Recent advancements in perception for autonomous driving are driven by deep learning. In order to achieve robust and accurate scene understanding, autonomous vehicles are usually equipped with different sensors (e.g. cameras, LiDARs, Radars), and multiple sensing modalities can be fused to exploit their complementary properties. In this context, many methods have been proposed for deep multi-modal perception problems. However, there is no general guideline for network architecture design, and questions of “what to fuse”, “when to fuse”, and “how to fuse” remain open. This review paper attempts to systematically summarize methodologies and discuss challenges for deep multi-modal object detection and semantic segmentation in autonomous driving. To this end, we first provide an overview of on-board sensors on test vehicles, open datasets, and background information for object detection and semantic segmentation in autonomous driving research. We then summarize the fusion methodologies and discuss challenges and open questions. In the appendix, we provide tables that summarize topics and methods. We also provide an interactive online platform to navigate each reference: https://boschresearch.github.io/multimodalperception/.

Deep Learning methods are widely applied in Robotics and Automated Driving scenarios. The task of perception for Automated Driving in the real world is particularly challenging and requires a sufficient amount of high quality labeled training data for the algorithms to perform well. However, the means of obtaining real world datasets are limited. It is common practice to have human labelers involved at least to some extent. Regardless of whether the process is partially automated or not, these labels never represent perfectly accurate ground-truth. By investigating the recognition performance of a state-of-the-art object detector as a function of the quality of a labeled real world training set, we study the effect of labeling errors of various types and severity. To this end, the given labels are treated as a reference to which synthetic errors are added systematically in order to determine the performance of the object detector if trained on the erroneous dataset.

Autonomous driving will significantly shape the near future of transportation that requires the distinct knowledge of the driving environment, especially the lane boundaries ahead of the vehicle. For this sensing task, optical and automotive radar sensors are mostly applied, while the radar sensor is less sensitive to non-ideal illumination conditions. Road boundaries can be detected by radar sensors through objects like guardrails, delineators, road curbs, and so on. However, in a multi-lane roadway or with missing roadside infrastructure, the adjacent lanes and the road boundary also have to be recognized by the radar sensors. This makes it necessary to integrate appropriate radar reflectors into the lane or road boundaries. Such reflectors, when integrated in the road, should not harm the vehicle tires, so their height shall be low, but they still have to be able to reflect the radar signals properly. Conventional road markings can be accordingly adjusted with such reflectors to support vehicle guidance with radar sensors. In this paper, the scattering property of various types of reflectors is evaluated by simulations over a wide angular and range geometry. The simulation results are analyzed with regard to the view angle influence on the radar cross section. Then, the specimen measurement results will be presented and finally the clustering process will be introduced.

The first radar has been patented 110 years ago. Meanwhile the applications became numerous and the system concepts have been adopted to the available technologies. Typical applications are speed control, air traffic control, synthetic aperture radar, airborne and spaceborne missions, military applications and remote sensing. Research for medical radar applications is well progressing for breast cancer detection and tumor localization. Automobile radar for save and autonomous driving are meanwhile produced in millions per year. In the next years the state-of-the-art radar system concepts will experience almost a revolution. Despite the significant advancements, the radar system technology did not develop like communications or other technologies during the last 20 years. Some of these new technologies will within a few years penetrate radar and revolutionize radar system concepts. This will then allow for new radar features and radar signal processing approaches.

In this paper, we introduce a novel multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) concept for multimodal operation. The proposed system employs waveforms based on the orthogonal frequency division multiplexing (OFDM) technique and digital beamforming (DBF) on receive. Thereby, it becomes feasible to maximize spatial degrees of freedom, which are necessary for the multimodal operation. The proposed MIMO SAR system produces multiple high-resolution wide-swath SAR imageries that are used for coherent postprocessing. Through this paper, we aim to open up a new perspective of using MIMO concept for a wide-swath SAR imaging with high resolution in interferometric and polarimetric modes, based on OFDM and DBF techniques. Therefore, this paper encompasses broad theoretical backgrounds and general system design issues as well as specific signal processing techniques and aspects.

In this letter, we present a new waveform technique for the use of multiple transmitters in synthetic aperture radar (SAR) data acquisition. This approach is based on the principle of the orthogonal-frequency-division-multiplexing technique. Unlike multiple subband approaches, the proposed scheme allows the generation of multiple orthogonal waveforms on common spectral support and thereby enables to exploit the full bandwidth for each waveform. This letter introduces the modulation and the demodulation processing in regard to typical spaceborne SAR receive signals. The proposed processing techniques are verified by a simulation for the case of pointlike targets.

