Research ProposalPDF Available

The concept behind the user-classes inside of JANUS



The table I in the ANEP-87, Edition A Version 1 of the STANAG 4748 "JANUS" from 24. March 2017 based on an User-Application-Class concept. The idea behind it will be presented in this two-pager.
The concept behind the user-classes inside of JANUS
Ivor Nissen, 06.12.2020, Speaker FG UWK MCN
The table I in the ANEP-87, Edition A Version 1
of the STANAG 4748 „JANUS“ from 24. March
2017 /1/ based on an User-Application-Class con-
cept. The idea behind it will be presented in this
two-pager, because questions arose about the si-
tuation, that mostly the 256 class-user-id‘s are
defined as „open=non defined“ in the appendix A.
In the first phase after JANUS was born with the
input of Walter Munk, Kim McCoy and us at our
Mediterranean Sea trial CCUP07 with the Re-
search vessel FS Planet in 2007 /2/, we wanted to
implement an open, digital emergency-help-chan-
nel for the underwater world. The design criteria
behind was: „The intent of JANUS is to provide figure 1: bit allocation table of the JANUS preamble /1/
a message containing information about the trans-
mitter and allow the receiver(s) to make decisions based upon additional knowledge.“ /2/ Similar to
simple RSTC-hand-signals of divers, the hassle-free beacon-approach is based on the INitiatior-
RESponder processes. This technology is meant to easily define the communication stack from the
waveform to applications together with the goal that every (SONAR) system can transmit and
receive/decode the signals and interpret the 64 bits in the same manner. From the „first contact“ in
emergency scenarios, underwater language switching, Channel-16-chat between humans or to re-
duce the Lombard-Effect as EMCON-procedure, this „international language“ should help as great-
est common divisor. If we think about auto gain control, channel sensing and other techniques,
spectrum management for hydro acoustics is not the exclusive key enabler to avoid collisions be-
tween different types of coexisting services. JANUS could be the active enabler to maximize the
number to coexisting interests in the hydro acoustic spectrum.
At the second JANUS workshop in La Speza the „all applications in one bit allocation map“-
approach collapsed. It was not possible to find a way to define the last NINE „unused“ bits. The
broad expectations from the users are to diverse.
The workshop was interrupted; a few years no
follow-up workshop was performed.
In 2010 we restructured the bit allocation map.
Based on the initial values, to be open and robust
for many also civilian applications, and to achieve
interoperability, an all applications in own bit
allocations maps“-approach was implemented.
Hereby we have to divide into different groups:
Open known applications for everyone, like emer-
gency procedures, NATO’s own procedures and
„mostly“ individual applications of separate na-
tions. The idea behind JANUS was, that it is
public to the world, that also includes, that based figure 2: old „all in one“ bit allocation field in 2009 /3/
on the ISO 3166-1 all ~200 nations are represen-
ted. That is the reason to spend 8 bits for the user-class-id-field. It is a great challenge an evo-
lution – to find robust and stable communication procedures for different applications with the re-
stricted bit volume of 64 bits. Each user-class has the freedom to define 64 messages for request,
answers, command&control or human chat the application type. Good candidates could be
overtaken to the open user class area. The custodian CMRE is responsible for this registration task.
The original JANUS user classes are defined in the
document /4/. In Germany the specialist group „Subsea
Communications” of the Maritime Cluster Northern
Germany (MCN e.V.) is responsible for the german
user-class number regulation. This groups splits the 64
application types into the following areas: Manufac-
turers of devices, research institutions and universities
as well as national equipment users e.g. the sea sign
authority. Every unit receives one application type num-
ber for 10 years. Manufacturers can use the number for
resource identification of own products or for a service
process between their products. National user classes
are important for own – not public - SONAR applicat-
ions and activities, for national procedures for the up-
load of parameter sets for new device behaviors, under-
water digital twins, and many more.
During the STANAG ratification process the table II
was changed, many classes are now undefined.
The main applications for JANUS are from the begin-
ning discovery, collision avoidance, UW navigational
aid, resource information exchange and a language
switch to higher communication schemes. If submer-
ged subjects don’t have the same communication re-
sources; it is well known that the greatest common
divisor that is JANUS, is less efficient than if the sub-
jects would communicate on an equal level. JANUS is figure 3: The original user classes defined /4/.
therefore not broadband efficient. If we include the wake-
up, the minimum transfer rate is 64/((12+32+144)* 0.00625 + 0,4) bps = 41 bps in the JANUS test
band. The Optional Data Cargo Payload has to be transmitted mostly in a higher rate. First contact
and language switch procedures, emergency requests and wrack pingers do not need any Cargo
Payload. In SONAR applications silence is more important, a Cargo Payload transmission with fre-
quency hopping should be the exception. The ISO IEC 30141 defines the JANUS domains:
application & service, resource interchange and operation & management. The pure 64-bit-pre-
amble inside of JANUS procedures fulfills these requirements and builds the user-class basement
for the future.
I hope that every nation will order their own user class number and will work on efficient JANUS
procedures with a maximal trustworthiness level to have in the underwater world interoperability
with new underwater services for human and digital users.
/1/ STANAG 4748 „JANUS“ with the technical document ANEP-87, Edition A Version 1
/2/ Kim McCoy, JANUS: From Primitive Signal to Orthodox Networks, 3rd International Conference UAM 2009,
/3/ Kim McCoy, second workshop 2009,
/4/ J. Potter, J. Alves, D. Green, G. Zappa, I. Nissen and K. McCoy, "The JANUS underwater communications
standard," 2014 Underwater Communications and Networking (UComms), Sestri Levante, 2014, pp. 1-4, doi:
10.1109/Ucomms.2014.7017134 or see at
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