MIL-STD-188-141A ("141A")
+ Unproto + ARQ FAE

Traduction anglaise.

    Multipsk proposes a sub-set of ALE functions. However, it exists other ALE functions and also other mode (i.e MIL-STD-188-110). But Multipsk gives several additional functions compared to the FS 1045A specifications, as, for example, the Unproto mode which permit to work as in PSK31, or the ARQ FAE mode which permits QSO fast and error-free.

For complete ALE softwares (PCALE, MARS-ALE...) and for more information about ALE, look to the following WEB sites: http://www.hflink.com/beta/ et http://www.hflink.com/beta/ et http://www.n2ckh.com/MARS_ALE_FORUM/

Introduction to ALE (extracts from ARRL Web site) :

General : Automatic Link Establishment (ALE) was developed to automatically select a frequency that will support automatic linking between stations in a network or point-to-point communication.without operator assistance.
In high-frequency (HF) radio, ALE makes possible for a station to make contact, or initiate a circuit, between itself and another specified radio station, without human intervention and usually under processor control.

Allowed functions : ALE techniques include automatic signaling, selective calling, and automatic handshaking. Other automatic techniques that are related to ALE are automatic channel scanning, link quality analysis (LQA), polling, sounding, message store-and-forward, address protection, exchange of orderwire commands and messages.
   

   This mode is included into the software MULTIPSK by Patrick F6CTE, there is the description of this mode and its variants as well as the specifications coming from his software :

Click on the copy of the screen in order to listen to the corresponding audio signal.

Click on the copy of the screen in order to listen to the corresponding audio signal.

- Standard mode

Description (standard) :
Baud rate : 125 bauds
Speed : about 76 wpm
Modulation : FSK 8 tones (3 bits)
Reception mode : only one side (USB or LSB), USB is recommended
Character set : ASCII characters
Shape of pulse : rectangular
Space between tones : 250 Hz,
Bandwidth : 2000 Hz,
Demodulation : non-coherent,
Synchronization : automatic using the signal
Coding : Golay and average on 3 frames (with a 2/3 voting logic)
Interleaving : yes (within a block of 48 bits)
Drift tolerance : 10 à 20 Hz/mn according to signal-to-noise ratio,
Pmean/Ppeak : 1
Lowest S/N : -4 dB

Note : pieces of information about this mode can be found on the FS-1045A specification ("Telecommunications: HF radio Automatic Link Establishment") and in the WEB sites:

* http://www.hflink.com/beta/  (PCALE software, Charles Brain G4GUO)
* http://www.n2ckh.com/MARS_ALE_FORUM/ (MARS-ALE software, Steve Hajducek N2CKH/AAR2EY)

Before each frame, it is transmitted 12 symbols, alternately on the lowest frequency and then on the highest frequency, so for a duration of about 0.1 second (12/125 s). This is aimed to permit the symbol synchronization just before the frame reception. This does not exist within the FS-1045A specification:

Unproto mode :

It is proposed an Unproto (for "without protocol") mode. For this, special frames are transmitted. They contain the necessary information and don't obey to any protocol. Each frame is formed in the following way:

a) the information LQA (BER+SINAD) corresponding to the last received frame, transmitted according to the FS-1045 specification,
b) the preamble "COMMAND" followed by CHR(0) and by the ASCII message (CHR(0) to CHR(127)), transmitted according to the FS-1045 specification. As soon as, at least, one character is present in the editor, this command is formed. It can't be transmitted more than 32 characters by frame.
If there is no character to transmit, this command is not transmitted. So, it will remain the LQA and the preamble THIS WAS followed by the call. This small frame will be the idling frame.

c) the preamble THIS WAS followed by the call, transmitted according to the FS-1045 specification.

Before each frame, it is transmitted 28 symbols, alternately on the lowest frequency and then on the
highest frequency, so for a duration of about 0.22 second (28/125 s).

Advantages: this mode permits to work as in PSK31, the transmission and the reception being freely done by the Hams. There is no previous connection (link). The systematically transmitted LQA permits to each Ham to know, at any moment, how he is received by the other Ham.
However this mode needs a big PC (>1000 MHz).

"Unproto" beacon: it is proposed a beacon working (TX then RX, alternately), which in TX, transmits according to the Unproto mode previously defined. The advantage of this beacon is that it will be enough to a Ham to transmit an Unproto frame between the Unproto frames from the beacon, to know how it is received by the beacon (thanks to the LQA).


ARQ FAE mode :

This new ARQ mode is located, for the modulation, between the FS1045A DTM and DBM ARQ modes. For the protocol it is located between the FS1045A DTM and DBM modes and PAX/PAX2 modes.

"ARQ" is worth for "Automatic Repetition reQuest" and "FAE" for "Fast Acknowledged Exchange".

It is a bilateral mode, which means that messages can be transmitted from A to B and from B to A, in full duplex (protocol one, not physical one). The ACK or NAK answer can be accompanied or not by a message (as in PAX/PAX2).
The characters exchanged are 8 bits length so as to permit exchange in all ASCII-ANSI languages (English, French, German, Russian...), but not those with ideograms (as Japonese).
Contrary to DBM mode, the length of the frame is variable and depends of the message length (as in DTM mode). But as DBM mode, the blocks are not redundantly repeated and there is a global message interleaving (but with a variable ID).

ARQ FAE modulation description :
Baud rate : 125
Rough speed : maximum: 148 wpm (for 30 characters length message) or 184 wpm (for 63 characters length message)
Use speed : maximum in unilateral: 88 wpm (for 30 characters length message) and 125 wpm (for 63 characters length message)
                        : maximum in bilateral: 120 wpm (for 30 characters length message) and 164 wpm (for 63 characters length message)
Modulation : FSK 8 tones (3 bits)

Reception mode : only one side (USB or LSB), USB is recommended

Character set : ASCII +ANSI characters (8 bits)
Shape of pulse : rectangular
Space between tones : 250 Hz,
Bandwidth : 2000 Hz,
Demodulation : non-coherent,
Synchronization : automatic using the signal
Coding : Golay
Interleaving : yes (global within a block of data (message + CRC))
Drift tolerance : 10 to 20 Hz/mn according to signal-to-noise ratio,
Pmean/Ppeak : 1
Lowest S/N : - 6.5 dB (- 8.5 dB with many repetitions)

A "soft decision" Memory Arq is implemented. It makes the transmission more reliable (see details in the ARQ FAE protocol).

ARQ FAE protocol :

The detailled specifications of the protocol are given, in English, in the Word 95 document "ARQ_FAE_version_1" situated in the "Specifications" heading on F6CTE's WEB site (English page).

Recommanded frequencies for
.

Back to the list of modes included in MULTIPSK