Frequency point selection method of 230MHz frequency band multi-frequency point FSK (Frequency Shift Keying) system

Abstract

The invention provides a frequency point selection method of a 230MHz frequency band multi-frequency-point FSK (Frequency Shift Keying) system, which comprises the following steps of: sending a test signal in a 230MHz frequency band from a sending side to a receiving side of the multi-frequency-point FSK system according to a set period, monitoring channel quality on each frequency point after the receiving side receives the test signal, selecting the frequency point with the maximum channel quality as a target frequency point, and selecting the frequency point with the maximum channel quality as the target frequency point. A feedback signal is sent to the sending side; and after the sending side receives the feedback signal, the channel quality of the target frequency point is compared with the channel quality of the currently used frequency point, whether the frequency point needs to be updated or not is judged, and the target frequency point is automatically updated according to a set period by repeating the process. According to the invention, frequency point screening is carried out at the two ends of the sending side and the receiving side, so that signals are prevented from being sent at frequency points which are interfered for a long time, and the problem of power consumption in the prior art is reduced while the anti-interference capability of signal transmission is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a frequency selection method for a 230MHz frequency band multi-frequency FSK system. Background Art

[0002] There are three types of interference in the 230MHz private network frequency band: broadband full-frequency interference, narrowband co-frequency interference and narrowband adjacent frequency interference. Among them, broadband full-frequency interference is mainly caused by various LED electronic screens, electronic billboards, electronic nameplates, and spotlights or lighting lamps; narrowband co-frequency interference is mainly caused by authorized radio stations and temporary interference in the 230MHz frequency band; narrowband adjacent frequency interference is mainly caused by other 230MHz narrowband communication systems using non-power frequency points.

[0003] In the case of broadband full-frequency interference, technologies such as spread spectrum communication and narrowband transmission can be used to improve the receiving performance. Multi-frequency shift keying (multi-frequency FSK) modulation technology is a type of narrowband transmission technology. Compared with OFDM (orthogonal frequency division multiplexing) technology, multi-frequency FSK has the following advantages: the modulation information only changes in frequency, does not use amplitude modulation information, has a peak-to-average ratio of zero, maintains low power consumption characteristics, and all power is concentrated on one carrier, which has a strong ability to resist broadband interference.

[0004] However, the performance of multi-frequency FSK will be affected by narrowband co-channel interference and narrowband adjacent channel interference. In the face of narrowband interference, the existing technology uses sampling frequency hopping technology to deal with it, that is, the terminal signal is sent at a frequency point according to a pre-agreed frequency point pattern; this method effectively reduces the probability of signal interference, but it also increases the power consumption of the terminal, and the terminal needs to send the same signal at multiple frequency points. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a frequency selection method for a 230MHz frequency band multi-frequency FSK system that reduces terminal power consumption while avoiding long-term interference.

[0006] Technical solution: A frequency selection method for a 230MHz frequency band multi-frequency FSK system, comprising the following steps:

[0007] (1) A test signal in the 230 MHz frequency band is sent from the transmitting side of the multi-frequency FSK system to the receiving side according to a set period;

[0008] (2) After receiving the test signal, the receiving side monitors the channel quality at each frequency point in the test signal bandwidth, selects the frequency point with the highest channel quality as the target frequency point, and sends a feedback signal to the sending side;

[0009] (3) After receiving the feedback signal, the sending side compares the channel quality of the target frequency with the channel quality of the currently used frequency. If the channel quality of the target frequency exceeds the sum of the channel quality of the currently used frequency and the set positive value, the target frequency is used to send a signal to the receiving side. Otherwise, the currently used frequency remains unchanged.

[0010] (4) Repeat steps (2)-(3) to automatically update the target frequency according to the set period.

[0011] Preferably, step (3) also includes: the sending side monitors and counts the energy of each frequency point through the feedback signal. Within the set period, if the cumulative energy obtained by counting the currently used frequency point is the smallest, the currently used frequency point is kept unchanged; otherwise, the frequency point with the smallest cumulative energy within the set period is selected as the target frequency point, and the signal is sent using the target frequency point.

