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Spread spectrum communication

Grant number: 91/00517-2
Support type:Research Projects - Thematic Grants
Duration: January 01, 1992 - December 30, 1993
Field of knowledge:Engineering - Electrical Engineering
Principal Investigator:Normonds Alens
Grantee:Normonds Alens
Home Institution: Escola Politécnica (EP). Universidade de São Paulo (USP). São Paulo , SP, Brazil


The technique of spread spectrum communication has been used in military communications for decades due to its peculiar properties of low detectability, secrecy, immunity from interference and possibility of multiplex use. More recently its use has been spreading to civil communications, due to the characteristics mentioned allied to a growing digitalization and integration of the complex processing of signals required, which tends to drastically reduce the costs. This thematic project aims to consolidate, in the Electronic Engineering Department of EPUSP, training in this transmission technique. This objective will be realized through six lines of activity: a) simulation: development of software, in conjunction with other programs acquired, to simulate the behavior of suitably modeled spread spectrum transmission systems, in the presence of channel limitations, interferences and fading distortions (see item III.2); b) study of codes: study of the usual codes employed in spread spectrum communication, with special attention to their properties of partial cross-correlation. The study will be analytical and by simulation (see item III.3); c) experimental set-ups: we will carry out experimental set-ups of sets of transmitter/receiver operating with spread spectrum by direct sequence (DS) and frequency hopping (FH), to check its operation and performance. The results measured will be compared with those obtained by simulation(see item III.4); d) coders for voice signals: this study aims to find coding schemes for voice signals, capable of reproducing them with good quality using low levels of transmission, but still with relative immunity from interference. Used in conjunction with spread spectrum transmission, such schemes lead to high processing gains (see item III.5); e) digital processing of signals: this activity aims to incorporate DSP techniques in signaling processes used in spread spectrum communication. Such techniques could also be used in the simulations (see item III.6); f) ASICs for spread spectrum communication systems: this activity proposes to integrate in dedicated circuits various functions of the spread spectrum communication system. From the start of the developments there will be interaction of this team with that of other lines in order to make viable and optimize the integration (see item III.7). (AU)