Method for tracking sending power and pick-up power in wifi system

Abstract

The invention discloses a method for tracking transmitting power and receiving power in a wifi (Wireless Fidelity) system, which performs power tracking at frequency by utilizing the characteristics of pilot frequency pilot subcarriers of wifi OFDM (Orthogonal Frequency Division Multiplexing) symbols, and specifically comprises the following steps: S1, calculating the average power of all frequency domain pilot frequency subcarriers according to a fixed symbol interval Navg; s2, recording a first output result as reference power of power tracking; s3, smoothing the instantaneous value of power tracking according to a fixed symbol interval Navg; and S4, according to a fixed symbol interval Navg, making power tracking value power according to a formula. According to the method, power estimation is carried out according to Pilot, the PA output power can be effectively tracked, and the problem that in the prior art, due to the non-constant amplitude characteristic and the high peak-to-average ratio of the time domain signal, the average power of the time domain signal cannot be used for power tracking of the OFDM signal is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of communication signals, and in particular to a method for tracking transmission power and receiving power in a Wi-Fi system. Background Art

[0002] Affected by the non-ideal temperature characteristics of RF devices such as PA, the power of WiFi signals varies over time within a frame, and the long pilot symbol of OFDM signals (used for channel estimation) only exists in the frame header (except when HE midamble is enabled). At the same time, the transmission / reception of high-order modulation methods such as MCS11 has very high requirements for power control (<0.1dB), that is:

[0003] When receiving, it is necessary to track and compensate the power of the received signal;

[0004] When sending, it is necessary to track and compensate the power of the transmitted signal.

[0005] However, due to the non-constant amplitude characteristics and peak-to-average ratio problem of OFDM signals in the time domain, it is impossible to use the average power of the time domain signal for power tracking.

[0006] Therefore, a method for tracking the sending power and receiving power in a WiFi system is proposed. Summary of the invention

[0007] The object of the present invention is to provide a method for tracking sending power and receiving power in a WiFi system.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] The present invention proposes a method for tracking the transmission power and receiving power in a wifi system, which uses the characteristics of the pilot subcarrier of the wifi OFDM symbol to track the power at frequency, and specifically includes the following steps:

[0010] S1, at a fixed symbol interval N aυg Calculate the average power of all frequency domain pilot subcarriers;

[0011] S2, recording the first output result as the reference work of power tracking;

[0012] S3, at a fixed symbol interval N aυg , the instantaneous value of power tracking is smoothed;

[0013] S4, at a fixed symbol interval N aυg , follow the formula to calculate the power tracking value:

[0014]

[0015] Rmax is the threshold value that triggers power adjustment, L step is the step value of power adjustment;

[0016] At a fixed symbol interval N aυg , adjust the digital power gain;

[0017] DAGC Cur =DAGC Cur ·(1+L track ).

[0018] In some possible implementations, in step S4,

[0019] When receiving power tracking, press DAGC cur A digital power gain compensation module for adjusting the receiving path;

[0020] When transmitting power tracking, press DAGC cur Adjust the digital power gain compensation module of the transmission path.

[0021] In some possible implementations, during the transmit power tracking, the transmit output signal needs to be looped back to the Rx path input, and the Rx path needs to be opened for corresponding demodulation.

[0022] In some possible implementations, the characteristics of the pilot subcarrier of the wifi OFDM symbol include the following:

[0023] The pilot subcarrier is fixed at the frequency subcarrier position, that is, the fading is consistent and is not affected by the frequency fading of the wireless channel;

[0024] The pilot subcarrier modulation mode is fixed to BPSK, that is, the signal power of different time domain symbols is fixed.

[0025] In some possible implementations, in step S1, the calculation formula for the average power of all frequency domain pilot subcarriers is as follows:

[0026]

[0027] In some possible implementations, in step S2, the first output result is recorded as the calculation formula of the reference power for power tracking as follows:

[0028] P Ref =P Pilot (0).

[0029] In some possible implementations, in step S3, the smoothing process smoothing filtering can be expressed as

[0030]

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention can effectively track the PA output power by performing power estimation based on the Pilot, and effectively solves the problem in the prior art that the average power of the time domain signal cannot be used for power tracking due to the non-constant amplitude characteristics and high peak-to-average ratio of the OFDM signal in the time domain. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a receiving power tracking flow chart of the present invention;

[0034] Figure 2 This is a flow chart of the transmission power tracking in the present invention;

[0035] Figure 3 It is a line graph of experimental data in the experiment of the present invention. DETAILED DESCRIPTION

[0036] 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.

