The Internet Radio Linking Project

Another Canadian Invention is Sweeping the World

by Paul Cassel VE3SY paul@ve3sy.com

IRLP is the brainchild of David Cameron, VE7LTD of Vancouver BC. IRLP is the abbreviation used for the Internet Radio Linking Project which David developed over the past several years. Back in 1998 Dave became frustrated with the unreliable operation of the Windows based Voice over IP software. All Windows based amateur linking software used VOX and was not secure from non-amateur access. The IRLP network uses a digital switching concept and produces an instant and secure link between licensed repeaters all around the world.

Eight months after Dave started his design work in 1998, the IRLP network was born and is now on Version 3.0 of the hardware and many updated releases of the software. As of 2009, IRLP is serving well over 2,000 nodes and steadily growing. Back in 2000 when we ordered our interface hardware here in Kitchener, there were only 63 active nodes. There is no need to worry about the frequent software updates as they are automatically pushed to the nodes over night and there is no need to reboot.

How It Works

David’s custom IRLP software -takes the audio from the receiver which is fed into the sound card - where it is converted into ADPCM digital data the same format used by the phone companies for Long Distance service. The Linux PC then converts this digital information into digital packets each assigned with IP addresses for the destination node. These packets now flow through the internet to the destination Linux PC where the packets are decoded then sent to the sound card and out to the transmitter microphone of the link radio which then transmits the audio out over the local repeater. The transmitter is keyed as soon as these TCP/IP (Internet Protocol) packets start to arrive. As soon as the data stops the link radio automatically un-keys and process reverses.

The underlying audio processing technology in IRLP is a freeware application called “Speak Freely”. Speak Freely produces Voice-Over-IP (VoIP) audio streaming and is very similar to other VoIP software packages such as Microsoft NetMeeting and the VocalTec iPhone with one major difference - It runs under Linux not Windows. Linux was David’s operating system of choice for the IRLP system as it allows the best in reliability, programmability, efficiency, and functionality. Since our repeaters don't need anything even close to MP3 audio quality, IRLP is using a low-bitrate VoIP to communicate. Most nodes use an encoding system that requires only 32KB/s of bandwidth, however some nodes with extremely limited bandwidth, use a GSM encoding method which only requires 17KB/s albeit at the cost of audio quality.

The control of the radio is performed using a small custom logic board build by Dave VE7LTD which is connected to the computers parallel port. This board samples the received audio for Touch Tone audio, detects when the link receiver is active, and feeds the TX PTT line to the link radio. All of the command I/O between the PC and the IRLP board is handled by a connection to the PC’s parallel port.

The whole system is DTMF (touch-tone) controllable. The control codes lie imbedded in a separate program that reads the DTMF tones from the decoder located on the interface controller board and activates various parts of the software. DTMF codes are used to enable/disable linking, open/close links and set identifiers. Every site has the ability to connect direct to any other site(s), either using direct connections or reflector sites. There are also 3 N/O Mosfett switches on the board that have ON/OFF control commands via DTMF.

To host an IRLP node you require; a) a full time high speed Internet connection – DSL or Cable - b) a dedicated PIII or better, c) the IRLP custom software/hardware and d), a link radio or direct connection to a repeater. Each node on the IRLP network is assigned an ID code and a central server keeps track of the IP addresses in use by all nodes. (IP= the routing code used by all packets of data flowing on the internet)

The Kitchener Ontario IRLP Node

The Kitchener Ontario IRLP Node I had read about Dave’s work on his web site and based on the low cost of entry US$120 I ordered the IRLP package which arrived within 10 days.

Using the IRLP Network

To connect to another repeater you simply dial a 4 digit on-code. (some node operators require a pre-access code much like an autopatch code) Within a few seconds that node will ID in plain voice with it's callsign and location. If the node is currently connected to another or to a reflector, you will receive a recording telling you which connection the other repeater is currently engaged with.

The first thing I had to do was sacrifice a surplus Windows based machine in favor of the CentOS Linux operating system for which I had no previous experience. Following the very detailed installation instructions posted on the IRLP web site, the installation went very smooth however I did encounter a weird inbound Telnet problem that was quickly resolved thanks to assistance from Dave VE7LTD and our resident K-W Linux guru Dave VA3DGS.

