A frequency adaptive handover method in a distributed wireless network

Abstract

The present application relates to the technical field of frequency adaptive switching, and discloses a frequency adaptive switching method in a distributed wireless network, comprising: setting a target time period, a switching trigger holding time and an upper limit of false trigger probability, combining the center frequencies of a service frequency band and an adjacent frequency band, obtaining and calculating a cross-frequency band signal quality difference sequence and an intra-band standard deviation; then, according to the terminal position change and the average moving speed in the target time period, selecting a dominant frequency and calculating an effective Doppler frequency, establishing a monotonic relationship between the effective Doppler frequency and the intra-band standard deviation; finally, combining the holding time and the false trigger probability constraint, solving a dynamic hysteresis threshold to realize adaptive frequency switching. The method can flexibly adjust the switching parameters according to the dynamic changes of the user moving speed and the wireless environment, effectively reduce the risk of excessive switching and ping-pong switching, ensure that the false switching probability is within a controllable range, and thus significantly improve the accuracy, stability and resource utilization efficiency of network switching.

Description

Technical Field

[0001] This invention relates to the field of frequency adaptive switching technology, and more specifically, to a frequency adaptive switching method in a distributed wireless network. Background Technology

[0002] With the development of mobile communications, network architecture has gradually evolved from centralized to distributed. In distributed deployments, macro base stations, small base stations, and hotspot cells often operate on different frequency bands, which vary significantly in terms of coverage, interference levels, and link stability. When users move between cells, their terminals must hand over between different frequency bands. Traditional handover methods are mostly based on fixed trigger thresholds and hold times, but this approach is insufficient in multi-frequency distributed scenarios and cannot adapt to dynamic propagation environments and user mobility states.

[0003] Current standardized mobility management mechanisms, such as A3 and A5 events in LTE and NR, provide triggering conditions for multi-frequency handovers, but their parameters are mostly statically configured. While fixed thresholds and hold times may be acceptable in low-frequency bands and low-speed mobility, in high-frequency bands or high-speed mobility, rapid channel fading and the Doppler effect cause significant signal fluctuations, leading to frequent fulfillment of triggering conditions and excessive handover attempts. Excessive handovers not only increase signaling overhead but also increase the risk of ping-pong handovers and dropped calls. Furthermore, overly conservative parameters can result in handover lag and a degraded user experience.

[0004] Therefore, in distributed multi-frequency scenarios, existing methods cannot balance stability and agility under different frequency points and speed conditions. Fixed parameters cannot guarantee that the probability of erroneous handover is within a controllable range throughout the entire service period, while dynamic adjustments lack precise quantitative basis. With the widespread application of distributed networks, this contradiction becomes increasingly prominent: on the one hand, operators need to ensure the effective utilization of high-frequency resources; on the other hand, the handover failure rate remains high when users are moving at high speeds. Summary of the Invention

[0005] This invention provides a frequency adaptive switching method in a distributed wireless network, solving the technical problems mentioned in the background art.

[0006] This invention provides a frequency adaptive switching method in a distributed wireless network, comprising:

[0007] S1, set the target time period, handover trigger hold time, upper limit of false trigger probability, and center frequency of the service band and center frequency of adjacent bands. The target time period is set based on the fading characteristics of the wireless network signal, and the handover trigger hold time is the time parameter configured in the radio resource control protocol.

[0008] S2, within the target time period, acquire the wireless signal quality parameters of the service frequency band and the wireless signal quality parameters of adjacent frequency bands, calculate and form a cross-frequency band signal quality difference sequence, and calculate the intra-band standard deviation based on the statistical characteristics of the cross-frequency band signal quality difference sequence;

[0009] S3, obtain the terminal position at the start and end of the target time period, calculate the average moving speed of the terminal during the target time period based on the duration of the target time period; select the larger value between the center frequency of the service band and the center frequency of the adjacent band as the dominant frequency, and calculate the effective Doppler frequency reflecting the time-varying characteristics of the wireless signal based on the dominant frequency and the average moving speed.

[0010] S4. Based on the effective Doppler frequency and the standard deviation within the band, a monotonic relationship is established between the frequency at which the cross-band signal quality difference crosses the hysteresis threshold and the hysteresis threshold per unit time.

