STANAG 4691

Overview

STANAG 4691, also known as “Mobile Ad hoc Relay Line of Sight Networking” (MARLIN), is a NATO specification designed to facilitate Internet Protocol (IP) data transfers in multi-node, multi-hop dynamic networks employing V/UHF Line-Of-Sight (LOS) and HF Extended Line-Of-Sight (ELOS) radio circuit networks. Both the networking protocol and waveform is specified.

Status

The first edition of the STANAG 4691, MARLIN was released in June 2016.

Relevance

In environments where SATCOM availability is constrained due to equipment limitations, cost considerations, or satellite-denied areas, MARLIN’s utilisation of HF LOS and V/UHF ELOS emerges as a practical alternative. MARLIN radio circuit networks offer interoperability of allied forces by allowing the exchange of tactical data with all sea-surface, subsurface, airborne (mobile) and land (fixed) platforms.

Key Features

• HF ELOS (24 kHz) Data Rates < 120 000 bps
• V/UHF LOS (25 kHz) Data Rates < 96 000 bps
• V/UHF LOS (20 kHz) Data Rates < 76 800 bps
• V/UHF LOS (100 kHz) Data Rates < 384 000 bps
• V/UHF LOS (300 kHz) Data Rates < 1 152 000 bps
• V/UHF LOS (500 kHz) Data Rates < 1 920 000 bps
• IPv4 Support – IPv4 data transfer over HF ELOS and V/UHF LOS
• Single-Hop Support – Point-to-Point packet delivery (no relaying)
• Multi-Hop Support – Packet delivery via Mobile Ad-hoc Networking relaying
• Reliable Data Transfer – Error-free data transfer using ARQ protocol
• Collision Avoidance – Synchronous Time-Division Multiple Access slots
• Adaptive Data Throughput Control – Dynamic bandwidth allocation
• Automatic Neighbour Discovery - Mobile Ad-hoc Networking relay control

Operation

The MARLIN controller utilises a synchronous Time Division Multiple Access (TDMA) scheme called Distributed Slot Reservation Media Access (DSRMA). Each MARLIN node, except during EMCON (radio silence), maintains a fixed allocation of time slots in each frame. The number of allocated slots per node adjusts automatically based on data demands through a dynamic bandwidth allocation mechanism.

The illustration below depicts an example of a STANAG 4691 MARLIN maritime network topology consisting of UHF LOS (blue) and HF ELOS (yellow) subnets. Direct ship-to-ship connections between network participants are established by connecting MARLIN LOS/ELOS bearers directly to the platform’s wireless routers. Unicast or multicast data transmissions occur among node members within the network. Connections between two subnetworks are possible when a platform supports both UHF and HF radio communications.

Waveform

The STANAG 4691 specification defines waveforms for 25, 100, 300 & 500 kHz bandwidths as described in Appendices B to E. The STANAG 4691 V/UHF waveforms occupy bandwidths ranging from 25 kHz to 500, offering user data rates between 16 kbps and 1920 kbps. The data rate and constellation type per appendix can be seen in the table below:

STANAG 4691 Annex B

STANAG 4691 Annex B presents a specification for a modem waveform and coding that can achieve data rates of 16, 32, 48, 64, 80, and 96 kbps while operating within an audio channel bandwidth of 25 kHz. This waveform uses a block interleaver with four available interleaver lengths: 20 ms, 80 ms, 320 ms, and 1.28 s

Table 2: STANAG S4691 Annex B - 25 kHz Basic Waveform Characteristics

STANAG 4691 Annex C

STANAG 4691 Annex C presents a specification for a modem waveform and coding that can achieve data rates of 32, 64, 128, 192, 256, 320, and 384 kilobits per second (kbps) within channel bandwidths of 100 kHz. A block interleaver is utilized to achieve four different interleaving lengths of 3 milliseconds (ms), 24 ms, 192 ms, and 1.536 seconds.

Table 3: STANAG S4691 Annex C - 100 kHz Basic Waveform Characteristics

STANAG 4691 Annex D

STANAG 4691 Annex D presents a specification for a modem waveform and coding that can achieve data rates of 112.5, 225, 450, 600, 768, 960, and 1152 kilobits per second (kbps), with operation within channel bandwidths of 300 kHz.

A block interleaver is used, with lengths referred to as Very Short, Short, Long, and Very Long. For 112.5, 225, 450, and 600 kbps, the Very Short interleaver is 1.6 ms, while all other data rates have a Very Short interleaver of 2.5 ms. For 112.5, 225, 450, and 600 kbps, the Short interleaver is 8 ms, while all other data rates have a Short interleaver of 10 ms. The Long and Very Long interleaver lengths are fixed at 80 and 640 milliseconds (ms) for all data rates.

Table 4: STANAG S4691 Annex D - 300 kHz Basic Waveform Characteristics

STANAG 4691 Annex E

STANAG 4691 Annex E provides the specification for a modem waveform and coding for data rates of 180, 360, 720, 960, 1280, 1600, and 1920 kilobits per second (kbps) operating within channel bandwidths of 500 kHz.

A block interleaver is employed, with four interleaving length options for each data rate, named Very Short, Short, Long, and Very Long. The Very Short interleaver is 0.6 ms for 180, 360, 720, and 960 kbps; for all other data rates, the Very Short interleaver is 1.5 ms. For all data rates, the Short, Long, and Very Long interleavers are 12, 96, and 768 milliseconds (ms).

Table 5: STANAG S4691 Annex E - 500 kHz Basic Waveform Characteristics