Telefonaktiebolaget Lm Ericsson (Publ)

Branislav M Popovi&cacute;

G&ouml;ran Klang

Matthlas Schulist

Frank Georg

Transmitting a signal in a transmit diversity wireless communication system using 4 antennae, using a complex, multilevel orthogonal space-time code of dimension 4&times;n, and length p&equals;n. In an exemplary embodiment the method includes the steps of: configuring a first row of a multilevel orthogonal 4&times;n matrix G as an arbitrary cyclic version of a Generalized Chirp-Like (GCL) sequence of length n; configuring a second row of a multilevel orthogonal 4&times;n matrix G as the complex-conjugated version of the first row having inverted signs of the first n/2 or the last n/2 out of n consecutive symbols in the first row; configuring a third row as a reverted version of the first row; and, configuring a fourth row as a complex-conjugated version of the third row having inverted signs of a first n/2 or a last n/2 out of n consecutive symbols in the third row.

Method and apparatus for efficient transmit diversity using complex space-time block codes

The present invention provides a search window delay tracking procedure for use in a multipath search processor of a CDMA radio receiver. A channel impulse responses is estimated for a received signal containing plural paths, each path having a corresponding path delay. A search window defines a delay profile that contains the plural paths of the received signal. A mean or average delay is calculated for the estimated channel impulse response (CIR), and an error is determined between the mean CIR delay and a desired delay position corresponding to the center of the CIR search window. An adjustment is made to reduce that error so that the center of the search window and the mean CIR delay are aligned. The error may be processed either linearly (in one embodiment) or non-linearly (in another embodiment) to minimize the error and to reduce an influence of noise. A non-linear filtering process includes calculating a delay spread from the mean CIR delay calculated for successive processing cycles of a window delay tracking procedure corresponding to each new input. A difference is determined between the successive delay spreads. Adjustment signal is set equal to the error signal if the difference is less than or equal to a threshold. Alternatively, the adjustment signal is set to zero if the difference is greater than the threshold. Consequently, if the delay spread in the current iteration is significantly different from the delay spread in the previous iteration, the new error sample calculated in the current iteration is considered unreliable, and no adjustment is made.

Search window delay tracking in code division multiple access communication systems

Incoming signals in a receiver for Direct Sequence Code Division Multiple Access systems are despread using Offset-QPSK spreading as the transmitting spreading format combined with arbitrary data modulation formats, such as BPSK and QPSK. The receiver has a pseudonoise (PN) generator for generating a unique PN sequence signal. The PN sequence signal is divided into a real and an imaginary component. The complex input signal is divided into inphase and quadrature components. The inphase and the quadrature components of the input signal are downsampled to provide either two complex samples per chip period or one complex sample per chip period. In the latter case, the downsampling instants are delayed by a quarter of a chip period. Each downsampled complex signal is correlated with the corresponding segment of the complex PN sequence signal of the receiver. In the case where two samples per chip are provided after downsampling, the correlation values obtained for odd and even complex samples of the downsampled input signal are summed.

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Stockholm, Sweden

Branislav M Popovi&cacute;