[0011] S5 combines the handover trigger hold time and the upper limit of the false trigger probability, substitutes the monotonic relationship to form an equality constraint, solves the equality constraint to obtain the hysteresis threshold, and performs adaptive handover based on the hysteresis threshold.

[0012] Furthermore, the wireless signal quality parameters of the serving frequency band and adjacent frequency bands are obtained, a cross-band signal quality difference sequence is calculated, and the intra-band standard deviation is calculated based on the statistical characteristics of the cross-band signal quality difference sequence, including:

[0013] At each sampling time within the target time period, the wireless signal quality parameters of the service frequency band and the wireless signal quality parameters of the adjacent frequency band are obtained respectively; wherein, the sampling interval between adjacent sampling times is equal;

[0014] Calculating the cross-band signal quality difference at the i-th sampling time includes: subtracting the wireless signal quality parameter of the serving band from the wireless signal quality parameter of the adjacent frequency band at the i-th sampling time;

[0015] A cross-band signal quality difference sequence is formed based on the cross-band signal quality difference at each sampling time.

[0016] The standard deviation of the cross-band signal quality difference sequence within the target time period is calculated as the intra-segment standard deviation.

[0017] Furthermore, the terminal positions at the start and end of the target time period are obtained, and the average moving speed of the terminal during the target time period is calculated based on the duration of the target time period, including:

[0018] Determine the start and end times of the target time period;

[0019] Obtain the start and end positions of the terminal at the start and end times, respectively;

[0020] The straight-line distance between the end position and the start position is taken as the displacement distance within the target time period;

[0021] The ratio of displacement distance to the duration of the target time period is used as the average moving speed.

[0022] Furthermore, the larger value between the center frequency of the serving band and the center frequency of the adjacent band is selected as the dominant frequency. Based on the dominant frequency and the average moving speed, the effective Doppler frequency reflecting the time-varying characteristics of the wireless signal is calculated, including:

[0023] Obtain the center frequency of the serving frequency band and the center frequencies of adjacent frequency bands;

[0024] The larger of the center frequency of the service band and the center frequency of the adjacent band is taken as the dominant frequency.

[0025] The effective Doppler frequency is calculated by multiplying the average moving speed and the dominant frequency by the speed of light constant.

[0026] Furthermore, based on the effective Doppler frequency and the standard deviation within the band, a monotonic relationship is established between the frequency at which the cross-band signal quality difference crosses the hysteresis threshold and the hysteresis threshold per unit time, including:

[0027] Set a hysteresis threshold, the value of which is greater than or equal to zero;

[0028] The frequency at which the cross-band signal quality difference crosses the hysteresis threshold per unit time is defined as the cross-band cross-pass frequency; where the cross-band cross-pass frequency is the number of times the cross-band signal quality difference crosses the hysteresis threshold per unit time.

[0029] Construct a functional relationship between the unit time travel frequency and the hysteresis threshold. The functional relationship is as follows: the unit time travel frequency is equal to the effective Doppler frequency multiplied by an exponential term, where the exponential term is the square of the negative hysteresis threshold divided by the square of twice the intra-segment standard deviation.

[0030] Furthermore, by combining the handover trigger hold time and the upper limit of the false trigger probability, a monotonic relationship is substituted to form an equation constraint. Solving this equation constraint yields the hysteresis threshold, which is then used to perform adaptive handover, including:

[0031] The probability of false triggering within a segment is calculated based on a monotonic relationship. The calculation method is: an exponential function with a base of the natural constant and an exponent of the negative product of the crossover frequency per unit time and the switching trigger hold time.

[0032] Let the false trigger probability within a segment equal the upper limit of the false trigger probability, thus forming an equality constraint;

[0033] Solving for the hysteresis threshold includes: expressing the hysteresis threshold as the product of the standard deviation within the segment and the square root of twice the natural logarithm through equation transformation, wherein the argument of the natural logarithm is the product of the effective Doppler frequency and the switching trigger hold time divided by one minus the negative value of the natural logarithm of the upper limit of the false trigger probability.

[0034] The obtained hysteresis threshold and the handover trigger hold time are used together as the handover trigger parameter, and adaptive handover is performed at the frequency according to the handover trigger parameter within the target time period.

