Correlation based method of determining frame boundaries of data frames that are periodically extended

• US 6,735,255 B1
• Filed: 02/29/2000
• Issued: 05/11/2004
• Est. Priority Date: 05/28/1999
• Status: Expired due to Fees

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Bevan, Scott A., Stoddard, Trent, Christiansen, Mark W., Dobson, William Kurt, Smart, Kevin J.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US09/515,800
• Time in Patent Office: 1,533 Days
• Field of Search: 375/130, 375/260, 375/316, 375/324, 375/326, 375/340, 375/342, 375/343, 375/354, 375/355, 375/357, 375/360, 375/362, 375/371, 370/203, 370/210, 370/320, 370/335, 370/342, 370/441, 370/479, 370/503, 370/506, 370/510, 370/515, 370/516, 708/422, 708/813, 455/59
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2676 Blind, i.e. without using known symbols

Abstract

A correlator for use in a timing recovery apparatus of a receiver in a multicarrier transmission system. The correlator locates the beginning of a data frame and initializes a pointer register with an address to a location within the receive signal buffer. Data is transferred to a signal converter from the receive signal buffer where the samples that are fed into the converter are determined by the address stored in the pointer register.

Claims

1. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence from the sample sequence, wherein the sample sequence is y[n], and the step of forming the difference sequence, z[n], is performed in accordance with the relationship;

z[n]=|y[n]−

y[n+N]|, wherein N, an integer, is the number of samples in a symbol, and n is an integer index;

forming a window sequence from selected points within the difference sequence;

forming a summation sequence by summing selected points within the summation sequence;

locating the minimum value of the window sequence; and

loading a pointer register based on a sequence index corresponding to a maximum value.

2. The method of claim 1, wherein the step of forming a window sequence, p[j,n], is performed in accordance with the relationship:

$p<br><br>\left[j,n\right]=\underset{i=0}{\overset{\hat{P}-1}{\sum <br><br>}}<br><br>z<br><br>\left[n+i+j·<br><br>\left(N+M+P\right)\right],$

where M+P is the length of a periodic extension, M is the length of a communication channel impulse response, i is an integer index, j is an integer index, P is an integer representing the difference between M and the length of the periodic extension, and {circumflex over (P)} is an integer where 0<

{circumflex over (P)}≦

P.

3. The method of claim 2 wherein the step of forming a summation sequence, w[n] is formed in accordance with the relation:

$w<br><br>\left[n\right]=\underset{j=0}{\overset{Q-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{i=0}{\overset{\hat{P}-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>z<br><br>\left[n+i+j·<br><br>\left(N+M+P\right)\right],\text{\hspace{1em}<br><br>}<br><br>\mathrm{where}<br><br>\text{\hspace{1em}<br><br>}<br><br>0<<br><br>\hat{P}\le <br><br>P,$

and Q is a number of frames being processed.

4. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence from the sample sequence, wherein the sample sequence is y[n], and the step of forming the difference sequence, z[n], is performed in accordance with the relationship;

z[n]=|y[n]−

y[n+N]|, where N, an integer, is the number of samples in a symbol, and n is an integer index;

forming a window sequence by weighting and summing selected points within the difference sequence;

locating the minimum value of the window sequence; and

loading a pointer register based on a sequence index corresponding to the minimum value.

5. The method of claim 4 wherein the step of forming a window sequence, w[n] is formed in accordance with the relation:

$w<br><br>\left[n-R+1\right]=\underset{k=0}{\overset{R-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>h_{\mathrm{MF}}<br><br>\left[n-k\right]<br><br>z<br><br>\left[k\right],$

wherein R is an integer offset, h_MF is a matched filter, and k is an integer index.

6. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence from the sample sequence, wherein the sample sequence is y[n], and the step of forming the difference sequence, z[n], is performed in accordance with the relationship;

z[n]=z_max−

|y[n]−

y[n+N]|, where z_max is the maximum value of |y[n]−

y[n+N]|, N, an integer, is the number of samples in a symbol, and n is an integer index;

forming a window sequence by weighting and summing selected points within the difference sequence;

locating the maximum value of the window sequence; and

loading a pointer register based on a sequence index corresponding to the maximum value.

