Method of determining a start of a transmitted frame in a frame-based communications network

• US 20030206559A1
• Filed: 04/04/2001
• Published: 11/06/2003
• Est. Priority Date: 04/07/2000
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Trachewsky, Jason Alexander, Corry, Alan, Ojard, Eric, Garlapati, Srinivasa
• Granted Patent: US 6,993,101 B2
• Time in Patent Office: Days
• US Class Current: 370/509
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0005 applied to payload information
• CPC Class Codes: H04L 1/0006 by adapting the transmission format
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1848 Time-out mechanisms
• CPC Class Codes: H04L 1/1877 for semi-reliable protocols, e.g. for less sensitive applications like streaming video buffer level management for video bitstream control arrangements H04N21/44004
• CPC Class Codes: H04L 1/1883 using multiple timers
• CPC Class Codes: H04L 1/1887 Scheduling and prioritising arrangements
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 12/40032 Details regarding a bus interface enhancer
• CPC Class Codes: H04L 12/4013 Management of data rate on the bus systems modifying transmission characteristics according to link quality H04L1/0001
• CPC Class Codes: H04L 12/40136 Nodes adapting their rate to the physical link properties LAN switches H04L49/351
• CPC Class Codes: H04L 12/40156 by using dedicated slots associated with a priority level
• CPC Class Codes: H04L 12/40163 by assigning priority to messages according to a message field
• CPC Class Codes: H04L 12/403 : with centralised control, e.g. polling
• CPC Class Codes: H04L 12/4035 : in which slots of a TDMA packet structure are assigned based on a contention resolution carried out at a master unit TDM/TDMA multiplex systems per se H04J3/1694; hybrid switching systems H04L12/64
• CPC Class Codes: H04L 12/407 : with decentralised control
• CPC Class Codes: H04L 12/413 : with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
• CPC Class Codes: H04L 12/417 : with deterministic access, e.g. token passing
• CPC Class Codes: H04L 2001/0093 : Point-to-multipoint
• CPC Class Codes: H04L 2001/125 : Arrangements for preventing errors in the return channel
• CPC Class Codes: H04M 11/00 : Telephonic communication systems specially adapted for combination with other electrical systems
• CPC Class Codes: H04M 11/06 : Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
• CPC Class Codes: Y02D 30/50 : in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

A method of determining a start of a transmitted frame at a receiver on a frame-based communications network. A preamble format for the transmitted frame is provided wherein a plurality of identical copies of a preamble symbol sequence are transmitted sequentially. A received transmitted frame is filtered using filter coefficients matched to the preamble symbol sequence to provide a correlation sequence. A squared-magnitude of the correlation sequence is computed. The squared-magnitude of the correlation sequence is low-pass filtered to provide a low-pass filtered correlation signal low-pass filtered signal. The low-pass filtered correlation signal is delayed to provide a delayed low-pass filtered correlation signal. The delayed low-pass filtered correlation signal is multiplied by a first fixed predetermined threshold to provide a multiplied correlation signal. The multiplied correlation signal is compared with the low-pass filtered correlation signal to provide a correlation difference indicator. Energy of the received transmitted frame is detected and the energy is low-pass filtered to provide a low-pass filtered energy signal comparing detected energy to a fixed energy threshold to provide a threshold compared energy signal. The low-pass filtered energy signal is multiplied by a second fixed predetermined threshold to provide a multiplied energy signal. The threshold compared low-pass filtered correlation signal is compared with the threshold compared mulitiplied energy signal to provide a correlation peak indicator. A logical-AND of the correlation difference indicator and the correlation peak indicator is formed to determine a match/no match comparison indicative of the start of a transmitted frame.

Claims

1. A method of determining a start of a transmitted frame at a receiver on a frame-based communications network, the method comprising:

providing a preamble format for the transmitted frame wherein a plurality of identical copies of a preamble symbol sequence are transmitted sequentially;

filtering a received transmitted frame using filter coefficients matched to the preamble symbol sequence to provide a correlation sequence;

computing a squared-magnitude of the correlation sequence;

low-pass filtering the squared-magnitude of the correlation sequence to provide a low-pass filtered correlation signallow-pass filtered signal;

delaying the low-pass filtered correlation signal to provide a delayed low-pass filtered correlation signal;

