OFDM Multiple Sub-Channel Communication System

Abstract

A transmitter for transmitting an OFDM signal in a communications channel, including: (a) a plurality of base-band OFDM modulators, each for modulating a respective baseband data signal onto a plurality of orthogonal sub-carriers and outputting a respective baseband sub-channel OFDM signal, and (b) a fast convolution filter and up-converter for applying fast convolution filtering and digital up-conversion to the sub-channel OFDM signals to output a combined OFDM signal that includes each of the sub-channel OFDM signals, the fast convolution and up-converter filtering each of the sub-channel OFDM signals and frequency shifting all of the sub-channel signals to respective designated frequencies within the combined OFDM signal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of and claims priority to U.S. patent application Ser. No. 10 / 166,872, filed Jun. 11, 2002, and issued Apr. 17, 2007 as U.S. Pat. No. 7,206,350.BACKGROUND OF THE INVENTION [0002] The present invention relates to the transmission and reception of orthogonal frequency division multiplexed (OFDM) signals, and more particularly, to communications systems using OFDM to communicate information in a multiple user two-way communication system. [0003] OFDM is a bandwidth efficient multi-carrier modulation technique where a data stream is divided into a set of lower rate digital data streams, each of which is modulated onto a separate data signal. Each data signal or sub-carrier have distinct carrier frequencies. OFDM is currently used in one-way wireless broadcasts of digital television and digital radio signals where it has demonstrated its robustness to certain types of channel impairments such as multi-path ...

AI Technical Summary

Benefits of technology

"The invention provides a transmitter for transmitting an OFDM signal in a communications channel. The transmitter includes a plurality of base-band OFDM modulators and a fast convolution filter and up-converter. The method involves segmenting data into parallel baseband signals, generating sub-channel OFDM signals with filtering and frequency shifting, and combining the sub-channel OFDM signals to output a combined OFDM signal. The technical effect is improved transmission of multiple sub-channel OFDM signals with reduced interference and improved signal quality."

Problems solved by technology

A limitation of prior OFDM systems that propose the use of multiple sub-channels that the transmitters and receivers of these systems are configured such that once the sub-channels have been allocated the sub-channels are static in that they can not be dynamically varied in quick response to changes in demands placed on system resources, leading to inefficient use of bandwidth.

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