MOBILE Trunked radio systems

TETRA Trunked Radio System ACCESSNET ®-T Trunked radio technology for Europe’s most advanced combat training center

The “Letzlinger Heide” training area BS BS BS BS BS BS of the German Armed Forces is the #1 #2 #3 #4 #5 #6 most advanced combat training center Communication network 1 (fiber optics)

in Europe. Up to 2500 soldiers can

practise with their vehicles within an Central Switching Control Node DMX-600

area of approx. 500 sq km. Their

Communication network 2 combat activities are recorded and

monitored fully electronically under Voice communication center Data handling center realtime conditions. FIG 2 Communication infrastructure of combat training center

Electronic duel: radio-monitored With TETRA (terrestrial trunked radio), a FIG 1 The compact and lightweight subscriber unit is usually mounted on the back and radio-controlled digital non-military radio technology is used, which is based on a European The activities of the exercising soldiers standard and was developed by are recorded and monitored fully elec- Rohde & Schwarz under the product tronically under realtime conditions. All name ACCESSNET ®-T as a professional of this is made possible by the “elec- trunked radio system for civil applica- tronic duel”, on which training in the tions [1, 2]. ACCESSNET ®-T, a COTS army’s combat training center is based. (commercial off-the-shelf) product devel- The combat situation is simulated with oped primarily for use in public networks, the aid of laser beams and optimized sen- industrial enterprises, public transport sors. The lasers are fixed to the soldiers’ systems and security organizations, has weapons and vehicles, and the sensors proven itself in this purely military are suitably distributed over the soldiers’ application. The subscriber unit also clothes and vehicle surfaces. Each sol- uses a commercial TETRA unit as radio dier and each vehicle are provided with modem. There were various reasons a subscriber unit which electronically why the German Armed Forces repre- registers all operations such as opening sented by EADS decided in favour of of fire, hits and movements of the soldier ACCESSNET ®-T. The main reasons are or vehicle, and transfers the information stated in the box on page 6. via radio to the command and control

Photo 43717/14N center (FIG 1).

8 News from Rohde&Schwarz Number 172 (2001/III) For full radio coverage of the area, base Ethernet TETRA air interface (TCP/IP) (ETS 300 392 Part 2) stations with transceivers are installed Data at six sites. Each site has its own set handling Peripheral equipment center interface of frequencies. The cellular organization (ETS 300 392 Part 5), Hayes AT of the radio network ensures that a sub- scriber unit is always in contact with that whose radio signals Interface Main ACCESSNET ®-T Radio are best received, as the subscriber unit processor ACCESSNET terminal controller moves around within the radio network. In addition to data transfer, voice com- CAN GPS bus munication for the observer/controller Command and receiver is also handled via these sites with control center Subscriber unit transceivers specially reserved for this purpose. FIG 4 The complete data communication chain

The communication infrastructure communication center is also handled electronic components of a commercial Networks via the fiber-optic network. Connection TETRA handheld transceiver with an RF The Trunked Radio System ACCESSNET®-T to the data handling center is made via output power of 1 W, a microprocessor from Rohde & Schwarz is embedded into a computer network (LAN with Ethernet and a GPS receiver. The sensors are the fixed network infrastructure of the and TCP/IP). connected via the CAN (controller area combat training center. The existing network) bus. This bus is also suitable fiber-optic network is used for network- The subscriber unit for downloading new software into the ing the base stations with the central The subscriber unit shown in FIG 1 TETRA radio module and microprocessor. switching control node of the trunked is a lightweight, compact unit fixed radio system (FIG 2). As shown in the to the sensor carrying harness on the Focus on data communication block diagram, connection to the voice back of the soldier. It consists of the Data communication is the main focus of the trunked radio system of the combat training center, which can be fully con- trolled and monitored by the command Photo 43717/12 and control center (FIG 3). The logical connection of the data communication chain is shown in FIG 4.

Up to 95% of the data traffic in the trunked radio system is triggered by events from the subscriber units such as position changes or lasers hitting the sensors on the soldiers and vehicles. The Trunked Radio System ACCESSNET ®-T serves as a transparent transport vehicle for data transfer to the command and control center.