[0035] The beneficial effects of this invention are as follows: By introducing an adaptive threshold calculation method based on terminal movement speed, dominant frequency, and statistical characteristics of cross-band signal quality differences, the optimal handover triggering conditions can be dynamically determined in multi-frequency distributed wireless networks. This effectively overcomes the frequent handover, ping-pong handover, and dropped connection problems caused by traditional fixed threshold methods in high-speed movement or high-frequency environments. Simultaneously, by strictly controlling the upper limit of the false trigger probability, this invention ensures handover agility while also considering system stability and user experience, thereby achieving intelligent, reliable, and accurate handover decisions and significantly improving the resource utilization efficiency and communication quality of distributed wireless networks. Attached Figure Description

[0036] Figure 1 This is a flowchart of a frequency adaptive switching method in a distributed wireless network according to the present invention. Detailed Implementation

[0037] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0038] like Figure 1 As shown, a frequency adaptive switching method in a distributed wireless network includes:

[0039] S1, set the target time period, handover trigger hold time, upper limit of false trigger probability, and center frequency of the service band and center frequency of adjacent bands. The target time period is set based on the fading characteristics of the wireless network signal, and the handover trigger hold time is the time parameter configured in the radio resource control protocol.

[0040] S2, within the target time period, acquire the wireless signal quality parameters of the service frequency band and the wireless signal quality parameters of adjacent frequency bands, calculate and form a cross-frequency band signal quality difference sequence, and calculate the intra-band standard deviation based on the statistical characteristics of the cross-frequency band signal quality difference sequence;

[0041] S3, obtain the terminal position at the start and end of the target time period, calculate the average moving speed of the terminal during the target time period based on the duration of the target time period; select the larger value between the center frequency of the service band and the center frequency of the adjacent band as the dominant frequency, and calculate the effective Doppler frequency reflecting the time-varying characteristics of the wireless signal based on the dominant frequency and the average moving speed.

[0042] S4. Based on the effective Doppler frequency and the standard deviation within the band, a monotonic relationship is established between the frequency at which the cross-band signal quality difference crosses the hysteresis threshold and the hysteresis threshold per unit time.

[0043] S5 combines the handover trigger hold time and the upper limit of the false trigger probability, substitutes the monotonic relationship to form an equality constraint, solves the equality constraint to obtain the hysteresis threshold, and performs adaptive handover based on the hysteresis threshold.

[0044] In one embodiment of the present invention, the wireless signal quality parameters of the serving frequency band and the wireless signal quality parameters of adjacent frequency bands are obtained, a cross-frequency band signal quality difference sequence is calculated, and the intra-band standard deviation is calculated based on the statistical characteristics of the cross-frequency band signal quality difference sequence, including:

[0045] At each sampling time within the target time period, the wireless signal quality parameters of the service frequency band and the wireless signal quality parameters of the adjacent frequency band are obtained respectively; wherein, the sampling interval between adjacent sampling times is equal;

[0046] Calculating the cross-band signal quality difference at the i-th sampling time includes: subtracting the wireless signal quality parameter of the serving band from the wireless signal quality parameter of the adjacent frequency band at the i-th sampling time;

[0047] A cross-band signal quality difference sequence is formed based on the cross-band signal quality difference at each sampling time.

[0048] The standard deviation of the cross-band signal quality difference sequence within the target time period is calculated as the intra-segment standard deviation.

[0049] In detail, the target time period is set based on the fading characteristics of wireless network signals to ensure that it can cover the signal change cycle required for a complete handover decision.

[0050] In detail, the sampling targets two types of signal quality parameters, including:

[0051] The wireless signal quality parameters of the service frequency bands currently providing services to terminals, such as RSRP, RSRQ, or SINR, are all standard parameters that characterize the quality of signals in wireless communication.

[0052] The wireless signal quality parameters of adjacent frequency bands that the terminal may switch to.

[0053] In detail, the cross-band signal quality difference is used to quantify the quality difference between adjacent frequency bands and the serving frequency band. When the cross-band signal quality difference is positive, it indicates that the quality of the adjacent frequency band is better than that of the serving frequency band at that sampling time; when it is negative, it indicates that the quality of the serving frequency band is better.

