Packet configuring method and packet receiver

• US RE39,981 E1
• Filed: 12/13/2005
• Issued: 01/01/2008
• Est. Priority Date: 07/08/1998
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Okanoue, Kazuhiro
• Primary Examiner(s): Pham; Chi
• Assistant Examiner(s): JONES, PRENELL P
• Application Number:
  US11/301,328
• Time in Patent Office: 749 Days
• Field of Search: 370/389, 370/401, 370/474, 370/352, 370/341, 370/441, 370/203, 375/233, 375/267, 375/231, 375/229, 375/232, 375/222, 375/206, 375/200, 375/147, 375/133, 455/503, 455/101, 455/273, 455/423, 455/518
• US Class Current: 370/389
• CPC Class Codes: H04L 2027/003 at baseband only
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal

Abstract

A packet receiver is provided that accurately estimates a frequency offset and a channel impulse response even when a transmitted packet is detected with an erroneous timing in a communication mode (typified by the LAN (local Area Network)) where packets are asynchronously transmitted, and thus provides a training sequence which can demodulate the received packet. The training sequence 101 is formed of K sequences 100-1 to 100-K serially connected, each formed of the same N symbols. Even in a channel where a intersymbol interference occurs when such a training sequence is used, a received signal shifted by the time corresponding to N-symbols becomes the signal which is different by a phase difference caused by a frequency offset between the transmitter and the receiver. Thus, even if the head of a packet is detected with an erroneous timing, the frequency offset can be estimated.

Claims

1. A method of configuring packets, said packets each including a training portion and a data portion, the method comprising forming said training portion by serially connecting K sequences (where K is an integer of 2 or more), each of said K sequences being formed of N symbols (where N is an integer of 2 1 or more), wherein a phase difference between two neighboring sequences of said K sequences is used for frequency-offset estimation, wherein an auto-correlation function for said sequence of N symbols is in an impulse state.

2. A packet receiver that receives packets, each packet including a training portion and a data portion used to initialize said packet receiver, said training portion being formed by serially connecting K sequences (where K is an integer of 2 or more), each of said K sequences being formed of N symbols (where N is an integer of 2 1 or more), the packet receiver comprising comprises:

a frequency-offset estimation means for estimating a frequency offset based on a phase difference between two neighboring sequences of K sequences of a received packet, each of said K sequences being formed of N symbols;

a frequency-offset compensation means for compensating a frequency offset contained in said received packet based on said frequency offset estimation; and

a channel impulse response estimation means for estimating an impulse response of a channel based on an output for which the frequency offset is compensated .

4. The packet receiver defined in claim 2, wherein said frequency offset estimation means comprises:

a delay circuit for delaying said received packet by a transmission period of time of a sequence of N-symbol sequences;

a phase difference detection circuit for detecting a phase difference between an output of said delay circuit and said received packet;

an integrator for integrating a detection output of said phase difference detection circuit over a transmission period of time of a sequence of M symbols (where M is an integer of 2 1 or more); and

a divider circuit for dividing an output of said integrator by a product of N and M.

13. The packet receiver as claimed in claim 2, further comprising:

a frequency-offset compensation means for compensating a frequency offset contained in said received packet based on said frequency offset estimation; and

a channel impulse response estimation means for estimating an impulse response of a channel based on an output for which the frequency offset is compensated.

6. A packet receiver for receiving packets, each of said packets including a training portion and a data portion used to initially set a receiver, said training portion being formed by serially connecting K sequences (where K is an integer of 2 or more), each of K sequences being formed of N symbols (where N is an integer of 2 1 or more), said packet receiver comprising comprises:

a frequency offset estimation means for detecting a phase difference between a sequence received prior to NT (where T is a continuous time of one symbol) and a currently received sequence, and for estimating a frequency offset based on said phase difference;

a frequency offset compensation means for compensating said frequency offset by rotating the phase of a received signal in the frequency offset compensation direction based on a frequency offset estimation value; and

a channel impulse estimation means for estimating an impulse response of a channel based on an output from an output for which the frequency offset is compensated .

3. The packet receiver defined in claim 2 14, wherein:

an auto-correlation function of said N symbol sequences is in an impulse state; and

said channel impulse response estimation means comprises means for estimating a channel impulse response based on a sequence for which the auto-correlation function is in an impulse state, and a received training sequence.

5. The packet receiver defined in claim 2 14, wherein said impulse response estimation means outputs a channel impulse response estimation value after inputting a pulse representing that said frequency offset estimation means has completed frequency offset estimation.

14. The packet receiver as claimed in claim 6, further comprising:

a frequency offset compensation means for compensating said frequency offset by rotating the phase of a received signal in the frequency offset compensation direction based on a frequency offset estimation value; and

a channel impulse estimation means for estimating an impulse response of a channel based on an output from an output for which the frequency offset is compensated.

9. A packet receiving method for receiving packets, each of said packets including a training portion and a data portion to initially set a receiver, said training portion being formed by serially connecting K sequences (where K is an integer of 2 or more), each of said K sequences being formed of N symbols (where N is an integer of 2 1 or more), said method comprising comprises:

estimating a frequency offset based on a phase difference between two neighboring sequences of K sequences of a received packet, each of K sequences being formed of N symbols;

compensating a frequency offset contained in said received packet based on a frequency offset estimation value; and

estimating an impulse response of a channel based on a received packet of which the frequency offset is compensated .

7. The packet receiver defined in claim 6 15, wherein an auto-correlation function of said N symbol sequences is in an impulse state;

and wherein said channel impulse response estimation means comprises means for estimating a channel impulse response based on a sequence in which the auto-correlation function is in an impulse state, and a received training sequence.

8. The packet receiver defined in claim 6 15, wherein said impulse response estimation means outputs a channel impulse response estimation value after inputting a pulse representing that said frequency offset estimation means has completed frequency offset estimation.

15. The packet receiving method as claimed in claim 9, further comprising:

compensating a frequency offset contained in said received packet based on a frequency offset estimation value; and

estimating an impulse response of a channel based on a received packet of which the frequency offset is compensated.

12. A method of configuring packets, said packets each including a training portion and a data portion, the method comprising forming said training portion by serially connecting K sequences (where K is an integer of 2 or more), each of said K sequences being formed of N symbol(s) (where N is an integer of 1 or more), wherein a phase difference between two neighboring sequences of said K sequences is used for frequency-offset estimation.

16. A packet transmitter that transmits packets, each packet including a training portion and a data portion, said training portion being formed by serially connecting K sequences (where K is an integer of 2 or more), wherein a phase difference between two neighboring sequences of said K sequences is used for frequency-offset estimation, each of said K sequences being formed of N symbols (where N is an integer of 1 or more).

10. The packet receiving method defined in claim 9 16, wherein said step of estimating an impulse response of said channel comprises estimating a channel impulse response by placing an auto-correlation function of said sequence of N symbols in an impulse state, and detecting a peak value of an autocorrelation value between a received signal and said sequence of N symbols.

11. The packet receiving method defined in claim 9 16, wherein said step of estimating an impulse response of said channel comprises the step of outputting a channel impulse response estimation value after frequency offset estimation has been completed.