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
-
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
Overview
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
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
.
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 Whitaker
Phenomenon
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
Radio
or
Repeat
er
Mobile
Station
Internet
Radio Link
Computer
Distant Radio
or Repeater
• Repeater: A station that simultaneously
retransmits the transmission of another
station over a wider area on another
441 MHz
frequency
down
446 MHz
up
Coverage from 320-ft in
West Raleigh
Ham Radio - Internet Linking
Radio-only Access
• IRLP (linux)
PC -or- Radio Access:
• eQSO (Windows)
• iLink (Windows)
• WIRES (Windows)
• EchoLink (Windows or linux)
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
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.
Dave VE7LTD and Pete VK2YX
IRLP Growth
November 1998 - 2
December 1999 +10= 12
June 2000 +20 = 32
December 2000 +29 = 61
June 2001 +61 = 122
December 2001 + 199 = 321
June 2002 + 236 = 557
December 2002 +263 = 820
database records 1/1/03
IRLP Network
445 United States
154 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
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
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
51.500
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
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
v.2 IRLP card
DB9
for
radio
inter
-face
+12VDC
from PC
DB25 for Data
Control from
LPT1 & IRLP
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/440
Control Xcvr
4270 Link Radio
4260 Link Radio
KD4RAA
Node 4260 / 4270
Configuration
Audio Equalizer and Broadcast Leveling
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
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).
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"
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).
NCSU
Bookstores:
Audio Compression
ADPCM
GSM
Jason Woodard, http://www-mobile.ecs.soton.ac.uk/speech_codecs/
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
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:
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:
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
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
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.
Raleigh Reflector
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
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 experimentation.
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.
More Info
•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
Thank You