Lateral distance measurement using optical spread spectrum radar

This paper deals with the application of spread spectrum techniques to MultiCarrier HF modems. OFDM modems are a special option for the transmission over the high dispersive HF medium in front of single carrier modems. Our present contribution is now focused on the application of Spread Spectrum techniques to improve its fading robustness. The transmission bandwidth is the standard voice band channel in the HF band where the spread spectrum characteristic means that one symbol is transmitted over N times the spectrum in the classical N-OFDM scheme. The motivation of this idea is the observation of the OFDM modems behaviour over fading channels with deep nulls showing a quite different performance between carriers: those in the vicinity of deep nulls provide a much higher Bit Error Rate (BER) than others far away of the nulls. Our proposal intends to spread different symbols over all the subcarriers simultaneously in order to homogenize performances. This approach, performed by orthogonal codes, shows an evident link with MC-CDMA techniques. In addition, Multi User Detection (MUD) strategies as Interference Cancellation (IC) with coherent detection are also applied in order to improve its performance.

Due to a world wide surge in the intelligent vehicle highway system (IVHS), the field of automatic vehicle identification (AVI) has been rapidly growing. The use of spread spectrum communications has not yet pervaded the AVI market. However, in the already cramped electromagnetic environment, spread spectrum techniques have gained significant popularity in many growing areas of wireless communication. AVI is perfectly suited to benefit. The fundamental advantage of spread spectrum technology in AVI applications is its invulnerability to interference and its ability to operate alongside narrow band communication systems already in place. The second advantage is the ease of licensing for spread spectrum AVI, since it does not require a dedicated frequency spectrum. It is also possible for several spread spectrum AVI systems to operate simultaneously in the vicinity of each other, using different spreading codes. This article concentrates on architecture as well as applied key signal processing techniques for a proposed direct sequence spread spectrum (DSSS) AVI system. A functional block diagram that outlines the major components of the system is presented. The system consists of three major functional parts: interrogator, transponder, and trigger. Free flow of traffic can be maintained only if the interrogator can isolate each vehicle in a common interrogation zone. DSSS allows this through code division multiple access (CDMA). The triggering system is based on the principles of speed enforcement radar. The proposed digital modulation scheme is BPSK. The DSSS modulator applies a Gold pseudo-random (PN) code to spread the spectrum of the binary signal. Despreading is carried out through the use of a PN matched filter. The antenna is assumed to have a 60/spl deg/ half-power radiation field and is placed on an existing overpass approximately 6 meters above the roadway. With 50 mW antenna transmit power, link budget analysis indicates that sufficient bit energy-to-noise power spectral density ratio is available at the receiver to generate an excellent bit error rate without requiring error control coding.

The status of plans and projects for intelligent vehicle-highway systems (IVHS) in Europe, Japan, and the US is examined. The four broad areas covered by IVHS are described. They are advanced traffic management systems. advanced traveler information systems commercial vehicle operations systems, and advanced vehicle control systems. A variety of projects in Europe, Japan, and the US which aim at proving the feasibility and practicality of IVHS are described. Socioeconomic factors then could delay or even arrest the development of IVHS are examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

&lt;div class="htmlview paragraph"&gt;The concept of the intelligent Vehicle/Highway System (IVHS) is a direct descendent of earlier work on “roadway automation”. Recent advances in a variety of technologies have now made automatic control of the operation of road vehicles a much more realistic proposition than it was even in the recent past. This paper begins by identifying three stages in the likely evolution of these advanced vehicle control systems (AVCS), showing how AVCS is related to the other IVHS functions. The technological elements of AVCS, corresponding to needed research and technology development work, are then described. The current international state of the art in these technologies is reviewed, and the paper concludes with a discussion of an evolutionary progression that could be followed to lead from present-day driving to the long-term concept of an automated freeway network.&lt;/div&gt;

Intelligent Vehicle/Highway Systems (IVHS) is a multi-year research/demonstration program which aims at improving the vehicle/highway system operation and management techniques for the post-interstate construction era. The authors first describe the framework of IVHS, which as four major components: (1) advanced traffic management system (ATMS); (2) advanced driver information system (ADIS); (3) commercial vehicle operations (CVO); and (4) advanced vehicle control systems (AVCS). The ATMS related research and development plans to support the real-time traffic management systems and control strategies are considered. The state-of-the-art traffic engineering modeling software is reviewed. The discussion centers around the TRAF system, a family of microscopic and macroscopic traffic simulation software models for surface streets, freeways, and corridor networks. The gap between the capabilities provided by the current traffic modeling software and the functional requirement of the IVHS traffic models is also addressed. >

