Wireless frame having alternating cyclic prefixes

• US 20080080626A1
• Filed: 09/29/2006
• Published: 04/03/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Sahib, Anees A., Lawrence, Sean J., Biswas, Ashim
• Granted Patent: US 7,688,906 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

Embodiments of a wireless frame having alternating cyclic prefixes are presented herein.

Claims

1. An apparatus comprising:

a receiver to receive one or more frames having a plurality of symbols, wherein a cyclic prefix is associated with alternating said symbols; and

a module to demodulate the one or more frames to remove the cyclic prefix to obtain the symbols associated with cyclic prefix and at least one said symbol that is not associated with one or more of the cyclic prefixes.

2. An apparatus as described in claim 1, wherein the at least one said symbol is demodulated through calculation of a virtual cyclic prefix.

3. An apparatus as described in claim 2, wherein the virtual cyclic prefix is formed through estimation of inter-symbol interference due to each said symbol.

4. An apparatus as described in claim 2, wherein the virtual cyclic prefix is formed, at least in part, from a portion of a particular said symbol that is received previous to the at least one said symbol.

5. An apparatus as described in claim 1, wherein:

the one or more frames include a first, said symbol, a second said symbol and a third said symbol that are consecutively ordered, one to another;

the first said symbol and the third said symbol are each associated with a respective said cyclic prefix; and

the module is to demodulate the one or more frames by demodulating the first and third said symbols having the respective said cyclic prefixes, a result of which is then used to demodulate the second said symbol which does not have an associated said cyclic prefix.

6. An apparatus as described in claim 1, wherein the module is to demodulate the one or more frames through:

estimation of a diagonal matrix of channel coefficients;

estimation of said symbols transmitted with said cyclic prefixes through use of the matrix;

estimation of the at least one said;

symbol transmitted without a cyclic prefix through use of inter-symbol interference computed for a previously received said symbol; and

introduction of a virtual cyclic prefix for the at least one said symbol by removal of the inter-symbol interference -computed for the previously received said symbol and introduction of cyclic prefix inter-symbol interference for the at least one said symbol transmitted without the cyclic prefix.

7. An apparatus as described in claim 1, wherein the module is to demodulate the one or more frames through estimation of inter-symbol interference for each said symbol.

8. An apparatus as described in claim 7, wherein the module is to demodulate the symbols having associated cyclic prefixes by:

obtaining one or more time domain channel estimate samples by taking an Inverse Discrete Fourier Transform of a channel estimate;

obtaining a symbol estimate from the time domain channel estimate samples;

obtaining time domain coefficients of the estimated symbol from frequency domain samples of the symbol estimate;

computing a number of samples in a previous said symbol responsible for inter-symbol interference to the estimated said symbol;

convolving the number of samples in the previous said symbol responsible for inter-symbol interference with the time domain channel estimate samples to obtain a time domain channel affected signal;

calculating time domain inter-signal interference introduced from the time domain channel affected signal; and

obtaining inter-symbol interference frequency domain coefficients due to a particular said symbol transmitted with a respective said cyclic prefix by performing a Discrete Fourier Transform of the time domain inter-signal interference.

9. An apparatus as described in claim 7, wherein:

the one or more frames include a first said symbol, a second said symbol and a third said symbol that are consecutively ordered, one to another;

the first said symbol and the third said symbol are each associated with a respective said cyclic prefix; and

the module is to demodulate the second said symbol that is not associated with a respective said cyclic prefix through;

computation of an estimation of the third said symbol having the associated cyclic prefix;

estimation of the cyclic prefix of the third said symbol without inter-symbol interference from the second said symbol;

computation of a channel affected cyclic prefix in a time domain from the cyclic prefix estimate without inter-symbol interference;

obtain the frequency domain coefficients of the cyclic prefix of the third said symbol which has not been affected by inter-symbol interference through performance of a Discrete Fourier Transform of the channel affected cyclic prefix in the time domain;

estimation of inter-symbol interference due to the second said symbol from the estimation of the third said symbol having the associated cyclic prefix and the frequency domain coefficient of the cyclic prefix of the third said symbol; and

estimation of the second said symbol through use of the estimation of the inter-symbol interference due to the second said symbol and a frequency domain coefficient estimation of inter-symbol interference due to the first said symbol.

