Automatic Link Establishment
Automatic Link Establishment ( ALE for short , English for "automatic connection establishment") is a digital communication protocol and selective call procedure for establishing voice and data communication via shortwave in accordance with the US technical military standards MIL-STD-188-141 and MIL-STD-188- 110. It is de facto a worldwide standard for the digital establishment and maintenance of shortwave communication. In its primary function as a selective call procedure for synchronous communication, ALE enables the automatic establishment of a connection to a specific station or group of stations (network) worldwide in order to then communicate in a different operating mode. Furthermore, with the help of the MIL-STD-188-141 and the MIL-STD-188-110 protocol, data such as texts, files, e-mails or SMS can be transmitted without errors. It offers the end user the option of gaining access to the Internet regardless of the position on or above the surface of the earth without the direct availability of regular communication networks (e.g. dial -up or dedicated line , Internet via satellite , mobile Internet, etc.) . In this context, ALE is also used in the global WinLink network for asynchronous communication . It is also used in emergency and disaster communication between government agencies and radio amateurs in the United States.
function
A standalone ALE station consists of an SSB - transceiver and a hardware or software-based TNC . The latter requires a software-based computer with a sound card and a sound card interface. Each station has a unique ALE address , e.g. B. an amateur radio call sign . If the transceiver is not occupied, it scans a list of predefined frequencies ( channel ) and waits for ALE signals. If an ALE signal is detected, the transceiver remains on the channel to decode it. The beacon transmissions automatically sent out by other stations are then evaluated on the basis of the bit error frequency and stored in the LQA (Link Quality Assessment) database together with the frequency and transmitter address.
To reach an ALE station or an ALE network, the person operating the calling station specifies the address to be called. On the basis of the data collected by the scanning operation, the frequency with the best propagation conditions is automatically selected depending on the time and location of the respective station , in order to contact it with a selective call. If this does not succeed, it will be tried on other channels. If the called station decodes its address, a connection is established. The operator of the calling and called station is signaled that a connection has been established. Communication in ALE or another operating mode, e.g. B. Radiotelephony can be continued. The aim of this method is to be able to reach a desired remote station worldwide at any time without the operator being aware of propagation conditions or a special call frequency.
Transmission protocol
ALE uses two different error correction techniques. The forward error correction is used to achieve the lowest possible bit error rate at the receiving station during the transmission using redundant data records. The ARQ protocol can optionally be used to guarantee that the transmission is actually error-free . A packet sent by the ISS ( information sending station ) must be acknowledged as successfully received by the IRS ( information receiving station ) before the next packet is sent. The correct reception of a packet is checked using a check bit. The current data packet is repeated until the ISS has received confirmation of correct reception from the IRS.
Use in amateur radio
As early as the mid-1990s, radio amateurs were using ALE as a transmission protocol with commercial transceivers and hardware TNCs. In 2000 the PC ALE program was published, which enabled communication with ALE via the computer sound card without a commercial transceiver or hardware TNC. In 2001 the first radio amateurs organized themselves into the international ALE amateur radio network HFN ( English high frequency network , short wave network ). This led to the fact that in August 2005 radio amateurs in the USA were able to support the American Red Cross in emergency and disaster communication with ALE during Hurricane Katrina .
WinLink
Network control stations of the HFN network connected to the Internet enable SMS and e-mails to be sent, but without a file attachment via the WinLink 2000 network. Due to the low data throughput and the simple protocol structure, ALE is particularly suitable for short messages. The faster ARDOP and PACTOR protocols are used on shortwave to send larger messages and file attachments .
International coordination
International amateur radio ALE channels and corresponding frequency assignments are coordinated with all IARU regions for international, national, regional and local application in amateur radio service . All channels refer to the standard of the upper sideband (USB) that is usual for digital operating modes .
International channels
This is a list of internationally established ALE frequencies.