7. The method of claim 6 wherein the step of forming a window sequence, w[n] is formed in accordance with the relation:

$w<br><br>\left[n-R+1\right]=\underset{k=0}{\overset{R-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>h_{\mathrm{MF}}<br><br>\left[n-k\right]<br><br>z<br><br>\left[k\right],$

where R is an integer offset, h_MF is a matched filter, and k in an integer index.

8. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence for a window of values from the sample sequence, wherein the sample sequence is y[n], and the step of forming the difference sequence and comparing to a minimum value is performed in accordance with the relationship;

∀

m∈

[0,{circumflex over (P)}−

1],|y[n+m]−

y[n+m+N]|≦

ε

, where N, an integer, is the number of samples in a symbol, ε

is the minimum value to which the sequence is compared, {circumflex over (P)}, is an integer, where 0<

{circumflex over (P)}≦

P, and P is an integer number of samples that is a measure by which a periodic extension exceeds a channel impulse response;

comparing the difference sequence to a minimum value; and

loading a pointer register based on a minimum sequence index corresponding to the minimum value.

9. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence for a window of values from the sample sequence, wherein the sample sequence is y[n], and the step of forming the difference sequence and comparing to a maximum value is performed in accordance with the relationship;

∀

m∈

[0,{circumflex over (P)}−

1],[z_max−

|y[n+m]−

y[n+m+N]|]≦

ε

, where N, an integer, is the number of symbol samples, n is an integer index, m is an integer index, ε

is the maximum value to which the sequence is compared, {circumflex over (P)}, is an integer, where 0<

{circumflex over (P)}≦

P, and P is an integer number of samples that is a measure by which a periodic extension exceeds a channel impulse response;

comparing the difference sequence to a value; and

loading a pointer resister based on a minimum sequence index corresponding to a maximum value.

10. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence from the sample sequence, wherein the sample sequence is y[n], and the step of forming the difference sequence, z[n], is performed in accordance with the relationship;

$z<br><br>\left[n\right]=\underset{l=0}{\overset{\hat{P}-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br><br><br>y<br><br>\left[n+l\right]-y<br><br>\left[n+N+l\right]<br><br>,$

where N, an integer, is the number of samples in a symbol, l is an integer index, n is an integer index, {circumflex over (P)}, is an integer, where 0<

{circumflex over (P)}≦

P, and P is an integer number of samples that is a measure by which a periodic extension exceeds a channel impulse response;

forming a window sequence by weighting and summing selected points within the difference sequence;

locating the maximum value of the window sequence; and

locating a pointer register based on a sequence index corresponding to the maximum value.

11. A method of determining a symbol frame boundary in a multicarrier data signal, comprising the steps of:

forming a sample sequence from a received multicarrier signal;

calculating a difference sequence, z[n], from the sample sequence, wherein the sample sequence is y[n], and the step of calculating the difference sequence is performed in accordance with the relationship;

z[n]=z_max−

|y[n]−

y[n+N]|, where z_max is the maximum value of |y[n]−

y[n+N]|, N, an integer, is the number of samples in a frame, and n is an integer index;

forming a multiplicative estimate sequence from selected points within the difference sequence;

forming a window sequence by summing selected points within the product sequence;

locating the maximum value of the window sequence; and

loading a pointer register based on the sequence index corresponding to the maximum value.

12. The method of claim 11, wherein the step of forming a multiplicative estimate sequence, p[i,n], is performed in accordance with the relationship:

$p<br><br>\left[i,n\right]=\underset{i=0}{\overset{Q-1}{\prod <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>z<br><br>\left[n+i+j·<br><br>\left(N+M+P\right)\right],$

wherein Q is the number of frames being processed, M+P is the length of a periodic extension, M is the length of a communication channel impulse response, P is an integer number of samples that is a measure by which the periodic extension exceeds the channel impulse response, i is an integer index, and j is an integer index.

13. The method of claim 12, wherein the step of forming a window sequence, w[n] is performed in accordance with the relationship:

$w<br><br>\left[n\right]=\underset{i=0}{\overset{\hat{P}-1}{\sum <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\underset{j=0}{\overset{Q-1}{\prod <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>z<br><br>\left[n+i+j·<br><br>\left(N+M+P\right)\right],$

where {circumflex over (P)} is an integer and 0<

{circumflex over (P)}≦

P.