This article presents two-dimensional (2-D) scattering centres' parameter estimation based on linear uniform multi-input multi-output (MIMO) radars. Unlike single-input single-output (SISO) radars, MIMO radars transmit multiple detection signals at the same time. We assume that each antenna of a MIMO radar transmits signals with a set of different spread spectrum codes so as to distinguish the echoes from all antennas. Then, with spread spectrum and de-spread spectrum techniques, each antenna of a MIMO radar could distinguish its own stepped-up frequency echoes transmitted by itself. In this article, we take m sequences as spread spectrum codes and assume that the ratio between the MIMO radars array aperture and the target distance is much less than 1, then we use 2-D fast Fourier transform (FFT) and matrix extended matrix pencil (MEMP) methods to extract 2-D scattering centres' parameters after MIMO radar have received de-spread echoes. Simulations illustrate that both SISO radars and linear uniform MIMO radars using the spread spectrum technique can get similar estimation results, and the MEMP method can afford super-resolution estimation results, whereas the 2-D FFT method is more useful when the number of MIMO radar array elements are no more than the number of scattering centres.

Inter-vehicle communication is an essential part of any intelligent transportation system (ITS). It allows vehicles to share surrounding road traffic information to support safe driving and road traffic management. Current systems use spread spectrum (SS) techniques: direct sequence (DS) or frequency hopping (FH). This paper proposes an implementation of a hybrid system in which DSSS and FHSS techniques are combined to provide performance and scalability improvements over a system that uses either of the SS techniques. Also this paper presents a theoretical analysis showing the improvement in the overall system capacity of the proposed system and the results of the computer simulations conducted. The results show that given an equal bandwidth, the hybrid system out performed the DS or FH systems. It showed superior bit error rate (BER) performance and scalability.

Current research on advanced vehicle control systems (AVCS) emphasizes the regulation of individual vehicles from a vehicle-level point of view. To improve the roadway operational efficiency, however, it is necessary to coordinate the operations of the vehicles on the highway. In this paper, a highway-level control algorithm is proposed which optimizes the traffic flow from a system-level viewpoint. The highway is divided into cells. The density and average speed of vehicles in these cells are assumed to be measured in real-time. Desired vehicle acceleration and lane change commands are assumed to be transmitted through communication devices to the vehicles, which optimize the traffic flow over the whole highway section. The system-wide traffic is optimized by using the downstream traffic status as the “preview” information for upstream traffic regulation. Numerical simulations were performed to validate the effectiveness of the proposed control algorithms.

Recently electric power steering system has been developed. Steer-by-wire system has big advantages of packaging flexibility, advanced vehicle control system, and superior performance. Steer-by-wire system has no mechanical linkage between the steering gear and the steering column. It is possible to control the steering wheel and the front-wheels steering independently. The active steering which reduce the difference between actual and estimated vehicle yaw rate can be realized. Since the information from the steering wheel is important for the driver to know the road condition, tire force should be fed back to the steering wheel. But unexpected disturbance is better suppressed without affecting to the steering wheel. Based on estimating the vehicle side slip angle from the internal sensor response, the tire self-aligning torque can be estimated. This torque is fed back to the steering wheel so that the driver can know the road condition. In this paper, we propose the method to control the vehicle yaw rate using steer-by-wire system, also disturbance applied to the front tires is suppressed by disturbance observer without affecting to the steering wheel. Numerical simulations are carried out to show the validity of the proposed method.

Troposcatter radio links may be a low cost alternative for long distance communications, or when the transmitter and the receiver are separated by difficult terrain that prevent from line-of-sight communications. These links permit one to preserve satellite resources in the case of civil applications, so as to overcome geographical barriers (oceans, mountains, desert, etc.). They also can easily and rapidly be installed for emergency situations in both civil and military cases. They represent a good solution in the case of single transhorizon hops of length limited to several hundreds of kilometers. The problem is that the transmission is based on the presence of multipath, whose dispersion is very varying on long periods. Wide-band transmission schemes can be then employed, like OFDM or spread spectrum techniques. The limitations of OFDM in presence of non-linearities of the amplifiers has often led one to prefer spread spectrum techniques in the case of troposcatter links: direct sequence (DS) or frequency hopping (FH). All the more so as other characteristics of spread spectrum are exploited for performance and also discretion purposes, as we are concerned with military tactical transmissions. The implementation of hybrid DS/FH spread spectrum receivers, which realize a maximal ratio combination of the paths (RAKE) is presented. After a description of the channel, we then describe the communication systems involved, and finally estimate the bit error rate.