multiplying the delayed low-pass filtered correlation signal by a first fixed predetermined threshold to provide a multiplied correlation signal;

comparing the multiplied correlation signal with the low-pass filtered correlation signal to provide a correlation difference indicator;

detecting energy of the received transmitted frame and low-pass filtering the energy to provide a low-pass filtered energy signal comparing detected energy to a fixed energy threshold to provide a threshold compared energy signal;

multiplying the low-pass filtered energy signal by a second fixed predetermined threshold to provide a multiplied energy signal;

comparing the threshold compared low-pass filtered correlation signal with the threshold compared mulitiplied energy signal to provide a correlation peak indicator; and

forming a logical-AND of the correlation difference indicator and the correlation peak indicator to determine a match/no match comparison indicative of the start of a transmitted frame.

2. The method of claim 1, wherein the filtering includes low-pass filtering the received transmitted frame using filter coefficients matched to the preamble symbol sequence to provide a filtered received signal and averaging a squared-magnitude of the filtered received signal.

3. The method of claim 1, wherein the filtering is linear matched filtering.

4. The method of claim 3, wherein the filter coefficients are a time-reversed complex-conjugated repeated preamble symbol sequence.

5. The method of claim 4, wherein the time-reversed complex-conjugated repeated preamble repeated preamble symbol sequence is a constant-amplitude zero-autocorrelation sequence.

6. The method of claim 4, wherein the time-reversed complex-conjugated repeated preamble symbol sequence includes complex symbols drawn from a Quadrature Phase Shift Keying or 4-Quadrature Amplitude Modulation constellation.

7. The method of claim 4, wherein the time-reversed complex-conjugated repeated preamble symbol sequence includes 16 symbols repeated at least 3 times, every 4-symbol sub-sequence of which being constant amplitude, zero autocorrelation.

8. The method of claim 1, wherein the steps of multiplying include first computing 10*log10(.), or an approximation of 10*log10(.), of each operand to provide a plurality of log operands and then adding each of the plurality of log operands.

9. A method of determining a a start of a transmitted frame at a receiver on a frame-based communications network, the method comprising:

providing a preamble format for the transmitted frame wherein a plurality of identical copies of a preamble symbol sequence are transmitted sequentially;

filtering a received transmitted frame using filter coefficients matched to the preamble symbol sequence to provide a correlation sequence by low-passlinear matched filtering the received transmitted frame using filter coefficients matched to the preamble symbol sequence to provide a filtered received signal and averaging a squared-magnitude of the filtered received signal, the filter coefficients being a time-reversed complex-conjugated repeated preamble symbol including time-reversed complex symbols drawn from a Quadrature Phase Shift Keying or 4-Quadrature Amplitude Modulation constellation and having 16 symbols repeated at least 3 times, every 4-symbol sub-sequence of which being constant amplitude, zero autocorrelation;

computing a squared-magnitude of the correlation sequence;

low-pass filtering the squared-magnitude of the correlation sequence to provide a low-pass filtered correlation signallow-pass filtered signal;

delaying the low-pass filtered correlation signal to provide a delayed low-pass filtered correlation signal;

multiplying the delayed low-pass filtered correlation signal by a first fixed predetermined threshold by first computing 10*log10(.), or an approximation of 10*log10(.), of each low-pass filtered correlation signal operand to provide a plurality of low-pass filtered correlation signal log operands and then adding each of the plurality of low-pass filtered correlation signal log operands to provide a multiplied correlation signal;

comparing the multiplied correlation signal with the low-pass filtered correlation signal to provide a correlation difference indicator;

detecting energy of the received transmitted frame and low-pass filtering the energy to provide a low-pass filtered energy signal comparing detected energy to a fixed energy threshold to provide a threshold compared energy signal;

multiplying the low-pass filtered energy signal by a second fixed predetermined threshold by first computing 10*log10(.), or an approximation of 10*log10(.), of each low-pass filtered energy signal operand to provide a plurality of low-pass filtered energy signal log operands and then adding each of the plurality of low-pass pass filtered energy signal log operands to provide a multiplied energy signal;

comparing the threshold compared low-pass filtered correlation signal with the threshold compared mulitiplied energy signal to provide a correlation peak indicator; and

forming a logical-AND of the correlation difference indicator and the correlation peak indicator to determine a match/no match comparison indicative of the start of a transmitted frame.