US 7,031,371 B1Granted

CDMA/TDMA communication method and apparatus for wireless communication using cyclic spreading codes

OwnerIsmail A. Lakkisinventor

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Abstract

A communication system (20) uses TDMA techniques to distinguish intended recipients of a communication signal (26) from one another, and direct sequence spread spectrum (DSSS) techniques to encode and distinguish diverse parallel substreams (70, 74) of each user's data stream. Parallel unspread substreams (70) are spread using cyclic variations of a common spreading code (38). In one embodiment, the common spreading code (38) is chosen for low aperiodic autocorrelation sidelobes and a substantially flat spectral analysis. In another embodiment the common spreading code (38) is chosen for low periodic autocorrelation sidelobes and a substantially flat spectral analysis. In one embodiment, the use of cyclic variations of the spreading code (38) along with a cyclic prefix (114) enables the mathematical communicative matrix multiplication property, thereby permitting equalization for multipath to occur following or in conjunction with despreading.

Claims22

Dependent claims

A method of operating a spread-spectrum-based wireless communication system to efficiently utilize spectrum in the presence of multipath interference, comprising:

dividing a stream of data-conveying symbols into a plurality of unspread substreams at a transmitter;
generating a common spreading code at said transmitter;
spreading, at said transmitter, each of said plurality of unspread substreams using said common spreading code to form a plurality of spread substreams, said spreading activity comprising a respective temporally offsetting application of said common spreading code to each of said plurality of unspread substreams so that said plurality of spread substreams correspond to said plurality of unspread substreams modulated by respective cyclic variations of said common code;
performing a first time-frequency domain transformation on said plurality of unspread substreams at said transmitter prior to said spreading activity;
combining, at said transmitter, said plurality of spread substreams to form a composite signal;
wirelessly transmitting, from said transmitter, a communication signal formed from said composite signal;
receiving said received communication signal at a receiver;
despreading said communication signal at said receiver using a mismatched filter to generate a baseband signal;
and
performing a second time-frequency domain transformation on said communication signal at said receiver prior to said despreading activity.

7 more elements

A spread-spectrum-based communication system which efficiently utilizes spectrum in the presence of multipath, said communication system comprising:

a demultiplexer for dividing a stream of data-conveying symbols into a plurality of unspread substreams;
a spreading section coupled to said demultiplexer and configured to generate a plurality of spread substreams from said plurality of unspread substreams, said spreading section being configured so that said plurality of spread substreams correspond to respective ones of said unspread substreams modulated by respective cyclic variations of a common spreading code;
a first time frequency domain transformation section coupled between said demultiplexer and said spreading section;
and
a combining section coupled to said spreading section and configured to form a composite signal in response to said spread substreams;
a transmission section coupled to said combining section and configured to wirelessly transmit a communication signal formed from said composite signal;
a receiving section configured to receive said communication signal;
a despreading section coupled to said receiving section, said despreading section comprising a frequency domain equalizer to compensate for multipath, said despreading section being configured to generate a baseband signal in response to said communication signal;
and
a second time-frequency domain transformation section coupled between said receiver and said despreading section.

7 more elements

Dependencies are inferred from the claim text.