Location information is one of the most vital information required to achieve intelligence and context-awareness for Internet of Things applications such as driverless cars. However, related security and privacy threats are a major holdback. With increasing focus on the use global navigation satellite system (GNSS) for autonomous navigation and related applications, it is important to provide robust navigation solutions. Radio frequency interference, either intentional or unintentional, has a direct impact on GNSS navigation performance related to observability and accuracy. In terms of security, spoofing is the major issue of concern. This paper focuses on multiantenna GNSS and inertial navigation system (INS)-odometer integration to improve robustness, security, and privacy of navigation solutions. Multiantenna GNSS provides robustness against different interference sources and integration with INS provides continuous navigation solutions during short-term signal outages. Performance of the proposed architecture is evaluated using different user scenarios in the presence of spoofing and interference signals in real vehicular environments.

This special issue addresses various jammers and their effect on different processing stages and overall Global Navigation Satellite System (GNSS) receiver performance, and presents countermeasures and solutions to combat interference.

GNSS-dependent positioning, navigation, and timing synchronization procedures have a significant impact on everyday life. Thus, such an extensively used system progressively become an attractive target for illegal exploitation and attacks. Position and timing solutions provided by GNSS receivers can be threatened by structural interference such as spoofing threats. This paper provides an overview of recent research work on GNSS signal authentication utilizing spatial processing methods. Different spatial processing approaches for spoofing detection, classification and mitigation are characterized and compared. Three different processing methods, namely antenna array processing, moving receiver and cloud based spoofing countermeasure are analyzed in details. The benefits and disadvantages of each are discussed.

This paper describes a hybrid AOA/TODA mobile station (MS) location estimation method based on the CDMA wireless communications signals. The method utilized estimates the angle of arrival (AOA) and time difference of arrival (TDOA) of downlink pilot channel. In this paper, signal parameter estimations including AOA and TDOA, and position estimation challenges in real wireless communications systems are denoted. For position estimation, the mathematical model and its linearized model for a hybrid TDOA/AOA method based on the Taylor series expansion are derived. The performance analysis of the high-resolution MUSIC angle and double delta delay estimators using field measurements from a typical outdoor IS-95 CDMA radio propagation channel are demonstrated. In this paper, practical considerations on the implementation of a standalone positioning system are described. The performance of TDOA and hybrid AOA/TDOA positioning system when the receiver has access to minimum LOS signals are compared.

In this paper, a new method for AOA estimation, based on the synthetic ESPRIT algorithm is described and tested with actual CDMA signals. Physical size constraints of handheld devices typically exclude the possibility of using multiple antennas. To overcome this limitation, antenna array can be synthesized by physically moving a single antenna in an arbitrary trajectory while collecting a snapshot of the received signal. By taking advantage of the rotational invariance of the ESPRIT algorithm, antenna array can be synthesized by moving a single doublet without using controllable moving motors or external aiding sensors. This configuration can be installed in any translationally rotational moving platforms such as vehicles. With this configuration, system complexity reduces considerably. Experimental and field test results of AOA estimation of synthetic ESPRIT algorithm based on actual CDMA IS-95 signals represents applicability of proposed method.

The accuracy of time of arrival (TOA) measurements is significantly compromised due to the multipath components which coexist with the desired line of sight (LOS) components in the received signal. Effective mitigation of multipath is offered by using an antenna array with beamforming capabilities. However, arrays are physically large and unwieldy from a signal processing perspective and hence not suitable for a small handheld device. In this paper, a receiver consisting of a single antenna that is moved arbitrarily in space forming a synthetic antenna is considered. Blind calibration of the resultant spatial array is achieved through the use of fourth order cummulants. As demonstrated in this paper, a synthetic array, based on this blind calibration method can practically enhance the LOS signal by suppressing multipath through spatial filtering and thereby improve the TOA performance. Monte Carlo simulations are performed to demonstrate the performance of the proposed method.