Method for enhancing noise estimation in wifi system

Abstract

The invention discloses a method for enhancing noise estimation in a wifi (Wireless Fidelity) system. The method comprises the following steps of: S1, performing SNRtime and # imgabs0 # estimation by using two repeated legacy LTFs (Long Term Frequency) of a time domain signal; s2, noise estimation is carried out by using the frequency domain symbol L-SIG and the reconstructed symbol Sk thereof; and S3, final noise estimation confirmation is carried out in combination with the step S1 and the step S2. According to the method, the time domain and the frequency domain are combined to perform noise estimation, so that the problems that in the prior art, the noise estimation is performed by purely using two repeated legacy LTFs in the time domain, the accuracy is insufficient due to the existence of DC and frequency offset, the frequency estimation algorithm is purely used, the channel estimation accuracy is insufficient and ICI is caused, and the accuracy is insufficient due to direct frequency estimation are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of communication signals, and in particular to a method for enhancing noise estimation in a wifi system. Background Art

[0002] When the frequency conversion receiver is in the case of high SNR (>=35dB), the noise estimation using two repeated legacy LTFs in the time domain is not accurate enough due to the existence of DC and frequency offset. The frequency estimation algorithm is not accurate enough due to the insufficient channel estimation accuracy and ICI problem.

[0003] Therefore, a method for enhancing noise estimation in WiFi system is proposed. Summary of the invention

[0004] The object of the present invention is to provide a method for enhancing noise estimation in a wifi system.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A method for enhancing noise estimation in a wifi system proposed by the present invention comprises the following steps:

[0007] S1. Use 2 repeated legacy LTFs of the time domain signal to do SNR time and estimate;

[0008] S2. Using the frequency domain symbol L-SIG and its reconstructed symbol S k Make noise estimates;

[0009] S3. Combining step S1 and step S2, the final noise estimation is confirmed.

[0010] In some possible implementations, the formula used in step S1 is as follows:

[0011]

[0012] In some possible implementations, the formula used in step S2 is as follows:

[0013]

[0014] In some possible implementations, for step S2, the following formula is used for correction:

[0015]

[0016] In some possible implementations, in step S3, the final noise estimation confirmation formula is as follows:

[0017]

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention combines the time domain and the frequency domain for noise estimation, thereby solving the problems in the prior art of simply using two repeated legacy LTFs in the time domain for noise estimation, which has insufficient accuracy due to the existence of DC and frequency offset, and directly using frequency estimation algorithm, which also has insufficient accuracy due to the insufficient channel estimation accuracy and ICI problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram showing that the ICI problem caused by the noisy channel estimation and the frequency offset of the OFDM system in the present invention is more obvious in the SNR region. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] A method for enhancing noise estimation in a wifi system proposed by the present invention comprises the following steps:

[0023] Using 2 repeated legacy LTFs of the time domain signal to calculate SNR time and estimate,

[0024]

[0025] Using the frequency domain symbol L-SIG and its reconstructed symbol S k Make noise estimate

[0026] Y k =H k S k +n

[0027]

[0028] The reconstructed symbol can be the result of hard judgment based on the equalized signal, which has the advantages of simple implementation and low latency. It can also be the frequency domain signal regenerated from the bits after channel decoding through the process specified by the protocol, which has the advantage of no bit errors.

[0029] Another advantage of using L-SIG is that the symbol uses BPSK modulation, and the power of each subcarrier is fixed, which is conducive to improving the accuracy of noise estimation.

[0030] For HT frames, HT-SIG symbols can also be used for noise estimation. For VHT frames, VHT-SIG symbols can also be used for noise estimation. For HE frames, HE-SIG symbols can also be used for noise estimation. The above symbols have the same advantages as L-SIG.

[0031] Since H′ in the above formula k The ICI problem caused by the noisy channel estimation and the frequency offset of the OFDM system leads to the above estimation It will be over estimated, and it is more obvious in the high SNR area, as shown in the following figure (the horizontal axis is the actual SNR, the vertical axis is ).

[0032] Therefore, the following formula is used to correct the frequency domain estimation noise

[0033]

[0034] The final noise estimate is determined as

[0035]

[0036] Comparative Example

[0037]

[0038]

[0039] 1) When DC residual and frequency offset do not exist at the same time, the conventional scheme and the proposed scheme provide similar performance, with an estimated error of 0.1dB-0.2dB.

[0040] 2) When there is both DC residual and frequency offset, the estimation error of the traditional scheme is 6.5dB, while the estimation error of this scheme is 0.3dB, which is much better than the traditional scheme.

[0041] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0042] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for enhancing noise estimation in a wifi system, characterized by: The following steps are involved: S1. Use 2 repeated legacy LTFs of the time domain signal to do SNR time and estimate; S2. Using the frequency domain symbol L-SIG and its reconstructed symbol S k Make noise estimates; S3. Combining step S1 and step S2, the final noise estimation is confirmed.

2. The method for enhancing noise estimation in a wifi system according to claim 1, characterized in that: The formula used in step S1 is as follows:

3. The method for enhancing noise estimation in a wifi system according to claim 1, characterized in that: The formula used in step S2 is as follows: Y k =H k S k +n 4. The method for enhancing noise estimation in a wifi system according to claim 2, characterized in that: For step S2, the following formula is used for correction:

5. The method for enhancing noise estimation in a wifi system according to claim 1, characterized in that: In step S3, the final noise estimation confirmation formula is as follows:

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