlp_call and irlp_answer send keepalives in the background. If keepalive fails, the connection drops (every 15 sec) • Irlp_call and irlp_answer keep open info channel to pass dtmf regeneration info, disconnect/timeout message VE7LTD

    35. Disconnects • Disconnecting node uses TCP info channel to send disconnect message. Both nodes run the off script • Unexpected drop in the TCP connection prompts reset of IRLP node • If the timeout elapses, disconnect is sent VE7LTD

    36. NCSU Bookstores: Sending Audio Audio streaming is enabled when the link radio receives a signal with COS and keys the IRLP interface card. The sound card receives the radio’s audio and creates a continuous mono 8-bit digital stream of raw audio at 8000Hz (64k bps). Speak Freely’s sfmike program compresses the audio stream by a factor of two (32k bps) using an audio compression algorithm (codec).

    37. NCSU Bookstores: The audio is split into packets, which are transmitted over port 2074 using a User Datagram Protocol (UDP) stream. UDP does NOT confirm the reception of packets - it "fires and forgets"

    38. NCSU Bookstores: Receiving Audio Speak Freely’s sfspeaker receives the packets on port 2075 and rejoins them into an 8-bit ULAW stream. . Next the ULAW stream is uncompressed back into an 8-bit raw stream of audio. . The raw audio is streamed through the digital to analog (D/A) converter (the output device of your sound card). . The IRLP interface card keys the radio when the audio stream is present (live -- no buffering).

    39. NCSU Bookstores: Audio Compression ADPCM GSM Jason Woodard, http://www-mobile.ecs.soton.ac.uk/speech_codecs/

    40. NCSU Bookstores: • ADPCM(Adaptive Differential Pulse Code Modulation) • only 32 kb/s - more efficient than the PCM codec used by WAV, AIFF and CD audio (and is used on the Sony Mini Disc) • cuts the data rate from 8000 to 4000 bps • superior sound quality vs. GSM

    41. NCSU Bookstores: • GSM(Global System for Mobile Communications) • requires only 13 kb/s bandwidth • reduces the data rate from 8000 to 1650 bps, which makes a 28.8 Kb modem usable • serves 71% of the total digital wireless market and provides good quality speech

    42. NCSU Bookstores: ADPCM quantizes the difference between the sampled signal and a prediction. If the prediction is accurate, the difference between the real and predicted samples will have a lower variance than the real speech samples and will be accurately quantized with fewer bits than needed for the original. At the decoder the quantized difference signal is added to the predicted signal to give the reconstructed speech signal. Performance is aided by using adaptive prediction and quantization, so that the predictor and difference quantizer adapt to the changing characteristics of the sampled speech.

    43. NCSU Bookstores: GSM uses a Regular Pulse Excited (RPE) codec. Input is split into 20ms frames, each with 8 short term predictor coeffiecients. Frames are further split into four 5ms sub-frames, each with a delay and gain for a long term predictor. After short and long term filtering, the residual signal for each sub-frame is decimated into three possible excitation sequences, each 13 samples long. The sequence with the highest energy is chosen as the best rep-resentation of the excitation sequence, and each pulse in the sequence has its amplitude quantized with three bits. At the decoder the reconstructed excitation signal is fed through the long term and short term synthesis filters to reconstruct the speech. A postfilter improves perceptual quality

    44. Ports Required 2074 - 2093 Audio (bi-directional UDP) 15425-7 IRLP Control/Update (TCP) Outbound ports used: 80 (http) for updates 873 or 8873 (rsync) for downloading updates 10000 (for IP determination) parallel port set to "standard" or "compatible" mode, not to ECP, EPP or bi-directional