Since the U.S. Federal Communications Commission (FCC) opened the spectrum from 3.1 to 10.6 GHz for unlicensed radio applications with an EIRP of up to 41.3 dBm/MHz, numerous papers have been published on ultrawideband (UWB) antennas. Often the goal in these publications is to present an antenna, which has a satisfactory input reflection coefficient and a reasonable, constant radiation diagram versus frequency. However, in the case of UWB, there are numerous additional critical characteristics, which must be considered in the proper wireless system design. The publications, which treat this topic with sufficient proficiency, use such quantities as transient gain, group delay, ringing, dispersion, signal fidelity, polarization, efficiency, and the peak value of the transient response. For practical applications based on signals with an UWB instantaneous bandwidth occupation, all criteria are of vital importance, because they determine the sensor resolution, accuracy, or increase the bit error rate in communications systems. This paper gives an overview of UWB antenna designs together with their suitability for different applications with respect to the aforementioned critical characteristics. Additionally, UWB antenna array design, polarization diversity, and application in body area network (BAN) will be discussed. In nearly all cases the time-domain characteristics are taken into account, as they are more intuitive to interpret and very convenient for time-domain UWB system design.

Since traditional radar signals are “unintelligent,” regarding the amount of information they convey on the bandwidth they occupy, a joint radar and wireless communication system would constitute a unique platform for future intelligent transportation networks effecting the essential tasks of environmental sensing and the allocation of ad-hoc communication links, in terms of both spectrum efficiency and cost-effectiveness. In this paper, approaches to the design of intelligent waveforms, that are suitable for simultaneously performing both data transmission and radar sensing, are proposed. The approach is based on classical phase-coded waveforms utilized in wireless communications. In particular, requirements that allow for employing such signals for radar measurements with high dynamic range are investigated. Also, a variety of possible radar processing algorithms are discussed. Moreover, the applicability of multiple antenna techniques for direction-of-arrival estimation is considered. In addition to theoretical considerations, the paper presents system simulations and measurement results of complete “RadCom” systems, demonstrating the practical feasibility of integrated communications and radar applications.

The 2009 IEEE Geoscience and Remote Sensing Society's (GRS-S) Awards were presented at IGARSS 2009. These awards included Fellow Recognitions, Major Awards, Publication Awards, and Certificates of Recognition. Those presented with awards are listed here.

Vehicle-to-vehicle (V2V) or vehicle-to-infrastructure (V2I) communications are enabling technologies for a host of applications, ranging from infotainment and web browsing to cooperative driving for enhanced traffic safety and efficiency. The latter two application areas, traffic safety and efficiency, address the issue of sustainable mobility and are high on the political agendas around the world.

In this paper the possibility of designing an OFDM system for simultaneous radar and communications operations is discussed. A novel approach to OFDM radar processing is introduced that overcomes the typical drawbacks of correlation based processing. A suitable OFDM system parameterization for operation at 24 GHz is derived that fulfills the requirements for both applications. The operability of the proposed system concept is verified with MatLab simulations.

Basic principles for ultra-wide-band (UWB) radiation are presented and discussed in this paper. The discussion starts with a description of the influence of antennas on UWB transmission. The parameters characterizing antennas in time and in frequency domain are specified. Since the number of possible antenna structures is nearly unlimited, the focus will be on a classification according to different radiation principles. For each of these mechanisms, the typical advantages and disadvantages are discussed, and an example antenna and its characteristics are presented. For a wireless engineer, the problem to solve is the proper design of an antenna with the desired radiation characteristics. The final outcome of this paper is that there exist numbers of UWB antennas, but not each of them is suited for any application, especially in view of radar and communication systems requirements.

The 2008 IEEE Geoscience and Remote Sensing Society's (GRS-S's) Awards were presented at the International Geoscience and Remote Sensing Symposium (IGARSS) 2008. These included IEEE Fellow Recognition; GRS-S Distinguished Achievement Award; GRS-S Outstanding Service Award; GRS-S Education Award; IEEE Electromagnetics Award; several Publication Awards and two Certificates of Recognition.

Present paper aims to critically analyze and study the SAR interferometric RADARSAT-1 data for land subsidence monitoring system for New Orleans USA, using Differential SAR Interferometry (D-InSAR) approach. In Louisiana, areas along the coast are sinking as much as one inch a year, and New Orleans is among the worst affected area due to land subsidence. For mapping subsidence, 84 complex data sets from April 15, 2002 to March 15, 2007 were available. Out of this, we have chosen six sets of suitable differential interferometric pairs with approximately one year of temporal span and six interferometric pairs to provide DEM generation for the above differential pairs. In this paper, change detection due to surface deformation is identified using D-InSAR methodology and is compared with classical change detection approach using MRD (mean ratio detector). Results show that subsidence was widespread throughout New Orleans, with maximum subsidence near MRGO canal in period of March 01, 2005 to April 1, 2006.

In this paper, we introduce an innovative system concept for synthetic aperture radar (SAR) and investigate the performance. Based on multiple-input multiple-output (MIMO) configuration, a versatile SAR operation can be feasible, for instance interferometric and full polarimetric SAR operation over a wide area simultaneously. For this purpose the space-time coding (STC) and digital beamforming (DBF) are key elements of the proposed MIMO SAR concept. A waveform diversity gain is obtained from the STC scheme, applied on transmit and DBF on receive provides array gain and improved noise performance for each multiple SAR images. In this paper, using a simple transmit diversity technique, well known as Alamouti scheme, the complete processing topology is introduced. The performance is investigated from a system point of view.

