Automatic link establishment
Encyclopedia
Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard
De facto standard
A de facto standard is a custom, convention, product, or system that has achieved a dominant position by public acceptance or market forces...

 for digitally initiating and sustaining HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...

 radio communications. ALE is a feature in an HF communications radio transceiver system, that enables the radio station to make contact, or initiate a circuit
Telecommunication circuit
A telecommunication circuit is any line, conductor, or other conduit by which information is transmitted.A dedicated circuit, private circuit, or leased line is a line that is dedicated to only one use...

, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels.

How ALE works

A standalone ALE radio combines an HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...

 SSB
Single-sideband modulation
Single-sideband modulation or Single-sideband suppressed-carrier is a refinement of amplitude modulation that more efficiently uses electrical power and bandwidth....

 radio transceiver with an internal microprocessor
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...

 and MFSK modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...

. It is programmed with a unique ALE Address
Logical address
In computing, a logical address is the address at which an item appears to reside from the perspective of an executing application program....

, similar to a phone number (or on newer generations, a username). When not actively in contact with another station, the HF SSB transceiver constantly scans through a list of HF frequencies called channels
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...

, listening for any ALE signals transmitted by other radio stations. It decodes calls and soundings
Automatic sounding
In telecommunication, automatic sounding is the testing of selected channels for quality by providing a very brief identifying transmission that may be used by other stations to evaluate connectivity, and availability, and to identify known working channels for immediate or later use for...

 sent by other stations and uses the Bit error rate to store a quality score for that frequency and sender-address.

To reach a specific station, the caller enters the ALE Address. On many ALE radios this is similar to dialing a phone number. The ALE controller selects the best available idle channel for that destination address. After confirming the channel is indeed idle, it then sends a brief selective calling
Selective calling
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

 signal identifying the intended recipient. When the distant scanning station detects ALE activity, it stops scanning and stays on that channel until it can confirm whether or not the call is for it. The two stations' ALE controllers automatically handshake
Handshaking
In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...

 to confirm that a link of sufficient quality has been established, then notify the operators that the link is up. If the callee fails to respond or the handshaking fails, the originating ALE node usually selects another frequency either at random or by making a guess of varying sophistication.

Upon successful linking, the receiving station generally emits an audible alarm and shows a visual alert to the operator, thus indicating the incoming call. It also indicates the callsign or other identifying information of the linked station, similar to Caller ID
Caller ID
Caller ID , also called calling line identification or calling number identification or Calling Line Identification Presentation , is a telephone service, available in analog and digital phone systems and most Voice over Internet Protocol applications, that transmits a caller's number to...

. The operator then un-mutes the radio and answers the call then can talk in a regular conversation or negotiates a data link using voice or the ALE built-in short text message format. Alternatively, digital data can be exchanged via a built-in or external modem (such as a STANAG 5066
STANAG
STANAG is the NATO abbreviation for Standardization Agreement, which sets up processes, procedures, terms, and conditions for common military or technical procedures or equipment between the member countries of the alliance. Each NATO state ratifies a STANAG and implements it within their own...

 or MIL-STD-188-110B serial tone modem) depending on needs and availability. The ALE built-in text messaging facility can be used to transfer short text messages as an "orderwire" to allow operators to coordinate external equipment such as phone patches or non-embedded digital links, or for short tactical messages.

Use of ALE by unskilled operators

Due to the vagaries of ionospheric communications, HF radio as used by large governmental organizations in the mid-20th century was traditionally the domain of highly skilled and trained radio operators. One of the new characteristics that embedded microprocessors and computers brought to HF radio via ALE, was alleviation of the need for the radio operator to constantly monitor and change the radio frequency manually to compensate for ionospheric conditions or interference. For the average user of ALE, after learning how to work the basic functions of the HF transceiver, it became similar to operating a cellular mobile phone. For more advanced functions and programming of ALE controllers and networks, it became similar to the use of menu-enabled
Menu (computing)
In computing and telecommunications, a menu is a list of commands presented to an operator by a computer or communications system. A menu is used in contrast to a command-line interface, where instructions to the computer are given in the form of commands .Choices given from a menu may be selected...

 consumer equipment
Consumer electronics
Consumer electronics are electronic equipment intended for everyday use, most often in entertainment, communications and office productivity. Radio broadcasting in the early 20th century brought the first major consumer product, the broadcast receiver...

 or the optional features typically encountered in computer software
Computer software
Computer software, or just software, is a collection of computer programs and related data that provide the instructions for telling a computer what to do and how to do it....