[0054] In detail, the standard deviation within a segment is used to quantify the fluctuation range of cross-frequency band quality difference within the target time period: the larger the standard deviation, the more drastic the fluctuation of quality difference and the more unstable the signal quality; the smaller the standard deviation, the smoother the fluctuation of quality difference and the more stable the signal quality, and the parameter settings can be appropriately relaxed.

[0055] In one embodiment of the present invention, obtaining the terminal position at the start time and the terminal position at the end time of the target time period, and calculating the average moving speed of the terminal within the target time period based on the duration of the target time period, includes:

[0056] Determine the start and end times of the target time period;

[0057] Obtain the start and end positions of the terminal at the start and end times, respectively;

[0058] The straight-line distance between the end position and the start position is taken as the displacement distance within the target time period;

[0059] The ratio of displacement distance to the duration of the target time period is used as the average moving speed.

[0060] In detail, average moving speed focuses on the overall movement range of the terminal over a time period, rather than the specific movement path (such as turning, detouring, and other detailed path details). Straight-line distance can quantify spatial displacement simply and efficiently, with low computational complexity, making it suitable for the lightweight processing requirements of distributed base stations.

[0061] In one embodiment of the present invention, the larger value between the center frequency of the serving frequency band and the center frequency of the adjacent frequency band is selected as the dominant frequency. The effective Doppler frequency, reflecting the time-varying characteristics of the wireless signal, is calculated based on the dominant frequency and the average moving speed, including:

[0062] Obtain the center frequency of the serving frequency band and the center frequencies of adjacent frequency bands;

[0063] The larger of the center frequency of the service band and the center frequency of the adjacent band is taken as the dominant frequency.

[0064] The effective Doppler frequency is calculated by multiplying the average moving speed and the dominant frequency by the speed of light constant.

[0065] In detail, the center frequency of the serving band and the center frequencies of adjacent bands are the band identifiers in the case of inter-frequency handover, determining the signal propagation characteristics and time-varying characteristics of different bands. In a distributed wireless network, the serving band is the operating band currently accessed by the terminal, and the adjacent bands are the alternative bands that the terminal may switch to. The difference in their center frequencies will lead to significant differences in the time-varying characteristics of the signal (such as the intensity of the Doppler effect).

[0066] In detail, the higher the carrier frequency, the more pronounced the Doppler effect caused by terminal movement, the shorter the signal coherence time, and the more drastic the temporal variation of signal quality. This leads to a greater fluctuation in cross-band signal quality and a higher risk of false handover. Selecting a larger center frequency as the dominant frequency allows for prioritizing the focus on the most drastically time-varying frequency band characteristics, avoiding underestimating the time-varying risks of high-frequency bands due to selecting low-frequency bands.

[0067] In detail, the calculation of the effective Doppler frequency follows the laws of the Doppler effect. Specifically, it involves multiplying the terminal's average moving speed by the dominant frequency and dividing by the speed of light. The average moving speed reflects the terminal's dynamic movement, while the dominant frequency reflects the time-varying sensitivity of the frequency band. The ratio of their product to the speed of light quantitatively describes the degree of signal frequency shift under the combined effects of terminal movement and high-frequency characteristics, i.e., the time-varying intensity of the signal. In other words, a higher effective Doppler frequency indicates a more drastic change in signal quality over time, and a higher probability that cross-band quality differences will cross the hysteresis threshold.

[0068] In one embodiment of the present invention, based on the effective Doppler frequency and the standard deviation within the band, a monotonic relationship is established between the frequency at which the cross-band signal quality difference crosses the hysteresis threshold and the hysteresis threshold per unit time, including:

[0069] Set a hysteresis threshold, the value of which is greater than or equal to zero;

[0070] The frequency at which the cross-band signal quality difference crosses the hysteresis threshold per unit time is defined as the cross-band cross-pass frequency; where the cross-band cross-pass frequency is the number of times the cross-band signal quality difference crosses the hysteresis threshold per unit time.

[0071] Construct a functional relationship between the unit time travel frequency and the hysteresis threshold. The functional relationship is as follows: the unit time travel frequency is equal to the effective Doppler frequency multiplied by an exponential term, where the exponential term is the square of the negative hysteresis threshold divided by the square of twice the intra-segment standard deviation.

