Multifunctional Information Distribution System

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Multifunctional Information Distribution System ( MIDS ; German Multi-Functional Information Distribution System ) is a military radio system that can work according to the time division multiplex method (TDMA) in the frequency range 890–1215 MHz.

MIDS is the improved version of the JTIDS developed by the USA and is largely compatible with it.

commitment

Originally developed for the armed forces of the USA, the system is now used, among other things, in the overall area of ​​NATO air defense. It operates in the frequency range 960 - 1215 MHz, which according to VO Funk is assigned to the air navigation service as the primary user worldwide. In addition, this frequency range is reserved on a worldwide basis for the use and development of electronic flight navigation aids on board aircraft and the use and development of the associated facilities on board. Therefore, the overall MIDS / JTIDS system in NATO Europe only has one frequency availability with restrictions and requirements.

Performance characteristics

  1. Radio data transmission, Tactical Data Link 16 ,
  2. Secure, digital voice transmission,
  3. Flight navigation ( Tactical Air Navigation , TACAN),
  4. Relative navigation ,
  5. Identification ( Precise Participant Location and Identification , PPLI).

MIDS terminals are used by the air force , the navy and the army . The technical properties of the MIDS terminal are specified in the Standardization Agreement ( STANAG ) 4175.

A cross-sectional variant of the MIDS is the MIDS Low Volume Terminal (MIDS-LVT), which is financed by the USA, France, Germany, Italy and Spain and by MIDSCO, a joint venture between Thomson CSF, GEC, Siemens, Italtel and Enosa , was developed. After production was ready for series production, production was transferred to ViaSat , DataLinkSolution and EuroMIDS . EuroMIDS, a joint venture of the European defense companies EADS (Germany), SELEX (Italy), THALES (France) and INDRA (Spain), produces MIDS-LVT mainly for European MIDS users. As the successor to the MIDS-LVT, the MIDS-JTRS (MIDS Joint Tactical Radio System ) is currently being developed under American leadership . In Germany the MIDS-LVT is used by all military organizational areas. The weapons system command of the Air Force Department VI 1- (WaSysKdoLw VI 1) was responsible for the usage control until 2012.

Technical principle

MIDS uses a time division multiple access (TDMA) method in the frequency band 960 - 1215 MHz to transmit information . The MIDS terminal switches between 51 different working frequencies ( Frequency Hopping Spread Spectrum , FHSS, selection in the pseudo-random procedure) in very quick succession in order to send or receive its information. The basis is a periodically repeated 12-second period, the frame ; the smallest information unit assigned to a specific terminal is called the time slot . The frequency is also changed in pulses within the time slot . The sequence in which the individual working frequencies are run through is defined by a key algorithm. The carrier is additionally modulated with a pseudo-random noise pattern ( Direct Sequence Spread Spectrum , DSSS), which can only be removed again using a crypto key that is only available to allied forces. This key is also used to determine the transmission and reception frequency and to encrypt the data stream. By distributing the signal in connection with redundant transmission and additional error correction data according to the Reed-Solomon method, MIDS provides a reliable, secure and difficult to disrupt data radio link. Depending on the effort involved in correcting errors, data rates between 57 and 114 kbit / s can be achieved in practice.

As a rule, only one terminal sends in each time slot ( dedicated access ), but there are also methods for network optimization in which certain time slots can be used by any terminal if required ( contention access ). This applies above all to information for which, due to a high repetition rate, the reliable transmission at a certain point in time is not important, especially in the case of digital voice transmission.

Since the terminals only transmit on one of the available frequencies at any given time, intelligent nesting / allocation of the time slots makes it possible to create different, independent sub-networks that do not interfere with one another. In practice, however, this is very limited, as the use of multi-netting increases the energy input into the frequency band ( time slot duty factor ) to such an extent that there is a risk that the civil air traffic control ( DME , IFF ) frequencies in the same frequency band disturb. The permitted upper limits are set out in national frequency releases that apply to a specific area of ​​air traffic control (Flight Information Region, FIR).

The assignment of the time slots to certain terminals is made by the MIDS network design . This determines when a MIDS terminal is allowed to listen or transmit on which time slot. The MIDS network is loaded into the terminal in digital form and configures the hopping frequency transmitter according to the design specifications.

To ensure that the individual data packets do not overlap, MIDS terminals need a time standard, the net time reference (NTR), to identify the correct time of transmission . One of the terminals in the network works as an NTR. The time signals it sends are considered correct by definition. The other terminals adjust their internal clocks accordingly. Depending on the progress of the synchronization process, the terminals are in the following states:

  • starting net entry (synchronization starts)
  • coarse sync (coarse synchronization achieved, data reception is possible from here)
  • fine sync (fine synchronization achieved, sending is only possible here)

The NTR itself usually takes its time from a binding time standard such as GPS time.

To avoid the dependency on the local time reference NTR, MIDS terminals meanwhile also offer the possibility of the External Time Reference (ETR). For this, however, a highly precise time standard such as GPS is absolutely necessary on every MIDS platform.

A mixture of ETR and NTR-based networks is possible, provided that an ETR terminal is selected as the NTR for those network participants who cannot use the ETR method.

Services of the MIDS

The communication services listed below can be carried out simultaneously by MIDS, with the individual services sharing the bandwidth among themselves:

Data link

Tactical information is transmitted in "fixed format messages" in accordance with the Link 16 standard. The information transmitted here is transmitted to the management system in which the MIDS is integrated.

Secure Voice

MIDS offers two encrypted digital radio channels that can be used in 127 different virtual channels. Depending on the available bandwidth, modulation speeds of up to 16 kbit / s can be used. Audio information is transmitted in "free format messages".

TACAN

MIDS contains a full-fledged TACAN plug-in card set as a hardware module. The terminal is installation-compatible (fit in form & function) with many military TACAN receivers.

Relative navigation

MIDS contains complex algorithms for the evaluation and Kalman filtering of other received MIDS signals. The corrected own position calculated from this is in turn broadcast by means of the Link 16 PPLI message.

Relative navigation was originally intended primarily to help aircraft achieve improved positional accuracy. However, due to the widespread use of GPS , this function is no longer as important as it used to be.

See also

Web links

Individual evidence

  1. ↑ Frequency availability for JTIDS / MIDS see NATO Joint Civil / Military Frequency Agreement (NJFA) frequency range 960–1215 MHz.
  2. ↑ Article 709, Frequency Band Allocation Plan for the Federal Republic of Germany, 1994.