Research

Orthogonal signals with jointly balanced spectra: Application to cdma transmissions

Thierry Chonavel

• Correspondence: Thierry Chonavel thierry.chonavel@telecom-bretagne.eu

Author Affiliations

Télécom Bretagne, UEB, Lab-STICC UMR CNRS 3192, Technopôle Brest-Iroise, Institut Télécom, CS 83818, 29238 Brest Cedex 3, France

EURASIP Journal on Wireless Communications and Networking 2011, 2011:176 doi:10.1186/1687-1499-2011-176

Published: 21 November 2011

Abstract

This paper presents a technique for generating orthogonal bases of signals with jointly optimized spectra, in the sense that they are made as close as possible. To this end, we propose a new criterion, the minimization of which leads to signals with close energy inside a set of prescribed subbands. Starting with the case of a single subband, we illustrate it by building orthogonal signals with maximum energy concentration in time and in frequency, with the same energy rate outside a fixed frequency interval or a fixed time interval, by resorting to Slepian sequences or Slepian functions, respectively. Then, we present spectrum balancing in a set of frequency intervals. We apply this method to Slepian sequences and Slepian functions, as well as to Walsh-Hadamard codes. On these examples, we point out a number of nice properties of the so-built orthogonal families that are of interest for signaling applications.

PACS: signal processing techniques and tools; modulation techniques