Spread Spectrum

To improve interference robustness of wireless communication, spread spectrum techniques are often used. We use the chirp spreading technique along with FSK and PSK binary modulation schemes to obtain interference robust radio communication. The performance of chirped-FSK and chirped-PSK modulation through a white gaussian noise channel is simulated assuming a synchronized clock between transmitter and the receiver. We analyzed and simulated the error probability (BER) of the overall system in the presence of partial band of interference in the channel. The simulated BER is close to the estimated BER and they prove the superior performance of chirp-based modulation in the presence of interference.

Spread spectrum code-division multiple-access (CDMA) systems are currently considered as very attractive alternatives to the more familiar FDMA and TDMA systems, especially in the presence of multipath fading and external interference. The problem of code selection in a CDMA system with a finite number of users is addressed in this paper. A simple and efficient method for the selection of finite code sets with relatively high processing gain from Gold and Kasami code families of relatively large sizes is described in detail. Selected code sets of period 63 are presented along with their overall average performance parameters for different number of users.

The objectives of this paper are to study, analyze and evaluate the performance of BER (Bit Error Rate) in mobile multipath fading propagation channel. The parameters which are considered for the performance evaluation are AWGN, AWGN Multipath, Rayleigh fading channel and Hadamard code generator.

In modern communication systems, spread spectrum is playing an increasingly important role day by day due to its inherent advantages like noise immunity and also due its practical applications like mobile communications in CDMA. Our project is in accordance with this increasingly important communication technology. This project aims to Generate Gold Code sequence and modulate a message signal to produce a corresponding spreaded baseband modulated signal which is actually used in much higher proportions for transmission of voice and data signals in technologies like CDMA. The project also incorporates a receiver unit which demodulates the entire received signal with the assistance of the same gold code to generate the original message signal. An addition to this primary aim of our project is to study the cross correlation of two Gold Codes sequences and two Pseudo Noise sequences to ascertain which is a better tool for modulating the given message signal in terms of better noise immunity and security with the help of graphs using the MATLAB programming language.

Un esperimento iniziato nel 2001, e divenuto nel tempo un riferimento culturale su scala nazionale. Ritengo che il fine del mio lavoro sia aiutare a comprendere, e che la cultura debba essere libera e senza ostacoli di accesso. Chi acquista il formato cartaceo, ebook, od effettua una donazione, entra a far parte dei sostenitori del progetto, e può scaricare la versione PDF dell'edizione più recente, perfettamente navigabile e stampabile. L'edizione più recente è di Giugno 2019, la trovi presso https://teoriadeisegnali.it/

Recent years have seen a phenomenal growth in the field of satellite communications. Satcom systems offer many advantages for military applications which include wide area coverage, rapid deployment, flexible networking and long range service ...

This paper is focused on the design of a set of orthogonal linear periodic time varying (LPTV) filters and proposes to apply this result to spread spectrum multiuser transmissions. The construction method of such an orthogonal set is presented, emphasizing that only an invertible LPTV filter is required, since the full set is then deduced from this kernel element. Based on this theoretical result, a spread spectrum multiuser transmission is proposed. In order to appreciate the performance of the proposed system, simulations are performed and results are compared to a classical DS-CDMA system.