In this paper, we present the experimental results of a Digital Beam Forming (DBF) Synthetic Aperture Radar (SAR) performance on the purpose of the High-Resolution Wide-Swath (HRWS) SAR concept. A ground-based SAR system successfully demonstrated the DBF SAR operation. The demonstrator acquired SAR raw data with very dense spatial sampling rate in order to obtain various sampling rates. We evaluate DBF performance with respect to the image quality factor with two different types of the beam former, a fixed-beam former and an adaptive beam former. The results show that an adaptive DBF algorithm offers a wide range of the selection of the pulse repetition frequency (PRF). In addition we evaluate the noise performance compared to a reference mono-static SAR system on the same condition on single target experiment.

Digital Beamforming (DBF) technique is a promising technique for future Synthetic Aperture Radar (SAR). In this paper, we present the preliminary experiment and results. The measurements were accomplished by a ground-based DBF SAR system for a single target. The system is evaluated by mono-static SAR operation first. Comparing between DBF SAR and mono-static SAR images the channel imbalance effect is investigated. Since the experiment provides the SAR raw data containing the system response, from this raw data we estimate the linear phase error due to the channel imbalance and compensate it. The reconstructed DBF SAR images show that the minimum variation of the phase between the receive channel is crucial to obtain the theoretical improvement factor.

This paper describes the development and system concept for an active and highly integrated, digitally controlled SAR system calibrator. For precise and high-quality SAR data, precise ground targets are necessary for external calibration of the SAR data. Compared to passive targets, active radar targets like transponders offer more features. The recording of the transmitted radar signals from the satellite becomes possible and allows additional data analysis and data correction. A total of 18 active transponder and receiver systems and 16 receiver only systems were fabricated for the TerraSAR-X calibration campaign in summer 2007 [1], [2], [3]. TerraSAR-X is the first German spaceborne X-band SAR satellite mission.

High-Resolution Wide-Swath (HRWS) Synthetic Aperture Radar (SAR) is a multi-static spaceborne Radar. The performance of the Radar system is improved by the mean of DBF on receive in azimuth and in elevation. This requires an relieve antenna array with large number of elements. In this paper the performance of large antenna array under the influence of plane distortions is analyzed. Presented is the influence on the array factor of symmetrical, unsymmetrical and random mechnical distortion. The paper considers also the influence on the performance of the antenna distortion on the High-Resolution Wide-Swath (HRWS) Synthetic Aperture Radar (SAR) in elevation.

MERIT is a research-oriented Joint European Master on Information and Communication Technologies funded by the Erasmus Mundus program of the European Community. Its well funded scholarship scheme offers an outstanding opportunity for students, professors and researchers from non-European countries to participate in education programs (e.g remote sensing) in Europe.

For the design of an OFDM train communications system it is essential to characterise and consider the channel parameters. The transmission channel of a high-speed train scenario is frequency selective as well as time variant. Thus, delay spread and Doppler spread are investigated as crucial parameters for the OFDM system performance. Using a ray-tracing tool realistic impulse responses of the transmission channels are simulated. The investigated system includes three base stations operating in common frequency mode along a railway track and one mobile station situated on a high-speed train. For the mobile station different antenna patterns are included in the simulation model. The results are compared and assessed with respect to delay spread, Doppler spread and receive power. When using directional antennas a distinct reduction in Doppler spread is achieved.

The factorization method (FM) has been applied to measurement data from a multistatic ground-penetrating radar operating in close proximity to the ground, which was used in a measurement campaign on the Joint Research Centre mine test lane in Ispra, Italy. This paper is targeted toward a future hand-held demining system. The according space limits restrict an independent positioning of transmit and receive antennas. Hence, very small multistatic datasets are obtained, representing a difficult case for the reconstruction with the FM

Presents the winners of the 2006 IEEE Geoscience and Remote Sensing Society's (GRS-S) Awards, including the IEEE Fellow Awards, the Distinguished Achievement Award, the Outstanding Service Award, the Education Award, and five Paper Awards.

This paper describes the development and system concept for an active and highly integrated, digitally controlled SAR system calibrator. For precise and high-quality SAR data, precise ground targets are necessary for external calibration of the SAR data. Compared to passive targets, active radar targets like transponders offer more features. The recording of the transmitted radar signals from the satellite becomes possible and allows additional data analysis and data correction. A total of 18 active transponder and receiver systems and 16 receiver only systems will be fabricated for the TerraSAR-X calibration campaign in fall 2006.

In conventional SAR system high azimuth resolution and wide swath width are parameters that can not be improved simultaneously. A High-Resolution Wide-Swath (HRWS) Synthetic Aperture Radar (SAR) system was design to reconcile those two contradictory requirements. In the paper presented is a simulation of the HRWS SAR system including some of possible system failures and nonidealities of system components. The goal of the simulation is the evaluation of the influence of distortions and failures and prediction of the systems performance in elevation.

