Non-IP Modem Codecs for Node.JS

A Node.JS library for decoding and encoding efficient binary blob messages for Non-IP Modem data transport over constrained satellite networks.

It implements the Compact Binary Codec concept for use on server/cloud resources.

[!TIP] The key feature of NIM messages is that data field boundaries do not need to align with byte boundaries.

NB-NTN and CoAP

Narrowband Non-Terrestrial Networks provide low-power low-data connectivity for IoT devices operating in the most remote areas, and can serve as a fallback to conventional cellular LPWA (NB-IoT) networks through roaming arrangements.

NIMO

Non-IP Modem for ORBCOMM protocols is derived from a proprietary codec key file described by XML or JSON. The principle is the first 2 payload bytes comprise a message key describing services (aka SIN) made up of messages (aka MIN). Messages are defined for both uplink (aka Mobile-Originated) and downlink (aka Mobile-Terminated) operations.

Using this approach we can define up to 256 Service(s) each with up to 256 Message(s) in each direction of communication. The intent is that each micro-service encapsulates a set of related remote operations, and the messages represent the individual downlink (command/query) or uplink (response/report) operations.

[!NOTE] When using actual ORBCOMM-protocol based modems (IDP/OGx service) SIN 0-15 are reserved for system use, and SIN 16-127 are pseudo-reserved for ORBCOMM Lua apps.

An XML format for the codec file was historically uploaded to the Viasat/Inmarsat or ORBCOMM/SkyWave web service API gateways, typically with extension *.idpmsg. Some field types may not be supported on some gateways.

The JSON format provides a condensed version and supports an extended set of field types. The codec library is intended to prefer JSON representation for processing external to the service provider API gateways.