New PN Even Balanced Sequences for Spread-Spectrum Systems
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ew PN Even Balanced Sequences for Spread-Spectrum Systems ´ J. A. L. Inacio Instituto de Engenharia de Sistemas e Computadores (INESC), Rua Alves Redol 9, 1000 Lisboa Codex, Portugal ENIDH, Avenida Bonneville Franco, Pac¸o D’Arcos, 2780 Oeiras, Portugal Email: [email protected]
J. A. B. Gerald Instituto de Engenharia de Sistemas e Computadores (INESC), Rua Alves Redol 9, 1000 Lisboa Codex, Portugal Email: [email protected] Instituto Superior T´ecnico (IST), Universidade T´ecnica de Lisboa, Avenida Rovisco Pais, 1000 Lisboa, Portugal
M. D. Ortigueira Instituto de Engenharia de Sistemas e Computadores (INESC), Rua Alves Redol 9, 1000 Lisboa Codex, Portugal UNINOVA, Campus da FCT da UNL, Quinta da Torre, Monte da Caparica, 2825 - 114 Caparica, Portugal Email: [email protected] Received 30 October 2003; Revised 16 February 2005; Recommended for Publication by Alex Gershman A new class of pseudonoise even balanced (PN-EB) binary spreading sequences is derived from existing classical odd-length families of maximum-length sequences, such as those proposed by Gold, by appending or inserting one extra-zero element (chip) to the original sequences. The incentive to generate large families of PN-EB spreading sequences is motivated by analyzing the spreading effect of these sequences from a natural sampling point of view. From this analysis a new definition for PG is established, from which it becomes clear that very high processing gains (PGs) can be achieved in band-limited direct-sequence spread-spectrum (DSSS) applications by using spreading sequences with zero mean, given that certain conditions regarding spectral aliasing are met. To obtain large families of even balanced (i.e., equal number of ones and zeros) sequences, two design criteria are proposed, namely the ranging criterion (RC) and the generating ranging criterion (GRC). PN-EB sequences in the polynomial range 3 ≤ n ≤ 6 are derived using these criteria, and it is shown that they exhibit secondary autocorrelation and cross-correlation peaks comparable to the sequences they are derived from. The methods proposed not only facilitate the generation of large numbers of new PN-EB spreading sequences required for CDMA applications, but simultaneously offer high processing gains and good despreading characteristics in multiuser SS scenarios with band-limited noise and interference spectra. Simulation results are presented to confirm the respective claims made. Keywords and phrases: even balanced spreading sequences, PN sequences, processing gain, direct-sequence spread spectrum.
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INTRODUCTION
In the first half of the 20th century, spread-spectrum (SS) systems were conceived in order to guarantee privacy and low probability of interception (LPI) in military communications. Later, their applications began to include most of the tactical military communications (as in, e.g., location and positioning monitoring, weapons and missile armament control, electronic warfare, etc.). However, their properties, such as resistance against intentional or inadverThis is an open acc
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