The aim of this paper is to compare the performance of different smart antenna algorithms to the performance of a conventional SISO reference system in an urban multi-user MIMO scenario. A single cell with three 120 deg sectors and several moving users is used for evaluation. The scenario as well as the channel information is generated by means of a realistic urban channel model that consists of a model of the city of Karlsruhe, a mobility model and an accurate ray-tracing based wave propagation model. The smart antenna algorithms under test are two single-user MIMO algorithms (user specific beamforming, waterfilling) and two multi-user MIMO algorithms (block diagonalization, successive optimization). Simulation results show clearly the potential of downlink spatial-multiplexing to improve the system capacity, to reduce the exposure, the transmit power and therefore also the operating costs in future cellular mobile radio systems

3D ray-tracing has meanwhile advanced to a performance that it can provide channel parameters such as delay spread, Doppler spread, angular spread, distribution functions of long- and short-term fading with high accuracy for fixed to mobile and mobile to mobile communications. These parameters are absolutely required during the specification phase in order to define the air interface and a variety of other relevant system parameters. This paper shows state of the art 3D ray-tracing capabilities. The 3D ray-tracing model developed at the University of Karlsruhe is described and verified with wide-band non-directional and directional measurements at 2 GHz and 5.2 GHz respectively, showing a good agreement. The proposed 3D ray-tracing model can therefore be used in order to extract parameter sets for the specification of future mobile communications systems and to optimize existing ones

In this paper the performance of user specific beamforming, waterfilling, block diagonalization, and successive optimization is compared to the performance of a conventional SISO reference system in a single cell with a sectorized BS and several MTs. Whereas in the SISO reference system as well as in the beamforming and waterfilling algorithm the MTs are multiplexed by a conventional multiplexing method (TDMA, FDMA, CDMA) the two multi-user MIMO algorithms allow users to share the same spectrum by multiplexing them in space. Several multi-user scenarios are generated by means of a realistic urban channel model. The channel model incorporates a model of the city of Karlsruhe, a mobility model as well as a ray-tracing based wave propagation model. Simulation results show clearly the potential of downlink spatial-multiplexing to improve the system capacity, to reduce the exposure (power density) and to reduce the transmit power and therefore the operating costs in future cellular mobile radio systems.

The characteristics of propagation channels between high-speed trains and fixed base stations for multimedia communications links using orthogonal frequency division multiplexing (OFDM) is investigated. To model the system behaviour realistically, impulse responses of the transmission channels are generated by a ray-tracing tool. Typical environments along a railway track are taken into account as well as the train motion. Mobile station antennas with different patterns are included in the simulation model and the results are compared and assessed with respect to characteristic channel parameters.

In multiple input multiple output (MIMO) communication systems, multiple radio frequency (RF) chains are required at both transmit and receive side of the link, each corresponding to one antenna. Mutual coupling effects may occur not only at the antennas, but also among the RF chains integrated on a single chip. At the receive side, inter-chain coupling leads to a degradation of the receive signal power and a generation of correlated noise. The impact of these effects on bit error rate (BER) performance in space-time block coded MIMO systems is calculated analytically. Further on, design considerations are discussed.

This paper presents a framework including both digital signal processing and the analog RF part of the system. A MIMO OFDM system with various numbers of antennas at transmit and receive is investigated in a fast-fading urban environment. The hybrid framework is applied to assess performance degradation due to impairments in the RF part, e.g. fading, nonlinear high power amplifiers, phase noise and frequency offset of local oscillators. It is shown that bit error performance is affected most by distortion due to frequency offset of the local oscillator in the receive front-end. A simple frequency estimator designed for single antenna OFDM systems can be adopted to the MIMO case as it stands to combat for frequency offsets.

In this paper simulation results of the multiuser MIMO broadcast channel are presented. The MIMO broadcast channel corresponds to the downlink case where the base station sends simultaneously different information to several users in the cell. In contrast to many information theoretical studies, the presented results are based on a realistic MIMO channel model and are therefore a first step towards realistic performance evaluations. The channel model is called multiuser double-directional channel model (MDDCM) and was introduced recently in T. Fugen et al., (2004). It is based on a geometry approach with fixed scatterers. It enables a realistic description of the desired link as well as the spatially-colored interference in a macro-cellular environment. Based on the MDDCM the sum capacity of the MIMO broadcast channel for a varying number of users and varying antenna configurations in an isolated communication cell is presented. To achieve the sum capacity the duality to the MIMO multiple access channels is used

We appreciate that authors Kerr et al. concur that our paper [ibid., vol.42, no.7, p.1387-98 (2004)] provides the right approach to the analysis of potential interference from anthropogenic sources to remote sensing satellites. The potential for such interference is likely to grow as new active systems are developed, necessitating acceptable procedures for interference analysis based on accepted scientific knowledge and engineering principles. While some simple clarifications are in order to improve the acceptability of our procedure, we suggest, however, that Kerr et al. have not studied our paper in detail and misinterpret several points.

