Spread Spectrum • essential idea is to spread the information signal over a wider bandwidth • an important form of encoding for wireless communications • can be used to transmit either analog or digital data, using an analog signal • Types: - frequency hopping spread spectrum (FHSS) - direct sequence spread spectrum (DSSS) Spread Spectrum vs. Narrowband • Spread spectrum spreads the transmission over a range of frequencies • Varying wavelengths react differently to the environment through which they propagate - i.e.: wavelengths react to different object sizes and materials used in the environment • The multipath problem in SS is known as View Spread Spectrum.pdf from ELECTRICAL 123 at University of Mosul. Spread Spectrum Introduction to Spread Spectrum • Problems such as capacity limits, propagation effects, synchronization occur spread-spectrum communiCations, including a discussion on tbe applications referred to above, on the properties of commoll spreading sequences, and on techniques that can be used for ac - quisition and tracking. I. INTRODUCTION SPREAD-spectrum systems have been developed since about the mid-1950's. Spread Spectrum by Erol Seke spectrum of subband-0 spectrum of subband-3 f 0 f 1 f 0 f 1 f 2 f 3 t symbol period Orthogonal Carriers for a Symbol Period. M 0-PSK/M 0-QAM M N-1-PSK/M N-1-QAM X 0 X 1 X N 1: complex numbers for one symbol period M 1 A spread spectrum communications system is usually characterised as one in which the transmission bandwidth is much greater than that necessary to transmit the required information, and demodulation must be accomplished by correlating the received signal with a replica of the signal used to spread the information. Spread spectrum communications systems are often used when there is a need for 7 Detection of Spread-Spectrum Signals 387 7.1 Detection of Direct-Sequence Signals 387 387 390 398 398 401 401 407 408 Ideal Detection Radiometer 7.2 Detection of Frequency-Hopping Signals Ideal Detection Wideband Radiometer Channelized Radiometer 7.3 Problems 7.4 References Appendix A Inequalities 409 A.1 Jensen's Inequality 409 A.2 Abstract and Figures. In this letter, we propose dual-mode chirp spread spectrum (DM-CSS) modulation for low-power wide-area networks. DM-CSS is capable of achieving a higher spectral efficiency View SPREAD-SPECTRUM.pdf from MANAGEMENT 302 at Nairobi Aviation College, Nairobi Branch. INTRODUCTION TO SPREAD SPECTRUM ECE525E Thursday, July 19, 2018 CONCERNS IN COMMUNICATION SYSTEM 1. Most Spread Spectrum refers to a system originally developed for military applications, to provide secure communications by spreading the signal over a large frequency band. Figure 1 represents a narrow band signal in the frequency domain. These narrowband signals are easily jammed by any other signal in the same band. 7 Spread spectrum signature ensembles for CDMA applications 203 7.1 Data transmission via spread spectrum 203 7.1.1 Direct sequence spreading: BPSK data modulation and binary signatures 203 7.1.2 DS spreading: general case 207 7.1.3 Frequency hopping spreading 212 7.2 Designing signature ensembles for synchronous DS CDMA 214 7.2.1 Problem The 'spread spectrum' signal has properties which help to achieve these ends. Spread spectrum signals may be divided into two main groups - direct sequence spread spectrum (DSSS), and frequency hopping spread spectrum (FHSS). This experiment is concerned with demonstrating some of the principles of the first. principle of DSSS The