US 6,647,077 B1 · Multipath parameter estimation in spread-spectrum communications systems

Abstract

A training circuit includes resources for processing magnitude and phase information received in a main propagation path signal with magnitude and phase information concurrently received in a secondary propagation path signal to determine values for magnitude, phase, and time offset of the secondary propagation path signal relative to the main propagation path signal. Differential decoding circuitry within the training circuit provides a correlation circuit, also in the training circuit, with differentially decoded sequences of symbol phase values derived from concurrent main and secondary signal propagation path symbol phase value sequences provided to the training circuit by an associated communications receiver. Operating on theses phase value sequences, the correlation circuit determines the time offset between the main and secondary propagation path signals based on determining the correspondence between symbol phase values received via the main propagation path signal and those concurrently received via the secondary propagation path signal. The training circuit can identify time offsets less than or greater than a symbol period, for either leading or lagging secondary path time offsets. A phase difference circuit, further included in the training circuit, determines a phase offset for the secondary propagation path signal relative to the main propagation path signal using main and secondary propagation path symbol phase values in combination with the time offset information. The relative magnitude, phase, and time information represents a characterization of the secondary propagation path with respect to the main propagation path. This characterization information may be used to improve reception performance or cancel multipath interference.

Claims24

Dependent claims

An apparatus for characterizing a secondary path signal relative to a main path signal received in a multipath radio signal, said apparatus comprising:

main and secondary magnitude inputs adapted to receive main and secondary magnitude values from the main and secondary path signals;
a magnitude comparator adapted to receive the main and secondary magnitude values and to determine a magnitude of the secondary path signal relative to the main path signal;
main and secondary phase inputs adapted to receive main and secondary symbol values from the main and secondary path signals;
first main and secondary delay elements adapted to receive the main and secondary symbol values and to output delayed main and secondary symbol values;
main and secondary differential decoders adapted to receive the main and secondary symbol values and the delayed main and secondary values and to output differentially decoded main and secondary symbol values;
second main and secondary delay elements adapted to receive the differentially decoded main and secondary symbol values and to output delayed differentially decoded main and secondary symbol values;
a correlator adapted to receive the differentially decoded main and secondary symbol values and the delayed differentially decoded main and secondary symbol values, and to determine a time offset of the secondary path signal relative to the main path signal based on identifying a symbol correspondence between the differentially decoded main and secondary symbol values;
and
a phase comparator adapted to received the main and secondary symbol values and the delayed main and secondary symbol values and to determine a phase difference between corresponding main and secondary symbol values based, in part, on said symbol correspondence.

6 more elements

An apparatus for characterizing a secondary path signal relative to a main path signal received in a multipath radio signal, said apparatus comprising:

a correlation circuit adapted to concurrently receive sequences of differentially decoded main and secondary symbol values from the main and secondary path signals, and further adapted to determine a time offset of the secondary path signal relative to the main path signal based on identifying a symbol correspondence between main and secondary symbol values by cross-correlating selected ones in the sequence of differentially decoded main symbol values with selected ones in the sequence of differentially decoded secondary symbol values;
a phase comparison circuit adapted to concurrently receive one or more main and secondary symbol values from the main and secondary path signals, and further adapted to determine a phase offset of the secondary path signal relative to the main path signal based on computing a number of phase differences between selected ones of the main symbol values and selected ones of the secondary symbol values, and further based on selecting one of said number of phase differences as said phase offset based on said time offset determined by said correlation circuit;
and
a magnitude comparison circuit adapted to concurrently receive one or more main and secondary magnitude values from the main and secondary path signals, and further adapted to determine a relative magnitude of the secondary path signal relative to the main path signal based on comparing the one or more secondary magnitude values with the one or more main magnitude values;
said characterization of the secondary path signal provided based on said apparatus outputting said time offset, said phase offset, and said relative magnitude.

2 more elements

Dependencies are inferred from the claim text.

Multipath parameter estimation in spread-spectrum communications systems

Life of this patent

Multipath parameter estimation in spread-spectrum communications systems

Life of this patent

Abstract

Claims24