Nabil Jardak

Short Multipath Insensitive Code Loop Discriminator

It is well known that one of the most significant errors in GPS pseudo-range measurement is the multipath error. Many researchers have been involved in this major issue, and promising results have been achieved in mitigating multipath errors. Most of these studies, however, do not really improve the tracking error in presence of short multipath. A novel code loop discriminator, which is insensitive to multipath signals having a relative delay lower than one half the correlator spacing is addressed here. The benefit of this discriminator, called short-multipath insensitive code loop discriminator (SMICLD), has been evaluated theoretically and implemented using MatLab/Simulink. The proposed method requires neither hardware nor software complexity. The novel loop tracking error, as well as the narrow correlator (NC) tracking error, were determined and compared. Simulation results showed that the proposed code discriminator outperforms the narrow correlator discriminator in terms of simplicity and performance.

Multipath Insensitive Delay Lock Loop in GNSS Receivers

The code measurement suffers from multiple error sources and especially multipath. The latter is unpredictable and changes in space and over time. Many interesting multipath mitigation techniques have been proposed. Most of them are not sufficiently effective for precise positioning using the code measurement. This paper presents a multipath insensitive delay lock loop that aims to improve the pseudorange measurement precision in the presence of multipath. This code loop is simple and does not require postprocessing of observables. Simulation and real implementation results showed that the proposed code loop dramatically improves the tracking error due to multipaths. Tracking error is limited to 1 m on pseudorange in typical multipath environments. This loop is more sensitive than the standard delay lock loop to thermal noise and applies predominantly to strong GNSS signals.