Ranging in multi-band communication systems

• US 8,149,961 B1
• Filed: 08/04/2004
• Issued: 04/03/2012
• Est. Priority Date: 08/04/2003
• Status: Active Grant

• Current Assignee: Regents of The University of Minnesota (University of Minnesota)
• Original Assignee: Regents of The University of Minnesota (University of Minnesota)
• Inventors: Tewfik, Ahmed H., Saberinia, Ebrahim
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): Neff, Michael
• Application Number:
  US10/912,515
• Time in Patent Office: 2,799 Days
• Field of Search: 375/343, 375/259, 370/320, 708/300, 708/422
• US Class Current: 375/343
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/2665 Fine synchronisation, e.g. by positioning the FFT window

Abstract

System and methods include transmitting the same signal in all sub-bands in different time intervals and processing the corresponding received signals to achieve a time resolution proportional to the inverse of the whole bandwidth as opposed to that of a single sub-band. The systems and methods refine the coarse resolution that is achieved by conventional approaches, such as the correlation method, in a single sub-band by aligning the outputs of the matched filters to the received signals from all sub-bands and applying a fast Fourier Transform (FFT) in each time bin along the sub-band index.

Claims

1. A method for communications, the method comprising:

receiving a plurality of sub-band signals of a multi-band signal, wherein each of the plurality of sub-band signals has a corresponding base-band, each of the corresponding base-bands comprising a same base-band signal, and each of the same base-band signals are received at different tie intervals in each sub-band;

passing the plurality of sub-band signals through a plurality of matched filters to produce a plurality of filter outputs;

sampling the outputs of the plurality of matched filters to generate a plurality of sampled filter outputs;

aligning the plurality of sampled filter outputs into a matrix Y wherein matrix Y is aligned such that Y(m,n)=y_m(n/w_s) where y_m comprises a sub-band signal output of index m of a matched filter, n is a time index, and w_s comprises a sampling rate;

applying an inverse FFT along sub-band indexes of matrix Y to produce a matrix Z; and

estimating a signal delay by determining a maximum of the plurality of sampled filter outputs in matrix Z after application of the inverse FFT.

2. The method of claim 1, further comprising:

receiving an estimate of phase mismatch; and

compensating for the phase mismatch using the estimate after aligning the plurality of sampled filter outputs and before applying the inverse FFT.

3. The method of claim 1, wherein estimating the signal delay includes determining time index n and index m where the matrix Z has a maximum.

4. The method of claim 1, wherein the signal delay is determined according to index m and time index n where matrix Z has a maximum, the signal delay determined according to the formula

signal delay=(m+Nn)/(Nw_s)

where N comprises the number of sub-band signals.

5. A system for providing high time resolution signal multiband communication, the system comprising:

one or more processors;

a memory including instructions, which when executed by the one or more processors, cause the one or more processors to;

receive a plurality of sub-band signals of a multi-band signal, wherein each of the plurality of sub-band signals has a corresponding base-band, each of the corresponding base-bands comprising a same base-band signal, and each of the same base-band signals are received at different tie intervals in each sub-band;

pass the plurality of sub-band signals through a plurality of matched filters to produce a plurality of filter outputs;

sample the plurality of filter outputs to generate a plurality of sampled filter outputs;

align the plurality of sampled filter outputs into a matrix Y wherein matrix Y is aligned such that Y(m,n)=y_m(n/w_s) where y_m comprises a sub-band signal output of index m of a matched filter, n is a time index, and w_s comprises a sampling rate;

apply an inverse FFT along sub-band indexes of matrix Y to produce a matrix Z; and

estimate a signal delay based on matrix Z.

6. The system of claim 5, comprising the memory including instructions, which when executed by the one or more processors, cause the one or more processors to:

receive an estimate of phase mismatch; and

compensate for the phase mismatch in matrix Y.