. In a professional or military organization, this does not eliminate the need for skilled and trained communicators to coordinate the per-unit authorized frequency lists and node addresses - it merely allows the deployment of relatively unskilled technicians as "field communicators" and end-users of the existing coordinated architecture.

Common applications provided by ALE

An ALE radio system enables connection for voice conversation, alerting, data exchange, texting, instant messaging, email, file transfer, image, geo-position
Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

 tracking, or telemetry. With a radio operator initiating a call, the process normally takes a few minutes for the ALE to pick an HF frequency that is optimum for both sides of the communication link. It signals the operators audibly and visually on both ends, so they can begin communicating with each other immediately. In this respect, the longstanding need in HF radio for repetitive calling on pre-determined time schedules or tedious monitoring static is eliminated. It is useful as a tool for finding optimum channels to communicate between stations in real-time. In modern HF communications, ALE has largely replaced HF prediction charts, propagation beacons, chirp sounders, propagation prediction software, and traditional radio operator educated guesswork. ALE is most commonly used for hooking up operators for voice contacts on SSB (single sideband modulation), HF internet connectivity for email, SMS
SMS
SMS is a form of text messaging communication on phones and mobile phones. The terms SMS or sms may also refer to:- Computer hardware :...

 phone texting or text messaging
Text messaging
Text messaging, or texting, refers to the exchange of brief written text messages between fixed-line phone or mobile phone and fixed or portable devices over a network...

, real-time chat via HF text, Geo Position Reporting, and file transfer. High Frequency Internet Protocol
High Frequency Internet Protocol
High Frequency Internet Protocolacronyms: HFIP or HF-IP.Usually associated with Automatic Link Establishment and HF radio data communications.HFIP provides protocol layers enabling internet file transfer, chat, web, or email....

 or HFIP may be used with ALE for internet access via HF.

Techniques used

The essence of ALE techniques is the use of automatic channel selection, scanning receivers, selective
Selective calling
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

 calling
Selective calling
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

, handshaking
Handshaking
In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...

, and robust burst modems. An ALE node decodes all received ALE signals heard on the channel(s) it monitors. It utilizes the fact that all ALE messages utilize Forward error correction
Forward error correction
In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....

(FEC) redundancy. By noting how much error-correction occurred in each received and decoded message, an ALE node can detect the "quality" of the path between the sending station and itself. This information is coupled with the ALE address
Logical address
In computing, a logical address is the address at which an item appears to reside from the perspective of an executing application program....

 of the sending node and the channel the message was received on, and stored in the node's Link Quality Analysis (LQA) memory. When a call is initiated, the LQA lookup table
Lookup table
In computer science, a lookup table is a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation. The savings in terms of processing time can be significant, since retrieving a value from memory is often faster than...

 is searched for matches involving the target ALE address and the best historic channel is used to call the target station. This reduces the likelihood that the call has to be repeated on alternate frequencies. Once the target station has heard the call and responded, a bell or other signalling device will notify both operators that a link has been established. At this point, the operators may coordinate further communication via orderwire text messages, voice, or other means. If further digital communication is desired, it may take place via external data modems or via optional modems built into the ALE terminal.

This unusual usage of FEC redundancy is the primary innovation that differentiates ALE from previous selective calling
Selective calling
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

 systems which either decoded a call or failed to decode due to noise or interference. A binary outcome of "Good enough" or not gave no way of automatically choosing between two channels, both of which are currently good enough for minimum communications. The redundancy-based scoring inherent in ALE thus allows for selecting the "best" available channel and (in more advanced ALE nodes) using all decoded traffic over some time window to sort channels into a list of decreasing probability-to-contact, significantly reducing co-channel interference to other users as well as dramatically decreasing the time needed to successfully link with the target node.