This paper deals with the investigation of MIMO (multiple input multiple output) systems on a system level, including interference. The interference affects the capacity of each user and depends on the spatial characteristics of the propagation channel. It is spatially-colored. A necessary step towards a realistic performance evaluation is to include interference into the channel modelling process. A new multiuser double-directional channel model (MDDCM), that enables a correct interference description, is presented in this paper. It is based on a distributed scatterer approach and includes line-of-sight areas, far clusters and new models for street guided and over-rooftop propagation. Simulation results of a cellular multiuser MIMO system for the downlink case, based on the MDDCM, are presented. With this tool, it becomes possible to evaluate the performance of multiuser MIMO systems under realistic propagation and interference conditions.

The automotive industry is currently considering the introduction of Short Range Radars operating near 24 GHz for improving road traffic safety. Short Range Radars are intended to observe the full azimuthal space cover around a vehicle using up to eight sensors. The sensors would operate in an ultra wideband (UWB) mode, occupying 3 to 5 GHz of bandwidth. Interference from SRR transmitters with passive microwave remote sensing satellites could occur as the result of several coupling mechanisms, including direct coupling via the transmit antenna beam and scattering and diffraction of the transmitted signals from leading vehicles, buildings, and other nearby objects. In this study, we estimate the amount of coupling anticipated to occur from SRRs, including the direct and scattered contributions. The calculations are based on bistatic scattering measurements at of a typical automobile and ray optical simulations of reflection and propagation in an urban environment.

The IEEE Geoscience and Remote Sensing Society's Awards were presented at the IGARSS'03 banquet on Thursday, July 24 in the Hotel Dieu in Toulouse France. The GRS-S President Charles Luther, assisted by the Awards Committee Chairman Werner Wiesbeck, presented the awards. To promote excellence in research and service, each year the Geoscience and Remote Sensing Society of IEEE recognizes individuals among its members by bestowing IEEE certificates and awards.

The automotive industry is currently considering the introduction of short-range radars (SRR) operating near 24 GHz for improving road traffic safety. SSRs are intended to observe the full azimuthal space cover around a vehicle using up to eight sensors. The sensors would operate in an ultrawideband (UWB) mode, occupying 3-5 GHz of bandwidth. Interference from SRR transmitters with passive microwave remote sensing satellites used for weather and climate monitoring could occur as the result of several coupling mechanisms, including direct coupling via the transmit antenna beam and scattering and diffraction of the transmitted signals from leading vehicles, buildings, and other nearby objects. In this study, we estimate the amount of coupling anticipated to occur from SRRs, including the direct and scattered contributions. The calculations are based on bistatic scattering measurements of a typical automobile and ray optical simulations of reflection and propagation in an urban environment. Using these calculations, the maximum allowable SRR transmitted power for interference levels acceptable for meteorological and climatological remote sensing applications are quantified. The study provides criteria for SRR operation with the Earth Exploration Satellite Service on a noninterference basis.

The aim of this study is to assess the bare soil surface roughness parameter, i.e. the root mean square height (h/sub rms/) when the moisture is constant, using anechoic chamber measurements based on fully polarimetric scatterometer data. An incidence angle based algorithm has been proposed to assess the bare soil height h/sub rms/. For this purpose, sets of experimental backscattering data have been evaluated on different types of rough surfaces (Rough Gaussian, h/sub rms/ = 2.5 cm, Smooth Gaussian, h/sub rms/ = 0.4 cm and Medium Mixed surface, h/sub rms/ = 0.9 cm) with known geometrical and dielectric properties. The scattering matrix of those three surfaces under test was measured in monostatic mode vs. frequency ( 1 - 19 GHz) and incidence angles ( /spl theta/ = 10/spl deg/ to 50/spl deg/ in steps of 10/spl deg/ for h/sub rms/ = 2.5 cm and 0.9 cm and 5/spl deg/ for h/sub rms/ = 0.4 cm) data. An empirical relationship has been developed between backscattering, h/sub rms/ and incidence angle independently for L-, C-, X- and Ka-band for all polarizations (i.e. HH, VV and HV). This relationship provides the calculated backscattering values, which is helpful in the inversion process. A good agreement has been obtained between the observed and calculated h/sub rms/. The analyses show the strong dependence of h/sub rms/ on incidence angle, polarization and frequency. This type of work is also helpful in the near future to predict the optimum sensor parameters (i.e. incidence angle, polarization and frequency) for measuring the bare soil roughness.

The rapid progression in digital hardware and signal processing capabilities stimulates the development of radar systems. The tendency is to move the digital interface toward the antenna, replacing, whenever possible, analog RF-hardware. Based on software codes, these digital systems are more flexible and easier to reconfigure than RF-hardware. This letter illustrates the general concept for digital beamforming (DBF) in synthetic aperture radar systems and investigates their principle capabilities, limitations, and performance parameters. It is shown that using DBF a simultaneous improvement in azimuth coverage and resolution can be achieved.

This paper proposes multistatic measurements to increase the information content of ground penetrating radar data. Three different acquisition strategies are distinguished. To obtain measurement data, a flexible setup has been realized. Tomographic backpropagation and the nonlinearized factorization method are discussed with regard to their applicability to multistatic data.

