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

• US 6,785,349 B1
• Filed: 05/28/1999
• Issued: 08/31/2004
• 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: Dougall, John B. Jr., Rosenlof, John R., Smart, Kevin J.
• Primary Examiner(s): Fan, Chieh M.
• Application Number:
  US09/321,993
• Time in Patent Office: 1,922 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, 708/622, 708/873, 455/59
• US Class Current: 375/343
• CPC Class Codes: H04L 2025/03624 Zero-forcing
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• 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 27/2657 Carrier synchronisation
• CPC Class Codes: H04L 27/2662 Symbol synchronisation
• CPC Class Codes: H04L 27/2675 Pilot or 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;

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

forming a sliding window sequence by summing selected points within the multiplicative estimate sequence;

locating a maximum value of the sliding window sequence; and

,

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

2. The method of claim 1, wherein the sample sequence is y[n], and the step of calculating the difference sequence is performed in accordance with a relationship:

z[n]=z_max−

|y[n]−

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

y[n+N]|, and N is number of data samples in a frame.

3. The method of claim 2 wherein the step of forming the multiplicative estimate sequence, p[i, n], is performed in accordance with a relationship:

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

where M+P is the length of a periodic extension, Q is the number of frames being processed, and M is the length of a communication channel impulse response.

4. The method of claim 3 wherein the step of forming the sliding window sequence, w[n] is formed in accordance with a relationship:

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

where 0<

{circumflex over (P)}≦

P.

5. The method of claim 1, wherein the difference sequence is a non-negative-valued sequence.

6. The method of claim 1, wherein the difference sequence is an initial estimate of the correlation of samples from the sample sequence with samples shifted by N samples, and N is the number of data samples in a frame.

7. The method of claim 1, wherein the selected points used to form the multiplicative estimate sequence are spaced N+M+P points apart, where N is the number of data samples in a frame, M+P is the length of a periodic extension, and M is the length of a communication channel impulse response.

8. The method of claim 1, wherein the selected points used to form the sliding window sequence are adjacent points.