Techniques used in the ALE standard include automatic signaling, automatic station identification (sounding
Sounding
Sounding generally refers to a mechanism of probing the environment by sending out some kind of stimulus. The term derives from the ancient practice of determining the depth of water by feeding out a line with a weight at the end....

), polling
Polling (computer science)
Polling, or polled operation, in computer science, refers to actively sampling the status of an external device by a client program as a synchronous activity. Polling is most often used in terms of input/output , and is also referred to as polled or software driven .Polling is sometimes used...

, message
Message
A message in its most general meaning is an object of communication. It is a vessel which provides information. Yet, it can also be this information. Therefore, its meaning is dependent upon the context in which it is used; the term may apply to both the information and its form...

 store-and-forward, linking protection and anti-spoofing
Spoofing attack
In the context of network security, a spoofing attack is a situation in which one person or program successfully masquerades as another by falsifying data and thereby gaining an illegitimate advantage.- Spoofing and TCP/IP :...

 to prevent hostile denial of service by ending the channel scanning process. Optional ALE functions include polling and the exchange of orderwire
Return channel
In communications systems that use star topologies, the return channel is the transmission link from a user terminal to the central hub....

 commands and messages. The orderwire message, known as AMD (Automatic Message Display), is the most commonly used text transfer method of ALE, and the only universal method that all ALE controllers have in common for displaying text. It is common for vendors to offer extensions to AMD for various non-standard features, although dependency on these extensions undermines interoperability. As in all interoperability scenarios, care should be taken to determine if this is acceptable before using such extensions.

ALE historic background

ALE evolved from older HF radio selective calling
Selective calling
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

 technology. It combined existing channel-scanning selective calling concepts with microprocessors (enabling FEC decoding and quality scoring decisions), burst transmissions (minimizing co-channel interference), and transponding (allowing unattended operation and incoming-call signalling). Early ALE systems were developed in the late 1970s and early 1980s by several radio manufacturers. The first ALE-family controller units were external rack mounted controllers connected to control military radios, and were rarely interoperable across vendors.

Various methods and proprietary digital signaling protocols were used by different manufacturers in first generation ALE, leading to incompatibility. Later, a cooperative effort among manufacturers and the US government resulted in a second generation of ALE that included the features of first generation systems, while improving performance. The second generation 2G ALE system standard in 1986, MIL-STD-188-141A, was adopted in FED-STD-1045 for US federal entities. In the 1980s, military and other entities of the US government began installing early ALE units, using ALE controller products built primarily by US companies. The primary application during the first 10 years of ALE use was government and military radio systems, and the limited customer base combined with the necessity to adhere to MILSPEC standards kept prices extremely high. Over time, demand for ALE capabilities spread and by the late 1990s, most new government HF radios purchased were designed to meet at least the minimum ALE interoperability
Interoperability
Interoperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...

 standard, making them eligible for use with standard ALE node gear. Radios implementing at least minimum ALE node functionality as an option internal to the radio became more common and significantly more affordable. As the standards were adopted by other governments worldwide, more manufacturers produced competitively priced HF radios to meet this demand. The need to interoperate with government organizations prompted many non-government organizations (NGOs) to at least partially adopt ALE standards for communication. As non-military experience spread and prices came down, other civilian entities started using 2G ALE. By the year 2000, there were enough civilian and government organizations worldwide using ALE that it became a de facto HF interoperability
Interoperability
Interoperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...

 standard for situations where a priori channel and address coordination is possible.

In the late 1990s, a third generation 3G ALE with significantly improved capability and performance was included in MIL-STD-188-141B, retaining backward compatibility with 2G ALE, and was adopted in NATO STANAG 4538. Civilian and non-government adoption rates are much lower than 2G ALE due to the extreme cost as compared to surplus or entry-level 2G gear as well as the significantly increased system and planning complexity necessary to realize the benefits inherent in the 3G specification. For many militaries, whose needs for maximized intra-organizational capability and capacity always strain existing systems, the additional cost and complexity of 3G is far more compelling.