The IEEE Geoscience and Remote Sensing Society (GRSS) Technical Committee on Frequency Allocation in Remote Sensing (FARS) is charged with providing recommendations and responses to queries on interference and frequency allocation issues in passive and active microwave remote sensing. In response to questions stemming from proposals to develop ultra-wideband (UWB) vehicular radar systems operating in the 22-27 GHz frequency range a technical assessment on the potential for radio frequency interference to passive Earth remote sensing activities was prepared. The study suggests that interference to the passive services at power levels several orders of magnitude above threshold levels is likely from commercial deployment of vehicular UWB radar and telecommunications systems.

Cryosat is an approved ESA mission. Its objective is to determine fluctuations in the Earth's land mass and marine ice fields. The mission utilizes a completely new SAR/interferometric altimeter concept, which combines a nadir-looking configuration with pulse-limited altimetry. The concept has been verified by simulations, but no dedicated experimental validation has been performed so far. For this reason, an Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) is currently under development in the frame of an ESA contract. Due to the large bandwidth of the system, several components, i.e. the chirp generator, are critical and therefore require innovative solutions. A dedicated software performs SAR- and interferometric radar data processing and, in addition, supports internal instrument calibration. ASIRAS is intended to be tested, verified and optimized on a DO 228/100 aircraft carrier during a measurement campaign scheduled fall 2002 in the area of Fram Street north of Greenland. The paper presents mission objectives, the instrument concept of ASIRAS, and critical building blocks.

The rapid progression in digital hardware systems and signal processing capabilities is increasingly advantageous for the development of radar systems. The trend is to move the digital hardware towards the antenna front-end replacing, whenever possible, RF-hardware. Based on software codes these digital systems are more flexible and easier to reconfigure than RF-hardware. This paper investigates capabilities and limitations of synthetic aperture radar systems utilising digital beamforming.

The performance of future wireless communication systems can be highly increased by utilizing multiple antennas at both sides of a wireless communication link. A concept for MIMO double directional wide-band channel measurements is presented and high-resolution channel parameter estimation is applied. Furthermore, a procedure, where MIMO capacities are obtained by one single SISO channel transfer function, is discussed. Finally, a ray-tracing tool is used for comparison.

The inter-vehicle transmission channel is characterised based on narrow-band measurements at 5.2 GHz. The measurement setup consists of a transmitter and a receiver, which are installed in two different vehicles. While measuring the transmission channel, both vehicles are manoeuvred in realistic road traffic scenarios. Measurements are obtained for four different classes of environments: urban, suburban (village), motorway and highway. Statistical functions, such as the cumulative distribution function (CDF) of the received signal, the average Doppler power density spectrum and the level crossing rate (LCR), are derived for each class. The measured results are compared to analytical functions, such as the Rice, the Rayleigh, the Gauss or the Nakagami distribution. The least squares and the conjugate gradient method are used to fit the parameters of the analytical functions to the measurement data.

A novel stochastic channel model for the indoor propagation channel is presented. It is especially for, but not limited to future communication systems with multiple antennas like space division multiple access (SDMA), spatial filtering for interference reduction (SFIR), or multiple-input/multiple-output (MIMO). The model is designed for indoor scenarios, straight forward extendable to urban environments. It is based on physical wave propagation. The new approach describes the channel by multipath components, each characterized by its transfer matrix (including loss), delay, direction of arrival, and departure. The appearance and disappearance of multipath components over time is modeled as a birth and death process, a marked Poisson process. This enables first-time the correct modeling of spatial and temporal correlations. In each modeling step, path properties change according to the motion of transmitter and receiver. The changing delay times of propagation paths yield a realistic Doppler behavior of the channel. Deterministic ray tracing results are used to produce the huge data sets required for the statistical evaluation of the parameters of the proposed model. This method enables an automated parameter extraction for new environments or frequencies. The ray tracing tool has been verified by narrowband, wideband, and directional channel measurements. The novel stochastic spatial channel model allows the simulation of third-generation broadband radio systems including arbitrary antenna configurations and patterns. System simulations for the bit-error rate of radio links can be performed including intelligent antenna configurations like SDMA, SFIR, or MIMO. Furthermore, the capacity of complete systems can be investigated.

A new method to include stochastic rough surface scattering into deterministic ray-optical wave propagation modelling is derived. It can be utilized in conjunction with the concept of ray launching. Similar to the Kirchhoff formulations, the approach is based on a tangential plane approximation, i.e. it is applicable to surfaces with gentle undulations, whose horizontal dimensions are large compared to the incident wavelength. However, in contrast to the Kirchhoff models, which are only valid for either slightly rough or very rough surfaces, the proposed stochastic scattering approach includes both the coherent and incoherent components at the same time. The purely deterministic ray-based modelling is expanded by a "stochastic" component, allowing for the first time to account for non-deterministic scattering in ray-optical wave propagation modelling.

