GNSS Interference Mitigation Using Antenna Array Processing
Creators: name: Daneshmand, Saeed
Publisher: name: Graduate Studies
Year: 2013
Subjects: subject: Engineering--Aerospace
subject: Engineering--Electronics and Electrical
subject: GNSS
subject: Interference mitigation
subject: Antenna array processing

description: Although hundreds of millions receivers are used worldwide, the performance of location-based services provided by GNSS is still compromised by interference which can range from unintentional distortion due to multipath propagation to intentionally menacing spoofing signals. Hence, the requirement for proper mitigation techniques becomes a must in GNSS receivers for robust, accurate and reliable positioning. Recently, interference mitigation techniques utilizing antenna arrays have gained significant attention in GNSS communities. Although at the time of this thesis, employing antenna array in GNSS applications is mostly limited to academic research and possibly sophisticated military applications, it is expected that in the near future, antenna array-based receivers will become widespread in civilian markets as well. Rapid advances in electronic systems and antenna design technology make previously hardware and software challenging problems easier to solve. Furthermore, due to the significant effort devoted to miniaturization of RF front-ends and antennas, the size of antenna array-based receivers will no longer be an issue. Given the above, this thesis investigates the use of antenna arrays in GNSS interference mitigation applications. It starts by proposing a new spatial processing technique capable of mitigating both high power interference and coherent and correlated GNSS multipath signals. It then follows by introducing three new methods that take advantage of spatial and temporal processing in three different GNSS applications. In the first method, the use of spatial-temporal processing for multipath mitigation in the form of a synthetic array is studied. A new method utilizing a moving antenna array is proposed to deal with highly correlated multipath components and also to increase the degree of freedom of the beamformer by synthesizing a larger antenna array. Thus, the array’s degree of freedom is not limited to the number of physical antenna elements. This method can be employed to mitigate multipath signals in vehicular navigation applications. The second method investigates benefits of spatial-temporal processing algorithms for improving narrowband interference mitigation performance. The limitations of previous space-time filters are analyzed and a new approach that employs the inherent periodic feature of GNSS signals in conjunction with the spatial-temporal processing to improve the performance of existing space-time filters is proposed. It is shown that in some interference scenarios, a space-time filter subject to the distortionless constraint may cause a significant degradation to the signal-to-noise ratio (SINR), which can be alleviated by employing the periodicity in the structure of the filter. In the third method the advantage of spatial-temporal processing for the purpose of GNSS spoofing mitigation is studied. A new mitigation approach, which removes the spoofing signal LOS component as well as its multipath reflections before the despreading process of GNSS signals, is introduced. This in turn decreases the computational complexity and processing time. Therefore, this method can be either employed as an inline standalone pre-processing unit for conventional GNSS receivers or it could easily be integrated in the next generation of receivers. Several simulations and real data analyses are used to evaluate and show the effectiveness of the proposed methods.