ALE as a force multiplier

ALE enables rapid unscheduled communication and message passing without requiring complex message centers, multiple radios and antennas, or highly trained operators. With the removal of these potential sources of failure, the tactical communication process becomes much more robust and reliable. The effects extend beyond mere Force multiplication
Force multiplication
Force multiplication, in military usage, refers to an attribute or a combination of attributes which make a given force more effective than that same force would be without it. The expected size increase required to have the same effectiveness without that advantage is the multiplication factor...

 of existing communications methods; units such as helicopters, when outfitted with ALE radios, can now reliably communicate in situations where the crew are too busy to operate a traditional non-line of sight
Line-of-sight propagation
Line-of-sight propagation refers to electro-magnetic radiation or acoustic wave propagation. Electromagnetic transmission includes light emissions traveling in a straight line...

 radio. This ability to enable tactical communication in conditions where dedicated trained operators and hardware are inappropriate is often considered to be the true improvement offered by ALE.

ALE is a critical path toward increased interoperability
Interoperability
Interoperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...

 between organizations. By enabling a station to participate nearly simultaneously in many different HF networks, ALE allows for convenient cross-organization message passing and monitoring without requiring dedicated separate equipment and operators for each partner organization. This dramatically reduces staffing and equipment considerations, while enabling small mobile or portable stations to participate in multiple networks and subnetworks. The result is increased resilience, decreased fragility, increased ability to communicate information effectively, and the ability to rapidly add to or replace communication points as the situation demands.

When combined with Near Vertical Incidence Skywave
Near Vertical Incidence Skywave
Near Vertical Incidence Skywave, or NVIS, is a radio-wave propagation method that provides usable signals in the range between groundwave and skywave distances . It is used mainly for military and paramilitary communications and by radio amateurs...

(NVIS) techniques and sufficient channels spread across the spectrum, an ALE node can provide greater than 95% success linking on the first call, on a near-par with SATCOM
SATCOM
SATCOM or Satcom may refer to:* Short for Satellite Communications and used frequently in the context of VSAT * Communications satellites or comsats...

systems. This is significantly more reliable than cellphone infrastructure during disasters or wars yet is mostly immune to such considerations itself.

World standards and protocols

The common basic world protocol standards for ALE are based on the original US MIL-STD 188-141A and FED-1045, known as 2nd Generation or 2G ALE. 2G ALE uses non-synchronised scanning of channels, and it takes several seconds to half a minute to repeatedly scan through an entire list of channels looking for calls. Thus it requires sufficient duration of transmission time for calls to connect or link with another station that is unsynchronised with its calling signal. The vast majority of ALE systems in use in the world at the present time are 2G ALE.

Second generation (2G) ALE technical characteristics

The more common 2G ALE signal waveform is designed to be compatible with standard 3 kHz SSB narrowband voice channel transceivers. The modulation method is 8ary Frequency Shift Keying or 8FSK, also sometimes called Multi Frequency Shift Keying MFSK, with eight orthogonal tones between 750 and 2500 Hz. Each tone is 8 ms long, resulting in a transmitted over-the-air symbol rate of 125 baud or 125 symbols per second, with a raw data rate of 375 bits per second. The ALE data is formatted in 24-bit frames, which consist of a 3 bit preamble followed by three ASCII characters, each seven bits long. The receive decoder is usually done by digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...

 techniques and can decode the 8FSK signal at a negative signal to noise ratio, meaning it can pull the signal out when it is below the noise level. The over-the-air layers of the protocol involve the use of forward error correction
Forward error correction
In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....

, redundancy
Redundancy (information theory)
Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. Informally, it is the amount of wasted "space" used to transmit certain data...

, and handshaking
Handshaking
In information technology, telecommunications, and related fields, handshaking is an automated process of negotiation that dynamically sets parameters of a communications channel established between two entities before normal communication over the channel begins...

 transponding similar to those used in ARQ
ARQ
Automatic Repeat reQuest , also known as Automatic Repeat Query, is an error-control method for data transmission that uses acknowledgements and timeouts to achieve reliable data...

techniques.

