The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 16, 2001
Filed:
Jul. 31, 1997
Transmission system and method employing peak cancellation to reduce the peak-to-average power ratio
Geert Arnout Awater, Utreecht, NL;
Richard D. van Nee, De Meern, NL;
Arnout Hendrik de Wild, Utrecht, NL;
Lucent Technologies, Inc., Murray Hill, NJ (US);
Abstract
The present invention teaches a system and method to reduce the peak-to-average power ratio of systems transmitting parallel channels. Examples of such systems are Orthogonal Frequency Division Multiplex (OFDM) and Orthogonal Code Division Multiplex (OCDM), also known as multi-code CDMA. Both systems have the disadvantage of a large peak-to-average power (PAP) ratio, which degrades the efficiency of the power amplifier of the transmitter. The present invention reduces the PAP problem by canceling the large signal peaks through subtraction of an appropriate reference function. That is, a time shifted and scaled reference function is subtracted from the sampled signal, such that each subtracted reference function reduces the peak power of at least one signal sample. In accordance with the present invention, an appropriate reference function with approximately or exactly the same bandwidth as the transmitted signal is selected. In this way it is assured that the peak power reduction does not cause any out-of-band interference. One example of a suitable reference signal for use in the present invention is a sinc function. The present invention also describes a variety of systems for implementation of the peak reduction technique. In accordance with another embodiment of the present invention, forward error correction coding is applied across several OFDM/OCDM symbols, in order to correct for symbols with low average power. In case of packet transmission, a different data scrambling is applied for each retransmission, in order to ensure that the PAP ratios and error probabilities are uncorrelated for initial packets and retransmissions.