Now that I had the Linux box talking both ways to the internet I installed the IRLP hardware, and the machine booted flawlessly under Linux and immediately recognized the sound and ethernet cards. I was now ready to go on the air however Dave VE7LTD, the IRLP project leader was off sick and unable to send me node access codes.

The next morning "AJ", VE3ABZ checked in and indicated he had codes from the London club and keyed in the four digit code to bring up VE3SUE in London. Typical of many repeaters these days, no one was on the air so “AJ” then brought up the Denver reflector - a Reflector is a Linux based PC sitting on some serious bandwidth that allows multiple audio streaming out to many repeaters. Now connected to the reflector we were able to talk with amazing clarity to stations in California, Pennsylvania and Yellowknife in the NWT. The audio was awesome and anyone listening would swear the Yellowknife station was in Kitchener not the North West Territories in minus 35 degree weather.

Using the IRLP Network

To connect to another node (repeater) you simply dial a 4 digit on-code. Within a few seconds that node will ID in plain voice with its callsign and location. If the node is currently connected to another or to a reflector, you will receive a recording telling you which connection the other node (repeater) is currently engaged with. As of press time there were over 2,000 IRLP nodes QRV around the world with over 100 nodes in Australia linked full time.

Before placing a call you can always check the status of any node in real time by going to http://status.irlp.net and look at the node you wish to connect with. This page updates in real-time and refreshes every minute so it is always current.

Just as with any linking system, IRLP is subject to very minor delays which are mostly radio related. These delays are caused by the amount of time it takes for numerous radios to decode the Tone Squelch information so the first thing to remember is to slow down and be patient. (to dispel internet delay myths, the audio delay over the internet is the same as you experience when using a cell phone)

When completed with a QSO announce your call and dial the 4 digit OFF code at which time a voice ID indicating the link is dropping will play. Since many repeaters are not heavily used, there are always a number of nodes left connected to the main Reflector channels allowing you to place a CQ, or ORZ type call with an excellent chance to speak with someone somewhere in the world.

Click Here for complete node list and current status

IRLP Reflectors

A reflector is a server that allows multiple nodes (repeaters) to be linked together at the same time. As of press time there were 24 reflectors located around the world each with 10 virtual channels providing the ability to provide 250 separate reflector channels. The busiest reflector channels are the Western Reflector in Las Vegas and the Alaskan Reflector. Most reflectors are hosted by public service minded companies who have lots of bandwidth to support the requirement of a reflector. The amount of bandwidth required for a reflector is directly related to the number of connected nodes.

As for DX stations you can look for activity from over 30 countries. There is lots of activity from the 100 some active nodes in the “land down under” which reminds you of the movie “Back To The Future” as most QSOs with VK land are taking place tomorrow.

Summary

Where else can you witness an open world-wide VoIP wireless network using a free and open protocol like IRLP? This exciting new technology will be a tremendous catalyst to bring new young blood into our hobby. As we all know there has been a real challenge for us to draw kids into our hobby as they could previously talk on their poor quality iPhone connections over the Internet. Now with a basic HT they can enjoy far superior audio and be talking with their friends across town and around the world.

Since we brought our node on here in Kitchener our membership has taken a real boost. Many former members see the excitement back in the hobby and many new members are joining to be part of the IRLP system. The VE3RBM repeater has gone from possibly 2 QSOs per week to our busiest repeater and is dedicated to IRLP use. It is highly recommended that an IRLP node not be added to a high traffic repeater unless the reflector feature is locked out which is easily done.

Are You Interested?

If this article has piqued your interest and you seek additional information please browse the official IRLP web site at www.irlp.net and feel free to contact the IRLP designer Dave, VE7LTD at dcameron@irlp.net or the author at paul@ve3sy.com. 

The IRLP Designer and Project Leader
Dave Cameron VE7LTD
4708 Caufield Drive
West VANCOUVER, BC
V7W 1G2
e-mail: dcameron@irlp.net 

Author:
Paul Cassel VE3SY
54 Brewery St
Baden, ON
N3A 2S7
Canada
e-mail: paul@ve3sy.com 

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