Presentation on theme: "The Internet Radio Linking Project"— Presentation transcript:
1The Internet Radio Linking Project Presentation for the Triangle Linux Users Group by Jim Price WW4MApril 10, 2003Portions of this presentation courtesy of KD4RAA, VE3SY, VE7LTD, VK3JED
2Overview What is Amateur Radio? Ham Radio Activities IT and Amateur RadioHam Radio Internet LinkingThe IRLP NetworkIRLP HardwareIRLP SoftwareUsing IRLPListeningFor More Info...Demonstration
3What is Amateur Radio?Licensed as a public service by the Federal Communications Commissionvoluntary non-commercial communications, with an emphasis on providing emergency communicationsadvancement of the radio artadvancing communication and technical skills and provide trained operators, technicians and electronics expertspromote international goodwill680,000 hams in the U.S., 18,000 in NC
4Celebrity HamsEntertainers: Chet Atkins WA4CZD, Ronnie Milsap WB4KCG, Marlon Brando FO5GJ, Patty Loveless KD4WUJ, Gary Shandling KD6OY, Burl Ives KA6HVA, Arthur Godfrey K4LIB, Priscilla Presley N6YOSJoe Walsh WB6ACU
5A huge number of politicians and royals including: Gov . 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 VU2RGFamous 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 KA6UXRWalter Cronkite KB2GSD
8Amateur Radio Activities HF (shortwave)VHF/UHF and repeatersMorse code, analog voicePublic Service/ EmergenciesHome-building equipment“Dxing” (long distance contacts)ContestingAmateur Radio SatellitesDigital ModesTV
9IT and Amateur Radio Computer-Controlled Modes Packet Radio Narrow Band Teletype (e.g. PSK-31)Amateur TelevisionIEEE b WiFi / HSMMGPS & APRSAmateur Radio SatellitesInternet Radio LinkingRemote Bases and Web RadioDigital Signal ProcessingSoftware Defined RadioSpread Spectrum TechnologyContact Logging SoftwareAntenna Design
18Ham Radio - Internet Linking Radio-only AccessIRLP (linux)PC -or- Radio Access:eQSO (Windows)iLink (Windows)WIRES (Windows)EchoLink (Windows or linux)
19The Internet Radio Linking Project (IRLP) Uses the Internet to link distant radio sitesGives global coverage to normally localized VHF and UHF frequenciesEnables minimally equipped stations to communicate globallyAllows end user control of links via their radio’s DTMF (Touchtone) keypad
20The 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.
28IRLP is based on Speak Freely for 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).
29Typical IRLP Node Standard PC, P100 or better Linux (Red Hat 7.3) SB16 ISA soundcardCustom IRLP computer/radio control interfaceRadioDedicated internet connection
30IRLP Control Board Custom Red Hat CD-ROM Boot Diskette Custom IRLP SoftwareIRLP Control BoardDoes COS, PTT & DTMFDB9 IRLP to Radio InterfaceLPT1 to IRLP Jumper Cable
31DB9 for radio inter-face v.2 IRLP card+12VDC from PCDB25 for Data Control from LPT1 & IRLP
32Indicators on v.2 Control Board – DTMF Decode Sense – Carrier Operated Squelch Sense– PTT out to Link Radio or Controller
36What Happens During a Call? Notes from Dave Cameron, VE7LTD
37DTMF Decode DTMF program monitors COS and DTMF Once detected DTMF sequence passed to the decode scriptDecode script checks custom_decode for matchesAssuming a call is decoded, call script is started with the node number as the argumentVE7LTD
38Call Script Best server is determined by using find_best_server script Best server is asked for latest IP of node being calledIf IP received is different from IP in hosts file, a new hosts file is d/l from best serverIrlp_call is started, and a TCP connection is made to the called node on port 15425VE7LTD
39IRLP_CALL / IRLP_ANSWER Remote node starts irlp_answer in response to TCP call on port 15425PGP security performs a dual challenge to ensure calling node is an IRLP nodeCodec (GSM/ADPCM) is determinedIrlp_call and irlp_answer start speak freely software on UDP ports 2074 and 2075VE7LTD
40During the CallIrlp_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 messageVE7LTD
41DisconnectsDisconnecting node uses TCP info channel to send disconnect message. Both nodes run the off scriptUnexpected drop in the TCP connection prompts reset of IRLP nodeIf the timeout elapses, disconnect is sentVE7LTD
42NCSU Bookstores:Sending AudioAudio 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).
43NCSU 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"
44NCSU Bookstores:Receiving AudioSpeak 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).
