COMMON USER DIGITAL INFORMATION EXCHANGE SYSTEM

The Common User Digital Information Exchange System (CUDIXS) provides a bidirectional, ship-to-shore-to-ship, high-speed digital data communications link between a ship and a NCTAMS or NAVCOMMTELSTA. Subscriber stations use the NAVMACS as their terminal. The link consists of a single Fleet Satellite Communications (FLTSATCOM) half-duplex channel. The link is dedicated to synchronous communications between the CUDIXS shore station (Net Control Station (NCS)) and the subscribers afloat. Each CUDIXS communications link can operate with up to 60 subscribers. There are two types of subscribers: special and primary.

Special subscribers are those ships that are assigned subscriber identification (SID) numbers 1 through 10. Special subscribers can send and receive narrative traffic to and from CUDIXS.

Primary subscribers are assigned SID numbers 11 through 60. Primary subscribers are restricted to a send capability only. They can receive their shore-to-ship message traffic via other means, such as the fleet broadcast or fill-period terminations. Both types of subscribers can send or receive operator-to-operator (order wire) messages.

CUDIXS/Subscriber Net Cycle

CUDIXS/subscriber communications are accomplished through a modified round robin network discipline. The basic round robin net operating concept transfers net control from one subscriber to the next on a prearranged basis, completing one net cycle when each participating subscriber has transmitted.

In the CUDIXS/subscriber modified round robin operating concept, transmission timing and scheduling are determined solely by the CUDIXS shore station designated the NCS. Each net cycle starts when the NCS transmits a Sequence Order List (SOL) along with narrative traffic and operator-to-operator messages. The SOL specifies the order in which each subscriber transmits during the next net cycle and the amount of time allocated each transmission slot. Each subscriber, in turn, will transmit at a time computed from information in the SOL.

A net cycle can range from 20 to 120 seconds, depending upon the amount of transmit time requested by the subscribers and the amount of data transferred.

System Performance/Message Accountability

CUDIXS provides a shore operator with several means of monitoring system performance and maintaining message accountability for all messages processed by the CUDIXS NCS. Specifically, the system assigns sequence numbers to all messages processed, provides link status, traffic statistics, and system summary information in system reports. The system also allows the operator to assign parameter values that control net operations and to generate various alerts concerning immediate communications difficulties.

System Interfaces

CUDIXS serves as an extension of AUTODIN by storing and forwarding messages, normally without need for human intervention. CUDIXS interfaces with AUTODIN via the NAVCOMPARS and processes narrative traffic for general fleet communications teleprinter messages.

In accomplishing its tasks, CUDIXS supplements the traffic responsibilities previously assumed by ship-to-shore and broadcast HF circuits. CUDIXS can recognize EMERGENCY COMMAND, FLASH, IMMEDIATE, PRIORITY, and ROUTINE messages on a first-in-first-out (FIFO) basis within precedence. Through system reports, the operator has the following capabilities:

Detailed information on every message processed by CUDIXS;

Overall statistics on the volume of message traffic processed over the link; and

Information on the quality of link communications with each net subscriber.

COMMUNICATIONS DATA PROCESSING SYSTEM

The Communications Data Processing System (CDPS) provides the USS Tarawa (LHA-1) class ships with the necessary communications hardware and software to process narrative traffic and to ensure circuit reliability. CDPS is one of the most complex of the automated systems afloat and offers the following capabilities:

Automatic broadcast screening;

Frequency management;

Automatic message logging;

Automatic message continuity checks;

On-line message preparation and storage;

Backup control and operation;

High-speed data interface;

On-line operational readiness testing;

Quality monitoring with computer aid;

Message error analysis;

Circuit status and record-keeping functions;

Construction of communications circuits; and

Ability to act as a CUDIXS special or primary subscriber.

As with many of the automated systems, the operator has the ability to modify system configuration from the control console. The operator must know how to properly use, operate, and perform system changes. Your job will involve setting up and operating input/output (I/O) devices. Some systems allow the operator to patch receivers, transmitters, modems, and antennas directly from the console.

As a Radioman, part of your routine duties will be to energize electronic equipment and monitor power levels. In the event of primary power failure, equipment must be brought up on emergency or back-up power systems. Many of the automated systems in use today have uninterrupted power sources (UPS) or battery backups to preclude a complete system failure.

For more information on power requirements for individual components, refer to the equipment technical or operator manuals. You should become familiar with emergency power requirements and procedures prior to an actual emergency.