OFDM communication channel

• US 6,985,432 B1
• Filed: 01/28/2000
• Issued: 01/10/2006
• Est. Priority Date: 01/28/2000
• Status: Expired due to Fees

• Current Assignee: Zion Hadad Communications, Ltd.
• Original Assignee: Zion Hadad Communications, Ltd.
• Inventors: Hadad, Zion
• Primary Examiner(s): Phan, Man U.
• Application Number:
  US09/493,662
• Time in Patent Office: 2,174 Days
• Field of Search: 370/203, 370/208, 370/210, 370/206, 370/207, 370/343, 370/480, 370/482, 375/261, 375/364, 375/371, 375/222, 375/326, 375/344, 375/355
• US Class Current: 370/203
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03522 Frequency domain
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or known symbols

Abstract

In an OFDM-based receiver, a time synchronization unit comprising: A. a device for extracting pilot signals contained in the OFDM received signal; B. a device for analyzing pilot signals in the frequency domain and for issuing a signal indicative of a synchronization error in the received signal; C. a device for correcting the synchronization error, responsive to the signal indicative of the synchronization error. In an OFDM-based receiver, an automatic frequency correction device 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.

Claims

1. 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; and

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, further including means for computing an average distortion of two adjacent pilots and for using that average to correct the information between these pilots.

2. 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; and

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, further including means for computing, for each frequency between two adjacent pilots, an interpolated value of the distortion, and for using that interpolated value to correct the information at that frequency.

3. The channel sounder according to claim 2, wherein the interpolation is performed in the time domain or the frequency domain.

4. The channel sounder according to claim 2, wherein the interpolation is performed using a low pass filter or a FIR or convolver.