The tactical high-speed data super radio-access unit:
a success in Kosovo

by CW2 Andrew Llanos and MAJ David Are

The Signal Regiment professionally provides information services as a proud part of Task Force Falcon supporting Kosovo Forces and the U.N. mission in Kosovo. Day in and day out, the soldiers representing most Signal units in central Europe take their doctrinal training and doctrinal equipment and apply initiative, imagination and a magnanimous portion of hard work to fully support a non-doctrinal application of multinational peacekeeping.

The ability to "make something out of nothing" or to constantly improve our position has been a mainstay of U.S. military forces throughout history. Today�s military is no different. The soldiers of Task Force Falcon�s Team Signal continue this legacy as they do more with less and advance the process for KFOR and the Signal Regiment.

Our article describes one of the successes for the communications soldiers in Kosovo. We know the "super data radio-access unit" is neither the genesis of multiservice shelter capabilities (Communications-Electronics Command, General Dynamics and 121st Signal Battalion published the first super RAU installation procedures), nor will it be the last. Our effort merely represents a small portion of an ongoing endeavor to provide higher quality, more robust communications services to the soldiers who expect and deserve our best.

As new technology becomes available, we�ll see a change in the capabilities of our legacy systems. With some more equipment, the super data RAU can become a formidable solution for RAU coverage, telecommunications service and data-communications service for non-contingency-communications package or light CCP Signal units. It�s our intent to help others take the next step by facilitating new ideas and techniques that lead to legacy systems� evolution.

Although these systems are becoming obsolete, they�re all we have to work with. Signaleers will continue to adapt, since the ultimate goal of our Signal profession is to provide our customers with quality communications support which meets the commander�s intent, reduces residual impact on Signal operations and doesn�t diminish our capability to conduct contingency-communications operations.

To that end, here we present a how-to guide on adapting the Army�s standard RAU to allow data and wireline voice service from this terminal.


The 141st Signal Battalion deployed to Kosovo June 2, 2000, to support Task Force Falcon. The battalion deployed Bravo Company, an area Signal company consisting of two node centers, eight small extension nodes and two remote RAUs. To accommodate the tactical-communications-network infrastructure already in place, the battalion underwent a tactical high-speed data network fielding, completely retrofitting all its NC, SEN and large extension node switches before deploying to Kosovo.

Initial requirements left some tactical-network flexibility, but with new command-and-control requirements, conference calls and morale-support activities, all the battalion�s assets were soon put in-system.

In July 2000, Task Force 141st Signal Battalion (Task Force Signal) started looking for more ways to support the changing requirements of Task Force Falcon 2A units deployed in and around the Kososvo Multinational Brigade East sector. One requirement was to expand our network structure to provide tactical phone service to 2d Battalion, 320th Field Artillery, colocated at one of our RAU sites, with little or no impact to the tactical network or its customers.

In the Signal community, we always try and look for ways to support our customers, even though we don�t have the assets immediately at our disposal. That search eventually led us to the first "super RAU."

The mobile-subscriber equipment-enhanced RAU (also known as the "super RAU") was a concept first developed in 1995 by General Dynamics� Regional Support Center at Fort Hood, Texas. The super RAU was created to aid 1st Infantry Division in cutting rail-transportation costs to the National Training Center at Fort Irwin, Calif.

The super RAU was a good solution for us as well, allowing us to support our mobile subscribers in Kosovo with RAU coverage while supporting minimal tactical-telephone service at the RAU site. The super RAU met the telecommunications requirements; however, it didn�t meet newly developed data requirements.

Services stemming from the Army�s automation transition � which include email, Internet access, file sharing, intelligence reporting and network management � are quickly becoming standard services provided in tactical-communication networks. Again, we needed to find a cost-effective way to provide new services to the customer without degrading the network composition.

Using existing high-speed multiplexer II network design, THSDN flexibility and super RAU technology, we assembled a product similar to the AN/TTC-50 communications central (also known as the forced-entry switch), but without FES� network redundancy or subscriber-support capability. This product was the super data RAU.