| channel | Frequency (kHz) | SSB | use | network | description |
|---|---|---|---|---|---|
| 01 | 1845.0 | USB | Voice / data | - | Local |
| 02 | 1996.0 | USB | LANGUAGE / DATA | - | Local |
| 03 | 3584.5 | USB | DATA / LANGUAGE | QRZ | Test and extended traffic |
| 04 | 3596.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 05 | 3617.0 | USB | DATA / LANGUAGE | - | IARU Region 1 Internet, beacons |
| 06 | 3791.0 | USB | LANGUAGE | HFL | International emergency and disaster radio |
| 07 | 3845.0 | USB | LANGUAGE | HFL | North America |
| 08 | 3996.0 | USB | LANGUAGE | HFL | North America |
| 09 | 5371.5 | USB | LANGUAGE | - | Emergency radio only |
| 10 | 5403.5 | USB | LANGUAGE | - | Emergency radio only |
| 11 | 7049.5 | USB | DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, IARU Region 1, beacons |
| 12 | 7099.5 | USB | DATA | QRZ | Testing and expanded data traffic |
| 13 | 7102.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 14th | 7185.5 | USB | LANGUAGE | HFL | International emergency and disaster radio |
| 15th | 7296.0 | USB | LANGUAGE | HFL | North America |
| 16 | 10136.5 | USB | DATA / LANGUAGE | QRZ | Test and Extended Traffic, Asia / Pacific / Australia / New Zealand / Africa SSB |
| 17th | 10145.5 | USB | PRIMARY DATA | HFN | International Emergency / Relief, Internet |
| 18th | 14100.5 | USB | DATA | QRZ | Test and extended traffic |
| 19th | 14109.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 20th | 14346.0 | USB | LANGUAGE | HFL | International emergency and disaster radio |
| 21st | 18104.5 | USB | DATA | QRZ | Test and extended traffic |
| 22nd | 18106.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 23 | 18117.5 | USB | LANGUAGE / DATA | HFL | International emergency and disaster radio |
| 24 | 21096.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 25th | 21116.0 | USB | DATA | QRZ | Test and extended traffic |
| 26th | 21432.5 | USB | LANGUAGE | HFL | International emergency and disaster radio |
| 27 | 24926.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 28 | 24932.0 | USB | LANGUAGE | HFL | International emergency and disaster radio |
| 29 | 28146.0 | USB | PRIMARY DATA | HFN | Global ALE shortwave network , RF relay, data traffic, internet connectivity, beacons |
| 30th | 28312.5 | USB | LANGUAGE / DATA | HFL | International emergency and disaster radio |
| 31 | 50162.5 | USB | LANGUAGE / DATA | QRZ | Local |
| 32 | 144162.5 | USB | LANGUAGE / DATA | QRZ | Local |
Standard configurations
| Note | configuration | default |
|---|---|---|
| 1 | ALE system | MIL-STD 188-141A; FED-1045 (8FSK, 2kHzBW) |
| 2 | Duration of transmission | optimal 22 s; maximum 30 s. |
| 3 | Scan rate | 1 or 2 channels per second. |
| 4th | Beacon interval | 60 minutes or more (for some channels) |
| 5 | central audio frequency | 1625 Hz for digital data transmission |
| 6th | Message standard | AMD (Automatic Message Display) short text |
| 7th | Beacon type | TWS (This Was Sound) Bake |
International networks
| network | Members | purpose |
|---|---|---|
| HFL | 10 | All ALE language stations, open selective call procedure |
| HFN | 10 | Global ALE shortwave network |
| QRZ | 3 | open call procedure on all channels |
| GPR | 3 | GPS messages |
| RPT | 3 | Stations status messages |
software
| program | basis | License |
|---|---|---|
| PC ALE | Windows XP and above | Freeware |
| MARS-ALE | Windows XP and above | Freeware for MARS members |
| Sorcerer (decoder) | Windows XP and above | Freeware |
Web links
- Automatic Link Establishment in the Signal Identification Wiki (audio files, waterfall graphics and other information).
- Website of the HFN-ALE group (English)
- Overview of global ALE activity on amateur bands
- Use of ALE for tactical communication
- An ALE decoder for Linux
Individual evidence
- ↑ Interoperability and Performance Standards for Medium and High Frequency Radio Systems ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ↑ Interoperability and Performance Standards for Data Modems ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- ^ Telecom Bureau, ITU- D / SG: Frequency Agile Systems in the MF / HF Bands. (DOC; 65 kB) International Telecommunication Union , December 14, 2000, accessed December 17, 2012 (American English).
- ↑ Ronald E. Menold, AD4TB: ALE - The Coming of Automatic Link Establishment . February 1995 (American English, arrl.org [PDF]).
- ^ B. Crystal, A. Barrow: ALE for Emergency / Disaster Relief Communications. International Amateur Radio Union (IARU), August 17, 2007, accessed December 17, 2012 (American English).
- ↑ ARRL Technical Information Service page: ARRLWeb: ALE (Automatic Link Establishment). American Radio Relay League (ARRL), August 2005, accessed December 17, 2012 (American English).
- ^ ALE Automatic Link Establishment Channel List International Amateur Radio Service. HFLINK HFN, accessed December 17, 2012 (American English).
