Spread Spectrum Technique for Digital Broadcasting System in Rain Environment

The theoretical analysis of a digital satellite broadcasting system in the presence of phase noise is performed. An effective technique to design the carrier recovery circuit is also presented based on the analyzed loop parameters, such as degradation loss due to phase noise, average time to cycle slip, and carrier signal acquisition time. It is possible to design a system providing the optimal service and satisfying service requirements for a digital satellite broadcasting system. In this paper, the carrier recovery loop that provides optimal performance in the presence of phase noise exhibits the parameters of 0.707 for damping factor and 40 kHz for noise bandwidth. The designed phase-locked loop indicates a performance of 0.26 dB for impairment due to phase noise at 10/sup -3/ BER, 3.88/spl times/10/sup 6/ hours for average time to cycle slip, and 34 msec for carrier signal acquisition time. The carrier acquisition time of the designed carrier recovery circuit is in accordance with the analyzed result.

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.

Currently digitalization of analog broadcasting systems is taking place because digital broadcasting has many advantages such as efficient use of the frequency spectrum and provision of high-quality content broadcast services. However, service start time in digital broadcasting systems is slower compared to the analog broadcasting systems. Therefore, digital broadcasting systems require fast and efficient synchronization methods. In this paper, we propose a fast frame detection technique without sampling frequency correction for the Digital Radio Mondiale (DRM) receiver and show the performance of the proposed method using computer simulations and implementation on hardware.

A vehicle-to-vehicle communication and ranging system using spread spectrum technique has been proposed previously. Using this system, a vehicle (vehicle-A) obtains the information of the target vehicle (vehicle-B) and the distance between the vehicles simultaneously. However, in this system, the number of the target vehicle is only one. Using our proposed system, vehicle-A can communicate with a number of target vehicles at the same time. From computer simulations, it is confirmed that the proposed system is effective even when interference signals exist.

Orthogonal frequency division multiplex-single frequency network (OFDM-SFN) has been widely used in the digital audio broadcasting system (DAB) and the terrestrial digital video broadcasting system (DVB-T) as a scheme of downlink broadcasting service. A novel system structure of single frequency cellular network (SFCN) is proposed by applying OFDM-SFN to conventional cellular systems. Transmitter macrodiversity and receiver selective diversity are adopted in the downlink and the uplink respectively. Theoretical analysis and numerical simulation in comparison with conventional cellular systems demonstrate the performance improvement of the proposed system.

This paper proposes an underwater communication receive model based on the spread spectrum technique in order to provide the characteristic of a low probability of interception. To do this, turbo equalization techniques employing Bahl-Cocke-Jelinek-Raviv (BCJR) decoding to improve performance through repetition are applied to offer excellent performance even at a low signal to noise ratio (SNR) of transmitted signals due to the spread spectrum technique. A turbo equalization model based on RAKE which increase signal power by summing the received signal through the multipath is proposed to compensate distorted data due to multipath channel and the performance improvements were proven by applying the threshold and weighted coefficient in the RAKE receiver model. The model was applied to covert underwater communication in a multi-sensor environment, and the efficiency of the proposed method was proven through underwater experiments.

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.

Use of spread spectrum systems in telecommunications is studied. It is shown that spread spectrum techniques can substantially enhance noise and interference immunity in the currently deployed information transmission networks. Primitive polynomials are proposed to obtain respective spreading codes. A spreading code consisting of 1023 chips is synthesized and its characteristics are studied. It is deduced that powerful interferences can exceed dynamic range of the receiving part of the system and, as a result, deteriorate information transmission. To overcome this problem, utilization of limiters is proposed, in which limitation level equals that of the internal noise of the receiving part. Computer simulation is employed to test the performance of the proposed solution. Performance of the spread spectrum system for information transfer is studied both without the limiter and with the limiter. Research results show that, for binary modulation, performance of the system with limitation and without limitation is nearly identical while limiters can substantially reduce requirements for the dynamic range. Compared to the existing approaches, it is proposed to use the synthesized spreading coding sequence with the limitation technique in practical implementations of those telecommunication networks, in which noise immunity and transmission concealment are required, such as in unmanned aerial vehicles. This can replace currently used approaches, such as frequency hopping, transmission power adjustment and antenna pattern changes.

Filter-bank multi-carrier spread spectrum systems (FBMC-SS) provide a viable solution for communications in harsh environments where strong interferers may dominate portions of the spectrum. Thanks to spectrum localization of the individual sub-carrier bands in FBMC-SS, partial-band interferers can be easily removed. Previous studies of FBMCSS make use of filtered multi-tone (FMT), where sub-carrier bands are non-overlapping. This may simplify the tasks of carrier and timing synchronization as well as channel estimation, however, introduces a spectral footprint that may be undesirable in many applications. Instead, this paper adopts staggered multi-tone (SMT) filter banks that make use of offset/staggered quadrature amplitude modulation (OQAM) to remove any discernible footprint from the FBMC-SS spectrum. We propose a preamble design that facilitates development of carrier and timing synchronization algorithms as well as an effective channel estimation method. The performance of the proposed synchronization algorithms are evaluated through computer simulations. Moreover, the performance of the proposed channel estimator is bench marked against its respective Crammer-Rao lower bound (CRLB).

After a watermarked image is printed, copied several times and scanned, the watermark usually cannot be extracted rightly, as well as distorted by noise. In this paper, a spread spectrum technique was introduced to image watermarking which can be applied to print and generation copy. The watermarking message is modulated by the key-dependent pseudo-random sequences to produce a spread spectrum signal. The watermark is embedded into the cover image by modifying the gray value of each pixel. The cover image is not needed when the watermark is detected. The watermark is estimated exploiting the properties of HVS(Human Visual System) and extracted through the same key-dependent 2D sequences. Experimental results show that the scheme can resist print, generation copy and scan process.

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

Lateral distance measurement system for AVCS (advanced vehicle control systems) has been developed in the various countries. This paper describes a lateral distance measurement system using spread spectrum (SS) technique. Our method does not require significant infrastructure investment because it is based on the reflected signal from the guardrails currently installed on many roads. The range resolution of SS radar is generally equal to the length of one chip because it is based on the correlation using chip synchronization. We propose a short range measurement system utilizing the slope of the correlation function of m-sequence as an application of SS technique and indicate the results of the experiment.

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.

Indoor wireless infrared transmission is severely impaired by noise and interference produced by artificial ambient light. The interference produced by fluorescent lamps driven by electronic ballasts causes very large power penalties. In this paper spread spectrum techniques are proposed to combat the penalties caused by artificial light interference. Analytical, simulation and experimental results of bit error rate versus signal-to-noise ratio are presented for a 1 Mb/s spread spectrum wireless infrared system. The results show that spread spectrum techniques reduce the degradation due to artificial light interference.