In 1st Armored Division and 141st Signal Battalion, the super data RAU is able to provide RAU coverage, minimal telecommunications service, data-communications service and videoteleconferencing network access. We found the super data RAU to be a cost-effective approach that doesn�t require more manpower, maintains network integrity and has minimal residual impact on Signal operations.

Now we get down to the nitty-gritty: modifying equipment to create the super data RAU.

System capabilities for super data RAU System capabilities for the super data RAU include VTC, non-secure Internet protocol routed network, secure Internet protocol routed network, three digital non-secure voice telephones or digital secure voice telephones, eight RAU trunks and up to 50 affiliated mobile-subscriber radiotelephone terminals.

Super data RAU telephone modification procedures

These instructions go with the following figures.

  1. Remove the screws holding the communications modem, patch panel and drawer. The drawer must be removed from the bracket.
  2. Connect the line-of-sight-conversion cable connectors P3 and P4 to CM connectors J2 and J11 respectively (J2 and J11 did not previously have connectors on them).
  3. Disconnect the W43 cable from CM J5, connect the external-subscriber conversion cable P1 to J5 on the CM and reconnect the W43 cable to the P2 connector of the external-subscriber conversion cable.
RAU communications modeum cable modification RAU CM cable modification diagram.
RAU configuration instructions RAU configuration instructions.
RAU external subscriber conversion cable connections RAU external-subscriber conversion cable connections.
Table External-subscriber cable wiring. Parts: Connector P1 -- MS3126E22-55S with adapter; Connector P2 -- MS3120E22-55P with adapter; cable -- GTE Part #19-2733540-6 or equivalent; and external subscriber A-box -- any adequate subscriber termination/connector.
RAU configuration wiring RAU configuration wiring diagram.

HSMUX modification and network configuration

These instructions go with the following figures.

  1. Remove the MXDMX circuit-card assembly from CM Slot A10.
  2. Set the HSMUX2 CCA to a 16-kilobytes-per-second channel rate, 1,024 kbs aggregate data rate, with 256 kbs on Port 1 (P1 on the diagrams) and 512 kbs on Port 2 (P2 on the diagrams) � setting 00110010. Binary settings are set from Switch 8 to Switch 1 (highest to lowest) with 0 settings set towards the word "on" that�s stamped on the S1 switch block. For instance, 00110010 is 8=0, 7=0, 6=1, 5=1, 4=0, 3=0, 2=1, 1=0.
  3. Install the HSMUX2 CCA into Slot A10.
  4. Connect the HSMUX cable to P2, ensuring that Pin 1 on the HSMUX cable connector matches Pin 1 on P2.
  5. Close the CM cover and set the cable-length setting to the number of CX-11230 cable �-mile links between RAU and AN/TRC-190(V)1.
  6. Set data rate to 8 (1,024 kbs).
  7. Connect the RS-449 data-communications equipment end of HSMUX cable to the RS-449 data-terminal equipment end of the Cisco router cable.
  8. At the circuit switch, ensure the RAU digital-transmission group has an enhanced transmission-group-modem orderwire installed. Set the dip-switches to 1,024 kbs aggregate, 512 kbs circuit switch data (256 kbs RAU, 256 kbs VTC), 512 kbs router data.
  9. Build the RAU DTG with four nine-channel multiplexer/demultiplexer cards (512 kbs circuit-switch data), channel rate 16 kbs, 1,024 kbs group rate. Check the DTG to ensure the group-logic unit channel is assigned. Note: The RT-1539 very-high-frequency radios in the RAU are only compatible with 16 kbs channel rate.
HSMUX2 circuit-card assembly HSMUX2 circuit-card assembly. Example shown is S1=00110010 with 16 kbs channel rate, 1,024 kbs aggregate group rate, Port 1 @ 256 kbs and Port 2 @ 512 kbs.
router cabling and HSMUX connection Router cabling and HSMUX connection.

