AGC gain selection method in wifi system

Abstract

The invention discloses a method for AGC gain selection in a wifi system, and the method comprises the following steps: S1, enabling a receiver to know that a current receiving frame is in an HT format through a wifi frame header L-SIG or HT-SIG, and carrying out the look-up of a table, so as to obtain an AGC Headroom maximum allowed additional rollback value [delta] 1; a required minimum input signal Pmin is demodulated; an analog gain gear NFmin corresponding to the required minimum input signal Pmin is demodulated; s2, according to the current Pin and 2nd STF, obtaining an AGC headroom extra rollback value, and looking up a table to obtain an initial AGC gain value Ginit; and S3, finally determining an AGC gain value according to the step S2. According to the invention, the anti-ACI performance can be improved, the AGC analog gain is adaptively reduced on the premise of not influencing the receiving performance, the selected gain is reduced compared with the gain initial value on the condition of not influencing the receiver performance, and the possibility of receiving signal saturation caused by burst interference is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of communication signals, and in particular to a method for selecting an AGC gain in a wifi system. Background Art

[0002] In WiFi systems, automatic gain control (AGC) is one of the key technologies. Its main function is to optimize signal quality by automatically adjusting the gain of the receiver, achieve stable and reliable data transmission, and improve network performance. However, the current AGC gain selection method cannot improve the anti-ACI performance, and by reducing the AGC analog gain, it will affect the receiving performance.

[0003] Therefore, a method for selecting AGC gain in a wifi system is proposed. Summary of the invention

[0004] The object of the present invention is to provide a method for selecting AGC gain in a wifi system, in order to improve the anti-ACI performance, the AGC analog gain is adaptively reduced without affecting the receiving performance.

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

[0006] A method for selecting AGC gain in a wifi system proposed by the present invention comprises the following steps:

[0007] S1. The receiver learns that the current received frame is in HT format through the WiFi frame header L-SIG or HT-SIG, and obtains the following by looking up the table:

[0008] The maximum allowable additional fallback value of AGC Headroom is Δ1;

[0009] The minimum input signal P required for demodulation min ;

[0010] The minimum input signal P required for demodulation min Corresponding analog gain level NF min ;

[0011] S2, according to the current P in，2nd STF , obtain the additional AGC headroom fallback value, and look up the table to obtain the initial AGC gain value G init ;

[0012] S3. Finally determine the AGC gain value according to step S2.

[0013] In some possible implementations, in step S2, P in，2nd STF ≤P min , it means that the current input signal size has no margin in the current transmission mode, then

[0014] Δ headroom =0.

[0015] In some possible implementations, in step S2, P in,2nd STF ≥P NF , then the signal-to-noise ratio is not limited by NF at the current input power, so the AGC Headroom is backed off by Δ1.

[0016] Δ headroom =Δ1.

[0017] In some possible implementations, in step S2, P in,2nd STF <P NF , the maximum AGC headroom fallback value is determined according to the following criteria:

[0018] Δ∈[0,Δ1]

[0019] Δ headroom =maxΔ

[0020] Δ satisfies the condition (P in,2nd STF -P min ≥NF(G init -Δ)-NF min ).

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention can improve the anti-ACI performance, and adaptively reduce the AGC analog gain without affecting the receiving performance. Under the condition of not affecting the receiver performance, the selected gain is smaller than the initial gain value, thereby reducing the possibility of receiving signal saturation due to burst interference. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram showing that when a signal is input to the receiver in the present invention, the signal-to-noise ratio changes with the change of the signal. DETAILED DESCRIPTION

[0024] 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.

[0025] A method for selecting AGC gain in a wifi system proposed by the present invention comprises the following steps:

[0026] 1. The wifi frame formats HT, VHT, and HE have corresponding HT-STF symbols, VHT-STF symbols, and HE-STF symbols, which are used by the receiver to perform 2 nd AGC gain selection:

[0027] 1) According to the current received frame type (HE, HT, VHT), MCS, transmission mode combination (Nss, STBC, DCM, etc.) obtained from the SIG information, the corresponding table is obtained:

[0028] AGC Headroom maximum allowable additional backoff value Δ1 (the maximum allowable additional backoff value is limited by ADC accuracy and digital demodulation module fixed-point accuracy);

[0029] The minimum input signal P required for demodulation min ;

[0030] The minimum input signal P required for demodulation min Corresponding analog gain level NF min .

[0031] 2) According to the current P in,2nd STF When the additional AGC headroom fallback value is 0, the initial AGC gain value G is obtained by looking up the table init

[0032] 3) If P in,2nd STF ≤P min , it means that the current input signal size has no margin in the current transmission mode, so

[0033] Δ headroom =0

[0034] 4) If P in,2nd STF ≥P NF , then the signal-to-noise ratio is not limited by NF at the current input power, then according to

[0035] Δ1 is used for AGC Headroom rollback.

[0036] Δ headroom =Δ1

[0037] When the receiver input signal is a large signal (for example, ≥-50dBm), the performance of the RF receiver is limited by the receiver phase noise and IQ imbalance, which is reflected in the signal-to-noise ratio not changing with the signal size.

