Automatic Link Establishment

 

Automatic Link Establishment

Automatic link Establishment, commonly known as the ALE, is the standard protocol in RF and High-Frequency Communication channels. It establishes a link between the various networks to reduce noise error and disconnections between multiple stations. An ALE works by choosing the best frequency and establishing a fast and reliable network when a call is initiated and ensures the most optimal performing station is connected between the two parties. This helps eliminate the need to wait for any pre-calling requirements on radio channels, a radio channel is always scanning for the desired frequency signals as each ALE device has a pre-set signal called callsign. Whenever a callsign is detected, it automatically connects the transceiver channel to the radio by generating a handshake that confirms both ends a link is established via an alarm if one is muted. During the earlier era for HF communication manual, operators were always trying to figure out the correct frequencies. With the advancement and better understanding of the mechanism, frequency scanning became automatic. The advanced functions can still be controlled using user interface designs.

Applications Of ALE:

ALE is commonly used in many communication channels like voice and text exchange, data, and email transfer. Both audio and text information can be exchanged using this protocol between the two ends. The modern enhancements even allow the use of this method in geo-positioning and real-time chatting.

Techniques Used For ALE:

Forward Error Control: Forward error control keeps track of the error redundancy in a communication channel. It then estimates the network's quality and suggests which frequency channel is the best suit.

Link Quality Analysis: The information gathered from FEC is stored in an LQA memory in the form of addresses. When a message is received, it then scans the addresses and looks up the channel's most stable connection.

ALE in Modern Generation Systems:

The modern generation ALE programs have the following stages:

Automatic channel selection (ACS): A dynamic selection of the best channel using a combination of predictions from pre-saved sessions. Some additional calculations are made to select a channel with the best SNR to reduce the traffic link noise.

Scanning Receivers: A continuous scanning is performed by the equipment when a call is received to quickly connect the right receiver in the minimum time. This significantly reduces the overheads to establish the network.

Selective Calling: When a call is received, an ALE address is associated with the call, where the station call is generated, the receiver end has a record for these addresses, and it becomes convenient for the station to interpret the call and reduces the chance of interference by neglecting all addresses which are not in cache.