The DB-37 connector (figure below) connects to the Cisco proprietary RS-449 DTE cable (#72-0795-01). The eight-pin header connects to Port 2 of the HSMUX card.

DCE to HSMUX connection DB-37 RS-449 DCE to HSMUX RS-422 eight-pin pinouts.


Note that certain procedures used to troubleshoot the data link to the super data RAU differ slightly from procedures found in the THSDN operators guide or THSDN�s new-equipment-training material. One constant in any troubleshooting with THSDN: if the DTG doesn�t have a good status, the data link won�t either. It�s pointless to try and troubleshoot a data link if the DTG the data is assigned over is out of sync.

THSDN makes excellent use of available address space by assigning Internet-protocol unnumbered serial interfaces, increasing router network flexibility. However, when troubleshooting a router serial interface through THSDN, we discovered the "ping" IP echo test was greatly diminished. This posed problems during loopback testing.

Not being able to ping the distant-end router address already indicates a problem. Since IP unnumbered interfaces share an IP address, usually loopback 0 (zero), pinging yourself is no longer a good test since the loopback 0 address never goes down unless it has been administratively shut down. When checking the local-router serial port for a line-up and protocol-up status, a ping test is needed during the loopback to ensure the local router receives the packets sent from itself. If the router serial interface is IP unnumbered and sharing a loopback address, a ping test is no longer an accurate indication of connectivity since the serial interface will always be able to ping itself.

Assigning an IP address to the local and DE router serial ports greatly aids the troubleshooting process. When two routers are logically connected in the same network via their serial interfaces, a router won�t be able to ping the DE router�s serial IP address unless the link is in. Consequently, if the local router can ping its serial IP address, but can�t ping the DE router�s serial interface, there is loopback somewhere in the link.

A "show interface serial x/x" command in the priviledge executive mode of the router will verify a looped condition (where x/x=module/port number, for example, 1/2). Be careful, though � a local computer that has connectivity to the local router can ping the router serial IP address even though a person in the router cannot ping its serial IP address.

This is normal, but it doesn�t verify connectivity from the router, only from the computer to the router serial port. Only a successful ping test from the router by the network manager or supervisor via telnet or via the console port validates connectivity.

When conducting loopbacks during system-link troubleshooting, every successful loopback must be checked with a ping test. If the local router cannot ping itself, the loopback didn�t pass for data.

One of our problems was a bad triaxial cable in the patch panel of the LOS(V)1 connected to the super data RAU. The cable-loopback ping test passed, but when the LOS(V)1 put the super data RAU in a field loopback, we couldn�t ping ourselves; the test failed. At the node center, a cable-loopback test failed with five different CX-11230 cables before we found one that would pass the ping test.

Although each of the five cables passed when we applied high-speed forward-error correction during the loopbacks, HSFEC couldn�t be applied to the link since we didn�t have an HSFEC CCA installed in the super data RAU. Without HSFEC applied to the link, the cables and the radio sublink must be high quality.

CW2 Llanos, the super data RAU�s creator, is a network technician assigned to 141st Signal Battalion, 1st Armored Division. He served as the Task Force Falcon network technician for KFOR 2A.

MAJ Are is 141st Signal Battalion�s S-3. He commanded Task Force Signal on the KFOR 2A rotation.

Acronym QuickScan
BSC � black station clock
CCA � circuit-card assembly
CCP � contingency-communications package
CM � communications modem
DCE � data-communications equipment
DE � distant end
DNVT � digital nonsecure voice telephone
DSVT � digital secure voice telephone
DTE � data-terminal equipment
DTG � digital-transmission group
DVOW � digital voice orderwire
FES � forced-entry switch
GLU � group-logic unit
HSFEC � high-speed forward-error correction
HSMUX � high-speed multiplexer
IP � Internet protocol
Kbs � kilobytes per second
KFOR � Kosovo Forces
LOS � line of sight
NC � node center
RAU � radio-access unit
RCV � receive
SEN � small extension node
THSDN � tactical high-speed data network
XMT � transmit

dividing rule

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