Exploring spatial diversity techniques for future broadband multicarrier mobile radio systems

Abstract — In this paper, we investigate broadband OFDM systems which apply beamforming in combination with different space–time diversity techniques. Various beamforming scenarios with transmitter and/or receiver sided beamforming are considered. Space–time diversity is obtained by cyclic delay diversity (CDD) in order to artificially shape the spectrum of the received signal. Thus, an advantageous distribution of the errors before a Viterbi channel decoder is obtained. Simulation results for the bit error rate performance are presented and compared for OFDM systems applying different beamforming scenarios and CDD in a Rayleigh fading channel. Maximum ratio combining (MRC) of the signals received on multiple beams/antennas and inter-carrierinterference (ICI) is also taken into account in the performance analysis. I

Implicit Cooperative Positioning in Vehicular Networks

Absolute positioning of vehicles is based on Global Navigation Satellite Systems (GNSS) combined with on-board sensors and high-resolution maps. In Cooperative Intelligent Transportation Systems (C-ITS), the positioning performance can be augmented by means of vehicular networks that enable vehicles to share location-related information. This paper presents an Implicit Cooperative Positioning (ICP) algorithm that exploits the Vehicle-to-Vehicle (V2V) connectivity in an innovative manner, avoiding the use of explicit V2V measurements such as ranging. In the ICP approach, vehicles jointly localize non-cooperative physical features (such as people, traffic lights or inactive cars) in the surrounding areas, and use them as common noisy reference points to refine their location estimates. Information on sensed features are fused through V2V links by a consensus procedure, nested within a message passing algorithm, to enhance the vehicle localization accuracy. As positioning does not rely on explicit ranging information between vehicles, the proposed ICP method is amenable to implementation with off-the-shelf vehicular communication hardware. The localization algorithm is validated in different traffic scenarios, including a crossroad area with heterogeneous conditions in terms of feature density and V2V connectivity, as well as a real urban area by using Simulation of Urban MObility (SUMO) for traffic data generation. Performance results show that the proposed ICP method can significantly improve the vehicle location accuracy compared to the stand-alone GNSS, especially in harsh environments, such as in urban canyons, where the GNSS signal is highly degraded or denied.Comment: 15 pages, 10 figures, in review, 201

The 5G Localisation Waveform

Todays cellular networks have distinct services that come with different requirements, figures of merit, etc. for each application. A communication service such as voice communication relies on latency better than 150 ms and bit error rates lower than 1

Location-Aware Formation Control in Swarm Navigation

Goal-seeking and information-seeking are canonical problems in mobile agent swarms. We study the problem of collaborative goal-approaching under uncertain agent position information. We propose a framework that establishes location-aware formations, resulting in a controller that accounts for agent position uncertainty with a realistic ranging model. Simulation results confirm that, as the outcome of the controller, the swarm moves towards its goal, while emerging formations conducive to high-quality localization

Waveform Parameter Selection for ITS Positioning

In this paper, we investigate the performance of mobile vehicle positioning based on signal propagation delay estimation in the uplink case for a realistic propagation environment. In order to optimize the ranging performance, we introduce a parametric waveform. This waveform contains a scalar parameter for adjusting the distribution of the available signal power over the frequency. The optimization is achieved by a functional dependency between the waveform parameter and the positioning error. In order to derive a cost function, we combine the approaches of the Cramér-Rao and Ziv-Zakai bounds for position and propagation delay estimation. As an exemplary environment we consider a mobile vehicle located in an area surrounded by three base stations together with realistic propagation conditions provided by the WINNER II channel model. The results show that the waveform parameter has to be adjusted differently compared to a simple free space propagation scenario. Additionally, we compare the obtained results with a scenario with four base stations and a scenario where we use the WINNER II channel model in terms of line-of-sight received power and shadow fading to classify the effects of geometry and propagation conditions

On the Positioning Performance of VDES R-Mode

Ships nowadays greatly rely on Global Navigation Satellite Systems (GNSSs) in order to deter- mine their position. Since GNSS outages or jamming events do occur, there are efforts to reduce the dependency on GNSS for maritime navigation. One such effort is called R-Mode (Ranging Mode), and focuses on complementing maritime communication systems by a ranging compo- nent to enable a vessel to determine its position. One of the systems to be extended by R-Mode is the VHF Data Exchange System (VDES). The VDES communication system is currently in standardization and offers 100 kHz of bandwidth in the maritime VHF band. It utilizes sin- gle carrier modulation with pi/4-QPSK. The proposed R-Mode extension works by sending a precisely timed known data sequence, so that time of arrival estimation allows determination of the range. Using software defined radios (SDR), we implemented a test setup for VDES R-Mode with three base stations on land and one receiver located on a vessel. Using this setup, we performed the first VDES R-Mode positioning trials on the Lake Ammer in Germany. By determining the time of the arrival as well as the Doppler shift of the received signals we tracked the vessels position with an Unscented Kalman Filter. The positioning accuracy performance ranged to up to 22 m under favourable conditions. Crucial was the consideration of the Doppler measurements to enhance tracking performance considerably

VDES R-Mode Performance Analysis and Experimental Results

Global Navigation Satellite Systems (GNSS) have become an essential part of maritime navigation, in particular to improve situational awareness and vessel traffic management. The dependence on GNSS creates vulnerability for maritime shipping. Driven by this vulnerability, the desire for a backup system for maritime navigation has been emerging. The VHF Data Exchange System (VDES) standard provides communication capabilities for maritime applications. VDES is currently being revised. As part of this revision, VDES will be extended by ranging and navigation functionalities, called R-Mode, as an alternative for maritime navigation. In this paper, we address system design aspects and evaluate the positioning performance of VDES R-Mode. We derive estimation theory bounds on the accuracy of VDES R-Mode distance and velocity. In a case study, we discuss and evaluate the benefit of satellite links to complement VDES R-Mode positioning. Furthermore, we introduce a Kalman filter for position and velocity tracking, which we apply to experimental data. We describe an experiment we conducted at Lake Ammer, southwest of Munich, and evaluate the VDES R-Mode positioning performance for this setup. Our experimental results show that VDES R-Mode is capable of achieving a 95th-percentile horizontal position error of 22?m. Thus, VDES R-Mode is a promising approach for a maritime backup system that can meet the IALA accuracy requirements

Direct Position Estimation for VDES R-Mode

As maritime traffic strongly relies on Global Navigation Satellite Systems (GNSS) such as GPS or Galileo, there are efforts to mitigate the risks that come with this reliance. One such effort is the development of VDES R-Mode, which aims to provide a terrestrial contingency system to GNSS that is based on the VHF Data Exchange System (VDES). Terrestrial VDES provides a bandwidth of 100 kHz. To make best use of the available bandwidth, VDES R-Mode can use a signal that is optimized for a high effective bandwidth. This signal however, has a very regular structure that leads to ambiguities that degrade the ranging performance at lower SNRs. We found that this drawback can be mitigated by evaluating the signals of multiple base stations jointly in a direct position estimation approach. To assess the improvement, we applied the Ziv-Zakai Bound and performed simulations. We found that using the direct position estimation approach can significantly lower the SNR at which it is still possible to resolve the ambiguities caused by the regular signal structure