Third generation (3G) ALE technical characteristics

Newer standards of ALE called 3rd Generation or 3G ALE, use accurate time synchronization (via a defined time-synch protocol as well as the option of GPS-locked clocks) to achieve faster and more dependable linking. Through synchronization, the calling time to achieve a link may be reduced to less than 10 seconds. The 3G ALE modem signal also provides better robustness
Robustness
Robustness may refer to:*In biology**Robustness , the persistence of a system’s characteristic behavior under perturbations or conditions of uncertainty...

and can work in channel conditions that are less favorable than 2G ALE. Dwell groups, limited callsigns, and shorter burst transmissions enable more rapid intervals of scanning. All stations in the same group scan and receive each channel at precisely the same time window. Although 3G ALE is more reliable and has significantly enhanced channel-time efficiency, the existence of a large installed base
Installed base
Installed base or installed user base is a measure of the number of units of a particular type of system—usually a computing platform—actually in use, as opposed to market share, which only reflects sales over a particular period. Because installed base includes machines that may have been in use...

 of 2G ALE radio systems and the wide availability of moderately priced (often military surplus) equipment, has made 2G the baseline standard for global interoperability.

Basis for HF interoperable communications

Interoperation
Interoperability
Interoperability is a property referring to the ability of diverse systems and organizations to work together . The term is often used in a technical systems engineering sense, or alternatively in a broad sense, taking into account social, political, and organizational factors that impact system to...

 is a critical issue for the disparate entities which use radiocommunications to fulfill the needs of organizations. Largely due to the ubiquity of 2G ALE, it became the primary method for providing interoperation on HF between governmental and non-governmental
Non-governmental organization
A non-governmental organization is a legally constituted organization created by natural or legal persons that operates independently from any government. The term originated from the United Nations , and is normally used to refer to organizations that do not form part of the government and are...

 disaster relief and emergency communications entities, and amateur radio volunteers. With digital techniques increasingly employed in communications equipment, a universal digital calling standard was needed, and ALE filled the gap. Nearly every major HF radio manufacturer in the world builds ALE radios to the 2G standard to meet the high demand that new installations of HF radio systems conform to this standard protocol. Disparate entities that historically used incompatible radio methods were then able to call and converse with each other using the common 2G ALE platform. Some manufacturers and organizations have utilized the AMD feature of ALE to expand the performance and connectivity. In some cases, this has been successful, and in other cases, the use of proprietary preamble or embedded commands has led to interoperability problems.

Tactical communication and resource management

ALE serves as a convenient method of beyond line of sight communication. Originally developed to support military requirements, ALE is useful to many organizations who find themselves managing widely-located units. United States Immigration and Customs Enforcement and United States Coast Guard
United States Coast Guard
The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...

 are two members of the Customs Over the Horizon Enforcement Network(COTHEN), an MIL-STD 188-141A ALE network. All U.S. armed forces operate multiple similar networks. Similarly, shortwave utility listeners have documented frequency and callsign lists for many nations' military and guard units, as well as networks operated by oil exploration and production companies and public utilities in many countries.

Emergency / disaster relief or extraordinary situation response communications

ALE radio communication systems for both HF regional area networks and HF interoperability communications are in service among emergency and disaster relief agencies as well as military and guard forces. Extraordinary response agencies and organizations use ALE to respond to situations in the world where conventional communications may have been temporarily overloaded or damaged. In many cases, it is in place as alternative back-channel
Return channel
In communications systems that use star topologies, the return channel is the transmission link from a user terminal to the central hub....

 for organizations that may have to respond to situations or scenarios involving the loss of conventional communications. Earthquakes, storms, volcanic eruptions, and power or communication infrastructure failures are typical situations in which organizations may deem ALE necessary to operations. ALE networks are common among organizations engaged in extraordinary situation response such as: natural and man-made disasters, transportation, power, or telecommunication network failures, war, peacekeeping, or stability operations. Organizations known to use ALE for Emergency management
Emergency management
Emergency management is the generic name of an interdisciplinary field dealing with the strategic organizational management processes used to protect critical assets of an organization from hazard risks that can cause events like disasters or catastrophes and to ensure the continuance of the...