10. A method comprising:

associating a cyclic prefix with alternating ones of a plurality of symbols included in data such that at least one said symbol is not associated with a cyclic prefix; and

transmitting the data having the alternating symbols with the associated cyclic prefixes, the transmitted data having the at least one symbol that does not have an associated cyclic prefix.

11. A method as described in claim 10, wherein:

the plurality of symbols are included in data having a first said symbol, a second said symbol and a third said symbol that are consecutively ordered, one to another; and

the associating is performed such that the first said symbol and the third said symbol are each associated with a respective said cycle prefix and the second said symbol is not associated with a cyclic prefix.

12. A method as described in claim 10, wherein the plurality of symbols is included in an orthogonal frequency division multiplexing (OFDM) frame.

13. One or more computer-readable media comprising executable instructions that, when executed, direct a client to demodulate one or more frames having a first symbol, a second symbol and a third symbol that are consecutively ordered, one to another, and in which the first and third symbols are each associated with a respective cyclic prefix but the second symbol is not, wherein the demodulation includes estimation of inter-symbol interference for each said symbol.

14. One or more computer-readable media as described in claim 13, wherein the executable instructions direct the client to demodulate the second symbol through:

computation of an estimation of the third symbol having the associated cyclic prefix;

estimation of the cyclic prefix of the third symbol without inter-symbol interference from the second symbol;

computation of a channel affected cyclic prefix in a time domain from the cyclic prefix estimate without inter-symbol interference;

obtain frequency domain coefficients of the cyclic prefix of the third symbol which has not been affected by inter-symbol interference through performance of a Discrete Fourier Transform of the channel affected cyclic prefix in the time domain;

estimation of inter-symbol interference due to the second symbol from the estimation of the third symbol having the associated cyclic prefix and the frequency domain coefficient of the cyclic prefix of the third symbol; and

estimation of the second symbol through use of the estimation of the inter-symbol interference due to the second symbol and a frequency domain coefficient estimation of inter-symbol interference due to the first symbol.

15. One or more computer-readable media as described in claim 13, wherein the executable instructions direct the client to demodulate the first and third symbols by:

obtaining one or more time domain channel estimate samples by taking an Inverse Discrete Fourier Transform of a channel estimate;

obtaining a symbol estimate from the time domain channel estimate samples;

obtaining time domain coefficients of the estimated symbol from frequency domain samples of the symbol estimate;

computing a number of samples in a previous said symbol responsible for inter-symbol interference to the symbol estimate;

convolving the number of samples in the previous said symbol responsible for inter-symbol interference with the time domain channel estimate samples to obtain a time domain channel affected signal;

calculating time domain inter-signal interference introduced from the time domain channel affected signal; and

obtaining inter-symbol interference frequency domain coefficients due to a particular said symbol transmitted, with a respective said cyclic prefix by performing a Discrete Fourier Transform of the time domain inter-signal interference.

16. One or more computer-readable media as described in claim 13, wherein the estimation of inter-symbol interference for each said symbol results in computation of a virtual cyclic prefix for the second symbol.

17. A system comprising:

a receiver to receive, via a dipole antenna, one or more frames having a first symbol, a second symbol and a third symbol that are consecutively ordered, one to another, and in which the second symbol is not associated with a cyclic prefix and the first and third symbols are each associated with a respective cyclic prefix; and

a communication module to demodulate the first and third symbols, a result of which is used to demodulate the second symbol.

18. A system as described in claim 17, wherein the communication module is to demodulate the first, second and third symbols through calculation of inter-symbol interference for each said symbol.

19. A system as described in claim 17, wherein the communication module is to perform the demodulation such that a virtual cyclic prefix is created for the second symbol.

20. A system as described in claim 17, wherein the network connection device includes multiple antennas.