[0037] The present invention proposes a method for tracking the transmission power and receiving power in a wifi system, using

[0038] The following characteristics of the pilot subcarrier of the WiFi OFDM symbol allow power tracking at frequency:

[0039] 1) The pilot subcarrier is fixed at the frequency subcarrier position, that is, the fading is consistent and is not affected by the frequency fading of the wireless channel;

[0040] 2) The pilot subcarrier modulation mode is fixed to BPSK, that is, the signal power of different time domain symbols is fixed.

[0041] The details are as follows:

[0042] 1. According to the fixed symbol interval N aυg Calculate the average power of all frequency domain pilot subcarriers (to increase calculation accuracy)

[0043]

[0044] 2. Record the first output result as the reference power for power tracking, that is

[0045] PRef =P Pilot (0)

[0046] 3. According to the fixed symbol interval N aυg , the instantaneous value of power tracking is further smoothed, for example, a smoothing filter can be expressed as

[0047]

[0048] 4. According to the fixed symbol interval N aυg , do the power tracking value power as follows

[0049]

[0050] R max is the threshold value that triggers power adjustment, L step is the step value of power adjustment

[0051] At a fixed symbol interval N aυg , adjust the digital power gain

[0052] DAGC Cur =DAGC Cur ·(1+L track )

[0053] For the above, if it is receiving power tracking, press DAGC cur Adjust the digital power gain compensation module of the receiving path, such as Figure 1 shown.

[0054] For the above, if it is transmit power tracking, press DAGC cur Adjust the digital power gain compensation module of the transmit path. In addition, if transmit power tracking is used, the transmit output signal needs to be looped back to the Rx path input, and the Rx path needs to be opened for corresponding demodulation, such as Figure 2 shown.

[0055] The above method is used to conduct experiments, such as Figure 3 As shown, experimental data were obtained.

[0056] 1) From the blue line, we can see that the power estimation based on the Pilot can effectively track the changes in the PA output power;

[0057] 2) From the purple line, we can see that the compensation result is close to ideal;

[0058] 3) In addition, the experimental results show that when power compensation is not implemented, the EVM is 31dB. After power compensation is implemented, the EVM is increased to 40dB.

[0059] 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.

Claims

1. A method for tracking transmission power and receiving power in a wifi system, characterized by: Using the characteristics of the pilot subcarrier of the WiFi OFDM symbol to perform power tracking at frequency, the specific steps include: S1, at a fixed symbol interval N avg Calculate the average power of all frequency domain pilot subcarriers; S2, recording the first output result as the reference work of power tracking; S3, at a fixed symbol interval N avg , the instantaneous value of power tracking is smoothed; S4, at a fixed symbol interval N avg , follow the formula to calculate the power tracking value: R max is the threshold value that triggers power adjustment, L step is the step value of power adjustment; At a fixed symbol interval N avg , adjust the digital power gain; DAGC Cur =DAGC Cur ·(1+L track )。 2. The method for tracking the transmission power and receiving power in a wifi system according to claim 1, characterized in that: In the step S4, When receiving power tracking, press DAGC cur A digital power gain compensation module for adjusting a receiving path; When transmitting power tracking, press DAGC cur Adjust the digital power gain compensation module of the transmission path.

3. The method for tracking the transmission power and receiving power in a wifi system according to claim 2, characterized in that: During the transmission power tracking, the transmission output signal needs to be looped back to the Rx path input, and the Rx path needs to be opened for corresponding demodulation.

4. The method for tracking the transmission power and receiving power in a wifi system according to claim 1, characterized in that: The characteristics of the pilot subcarrier of the wifi OFDM symbol include the following: The pilot subcarrier is fixed at the frequency subcarrier position, that is, the fading is consistent and is not affected by the frequency fading of the wireless channel; The pilot subcarrier modulation mode is fixed to BPSK, that is, the signal power of different time domain symbols is fixed.

5. The method for tracking transmission power and receiving power in a wifi system according to claim 1, characterized in that: In step S1, the calculation formula for the average power of all frequency domain pilot subcarriers is as follows:

6. The method for tracking transmission power and receiving power in a wifi system according to claim 1, characterized in that: In step S2, the first output result is recorded as the calculation formula of the reference power for power tracking as follows: P Ref =P Pilot (0)。 7. The method for tracking transmission power and receiving power in a wifi system according to claim 1, characterized in that: In step S3, the smoothing process and smoothing filtering can be expressed as:

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