Galileo Advanced Applications (GalileoADAP)
|Fig. 1: Galileo applications|
Europe makes a significant contribution for the global provision of navigation infrastructures with the implementation of EGNOS and Galileo, which, by the increased positioning accuracy and satellite availability, will lead to a multiplicity of new applications both in the mass market and in the professional sector. The enhanced system integrity enables the application of the satellite navigation within safety of life (SoL) domains, and, in consequence, will force the development of new terminals and services within this area.
With view on this background the Institute of Communications and Navigation (IKN) carries out user specific research in these areas. Within the frame of the project GalileoADAP, two demonstrators were developed, one for indoor and one for SoL applications. Emphasis for indoor application was the combination of COM and NAV. For SoL applications emphasis was placed on interference mitigation, receiver development, integrity and local of elements. With these demonstrators applications shall be promoted, e.g. for the preparation of common projects with industry.
|Fig. 2: Signal propagation in buildings|
The goals of this subject area were the development, testing and demonstration of new technologies for navigation within buildings. Both the development of new concepts and their conversion to computer simulations and prototypes were made. The new concepts cover the integration of different sensor technologies (e.g. inertial systems, compass, GNSS, RFID), movement models and maps. Besides pure indoor navigation, the new technologies are also as much as possible suitable for the navigation of pedestrians outside of buildings in order to improve navigation e.g. in urban canyons and to ensure a smooth transition from outdoor to indoor. In order to represent the results convincingly, demonstrators were developed in all phases of the project, which proved the quality and feasibility of the developed concepts in realistic scenarios. The final stage of the indoor demonstrator integrates the algorithms developed in the subject area 'Galileo and mobile radio'. Therewith IKN assures its unique position to have a good grasp both of GNSS and of mobile radio, sensor technology and movement models.
Galileo and mobile radio:
Due to their in principle different tasks and requirements navigation and/or communication systems were so far separately regarded and designed. A goal of the project GalileoADAP was to examine in detail the possibilities which offer both the existing and future communication systems (i.e. portable radio systems of the 4. Generation, 4G; LTE) and link them with the satellite navigation. As important basis for reaching of these goals IKN performed a measurement campaign, in order to understand and model the propagation characteristics of the mobile radio signals in such a manner that the relevant parameters for positioning purposes could be accurately described. Such models did not exist before. With the help of these models the accuracy of positioning based on mobile radio was determined by computer simulations. The results have been ported also into the 4G signal design. This takes place in the context of the WWRF (wireless world research forum) in close coordination with industrial partners and research institutions. Furthermore, in GalileoADAP new positioning algorithms were developed, which consist in an almost optimal fusion of GNSS and mobile radio based positioning and which utilize the soft location concept developed by IKN. As a central part of the indoor demonstrator a LTE testbed was build up in HW.
SoL receiver development:
|Fig. 3: Integrity concept for Aviation|
|Fig. 4: Mitigation of interference and multipath signals with adaptively controlled multi-beam antennas|
Safety of Life applications (SoL) make substantial demands on accuracy and reliability of satellite navigation receivers, in particular for the use in critical operations such as CAT II/III landing. Galileo offers good conditions to fulfil the high SoL requirements by transmitting several wide-band signals on different frequencies and providing integrity information. For high availability and integrity the receiver must be hardened additionally against reception impairments by reflected signals and disturbances by unconsciously or intentionally transmitted external radio signals (interference and jamming). In order to fulfil these requirements systematic analysis of existing approaches and development of new concepts for integrity determination have been carried out with emphasis on aviation, but also for other application areas like shipping.
An effective method for suppression of interference, which was in particular investigated and realized within the project, is the use of an array antenna, whose reception pattern is adaptively controlled by suitable algorithms in the digital signal processing. In GalileoADAP a receiver demonstrator was built in order to prove the efficiency of the algorithms and techniques described above. Central unit is a real time Galileo digital signal processing unit in FPGA technology followed by a SW receiver. The complete SoL demonstrator (GALANT) includes a 4-element array antenna, a multi-channel RF front end and offers interfaces to external sensors, e.g. INS, and for the use of ground based augmentation information provided by local elements.
Interference and jamming:
|Fig.5: Example of interference measurement in the Galileo E6 band|
The robustness of the GNSS receiver against interference is of high importance for SoL applications. Because of the low receiving power of the GNSS signals, losses or impairments can occur easily due to unintentional interference. Also a relatively high potential and risk exists that the accuracy and availability of the GNSS signals are disturbed consciously by external interferences (jamming). The goal of this subject area was therefore the elaboration of measures both on the hardware side and on the algorithms side to detect and minimize disturbance by interference. A precondition for this is a good knowledge of the signal characteristics of the potential disturbers and a good understanding of their effects in the navigation receiver; then suitable algorithms in the signal processing can be developed for their detection and suppression. Emphasis of the intended work was therefore placed on:
- The modelling of interference sources;
- the development of methods in digital signal processing stage for detection and identification of interference as well as methods to the suppression of selected types of interference;
- the development of a multi channel receiver RF front-end with emphasis on interference suppression. The front-end is built in a modular way and suited for simultaneous reception of Galileo L1 and E5a signals and simultaneous reception of GPS and Galileo L1.
Field tests in the GATE testbed with the SoL receiver (GALANT) showed an enhancement of interference suppression and tracking robustness by 20 dB and more by the implemented mitigation methods in comparison to some commercial high end receivers.
|Fig. 6: Concept for utilization of local elements|
The use of local elements is a methodology to achieve the increased accuracy and integrity requirements for 'Safety of Life' applications in a local context. For local augmentation, GNSS/Galileo signals are received at reference locations and evaluated regarding their quality. From this, auxiliary and correction signals are generated and distributed to the users. The data and signals which must be made available by the respective local element are finally determined by the specific user requirements. Their specification takes place e.g. in the aviation sector by ICAO and in the maritime sector by IMO. In order to reach accuracies in the meter or sub-meter range and to detect malfunctions within a few seconds, the used algorithms and procedures must work with high stability and reliability in real time. In GalileoADAP fundamental algorithms were developed for local signal monitoring and for the generation and distribution of auxiliary and correction signals for different applications. The experimentation and verification network EVNET of IKN was used as basis platform for development and demonstration of new algorithms. Its infrastructure was adapted to the required service functionalities and to the interfaces of the SoL receiver demonstrator. Local elements were employed at the research airport Braunschweig and at the research harbour Rostock for experimental validation of the algorithms and associated developments.
funded by: internal
Project duration: 2006-2011