Five different constant false alarm rate (CFAR) radar processing schemes are considered and their performances analyzed in homogeneous and nonhomogeneous backgrounds, the latter specifically being the multiple target environment and regions of clutter transitions. The average detection threshold for each of the CFAR schemes was computed to measure and compare the detection performance in homogeneous noise background. The exponential noise model was used for clear and clutter backgrounds to get closed-form expressions. The processor types compared are: the cell-averaging CFAR, the 'greatest of' CFAR, the 'smallest of' CFAR, the ordered-statistics CFAR, and a modified ordered-statistics processor called the trimmed-mean CFAR. >

Analysis of CFAR processors in homogeneous background

Automotive radars, along with other sensors such as lidar, (which stands for "light detection and ranging"), ultrasound, and cameras, form the backbone of self-driving cars and advanced driver assistant systems (ADASs). These technological advancements are enabled by extremely complex systems with a long signal processing path from radars/sensors to the controller. Automotive radar systems are responsible for the detection of objects and obstacles, their position, and speed relative to the vehicle. The development of signal processing techniques along with progress in the millimeter-wave (mm-wave) semiconductor technology plays a key role in automotive radar systems. Various signal processing techniques have been developed to provide better resolution and estimation performance in all measurement dimensions: range, azimuth-elevation angles, and velocity of the targets surrounding the vehicles. This article summarizes various aspects of automotive radar signal processing techniques, including waveform design, possible radar architectures, estimation algorithms, implementation complexity-resolution trade off, and adaptive processing for complex environments, as well as unique problems associated with automotive radars such as pedestrian detection. We believe that this review article will combine the several contributions scattered in the literature to serve as a primary starting point to new researchers and to give a bird's-eye view to the existing research community.

Automotive Radars: A review of signal processing techniques

Intervehicle communication (IVC) networks, a subclass of mobile ad hoc networks (MANETs), have no fixed infrastructure and instead rely on the nodes themselves to provide network functionality. However, due to mobility constraints, driver behavior, and high mobility, IVC networks exhibit characteristics that are dramatically different from many generic MANETs. This paper elicits these differences through simulations and mathematical models and then explores the impact of the differences on the IVC communication architecture, including important security implications.

Challenges of intervehicle ad hoc networks

There has been increasing interest in the exploitation of advances in information technology in surface transportation systems. One trend is to exploit on-board sensing, computing and communication capabilities in vehicles, e.g., to augment and enhance existing intelligent transportation systems. A natural approach is to use vehicle-to-vehicle communications to disseminate information. In this paper, we propose MDDV, a mobility-centric approach for data dissemination in vehicular networks designed to operate efficiently and reliably despite the highly mobile, partitioned nature of these networks. MDDV is designed to exploit vehicle mobility for data dissemination, and combines the idea of opportunistic forwarding, trajectory based forwarding and geographical forwarding. We develop a generic mobile computing approach for designing localized algorithms in vehicular networks. Vehicles perform local operations based on their own knowledge while they collectively achieve a global behavior. We evaluate the performance of the MDDV algorithm using realistic simulation of the vehicle traffic in Atlanta area.

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MDDV: a mobility-centric data dissemination algorithm for vehicular networks

This is a book review of 'The Micro-Doppler Effect in Radar' by V. C. Chen. Artech House, 16 Sussex Street, London, SW1V 4RW, UK. 2011. 290pp + diskette. Illustrated. £90. ISBN 978-1-60807-057-2.

'The Micro-Doppler Effect in Radar' by V.C. Chen

Radar detection procedures involve the comparison of the received signal amplitude to a threshold. In order to obtain a constant false-alarm rate (CFAR), an adaptive threshold must be applied reflecting the local clutter situation. The cell averaging approach, for example, is an adaptive procedure. A CFAR method is discussed using as the CFAR threshold one single value selected from the so-called ordered statistic (this method is fundamentally different from a rank statistic). This procedure has some advantages over cell averaging CFAR, especially in cases where more than one target is present within the reference window on which estimation of the local clutter situation is based, or where this reference window is crossing clutter edges.