[0072] In detail, the hysteresis threshold functions to suppress false handovers caused by minor fluctuations in signal quality across frequency bands. The hysteresis threshold is set to a value greater than or equal to zero. If the value is zero, there is no hysteresis effect, and even minor fluctuations in signal quality can cross the threshold, resulting in a very high risk of false triggering. When the value is greater than zero, the fluctuation amplitude of the signal quality must exceed the threshold to be considered a valid trigger, thus reducing the probability of false triggering.

[0073] In detail, the number of times the signal quality difference across frequency bands crosses the hysteresis threshold per unit time is defined as the crossover frequency per unit time. The crossover frequency per unit time reflects the level of risk of false triggering: the larger the crossover frequency per unit time, the more times the signal quality difference reaches the threshold per unit time, and the higher the possibility of false triggering of handover; the smaller the value, the lower the risk of false triggering.

[0074] In detail, the functional relationship is constructed based on the time-varying characteristics and fluctuation patterns of the signal. Specifically, the crossover frequency per unit time equals the effective Doppler frequency multiplied by an exponential term. The effective Doppler frequency reflects the time-varying intensity of the signal; the larger the value, the more drastic the signal quality changes over time, and the higher the base frequency of the crossover threshold. It is the time-varying benchmark term that determines the crossover frequency. The exponential term is the square of the negative hysteresis threshold divided by twice the square of the intra-segment standard deviation. Its function is to quantify the adjustment of the crossover frequency by the threshold and signal fluctuations: the larger the hysteresis threshold, the smaller the exponential term, and the lower the crossover frequency, reflecting the inhibitory effect of the threshold on crossover; the larger the intra-segment standard deviation, the more drastic the signal fluctuation, the larger the exponential term, and the higher the crossover frequency, reflecting the promoting effect of fluctuations on crossover. This functional relationship establishes a monotonically decreasing relationship between the crossover frequency per unit time and the hysteresis threshold; that is, when the hysteresis threshold increases, the crossover frequency per unit time necessarily decreases, and vice versa.

[0075] In one embodiment of the present invention, combining the handover trigger hold time and the upper limit of the false trigger probability, a monotonic relationship is substituted to form an equation constraint. The hysteresis threshold is obtained by solving the equation constraint, and adaptive handover is performed based on the hysteresis threshold, including:

[0076] The probability of false triggering within a segment is calculated based on a monotonic relationship. The calculation method is: an exponential function with a base of the natural constant and an exponent of the negative product of the crossover frequency per unit time and the switching trigger hold time.

[0077] Let the false trigger probability within a segment equal the upper limit of the false trigger probability, thus forming an equality constraint;

[0078] Solving for the hysteresis threshold includes: expressing the hysteresis threshold as the product of the standard deviation within the segment and the square root of twice the natural logarithm through equation transformation, wherein the argument of the natural logarithm is the product of the effective Doppler frequency and the switching trigger hold time divided by one minus the negative value of the natural logarithm of the upper limit of the false trigger probability.

[0079] The obtained hysteresis threshold and the handover trigger hold time are used together as the handover trigger parameter, and adaptive handover is performed at the frequency according to the handover trigger parameter within the target time period.

[0080] In detail, the calculation method for the intra-segment false trigger probability is as follows: One is subtracted from an exponential function whose base is the natural constant and whose exponent is the negative of the product of the cross-cross frequency per unit time and the handover trigger hold time. This is based on the Poisson approximation of sparse events, meaning that within the target time period, the event of a cross-band signal with poor quality crossing the hysteresis threshold is a low-probability sparse event, conforming to the Poisson distribution characteristics. Here, the cross-cross frequency per unit time reflects the cross-cross risk per unit time, and the handover trigger hold time (TTT) is the duration for which the signal must meet the handover conditions. Their product represents the total cross-cross risk exposure within the segment. The exponential term, through natural exponential transformation, converts the risk exposure into the probability of no cross-cross event. Subtracting this probability from 1 yields the probability of at least one cross-cross (i.e., false trigger) occurring within the segment. This achieves a quantitative conversion from cross-cross frequency to false trigger probability.

