CDMA Reference Blockset

IS-95A Rev Ch Walsh Demodulator

Perform Walsh demodulation of the combined output of the rake fingers

Library

IS-95A Base Station Receiver

Description

This block performs Walsh demodulation of the combined output of the rake fingers. It outputs soft and hard decision values.

This block takes as input an array of 64 values whose value corresponds to the correlation result between the despread received signal and the 64-ary Walsh codes. The correlation result between the zeroth Walsh code and despread signal is the first value in the input array. For the hard decision outputs, this block determines the maximum value of the input array, and the index corresponding to the maximum value is a 6-bit hard decision output. For the soft decision values, this block applies the soft-decision algorithm specified in the book by Viterbi listed in References below.

Inputs

Real vector representing the combined output of the rake fingers. The vector size equals Number of input symbols times the Walsh code length. The Walsh code length equals 2^W, where W is the Walsh order parameter.

Outputs

Hard Dec

Binary scalar representing demodulated hard decision values.

Soft Dec

Real scalar representing demodulated soft decision values.

Dialog Box

Parameters

Walsh order

Integer scalar that specifies the order of the Walsh code used to encode each data symbol. The default value, 6, corresponds to a Walsh code length of 64.

Number of input symbols

Integer scalar that specifies the number of input Walsh symbols.

See Also

IS-95A Rev Ch Walsh Modulator
IS-95A Rev Ch Walsh Modulation and Spreading

References

Viterbi, Andrew J. CDMA Principles of Spread Spectrum Communications. Reading, Mass.: Addison-Wesley, 1995.

IS-95A Rev Ch Walsh Correlator

IS-95A Rev Ch Walsh Modulation and Spreading