[0038] When the receiver input signal is a small signal (for example, ≤-50dBm), the performance of the RF receiver is limited by the receiver noise factor, which is reflected in the decrease of signal-to-noise ratio as the signal decreases. NF For this purpose, the input signal power cutoff point P NF =-50dBm, such as Figure 1 shown.

[0039] 5) If P in，2nd STF <P NF , then the maximum backoff value of AGC Headroom Δ∈[0, Δ1] is determined according to the following criteria:

[0040] Δ headroom =maxΔ

[0041] Δ satisfies the condition (P in,2nd STF -P min ≥NF(G init -Δ)-NF min )

[0042] 6) Finally determine the AGC gain value

[0043] G=G init -Δ headroom .

[0044] 2. All WiFi frame formats have L-STF, which is used by the receiver to do 1 st AGC gain selection:

[0045] Since the currently received frame can be 11B, 11A, or other frame headers, the maximum allowable additional fallback value of AGC Headroom is selected according to the 11A 54M frame format. The other processes are the same as above (2 nd AGC gain selection).

[0046] Embodiment 1:

[0047] 1) The receiver learns from the WiFi frame header L-SIG and HT-SIG that the current received frame is in HT format, Nss=1, MCS=0, and obtains the following by looking up the table:

[0048] 1. The maximum allowable additional back-off value of AGC Headroom is Δ1 = 20dB;

[0049] 2. Minimum input signal P required for demodulation min =-79dBm;

[0050] 3. Minimum input signal P required for demodulation min Corresponding analog gain level NF min =7.5.

[0051] 2) Calculate the current signal power P according to HT-STF in,2nd STF =-45dBm, the corresponding analog gain required is G init =50dB, the noise coefficient corresponding to this analog gear is 17.2.

[0052] 3) Because P in,2nd STF =-45dBm>P NF =-50dBm, so

[0053] Δ headroom =Δ1=20dB.

[0054] 4) Therefore, the final selected 2nd AGC gain bit

[0055] G=G init -Δ headroom =30dB.

[0056] From the above analysis, we can see that although the final selected gain is 20dB smaller than the initial gain value, the performance of the RF receiver under large signals is limited by the receiver phase noise and IQ imbalance, and the signal-to-noise ratio does not change with the signal size, so the receiver performance is not affected. At the same time, because the selected gain is 20dB smaller than the initial gain value, the possibility of receiving signal saturation due to sudden interference is greatly reduced.

[0057] Embodiment 2:

[0058] 1) The receiver learns from the WiFi frame header L-SIG and HT-SIG that the current received frame is in HT format, Nss=1, MCS=4, and obtains the following by looking up the table:

[0059] 1.AGC Headroom maximum allowable additional back-off value Δ1 = 15dB

[0060] 2. Minimum input signal P required for demodulation min =-63dBm

[0061] 3. Minimum input signal P required for demodulation min Corresponding analog gain level NF min =8.6

[0062] 2) Calculate the current signal power P according to HT-STF in,2nd STF =-55dBm, the corresponding analog gain required is G init =60dB

[0063] 3) Because P in,2nd STF =-55dBm <P NF =-50dBm, so calculate:

[0064] P in,2nd STF -P min =8dB, look up the table to find the noise factor satisfies NF≤NF min The minimum gain level of =8.6+8=16.6dB is G=52dB.

[0065] Δheadroom =G init -G=8dB.

[0066] 4) Therefore, the final selected 2nd AGC gain bit

[0067] G=G init -Δ headroom =52dB.

[0068] From the above analysis, we can see that although the final selected gain is 8dB smaller than the initial gain value, it takes advantage of the fact that the received signal power is greater than the current transmission mode P min The selected gain is 8dB smaller than the initial value of the gain without affecting the receiver performance, which reduces the possibility of receiving signal saturation due to burst interference.

[0069] 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.

[0070] 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 selecting AGC gain in a wifi system, characterized in that: The following steps are involved: S1. The receiver learns that the current received frame is in HT format through the WiFi frame header L-SIG or HT-SIG, and obtains the following by looking up the table: The maximum allowable additional fallback value of AGC Headroom is Δ1; The minimum input signal P required for demodulation min ; The minimum input signal P required for demodulation min Corresponding analog gain level NF min ; S2, according to the current P in，2nd STF , obtain the additional AGC headroom fallback value, and look up the table to obtain the initial AGC gain value G init ; S3. Finally determine the AGC gain value according to step S2.

2. The method for selecting AGC gain in a wifi system according to claim 1, characterized in that: In step S2, P in，2nd STF ≤P min , it means that the current input signal size has no margin in the current transmission mode, then D headroom =0.

3. The method for selecting AGC gain in a wifi system according to claim 1, characterized in that: In step S2, P in，2nd STF ≥P NF , then the signal-to-noise ratio is not limited by NF at the current input power, so the AGC Headroom is backed off by Δ1. D headroom = Δ1.

4. The method for selecting AGC gain in a wifi system according to claim 2, characterized in that: For step S2, P in，2nd STF ≥P NF , the maximum AGC headroom fallback value is determined according to the following criteria: Δ∈[0,Δ1] Δ headroom =maxΔ Δ satisfies the condition (P in，2nd STF -P min ≥NF(G init -Δ)-NF min ).

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