The modelling of a realistic environment for road traffic scenarios is presented. The model serves as a basis for a new wave propagation tool for inter-vehicle communications. A proper modelling of the environment implies an accurate characterisation of the dynamic road traffic and a realistic description of the vehicle's vicinity. For an accurate model of dynamic road traffic and realistic driving behaviour, different individual characteristics of vehicles are taken into account. Characteristics such as desired velocity or safety margin are determined stochastically within certain limits. It is therefore possible to create complex traffic scenarios without the need of having detailed and extensive traffic data for selected roads. Additionally, the road surrounding is generated stochastically, depending on morphographic data. The result is a proper traffic scenario, which serves as input data for wave propagation calculations.

This paper considers automatic cell planning for mobile radio network design. The problem is how to determine the number of cells, the optimal cell sites and parameters in order to meet the system requirements while minimizing the costs involved, including the spectral cost and financial cost. Our solution consists of three parts. First, a fuzzy expert system is used to adjust the parameters of each cell. Second, an optimization strategy using the genetic algorithm is proposed to find the optimal cell sites. Furthermore, we develop an algorithm based on the technique of cell splitting to accommodate the traffic growth in an existing network.

A novel stochastic spatial propagation channel model for wide-band spread spectrum applications is presented. The model is set up for indoor scenarios, although in principle it can be extended easily to urban environments. Deterministic ray-tracing results are used to produce the huge data sets required for the statistical evaluation of the parameters of the proposed model. The approach for the stochastic model is based on physical wave-propagation, where the channel is described by multipath components including angles of arrival at the receiver and angles of transmission at the transmitter. In each modeling step, path properties change according to the movement of the radio stations (RSs). The appearance and disappearance of multipath components is modeled by a genetic process. Especially, changing delay times of the propagation paths yield a realistic Doppler behavior of the channel. A new approach to model the directions of multipath components in three dimensions has been developed. By relating the angles of arrival (or transmission) to the direct line between transmitter and receiver, a universal modeling approach, which is independent of the actual geometry, becomes possible. The novel stochastic spatial channel model allows the simulation of complex systems including arbitrary antenna configurations and patterns. A detailed description of the overall model is presented together with some initial simulation results.

A novel numerical algorithm based on the radiative transfer equation (RTE) is presented, which allows the calculation of the scattering and penetration of isolated vegetation specimens such as, e.g., single trees, bushes, etc., at mm-wave frequencies. For this purpose, the RTE is stated in a discrete form, and the vegetation structure is discretized in elementary volumes. A step-by-step solution is proposed to solve for the desired attenuation, and indications on the influence of the different parameters on the propagation characteristics are given. A qualitative justification to the approach is presented and finally, a comparison with scattering measurements of ficus trees at 75 GHz is shown.

A general procedure is developed for the analysis of electromagnetic (EM) scattering by multiple three-dimensional (3D) dielectric and/or conducting objects buried under one-dimensional (1D) multilayered media. In this first part of a two-part paper, general closed-form formulations for the electric fields excited by an arbitrarily oriented electric dipole under the layered media are first presented, from which electric-field integral equations for the buried dielectric objects, pure conducting objects, and their combinations are then obtained, and the scattered electric fields in the upper space are formulated. Finally, the physical significance of the above formulations is discussed. In the second part, numerical implementations for these integral equations and the scattered fields are investigated.

For pt.I see ibid., vol.36, no.2, p.526-34 (1998). In part I of this paper, coupled electric-field integral equations for dielectric objects, conducting objects, and multiple dielectric and/or conducting objects were derived when they were buried under one-dimensional (1D) multilayered media. In part II of this paper, numerical implementations for these integral equations are developed by use of the method of moments, in which the "self-actions" in the method are treated special because of the presence of singularity. Sample numerical results are presented for several cases of interest, which show the validity of the scheme.

In this paper the modeling of the street canyon effect in urban wave propagation is investigated. Multiple diffracted signal paths can be calculated using a simple ray tracer. However, significant power is also transmitted by a combination of wall reflection and wedge diffraction. This paper introduces a new deterministic algorithm which is able to calculate such paths using imaging techniques. Emphasis is put on the efforts made to reduce the problem's complexity since a straight forward application would suffer from enormous computing time and memory requirements. Comparisons with DCS1800 measurements show notable improvements of the field strength prediction.

This paper presents a ray optical approach for the three-dimensional modeling of wave propagation in urban areas. The "IHE-URBAN-MICRO" model has been developed for the fully polarimetric prediction of field-strength levels and channel impulse responses in the frequency range from 300 MHz up to 3 GHz. It can handle both, base station antenna heights above as well as below rooftop level. Terrain information in a grid data format with a resolution of about 5-10 m are required. A new, unsupervised search for dominant propagation paths within a vertical and a transverse propagation plane is introduced. Propagation simulations at 955 MHz in real urban environments are presented. A comparison with micro cell measurements shows a good agreement and verifies the new vertical and transverse propagation plane approach.

