Packet configuring method and packet receiver

• US RE44,137 E1
• Filed: 06/06/2006
• Issued: 04/09/2013
• 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): Phillips, Hassan
• Assistant Examiner(s): Jones, Prenell P
• Application Number:
  US11/447,278
• Time in Patent Office: 2,499 Days
• Field of Search: 370/389, 370/480, 370/467, 370/276, 370/465, 370/352, 370/401, 370/210, 370/400, 370/395, 370/392, 370/342, 370/347, 370/202, 370/394, 370/208, 370/474, 370/310, 370/316, 370/335, 370/476, 375/299, 375/267, 375/147, 375/231, 375/148, 375/149, 375/130, 375/343, 375/326, 375/232, 375/233, 375/206, 375/200, 375/234, 375/368, 340/825.49, 379/406, 704/223, 123/436, 455/452
• 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 inter-symbol 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 packet transmission in a transmitter, said packets each including a training portion and a data portion, the method comprising:

said transmitter 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 at least two neighboring sequences of said K sequences are used for frequency-offset estimation, wherein an auto-correlation function for said sequence of N symbols is in an impulse state; and

said transmitter transmitting said packets.

17. The method according to claim 1, wherein the frequency offset is estimated based on a phase difference between neighboring sequences of the training portion.

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 or more), the packet receiver comprising:

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.

3. The packet receiver defined in claim 2, 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.

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 or more); and

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

5. The packet receiver defined in claim 2, 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.

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 or more), said packet receiver comprising:

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.

7. The packet receiver defined in claim 6, 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, 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.

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 or more), said method comprising:

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.

10. The packet receiving method defined in claim 9, 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, 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.

12. A method of packet transmission in a transmitter, said packets each including a training portion and a data portion, the method comprising:

said transmitter 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 at least two neighboring sequences of said K sequences are used for frequency-offset estimation; and

said transmitter transmitting said packets.

18. The method according to claim 12, wherein the frequency offset is estimated based on a phase difference between neighboring sequences of the training portion.

13. A packet transmitter comprising:

a packet configuring unit, each packet including a training portion and a data portion, that forms 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 1 or more), wherein at least two neighboring sequences of said K sequences are used for frequency-offset estimation; and

a transmitting unit that transmits each said packet.

19. The packet transmitter according to claim 13, wherein the frequency offset is estimated based on a phase difference between neighboring sequences of the training portion.

14. A packet receiver comprising:

a receiving unit that receives a packet;

a packet estimating unit, 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), each of said K sequences being formed of N symbols (where N is an integer of 1 or more), said packet estimating unit estimating frequency offset by using at least two neighboring sequences of said K sequences.

20. The packet receiver according to claim 14, wherein the frequency offset is estimated based on a phase difference between neighboring sequences of the training portion.

15. A method of receiving a packet with a packet receiver, the method comprising:

the packet receiver receiving a packet;

the packet receiver estimating the packet, each packet including a training portion and a data portion and formed that 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 1 or more), the estimating step estimating frequency offset by using at least two neighboring sequences of said K sequences.

21. The method according to claim 15, wherein the frequency offset is estimated based on a phase difference between neighboring sequences of the training portion.

16. A communication system comprising:

a packet transmitter;

a packet receiver;

wherein said packet receiver comprises;

a receiving unit that receives a packet;

a packet estimating unit, 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), each of said K sequences being formed of N symbols (where N is an integer of 1 or more), said packet estimating unit estimating frequency offset by using at least two neighboring sequences of said K sequences.

22. The communication system according to claim 16, wherein the frequency offset is estimated based on a phase difference between neighboring sequences of the training portion.