Radar CFAR Thresholding in Clutter and Multiple Target Situations

The general requirement in the automotive radar application is to measure the target range R and radial velocity v
 r
 simultaneously and unambiguously with high accuracy and resolution even in multitarget situations, which is a matter of the appropriate waveform design. Based on a single continuous wave chirp transmit signal, target range R and radial velocity v
 r
 cannot be measured in an unambiguous way. Therefore a so-called multiple frequency shift keying (MFSK) transmit signal was developed, which is applied to measure target range and radial velocity separately and simultaneously. In this case the radar measurement is based on a frequency and additionally on a phase measurement, which suffers from a lower estimation accuracy compared with a pure frequency measurement. This MFSK waveform can therefore be improved and outperformed by a chirp sequences waveform. Each chirp signal has in this case very short time duration T
 chirp
. Therefore the measured beat frequency f
 B
 is dominated by target range R and is less influenced by the radial velocity v
 r
. The range and radial velocity estimation is based on two separate frequency measurements with high accuracy in both cases. Classical chirp sequence waveforms suffer from possible ambiguities in the velocity measurement. It is the objective of this paper to modify the classical chirp sequence to get an unambiguous velocity measurement even in multitarget situations.

New chirp sequence radar waveform

Conventional Traffic and Travel Information (TTI) systems are based on a centralized structure: Sensors deployed at the roadside monitor the traffic and transmit the results to a central unit, which performs a situation analysis. TTI is made available to the drivers via broadcast service (e.g. TMC/RDS) or on demand via cellular phone. In contrast to this centralized approach. a decentralized, Self-Organizing Traffic Information System (SOTIS) based on Inter-Vehicle Communication (IVC) has many advantages: It requires no expensive infrastructure. can provide detailed information for the local area with low delay and is available everywhere. In such an IVC based decentralized system, TTI is sensed by each individual vehicle. The information is analyzed, combined with TTI received from other vehicles and the results are distributed using recurring broadcast packets. In this paper; an adaptive broadcast scheme for efficient TTI distribution called Provoked Broadcast is presented. The algorithm favors the propagation of significant TTI changes within the self-organizing network. Nodes adapt their communication behavior to the local environment and avoid redundant transmissions. The performance of the proposed scheme is evaluated by using simulations of typical traffic scenarios. Compared to a strictly periodic broadcast, the new scheme decreases the average error of information available at an individual vehicle and still requires significantly less bandwidth.

Adaptive broadcast for travel and traffic information distribution based on inter-vehicle communication

Ad hoc networks provide data communication services without being bound to an existing infrastructure. An exciting application of highly dynamic ad hoc networks is the exchange of data between running vehicles. For air-interfaces based on a slotted time division multiple access (TDMA) scheme, slot synchronization is required among the rapidly moving vehicles. A scheme for completely decentralized slot synchronization of nodes in an inter-vehicle communication (IVC) environment is presented. To evaluate the performance of the proposed mechanism, the influence of real synchronization to the network throughput in case of a slotted ALOHA medium access protocol is investigated. Simulation results indicate only a minor throughput degradation compared to an ideal slot synchronization.

Decentralized slot synchronization in highly dynamic ad hoc networks

A method and arrangement for controlling a system of multiple traffic signals for regulating the traffic of vehicles is described. Traffic data is transmitted by wireless transmission to traffic data processing units assigned individually to a locally limited group of traffic signals, and each traffic data processing unit performs an analysis of the local traffic situation for the environment of the locally limited group of traffic signals up to, at the maximum, the neighboring locally limited groups of traffic signals.

Hermann Rohling

Papers

Radar CFAR Thresholding in Clutter and Multiple Target Situations

New chirp sequence radar waveform

Adaptive broadcast for travel and traffic information distribution based on inter-vehicle communication

Decentralized slot synchronization in highly dynamic ad hoc networks

Method and arrangement for controlling a system of multiple traffic signals