Synchronization with permutation codes and Reed-Solomon codes

D.Ing. (Electrical And Electronic Engineering)We address the issue of synchronization, using sync-words (or markers), for encoded data. We focus on data that is encoded using permutation codes or Reed-Solomon codes. For each type of code (permutation code and Reed-Solomon code) we give a synchronization procedure or algorithm such that synchronization is improved compared to when the procedure is not employed. The gure of merit for judging the performance is probability of synchronization (acquisition). The word acquisition is used to indicate that a sync-word is acquired or found in the right place in a frame. A new synchronization procedure for permutation codes is presented. This procedure is about nding sync-words that can be used speci cally with permutation codes, such that acceptable synchronization performance is possible even under channels with frequency selective fading/jamming, such as the power line communication channel. Our new procedure is tested with permutation codes known as distance-preserving mappings (DPMs). DPMs were chosen because they have de ned encoding and decoding procedures. Another new procedure for avoiding symbols in Reed-Solomon codes is presented. We call the procedure symbol avoidance. The symbol avoidance procedure is then used to improve the synchronization performance of Reed-Solomon codes, where known binary sync-words are used for synchronization. We give performance comparison results, in terms of probability of synchronization, where we compare Reed-Solomon with and without symbol avoidance applied

Performance Evaluation of Phase Optimized Spreading Codes in Non Linear DS-CDMA Receiver

Spread spectrum (SS) is a modulation technique in which the signal occupies a bandwidth much larger than the minimum necessary to send the information. A synchronized reception with the code at the receiver is used for despreading the information before data recovery. Bandspread is accomplished by means of a code which is independent of the data. Bandspreading code is pseudo-random, thus the spread signal resembles noise. The coded modulation characteristic of SS system uniquely qualifies it for navigation applications. Any signal used in ranging is subject to time/distance relations. A SS signal has advantage that its phase is easily resolvable. Direct-sequence (DS) form of modulation is mostly preferred over Frequency Hopping system (FH) as FH systems do not normally possess high resolution properties. Higher the chip rate, the better the measurement capability. The basic resolution is one code chip. Initially, some existing code families e.g. Gold, Kasami (large and smal..

Insertion of random spaces in time domain for frequency hopping sequences for RF systems

FFH es un método de acceso al canal con amplias aplicaciones pasadas y presentes, dentro de este método los códigos ortogonales usados en SFH-CDMA son de especial interés en amplias áreas de la tecnología. El presente trabajo implementa códigos ortogonales un coin-cidentes (1dOC) con restricciones en componentes espectrales adyacentes para el diseño de detectores auto correlacionados en RF que usan arreglos de sensores planos. La inclusión de retrasos temporales entre resonadores adyacentes es un método que permite disminuir la interferencia entre los usuarios (MAI), en contraposición a la disminución de la velocidad de transmisión y finalmente el ancho de banda del protocolo. La selección aleatoria de re-trasos entre símbolos adyacentes reduce los máximos en la correlación cruzada, aumentando el rango dinámico del detector asíncrono y por ende el número de usuarios que comparten el canal de comunicaciones.Improvements over the communications protocols are always a continuous research. Fast Frequency Hopping is an important method still in use and orthogonal codes used in SFH-CDMA are the special interest in several areas of technology. This research uses one coincident orthogonal code with restrictive adjacent spectral distance for the design of RF correlation detectors based on planar resonators arrays. Inclusion of uniform time delays sections between adjacent resonators is a well-known method to improve the MAI, at expenses of decrease the data rate and finally the bandwidth of protocol. Another strategy is selecting random delays between symbols in the way of adjacent peaks in cross correlation function vanishes, improving the dynamic range of asynchronous detector and accordingly the user number sharing the channel of communications

Chip and Signature Interleaving in DS CDMA Systems

Siirretty Doriast

Waveform Design and Related Processing for Multiple Target Detection and Resolution

The performance of modern radar systems mostly depends on the radiated waveforms, whose design is the basis of the entire system design. Today’s coherent, solid-state radars (either of the phased array type or of the single-radiator type as air traffic control or marine radars) transmit a set of deterministic signals with relatively large duty cycles, an order of 10%, calling for pulse compression to get the required range resolution. Often, power budget calls for different pulse lengths (e.g., short, medium, and long waveforms with a rectangular envelope) to cover the whole radar range. The first part of the chapter includes the topic of mitigating the effect of unwanted side lobes, inherent to every pulse compression, which is achieved both by a careful and optimal design of the waveform and by a (possibly mismatched) suitable processing. The second part of the chapter deals with the novel noise radar technology, not yet used in commercial radar sets but promising: (1) to prevent radar interception and exploitation by an enemy part and (2) to limit the mutual interferences of nearby radars, as in the marine environment. In this case, the design includes a tailoring of a set of pseudo-random waveforms, generally by recursive processing, to comply with the system requirements