TETRA-based mobile networks form a basis for successful operation in the police and emergency services, airports, railways and for many other professional users. These user groups demand reliable and safe network operation at best possible radio coverage.
These high requirements can be fulfilled with Willtek’s 8140 TETRA AirAnalyzer, a unique and versatile tool to continuously analyse and maintain a TETRA network. It is also suited to examine issues during the introduction of new system technology and to perform interoperability tests in system development.
Two powerful and highly sensitive measurement receivers form the heart of the 8140 TETRA AirAnalyzer. These receivers pick up the bidirectional communication between TETRA mobile stations and a base station. All time slots in the downlink and uplink of a selectable channel are analysed simultaneously.
The TETRA AirAnalyzer decodes the data received on the radio channel in real time and forwards them to a PC for further processing. Various PC applications can analyse the data under different aspects. The analysis can be performed either online or offline, using the data received and stored at a later date.
Suspect faults in the message flow?
The TetraMSC application visualises the signalling messages received over the air interface in a clear and concise way. Thanks to the structured layout, users can easily identify which message is transmitted on what protocol layer. The messages are individually tagged with a time stamp and the relevant RF parameters, such as frame number, frequency offset and signal strength. Signalling messages not conforming to TETRA standard EN 300 392 are marked with a different colour. With a click on the marked message, the application displays a detailed error description.
A number of filter functions eases fault tracing because the user can reduce the messages displayed to those which are of interest in the case at hand.
Analysing voice communication and voice quality
The 8140 TETRA AirAnalyzer and its associated PC software can output and store voice data received over the air interface, enabling users to evaluate the voice quality and to observe communications over the network. With the voice decoder function, users can monitor speech on two time slots and record it in Wavesound format for later analysis. The direction and time slot can be selected on a straightforward user interface.
Observing the RF
The TETRA Physical Data Analyzer application complements the 8140 TETRA AirAnalyzer to give a powerful modulation analyser. Received data are stored with all details so that spectrum, received signal strength and modulation quality can be assessed at a later time. The analyser software visualises these physical layer measurements in a graphic display (see examples in Fig 4). Useful functions like the display of individual bursts, the rotation of the graph in the constellation display and I/Q modulation fulfil many desires of those analysing the physical layer in more detail.
Finding TETRA carrier problems
The TETRA Scanner searches for TETRA carriers in a user-defined frequency range. In addition to the available TETRA channels, the broadcast parameters are displayed for each carrier with a Main Control Channel. This feature helps to easily identify network configuration problems. The channels available can be monitored because the usage of time slots for traffic (TCH) is displayed and permanently updated. Associated measurement values such as received signal strength or frequency error, are shown in a diagram. This tool offers an easy way to check the results of network planning in real life, so that the network can be optimised if necessary. The current network status in regard to quality and quantity can be evaluated, so the tool can be used to find the best possible utilisation of resources. With a GPS mouse connected to the computer, the 8140 TETRA AirAnalyzer can even be turned into a full featured drive test receiver with real-time storage of the current position.
8165 TETRA QoS Analyzer (option)
The optional 8165 TETRA QoS Analyzer application provides an easy way to evaluate the quality of service; the results of the QoS parameters are displayed graphically for easier interpretation. In the TETRA AirAnalyzer, quality of service means more than just radio coverage: To ensure that the TETRA network for safety-critical operations can perform the required service, more data are of importance. Call setup time, number of queued calls and associated wait time, call priorities and cell load are important parameters to describe the network quality. Emergency services have high demands on these parameters for safely performing their tasks.
8161 Static/Dynamic Air Interface Encryption Option
In organisations ensuring public safety and security, voice calls and data transmission over the TETRA network are confidential by nature and therefore protected by air interface encryption. In these types of networks, the functionality of the 8140 TETRA AirAnalyzer is ensured by the 8161 Static/Dynamic Air Interface Ecnryption Option. The encryption algorithm (TEA 1 through 4) and the encryption keys must be provided by the user.
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