Hans Dieter Lüke

Almost-perfect polyphase sequences with small phase alphabet

New classes of polyphase sequences with small phase alphabets of size k are presented. These almost-perfect sequences of length N have a vanishing periodic autocorrelation function /spl Theta/(/spl tau/) for all /spl tau//spl ne/0 mod (N/k). The sequences are derived from q-ary m-sequences by a k-valued character operation.

Mismatched filtering of periodic quadriphase and 8-phase sequences

Quadriphase and 8-phase sequences with good autocorrelation properties are required in higher order digital modulation schemes, e.g., for channel estimation or synchronization. Since such sequences with perfect periodic autocorrelation function exist only for a few lengths, mismatched filtering is discussed. Mismatched filtering entirely suppresses all sidelobes of the correlation function at the expense of a slightly reduced signal-to-noise ratio (SNR). We present new construction methods for quadriphase and 8-phase sequences which exist for many lengths and exhibit significantly lower SNR losses than any other known sequences.

Binary Alexis sequences with perfect correlation

Binary Alexis (1986) sequences are useful signals for fast start-up equalization, channel estimation, synchronization, or ranging. The aperiodic autocorrelation functions of Alexis sequences vanish in a broad window region when correlated using additional binary preamble and postamble sequences. Originally, Alexis sequences were found by computer search. Two methods are presented by which such sequences can be constructed for any length N=p/sup a/ and N=2(p/sup a/+1), where p, is an odd prime and a=1, 2, 3.

MISMATCHED FILTERING OF PERIODIC AND ODD-PERIODIC BINARY ARRAYS

Arrays with good correlation properties are required for coded-aperture imaging, as well as for other applications of two-dimensional signal processing. Since binary arrays with perfect periodic autocorrelation functions exist for only a few sizes, mismatched filtering is discussed. Mismatched filtering entirely suppresses any sidelobes of the periodic autocorrelation function at the expense of a slightly reduced signal-to-noise ratio. New construction methods for binary arrays are presented for which this loss, with respect to periodic or odd-periodic correlation, converges to zero with an increasing array size.

Cubical binary arrays with perfect odd-periodic autocorrelation

Three-dimensional arrays with good autocorrelation functions are required in multidimensional signal processing. A generalized folding procedure is derived that permits the construction of such arrays from good correlating sequences for many array sizes. This method is applied to the construction of cubical binary arrays with a single zero element and odd-periodic autocorrelation function with zero sidelobes.

Letter: Large families of polynomial phase sequences with low correlation

Large families of p Q (p prime, Q = 2, 3, 4..) polynomial phase sequences are presented. The p - ary sequences are of length p. Their correlation magnitudes are upper bounded by = Q √p. The families are suitable for application in asynchronous CDMA systems.

Sequences and sequence pairs with imaginary correlation sidelobes

Time-discrete signals with good correlation properties are used in various applications in communications engineering. In this paper, the construction of quadriphase and 8-phase sequences and sequence pairs with purely imaginary aperiodic, periodic and odd-periodic correlation sidelobes is discussed. Using coherent detection, these imaginary sequences show perfect correlation properties if only the real part of the correlation function is used. Copyright

Binärübertragung mit Tiefpasssignalen

In den bisherigen Kapiteln wurden Methoden zur Beschreibung determinierter und nichtdeterminierter Signale und ihrer Ubertragung uber einfache Systeme behandelt. Im Folgenden werden diese Kenntnisse zu einer quantitativen Betrachtung einer Anzahl grundlegender nachrichtentechnischer Ubertragungsverfahren benutzt.

Binärübertragung mit Bandpasssignalen

Im vorliegenden Kapitel wird das Problem der Ubertragung digitaler Signale auf Bandpasskanale erweitert. Die Verwendung von Kanalen und Tragersignalen, die nicht von der Frequenz Null aufwarts beginnen, sondern ein bestimmtes Frequenzband mit unterer und oberer Grenzfrequenz verwenden, ist beispielsweise bei jeglicher Art von Funkkanalen notwendig, wird aber auch in Verbindung mit den in Kapitel 11 eingefuhrten Multiplex-Verfahren verwendet.

Grenzen der Informationsübertragung

Die Konzepte der Informationstheorie erlauben es, systematische Vergleiche der Modulationsverfahren durchzufuhren und deren Grenzen zu erkennen; insbesondere aber wird deutlich, dass sich nur durch Kombination von Verfahren der Modulation und Codierung eine Ubertragungsqualitat nahe an der informationstheoretischen Grenze erreichen lasst. Hierbei wird weiter herausgearbeitet, warum digitale Ubertragungsverfahren den analogen Verfahren uberlegen sind und es insbesondere erlauben, gegebene Ubertragungskanale effizienter auszunutzen.