46ADPCM (Adaptive Differential Pulse Code Modulation) 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 bpssuperior sound quality vs. GSM
47GSM (Global System for Mobile Communications) NCSU Bookstores:GSM (Global System for Mobile Communications)requires only 13 kb/s bandwidthreduces the data rate from 8000 to 1650 bps, which makes a 28.8 Kb modem usableserves 71% of the total digital wireless market and provides good quality speech
48NCSU 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.
49NCSU 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
50Ports Required 2074 - 2093 Audio (bi-directional UDP) IRLP Control/Update (TCP)Outbound ports used: 80 (http) for updates873 or 8873 (rsync) for downloading updates10000 (for IP determination)parallel port set to "standard" or "compatible" mode, not to ECP, EPP or bi-directional
51Some IRLP Details512-bit bi-directional PGP authentication ensures connections only with other IRLP nodes.Redundant servers support IRLP-BIND (DHCP isn’t a problem) as well as download of pgp key rings, software updates, and station ID wavfiles.IRLP accepts commands from keyboard or via DTMF (dual tone multi frequency, i.e. “Touchtones”)
52IRLP and the GPL“I had released code under the GPL, and it led to nothing but 1000's of s criticising my code, asking for features, wondering why I built this that way, etc... I got tired of answering questions.”“There is a strong commercial potential for this product, and I did not want to hand several 1000 hours worth of code to the private sector just to be replicated.”“Closed code maintains a standard, which open releases would compromise.”VE7LTD
53IRLP AdminFCC regulations prohibit unlicensed people using amateur frequencies.IRLP links are accessible only on amateur radio frequencies within range of a node. No direct Internet access.OpenSSH used for remote administration.Linux packages updated automatically (up2date, autorpm, apt).Cron jobs to automate functions
54IRLP ScriptingThe IRLP software is composed largely of bash shell scripts.Flexible: easily customized to suit local needs.Almost anything that can be run from the console can be controlled via radio.Morse Code ID using MIDI or wav (per FCC legal requirements)Node status (link off/on and where linked to)Time of day (talking clock)Weather reports, Amber AlertsLocal AnnouncementsDownload and play radio news programs from internetRandom dialing*69 / “Call Waiting”
55IRLP Advantages User Flexibility - Custom Scripts Accessible only by radioSecurityStability of linux OSSuperior audio; COS (not VOX)Cost: linux is free, will run on old PCsContinues to function if servers fail
56Two ways to make contacts Point-to-PointandReflectors (like chat rooms -- multiple nodes connected together, hearing audio from one node at a time)
57IRLP ReflectorsEnable multiple nodes to link together into a network – number limited only by bandwidth.Running a reflector requires bandwidth (32 kbps per connected node) to handle the multiple data streams. Most reflectors are hosted by ISPs (like Inflow) who often donate the bandwidth.
58Raleigh ReflectorEstablished for coordinated response to severe weather events and for public serviceLinks NC repeaters beyond the range of conventional RF linking systemsDuring Hurricane Lily, linked stations in Louisiana with the National Hurricane Center in FloridaHas linked stations from Georgia to Maryland to track several winter stormsSimulcast a ham radio contact between the International Space Station and Chapel Hill middle school studentsParticipated in the Boy Scouts’ JOTA event
59Impact of Internet Linking on Amateur Radio Level of amateur activity has increased dramaticallyAmateurs who have been inactive for a long time are coming back on the airAmateur Radio is becoming more appealing to today’s Internet-oriented youthNew opportunities for experi- mentation.
60The FutureInternet linking is already becoming commonplace – over 800 IRLP nodes on the air.Advances in technology will improve performance of links.Technology can be ported to high-speed microwave and satellite links.Enhanced global slack.
61Listening to IRLP Live Demonstration Monitoring IRLP Reflector 2 via Live365 streaming audio (linked fromRecorded conversation with Antarctica, andRecorded school contact with the International Space Station (linked fromlocal frequencies via radio or scanner
62How to Become a Ham Radio Operator Radio amateurs are licensed by the FCC, after passing examinations in radio theory, electronics, regulations, and optionally, Morse Code.Examinations are conducted locally by individuals or clubs almost every week and cost about $12 (10-year renewals are free)Many radio clubs run study courses. 1-on-1 tutoring, book and online stuyding, and taking mock online exams are other study options.
63More Info IRLP in Raleigh - www.kd4raa.net IRLP in General -What is Amateur Radio? -Raleigh Amateur Radio Society -American Radio Relay League -