Performance Assessment of Navigation Signals in Realistic Multipath Environments

Abstract

A major error source within global navigation satellite systems, such as the Global Positioning System or the future European satellite navigation system Galileo, comes from multipath, the reception of additional signal replica due to reflections caused by the receiver environment. The reception of multipath introduces a bias into the time delay estimate of the delay lock loop of a conventional navigation receiver, which finally leads to a bias in the receiver’s position estimate. To mitigate and to reduce the impact of multipath on navigation receivers, the problem is approached from several directions, including the development of novel signal processing techniques as well as the design of more robust navigation signals. In this context hardware simulator has become a valuable tool for the test, assessment and validation of novel algorithms, signals and receivers under controllable environments. To allow hardware tests under realistic propagation conditions it is required to implement complex channel models, such as the one introduced by the German Aerospace Center DLR in 2005, into the existing hardware simulators, which is today still and unsolved challenge, since the number of available hardware taps is usually much smaller than the number of coexistent rays of the original channel models. In this paper the impact of model reduction is studied, whereas two reduction techniques are considered. To take the evolution with respect to future navigation signals and receiver algorithms into account the analysis is carried for the BPSK, BOC(1,1), and CBOC signal, whereas three types of receiver signal processing algorithms are considered, including the Narrow correlator, a maximum likelihood estimator, and a Bayesian minimum mean square error estimator. The results confirm the benefits of novel navigation signals and advanced mitigation techniques and reveal that a model reduction could be possible with moderate errors.