Random codekey selection using codebook without pre-shared keys for anti-jamming in WBAN

Application of spread spectrum techniques in conventional slotted ALOHA, namely spread-slotted ALOHA, offers relatively high capacity multiple simultaneously packet transmissions. Two adaptive versions of the transmit permission control (TPC) scheme applicable in multi-cell communication systems are proposed. In the basic TPC scheme, by prohibiting the transmissions from the users with relatively high propagation loss to their connecting hub stations, the level of multiple access interference is decreased, and hence the throughput characteristics are improved. In the proposed schemes, the prohibition condition becomes more intelligent by considering the level of the offered traffic loads to the hub stations. It is shown that the adaptive schemes exhibits significantly improved characteristics at all offered traffic loads.

Jamming, either intentional or unintentional, is a big, and increasingly prevalent, problem for many wireless communications systems. A well-known countermeasure is the application of spread spectrum techniques that spread the information over a bandwidth possibly larger than that of the jammer thereby exploiting processing gain for jammer suppression; an especially attractive spreading technique is multi-carrier code division multiple access (MC-CDMA), due to its flexibility to shape transmit spectra, resilience to inter-symbol interference, and ease of implementation. Such spreading needs to be combined with spectral notching at the receiver RF frontend, to avoid saturation of the low-noise amplifiers. Such notching, in turn, requires the receiver to sense the band over which the jammer is operating. In this paper, we consider an MC-CDMA transceiver that is being jammed by a wideband non-stationary jammer. For a Rayleigh fading channel, we derive the symbol error rate for the case that the jammer parameters are available at the receiver. We derive the Maximum-Likelihood-based and Log-Likelihood Ratio-based jammer parameter estimators for both the case where channel state information is available during jammer sensing and when it is not. The performance of various jammer parameter estimation schemes is studied using Monte Carlo simulations and with the channel impulse responses collected from the wireless propagation measurements conducted in the 10–12 GHz band.

&lt;div class="htmlview paragraph"&gt;Computer simulation and real-time, interactive approaches for analysis, interactive driving simulation, and hardware-in-the-loop testing are finding increasing application in the research and development of advanced automotive concepts, highway design, etc. Vehicle dynamics models serve a variety of purposes in simulation. A model must have sufficient complexity for a given application but should not be overly complicated. In interactive driving simulation, vehicle dynamics models must provide appropriate computation for sensory feedback such as visual, motion, auditory, and proprioceptive cuing. In stability and handling simulations, various modes must be properly represented, including lateral/directional and longitudinal degrees of freedom. Limit performance effects of tire saturation that lead to plow out, spin out, and skidding require adequate tire force response models. Additional steering and braking subsystem characterizations are necessary to represent important handling and stability requirements. Steering compliance and appropriate tire aligning torque effects provide a significant component of understeer. Front-to-rear brake proportioning plays a significant role in limit performance directional stability, including the effects of nonlinear brake pressure proportioning valves.&lt;/div&gt; &lt;div class="htmlview paragraph"&gt;This paper summarizes vehicle dynamics model requirements for various classes of interactive and computer simulations. General formulations include sets of force and moment equations, with subsidiary equations for effects such as tire force response, antilock, traction control, four-wheel steering, and other advanced vehicle control systems (AVCS). Examples of simple and complex models will be given, including validation methods, for vehicle and driver models.&lt;/div&gt;

In this paper a multiplexing technique based on Walsh functions (sequency multiplexing) is described for the mobile spread spectrum multiple-access (SSMA) communication system. At the base station, the bit streams forwarded to each of 2K users are partitioned into two branches. In each branch it is first multiplexed by the corresponding Walsh function identifying a user and then it is spread by a PN sequence identifying one of two orthogonal components of the carrier of the branches. This multiplexing method makes all spread spectrum channels orthogonal and perfectly separated in the ideal case (provided perfect synchronization is achieved) at the same path, so it decreases the multiple access interferences. It is shown that sequency multiplexing combined with the spread spectrum technique is a suitable method for use on the down link of CDMA mobile communication system.