OFDM communication channel

Inactive Publication Date: 2005-09-22
HADAD ZION
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0093] Superior performance may

Problems solved by technology

A possible problem in the above modulation scheme may be an error in the time synchronization between several signals

Method used

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  • OFDM communication channel
  • OFDM communication channel
  • OFDM communication channel

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Embodiment Construction

[0115] A preferred embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings.

[0116]FIG. 1 illustrates the spectrum of an OFDM signal, including pilots and data in the complex frequency domain, with amplitude axis (I) 110, amplitude axis (Q) 111 and frequency axis 12. The spectrum includes the spectrum of data, for example 131, 132, 133 and the pilots 141, 142, 143.

[0117] It is assumed that the transmitted signal includes pilots of equal amplitude and being in phase. Furthermore, the pilots are equidistant in the frequency domain. These properties are used in the present invention, as detailed below. The properties of the pilots are measured and deviations from the transmitted signal are indicative of distortions in the communication channel. The measured distortion are used to compute the correction parameters for the channel.

[0118]FIG. 2 illustrates a possible distortion in the phase of the pilots versus frequency...

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Abstract

In an OFDM-based receiver, means for achieving time synchronization comprising: A. means for extracting pilot signals contained in the OFDM received signal; B. means for analyzing the pilot signals in the frequency domain and for issuing a signal indicative of a synchronization error in the received signal; C. means for correcting the synchronization error responsive to the signal indicative of the synchronization error. In an OFDM-based receiver, automatic frequency correction means in a subscriber unit comprising: A. an inner frequency correction loop for generating a LO frequency related to a frequency of a received signal; B. an outer frequency correction loop for correcting the LO frequency according to instructions received from a base station. In an OFDM-based receiver, a channel sounder comprising: A. means for extracting pilot signals contained in the OFDM received signal; B. means for analyzing the pilot signals in the frequency domain and for issuing signals indicative of a distortion in each pilot signal, wherein each of said pilot distortion signals comprises both an amplitude and a phase component; C. means for analyzing the signals indicative of a distortion in each pilot signal and for computing therefrom corrective signals for correcting distortions in the received signal.

Description

[0001] The present application is a divisional from U.S. patent application Ser. No. 09 / 493,662 entitled “OFDM communication channel” filed on 28 Jan. 2000, and claims priority therefrom.FIELD OF THE INVENTION [0002] This invention relates to OFDM communication channels, and more particularly to improvements in channel performance using signal processing of pilot signals in the channel. BACKGROUND OF THE INVENTION [0003] Advanced communications today may use the Orthogonal Frequency Division Multiplex (OFDM) modulation for efficient transmission of digital signals. These signals may include video, voice and / or data. OFDM is a commonly used implementation of Multi-Carrier Modulation (MCM). [0004] The Orthogonal Frequency Division Multiplex (OFDM) is a modern advanced modulation method, that achieves better use of the frequency spectrum. [0005] OFDM has been used in recent years in many applications where robustness against severe multipath and interference conditions is required, or ...

Claims

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Application Information

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IPC IPC(8): H04L25/02H04L25/03H04L27/26
CPCH04L25/022H04L25/0232H04L25/03057H04L25/03159H04L27/2675H04L27/2662H04L2025/03414H04L2025/03522H04L27/2657
Inventor HADAD, ZION
Owner HADAD ZION
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