, disaster relief, ordinary communication or extraordinary situation response include: Red Cross
American Red Cross
The American Red Cross , also known as the American National Red Cross, is a volunteer-led, humanitarian organization that provides emergency assistance, disaster relief and education inside the United States. It is the designated U.S...

, FEMA
Federal Emergency Management Agency
The Federal Emergency Management Agency is an agency of the United States Department of Homeland Security, initially created by Presidential Reorganization Plan No. 1 of 1978 and implemented by two Executive Orders...

, Disaster Medical Assistance Team
Disaster Medical Assistance Team
A Disaster Medical Assistance Team is a group of professional and para-professional medical personnel organized to provide rapid-response medical care or casualty decontamination during a terrorist attack, natural disaster, or other incident in the United States...

s, NATO, Federal Bureau of Investigation
Federal Bureau of Investigation
The Federal Bureau of Investigation is an agency of the United States Department of Justice that serves as both a federal criminal investigative body and an internal intelligence agency . The FBI has investigative jurisdiction over violations of more than 200 categories of federal crime...

, United Nations
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

, AT&T
AT&T
AT&T Inc. is an American multinational telecommunications corporation headquartered in Whitacre Tower, Dallas, Texas, United States. It is the largest provider of mobile telephony and fixed telephony in the United States, and is also a provider of broadband and subscription television services...

, Civil Air Patrol
Civil Air Patrol
Civil Air Patrol is a Congressionally chartered, federally supported, non-profit corporation that serves as the official civilian auxiliary of the United States Air Force . CAP is a volunteer organization with an aviation-minded membership that includes people from all backgrounds, lifestyles, and...

, SHARES, State of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

 Emergency Management Agency (CalEMA), other US States' Offices of Emergency Services or Emergency Management Agencies, and Amateur Radio Emergency Service
Amateur Radio Emergency Service
In the United States and Canada, the Amateur Radio Emergency Service is a corps of trained amateur radio operator volunteers organized to assist in public service and emergency communications...

(ARES).

International HF telecommunications for disaster relief

The International Telecommunications Union (ITU), in response to the need for interoperation in international disaster response spurred largely by humanitarian relief, included ALE in its Telecommunications for Disaster Relief
Telecommunications for Disaster Relief
Telecommunications for Disaster Relief is a proposal by the International Telecommunications Union to establish worldwide standards of interoperability and availability of emergency communications...

 recommendations. The increasing need for instant connectivity for logistical and tactical disaster relief response communications, such as the 2004 Indian Ocean earthquake
2004 Indian Ocean earthquake
The 2004 Indian Ocean earthquake was an undersea megathrust earthquake that occurred at 00:58:53 UTC on Sunday, December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia. The quake itself is known by the scientific community as the Sumatra-Andaman earthquake...

 tsunami
Tsunami
A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake...

 led to ITU actions of encouragement to countries around the world toward loosening restrictions on such communications and equipment border transit during catastrophic disasters. The IARU Global Amateur Radio Emergency Communications Conference
Global Amateur Radio Emergency Communications Conference
The Global Amateur Radio Emergency Communications Conference or GAREC is a yearly conference held by the International Amateur Radio Union for discussion of amateur radio operation during natural disasters and other emergencies with the motto, "Saving lives through emergency communications"...

s (GAREC) and IARU Global Simulated Emergency Tests have included ALE.