FIG 3 The command and control center has everything under control: it monitors, records and evalu- ates all activities in the combat training area

9 News from Rohde&Schwarz Number 172 (2001/III) Trunked radio systems

the mobile application in the subscriber

Mobile System unit is to collect data and control the application application Data handling system sequence of operations. The system application in the Trunked Radio System Call number ACCESSNET ®-T integrates the GPS, gen- conversion erates the reference signal and initiates

Protocol Protocol Protocol Protocol regular transmission of the reference stack stack stack stack signal. This is also where the call number conversion occurs for the recod- Air interface TCP/IP interface ing of military tactical numbers into phys- Command and ical TETRA addresses and vice versa. The Subscriber unit ACCESSNET®-T control center LAN interface to the command and con- trol center and its protocol are also han- FIG 5 OSI layer model of data communication system dled here. The data handling system is a stationary application in the command and control center.

Further data traffic is generated, for the command and control center to the example, by the reference information subscriber units as a broadcast call. for the differential GPS (global position- ing system) and the general position The layer model shown in FIG 5 illus- information usually communicated by trates this configuration. The task of

Why the German Armed Forces decided in favour of TETRA and ACCESSNET ®-T

Data communication with the subscriber units and observer/ in which both services are integrated, thus providing an addi- controller voice communication should by no means technically tional economic benefit. affect tactical radiocommunication of the exercising units. The TETRA standard of ETSI (European Telecommunication Stan- The TETRA standard describes the most advanced technology dards Institute), which is specified for frequencies of approx. currently available for professional mobile radio. The main phys- 400 MHz and above, meets these requirements. Thanks to ical features of the air interface and the essential voice and the flexibility of ACCESSNET ®-T, it was possible to fulfill the data services are shown in FIG 6. Based on expected future customer’s special request for extending the frequency range market development, it is assumed that this technology will to 366 MHz to 371 MHz for this project: a typical example of have a lifespan of at least 20 years. a COTS product like ACCESSNET ®-T offering sufficient possibili- ties for adaptation. Channel spacing 25 kHz In particular, ACCESSNET ®-T and TETRA technology support Modulation π/4-DQPSK integrated voice and data communication. Instead of two Channel data rate 36 kbit/s independent radiocommunication systems as was originally Voice coder approx. 4.8 kbit/s intended, it was therefore possible to set up a single system Channel access TDMA, 4 timeslots Usable data rate 7.2 kbit/s per timeslot Variable data rate 2.4 kbit/s to 28.8 kbit/s Voice services individual call, group call, FIG 6 broadcast call Main physical features of air interface Data services status message, and services of TETRA short data message

10 News from Rohde&Schwarz Number 172 (2001/III) Photo: Author An excellent communication platform More information on ACCESSNET ®-T at www.rohde-schwarz.com (Homepage – The German Armed Forces have decided Products&More – Trunked Radio) in favour of ACCESSNET®-T, a modern digital TETRA trunked radio network available as a COTS product that can REFERENCES be used without any adverse effects [1] Countrywide ACCESSNET ® trunked radio on tactical radiocommunication equip- system in South Siberia. News from ment. In addition to the favourable price/ Rohde & Schwarz (1999) No. 162, pp 30–32 [2] A vision comes true – trunked radio performance ratio, the high flexibility for United Arab Emirates. News from and easy adaptability of the system to Rohde & Schwarz (1995) No. 151, pp 50–51 special requirements are further benefits. Max Zerbst

FIG 8 Central Switching Control Node DMX-600

FIG 7 TETRA Base Station DTX-500 The components of ACCESSNET ®-T

The Base Stations DTX-500 (FIG 7) and the Switching Control Node DMX-600 (FIG 8) are referred to as subsystems. The base stations are accommodated in shelters. Three transceiver modules each are provided for voice and data communi- cation. The maximum output power of each radiated via a common antenna is 25 W.

The Switching Control Node DMX-600 is accommodated in the central building of the combat training center and is con- nected to the data handling center via a LAN. FIG 8 shows that for redundancy reasons, two GPS receivers (yellow mod- ules) are provided in the DMX-600. Photo: Author

11 News from Rohde&Schwarz Number 172 (2001/III)