The Internet RadioThe Internet RadioLinking ProjectLinking Project

Portions of this presentation courtesy of KD4RAA, VE3SY, VE7LTD, VK3JED

Presentation for the Triangle Linux Users GroupTriangle Linux Users Group

by Jim Price WW4MJim Price WW4MApril 10, 2003

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

What is Amateur Radio?

• Licensed as a public service by the Federal Communications Commission

• voluntary non-commercial communications, with an emphasis on providing emergency communications

• advancement of the radio art• advancing communication and technical

skills and provide trained operators, technicians and electronics experts

• promote international goodwill• 680,000 hams in the U.S., 18,000 in NC

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

Celebrity Hams

Joe Walsh WB6ACU

.

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

Celebrity non-Hams

Forest WhitakerPhenomenon

Dennis Quaid

non-Celebrity Hams

Amateur Radio Activities

• HF (shortwave)• VHF/UHF and repeaters • Morse code, analog voice• Public Service/ Emergencies• Home-building equipment

• “Dxing” (long distance contacts)

• Contesting• Amateur Radio Satellites• Digital Modes

TV TV

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

Computer

Computer

Internet Distant Radio or RepeaterRadio Link

Mobile Station

Radio or Repeater

• Repeater: A station that simultaneously retransmits the transmission of another station over a wider area on another frequency

446 MHzup

441 MHzdown

Coverage from 320-ft in West Raleigh

PC -or- Radio Access:• eQSO (Windows)• iLink (Windows)• WIRES (Windows)• EchoLink (Windows or linux)

Radio-only Access• IRLP (linux)

Ham Radio - Internet Linking

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

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.

The Internet Radio Linking Project (IRLP)

Dave VE7LTD and Pete VK2YXDave VE7LTD and Pete VK2YX

November 1998 - 2December 1999 +10= 12

June 2000 +20 = 32December 2000 +29 = 61

June 2001 +61 = 122December 2001 + 199 = 321

June 2002 + 236 = 557 December 2002 +263 = 820

IRLP Growth

database records 1/1/03

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

IRLP Network

active nodes 4/1/03

Australia and New Zealand

Europe

North America

Example:Los Angeles Area Nodes

3520 WB6EGR Burbank 448.480

8590 KF6PXL Corona

7380 K7QT Highland 449.840

3190 WD8CIK Hollywood 446.560

3170 WD6AWP Huntington Beach 145.140

3609 K6GTZ Lakewood 51.500

3745 KE6HRV Long Beach 144.480

3040 WA6JFK Los Angeles 1294.600

3650 KE6PCV Los Angeles 447.720

3760 N6JVH Los Angeles 447.240

3830 WB5EKU Los Angeles 447.200

3910 WB6DAO Los Angeles 447.600

5610 KF6CPI Los Angeles 224.580

8630 KE6YGM Mission Viejo 144.440

3670 N6JVH North Hills

3140 KE6DGM Norwalk 449.340

5850 KJ6W Palmdale 445.600

3030 KB6THO Pasadena 224.480

3340 WR6JPL Pasadena 224.080

7170 W6EKZ Pomona 144.440

3448 KJ6KB Rancho Palos Verdes [WALA IV] 145.725

4810 KF6FM Riverside

5900 WB9RNW San Fernando Valley 445.180

3846 WB6T San Juan Capistrano 447.540

3100 N6KNW Santa Clarita 51.860

3510 WB6EGR Santa Clarita 927.500

3410 KD6GDB Santa Monica 145.800

4690 KF6JEE Woodcrest 446.280

IRLP 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).

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

IRLP Control Board

Does COS, PTT & DTMF

DB9 IRLP to Radio Interface

LPT1 to IRLP Jumper Cable

Custom Red Hat CD-ROM

Boot Diskette

Custom IRLP Software

DB9 for radio inter-face

DB25 for Data Control from LPT1 & IRLP

+12VDC from PC

v.2 IRLP card

Indicators on v.2 Control Board

– DTMF Decode Sense – Carrier Operated Squelch Sense

– PTT out to Link Radio or Controller

v.3 IRLP card features surface-mount components

100MB Switch

10MB Hub

Linksys Router

DualBand 2M/440Control Xcvr

4270 Link Radio 4260 Link Radio

Audio Equalizer and Broadcast Leveling

KD4RAANode 4260 / 4270

Configuration

What Happens During a Call?

Notes from Dave Cameron, VE7LTD

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

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

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

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

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

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).

NCSU Bookstores:

NCSU Bookstores:

Sending Audio

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"

NCSU Bookstores:

NCSU Bookstores:

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).

NCSU Bookstores:

NCSU Bookstores:

Receiving Audio

NCSU Bookstores:

NCSU Bookstores:

Jason Woodard, http://www-mobile.ecs.soton.ac.uk/speech_codecs/

GSM

ADPCM

Audio Compression

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

NCSU Bookstores:

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

NCSU Bookstores:

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.

NCSU Bookstores:

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

NCSU Bookstores:

NCSU Bookstores:

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 updates10000 (for IP determination)

parallel port set to "standard" or "compatible" mode, not to ECP, EPP or bi-directional

Ports Required

Some IRLP Details

512-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”)

IRLP and the GPL

“I had released code under the GPL, and it led to nothing but 1000's of emails 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

IRLP Admin

• FCC 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

IRLP Scripting• The 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 Alerts– Local Announcements– Download and play radio news programs from internet– Random dialing– *69 / “Call Waiting”

IRLP Advantages

• User Flexibility - Custom Scripts• Accessible only by radio

• Security• Stability of linux OS

• Superior audio; COS (not VOX)• Cost: linux is free, will run on old PCs• Continues to function if servers fail

Two ways to make contacts

Point-to-Point

and

Reflectors(like chat rooms -- multiple nodes connected together, hearing audio from one node at a

time)

IRLP Reflectors

• Enable 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.

Established for coordinated response to severe weather events and for public service

Links NC repeaters beyond the range of conventional RF linking systems

During Hurricane Lily, linked stations in Louisiana with the National Hurricane Center in Florida

Has linked stations from Georgia to Maryland to track several winter storms

Simulcast a ham radio contact between the International Space Station and Chapel Hill middle school students

Participated in the Boy Scouts’ JOTA event

Raleigh Reflector

Impact of Internet Linking on Amateur Radio

• Level of amateur activity has increased dramatically

• Amateurs who have been inactive for a long time are coming back on the air

• Amateur Radio is becoming more appealing to today’s Internet-oriented youth

• New opportunities for experi-mentation.

The Future

• Internet 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.

Listening to IRLP

• Live Demonstration• Monitoring IRLP Reflector 2 via Live365 streaming

audio (linked from www.irlp.net)• Recorded conversation with

Antarctica, and• Recorded school contact with the

International Space Station (linked from www.kd4raa.net)

• local frequencies via radio or scanner

How 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.

•IRLP in Raleigh• - www.kd4raa.net•IRLP in General - www.irlp.net•What is Amateur Radio? - www.howstuffworks.com/ham-radio.htm•Raleigh Amateur Radio Society - www.rars.org•American Radio Relay League - www.arrl.org

More Info

Thank You