[0012] Further preferably, in step (3), if the sum of the accumulated energy of the target frequency and the set positive value is lower than the accumulated energy of the currently used frequency, the sending side sends the signal using the target frequency.

[0013] Optionally, in step (3), the sending side simultaneously receives the feedback signal according to the test signal bandwidth, and monitors and counts the energy of all frequency points on the test signal bandwidth at one time.

[0014] Optionally, in step (3), the sending side receives the feedback signal at one frequency point each time, and monitors and counts the energy of the frequency point.

[0015] Optionally, the granularity of listening is 25kHz carrier width.

[0016] Optionally, the granularity of the monitoring is an integer multiple of the 25kHz carrier width.

[0017] Optionally, the test signal is sent independently at each frequency point in the 230 MHz frequency band.

[0018] Optionally, the test signal is sent over a set bandwidth within the 230 MHz frequency band.

[0019] Specifically, in step (2) and step (3), the target frequency point is obtained by filtering.

[0020] Beneficial effect: Compared with the prior art, the significant effect of the present invention is: by sending a test signal on the sending side of the multi-frequency FSK system, the channel quality is obtained by listening on the receiving side, and a feedback signal is returned, which is compared with the channel quality of the currently used frequency, so as to update the frequency used to send the signal and reduce interference. The energy of each frequency contained in the feedback signal of the receiving side is counted on the sending side, and the target frequency is screened from the energy perspective. The signal is avoided from being sent on a frequency that is interfered with for a long time on both the sending and receiving sides. While enhancing the anti-interference ability of signal transmission, the power consumption problem existing in the prior art is reduced. At the same time, the target frequency used for signal transmission can be automatically updated according to the period of the test signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flow chart of the method of the present invention.

[0022] Figure 2 It is a structural diagram of the sending side and the receiving side of the multi-frequency FSK system of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with the accompanying drawings.

[0024] See also Figure 1 As shown, the present invention provides a frequency selection method for a 230MHz frequency band multi-frequency FSK system, comprising the following steps:

[0025] (1) A test signal in the 230 MHz frequency band is sent from the transmitting side of the multi-frequency FSK system to the receiving side according to a set period.

[0026] In the present invention, a multi-frequency FSK system (MFSK) is adopted, and there are M orthogonal modulation frequencies [f0...f k ...f M-1 ], M is a power of 2, a frequency point k∈[0,M-1] is selected through a certain mapping method, and this frequency point is selected for modulation and transmission, and the transmitted signal is: s(t)=cos(f c t+2π*f k t), where f c is the carrier frequency. Assume that the interval between the frequencies is SCS, and the duration of each multi-frequency FSK modulation symbol must be greater than 1 / SCS. According to the multi-frequency FSK modulation order M and the frequency interval SCS, the signal occupied bandwidth BW = M*SCS.

[0027] 230MHz has some cross-band usage, and the carrier granularity is 25kHz. At the same time, multiple frequency points can be selected for joint use to increase the rate. Therefore, the granularity of the listening is 25kHz carrier width or an integer multiple of 25kHz carrier width.

[0028] The transmitting side periodically sends a test signal, which can be a multi-carrier signal based on a constant modulus in the time-frequency domain, that is, sent on a set bandwidth on the 230MHz frequency band, or it can be sent on various frequency points on the 230MHz frequency band in turn due to limitations on the transmitting end.

[0029] (2) After receiving the test signal, the receiving side monitors the channel quality at each frequency point in the test signal bandwidth, selects the frequency point with the highest channel quality as the target frequency point, and sends a feedback signal to the sending side.

[0030] The listening is performed according to the set period, and the formula for the channel quality is:

[0031] CQI(i,n)=αCQI i (i,n)+(1-α)CQI(i,n-1)

[0032] CQI i (i,n) is the channel quality at frequency i at the current moment, CQI(i,n) is the channel quality after filtering at the current moment, and α is the time filtering coefficient, that is, the weighted average coefficient of historical data.