It is the purpose of this paper to present a deterministic approach for UHF/EHF outdoor and indoor propagation modeling in micro and pico cells. The approach takes into account multiple reflected and multiple wall-penetrated ray paths as well as combinations of multiple reflected/penetrated ray paths. Building walls are modeled as multi layered media with different material parameters. For micro and pico cells the important issue of building penetration from outdoors to indoors can be regarded as well as indoor propagation. This modeling approach results in an area wide prediction of path loss. Further on, the channel impulse response in magnitude, phase, delay, angle-of-departure, and angle-of-arrival is obtained for arbitrary selected receive locations. Simulation results are presented and a comparison with measurements is given.

A dual channel microwave Doppler-sensor-module for 24 GHz is presented. The microwave components like oscillator, mixer, antenna and their characteristics in the integrated MIC are discussed. The influence of the antenna pattern and the road surface is considered. A simulation of the system shows their influence on the Doppler spectra and the data evaluation.>

Network planning in mobile communications requires a realistic description of the propagation phenomena. Common wave propagation models for rural areas consider mainly the influence of topography. However, shadowing effects of the morphography in the vicinity of the mobile cause additional path loss. Usually this path loss is accounted for either by empirical corrections or by additional knife edges. In this paper new ray optical approaches for the calculation of the additional path loss for mobile locations within forested or urban environments are presented. For these situations typical macro situations are defined. In the case of urban environments the additional path loss is determined by means of the Uniform Theory of Diffraction whereas in forested areas a lateral wave propagation approach is used. The model is applied to an existing GSM-network. The results achieved by this model show good agreement with both wideband and narrowband measurements.>

Mobile communication links are severely influenced by propagation effects. Wave propagation in the VHF/UHF frequency range over natural and man-made terrain is strongly dependent on topography and morphography. Propagation modeling is based on a ray-optical approach. Wave interactions, like diffraction and scattering, over the propagation path are described by the uniform theory of diffraction (UTD) and physical optics (PO). Propagation models for rural and urban areas are presented for 2-D and 3-D ray tracing. Near-range models apply to the corresponding areas in forest and urban sites. The field-strength delay spectrum describes ray contributions with deterministic amplitudes but statistical phases are used to derive time-and frequency-domain channel characteristics. Comparisons between measured and predicted data are presented.>

The gain of different diversity techniques that reduce the effects of amplitude and phase fluctuations in radio transmission systems depends on the correlation between the signals in various diversity channels. This paper presents a new approach for the prediction of the envelope correlation coefficient which is the term of interest for combining techniques with phase synchronization. It is based on the results of a deterministic 3D wave propagation model and on the assumption of ergodicity.>

A calibration technique for laboratory type polarimetric, bistatic instrumentation radars is presented. It describes the errors induced by the standard radiation transfer approach (I-SRT) in a way similar to that for the monostatic case. A 12-term error correction and absolute polarimetric calibration is performed with two external reference targets. Only the polarimetric bistatic reference of the first target must be theoretically determined. The scattering reference of the second target is determined by a measurement during the calibration process (single reference calibration). The simulation of a third cross-polarization measurement is performed by an antenna rotation and a remeasurement of the second target. Thus all data are gained for the determination of the error terms and measurements of unknown objects can be full polarimetrically calibrated. The procedures are shown for an adapted dihedral corner reflector. Misalignment errors are discussed.>

The authors present a scheme for absolute calibration of a polarimetric scattering range. All free-space polarimetric radar cross section (RCS) and antenna measurements are subject to errors like coupling and residual reflections. The modeling of these errors results in a 12-term error correction. The procedure for the error correction with three linear independent calibration targets and an isolation measurement is shown. Based on network analysis, a single reference calibration is introduced. This single reference calibration requires the precise calculation of only one reference target. As single references, spheres or flat plates are used. The references of the other targets are determined by the calibration procedure. The single reference calibration is suitable for all narrow and wideband, complex, polarimetric RCS, and antenna measurements. Measurements are shown for different targets which demonstrate the benefits of the single reference calibration.>

Information about radar targets has to go beyond the scalar radar cross section (RCS) for target classification purposes. The necessary target information is constrained in the complex RCS matrix. The authors show the theoretical derivation of this matrix and of the related scattering matrix. Both matrices contain the target's complex RCS for arbitrary polarization. The mathematical procedures for basis transformation that is, the evaluation of influences of polarization, are given. Equipment for wide-band, coherent RCS measurements with calibration targets and a 20-term error correction algorithm is presented. Using the complex RCS matrix, polarimetric target signatures are derived and plotted for simple objects. The target classification is finally based on the polarimetric signatures and the characteristic parameters derived from them. The basis of these are measurements of relevant samples and target RCS modeling.>

Anomalous gating of asynchronous signals in synchronizers and arbiter circuits may cause significant errors and system failures. Since the probability of logically undefined states at the output of flip-flops increases rapidly with clock rate, the errors were reduced by lower frequencies, at the price of severe time loss, until now. The paper presents a J-K flip-flop in which the duration of an oscillatory or metastable behavior is reduced by a factor of 5 to 15. In this flip-flop the switching of two gates is accelerated by tunnel diodes.