ALE use in international amateur radio

Amateur Radio operators began sporadic ALE operation on a limited basis in the early to mid 1990s, with commercial ALE radios and ALE controllers. In 2000, the first widely available software ALE controller for the Personal Computer, PCALE, became available, and hams started to set up stations based on it. In 2001, the first organized and coordinated global ALE nets for International Amateur Radio began. In August 2005, ham radio operators supporting communications for emergency Red Cross
American Red Cross
The American Red Cross , also known as the American National Red Cross, is a volunteer-led, humanitarian organization that provides emergency assistance, disaster relief and education inside the United States. It is the designated U.S...

 shelters used ALE for Disaster Relief operations during the Hurricane Katrina
Hurricane Katrina
Hurricane Katrina of the 2005 Atlantic hurricane season was a powerful Atlantic hurricane. It is the costliest natural disaster, as well as one of the five deadliest hurricanes, in the history of the United States. Among recorded Atlantic hurricanes, it was the sixth strongest overall...

 disaster. After the event, hams developed more permanent ALE emergency/disaster relief networks, including internet connectivity, with a focus on interoperation between organizations. The amateur radio HFLink Automatic Link Establishment system uses an open net protocol to enable all amateur radio operators and amateur radio nets worldwide to participate in ALE and share the same ALE channels legally and interoperably. Amateur radio operators may use it to call each other for voice or data communications.

ALE adaptations to amateur radio for interoperability

Amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

 operators commonly provide local, regional, national, and international emergency / disaster relief communications. The need for interoperability on HF led to adaption of Automatic Link Establishment ALE open networks by hams. Amateur radio adapted 2G ALE techniques, by utilizing a common denominator the 2G ALE protocol, with a limited subset of features found in the majority of all ALE radios and controllers. Each amateur radio ALE station uses the operator's callsign as the address
Logical address
In computing, a logical address is the address at which an item appears to reside from the perspective of an executing application program....

, also known as the ALE Address, in the ALE radio controller. The lowest common denominator
Lowest common denominator
In mathematics, the lowest common denominator or least common denominator is the least common multiple of the denominators of a set of vulgar fractions...

 technique enables any manufacturer's radios or software to be utilized for interoperative communication and networking. Known as Ham-Friendly ALE, the amateur radio ALE standard is used to establish radio-communications, through a combination of active ALE on internationally recognized automatic data frequencies, and passive ALE scanning on voice channels and all other channels. In this technique, active ALE frequencies include pseudo-random periodic polite station identification, while passive ALE frequencies are silently scanned for selective calling. Ham-Friendly ALE technique is also known as 2.5G ALE, because it maintains 2G ALE compatibility while employing some of the adaptive channel management features of 3G ALE, but without the accurate GPS
Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

 time synchronization of 3G ALE.

Global amateur radio high frequency network for interoperable emergency disaster relief communications

Hot standby nets are in constant operation 24/7/365 for International Emergency and Disaster Relief communications. The Ham Radio Global ALE High Frequency Network, which began service in June 2007, is the world's largest intentionally open ALE network for internet connectivity. It is a free open network staffed by volunteers, and utilized by amateur radio operators supporting disaster relief organizations.

International amateur radio ALE coordination details

International amateur radio ALE High Frequency
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...

 channels are frequency coordinated with all Regions of the International Amateur Radio Union(IARU entity of ITU), for international, regional, national, and local use in the Amateur Radio Service. All Amateur Radio ALE channels use "USB" Upper Sideband
Sideband
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier...

 standard. Different rules, regulations, and bandplans of the region and local country of operation apply to use of various channels. Some channels
Channel (communications)
In telecommunications and computer networking, a communication channel, or channel, refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel...

 may not be available in every country. Primary or global channels are in common with most countries and regions.

International amateur radio ALE channels

This listing is current as of October 2010. See HFLINK for more information about Amateur Radio ALE Automatic Link Establishment.

See also

  • Multiple frequency-shift keying
    Multiple frequency-shift keying
    Multiple frequency-shift keying is a variation of frequency-shift keying that uses more than two frequencies. MFSK is a form of M-ary orthogonal modulation, where each symbol consists of one element from an alphabet of orthogonal waveforms...

  • Selective calling
    Selective calling
    In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel...

  • Amateur radio
    Amateur radio
    Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

  • Amateur radio emergency communications
    Amateur radio emergency communications
    In times of crisis and natural disasters, amateur radio is often used as a means of emergency communication when wireline, cell phones and other conventional means of communications fail....

  • ARES
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