[0033] (3) After receiving the feedback signal, the sending side compares the channel quality of the target frequency with the channel quality of the currently used frequency. If the channel quality of the target frequency exceeds the sum of the channel quality of the currently used frequency and the set positive value, the target frequency is used to send a signal to the receiving side. Otherwise, the currently used frequency remains unchanged. At the same time, the sending side monitors and counts the energy of each frequency through the feedback signal. Within a set period, if the accumulated energy obtained by the currently used frequency is the smallest, the currently used frequency remains unchanged. Otherwise, the frequency with the smallest accumulated energy within the set period is selected as the target frequency, and the signal is sent using the target frequency.

[0034] The listening is performed according to the set period, and the statistical frequency energy formula is:

[0035] R(i,n)=αR n (i,n)+(1-α)R(i,n-1)

[0036] Where R(i,n) is the energy counted at frequency point i at the current moment, and R n (i,n) is the energy after filtering at the current moment, and α is the time filtering coefficient, that is, the weighted average coefficient of historical data.

[0037] To ensure the superiority of the target frequency, in some actual scenarios, if the sum of the accumulated energy of the target frequency and the set positive value is lower than the accumulated energy of the currently used frequency, the target frequency is updated and the sending side uses the target frequency to send signals.

[0038] (4) Repeat steps (2)-(3) so that the target frequency point used for signal transmission can be automatically updated according to the set period as the signal transmission and interference change.

[0039] Please refer to Figure 2 The figure shows a schematic diagram of the receiving side and the transmitting side. RF is the radio frequency front end. After the receiving side and the transmitting side receive the signal through the receiving antenna, the signal passes through the radio frequency front end and is filtered to obtain the target frequency point. The channel quality and energy are statistically analyzed and compared respectively.

Claims

1. A frequency selection method for a 230MHz frequency band multi-frequency FSK system, characterized in that: The following steps are involved: (1) A test signal in the 230 MHz frequency band is sent from the transmitting side of the multi-frequency FSK system to the receiving side according to a set period; (2) After receiving the test signal, the receiving side monitors the channel quality at each frequency point in the test signal bandwidth, selects the frequency point with the highest channel quality as the target frequency point, and sends a feedback signal to the sending side; (3) After receiving the feedback signal, the sending side compares the channel quality of the target frequency with the channel quality of the currently used frequency. If the channel quality of the target frequency exceeds the sum of the channel quality of the currently used frequency and the set positive value, the target frequency is used to send a signal to the receiving side. Otherwise, the currently used frequency remains unchanged. (4) Repeat steps (2)-(3) to automatically update the target frequency according to the set period.

2. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 1, characterized in that: The step (3) also includes: the sending side monitors and counts the energy of each frequency point through the feedback signal. Within a set period, if the accumulated energy obtained by the statistics of the currently used frequency point is the smallest, the currently used frequency point is kept unchanged; otherwise, the frequency point with the smallest accumulated energy within the set period is selected as the target frequency point, and the signal is sent using the target frequency point.

3. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 2, characterized in that: In the step (3), if the sum of the accumulated energy of the target frequency point and the set positive value is lower than the accumulated energy of the currently used frequency point, the sending side uses the target frequency point to send the signal.

4. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 2, characterized in that: In the step (3), the sending side simultaneously receives the feedback signal according to the test signal bandwidth, and monitors and counts the energy of all frequency points on the test signal bandwidth at one time.

5. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 2, characterized in that: In the step (3), the sending side receives the feedback signal at one frequency point each time, and monitors and counts the energy of the frequency point.

6. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 1, characterized in that: The granularity of the monitoring is 25kHz carrier width.

7. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 1, characterized in that: The granularity of the monitoring is an integer multiple of the 25kHz carrier width.

8. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 1, characterized in that: The test signal is sent independently at each frequency point in the 230 MHz frequency band.

9. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 1, characterized in that: The test signal is sent over a set bandwidth within the 230 MHz frequency band.

10. The frequency selection method of the 230MHz frequency band multi-frequency FSK system according to claim 1, characterized in that: In the steps (2) and (3), the target frequency point is obtained by filtering.

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