[0081] In detail, the upper limit of the false trigger probability is a preset switching performance target used to limit the maximum acceptable probability of false triggering within a target time period, ensuring switching stability. The false trigger probability within a period is set equal to the upper limit of the false trigger probability, thus establishing an equation constraint between actual risk and target risk. The role of this equation constraint is to transform the vague requirement to reduce false triggering into a clear mathematical equation, so that the subsequent solution to the hysteresis threshold no longer relies on experience, but rather revolves around meeting the preset risk target.

[0082] In detail, the size of the hysteresis threshold is jointly determined by the signal's time-varying characteristics (effective Doppler frequency), signal fluctuation intensity (intra-segment standard deviation), time parameter (TTT), and risk target (upper limit of false trigger probability). That is, the larger the effective Doppler frequency or intra-segment standard deviation (the more drastic the signal's time-varying / fluctuating nature), or the stricter the upper limit of the false trigger probability (the lower the risk tolerance), the larger the hysteresis threshold will be. Conversely, the more lenient the upper limit of the false trigger probability (the higher the risk tolerance), the smaller the hysteresis threshold will be.

[0083] In detail, the hysteresis threshold and the preset handover trigger hold time are used together as handover trigger parameters. These two parameters work synergistically in handover determination: the handover trigger hold time ensures the continuity of signal compliance (avoiding false triggers due to instantaneous fluctuations), and the hysteresis threshold ensures that the fluctuation amplitude of poor signal quality reaches a reasonable threshold (avoiding false triggers due to minor fluctuations). Within the target time period, frequency-adaptive handover is performed based on these two parameters. Essentially, this adapts the handover determination criteria to the signal characteristics and risk objectives of the current scenario. Specifically, high-frequency / high-speed scenarios (with larger effective Doppler frequencies) correspond to a larger hysteresis threshold, while low-frequency / low-speed scenarios correspond to a smaller hysteresis threshold. All adjustments are made to meet the preset upper limit of the false trigger probability. Thus, without changing the handover criterion structure of the 3GPP standard (such as the logic of service degradation and neighboring cell improvement in the A5 event), performance is optimized solely through parameter adaptation. This ensures compatibility with existing networks while achieving dynamic handover control in distributed scenarios, solving the scenario adaptation defects of traditional fixed parameters.

[0084] The embodiments of this example have been described above. However, this example is not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms based on the guidance of this example, and all of them are within the protection scope of this example.

Claims

1. A frequency adaptive handoff method in a distributed wireless network, characterized by, The method comprises the following steps: S1, setting a target time period, a handover trigger holding time, an upper limit of false triggering probability, and a center frequency of a service frequency band and a center frequency of an adjacent frequency band, the target time period being set based on a fading characteristic of a wireless network signal, and the handover trigger holding time being a time parameter configured in a radio resource control protocol; S2, in the target time period, acquiring a wireless signal quality parameter of the service frequency band and a wireless signal quality parameter of the adjacent frequency band, calculating a cross-frequency signal quality difference sequence, and calculating an intra-period standard deviation based on a statistical characteristic of the cross-frequency signal quality difference sequence; S3, acquiring a terminal position at a starting moment of the target time period and a terminal position at an ending moment of the target time period, and calculating an average moving speed of the terminal in the target time period according to a time length of the target time period; selecting a larger value between the center frequency of the service frequency band and the center frequency of the adjacent frequency band as a dominant frequency, and calculating an effective Doppler frequency reflecting a time-varying characteristic of a wireless signal according to the dominant frequency and the average moving speed; S4, based on the effective Doppler frequency and the intra-period standard deviation, establishing a monotonic relationship between a frequency of the cross-frequency signal quality difference crossing a hysteresis threshold in a unit time and the hysteresis threshold, comprising: setting the hysteresis threshold, the value of the hysteresis threshold being greater than or equal to zero; defining the frequency of the cross-frequency signal quality difference crossing the hysteresis threshold in a unit time as a unit time crossing frequency; wherein the unit time crossing frequency is the number of times of the cross-frequency signal quality difference crossing the hysteresis threshold in a unit time; constructing a functional relationship between the unit time crossing frequency and the hysteresis threshold, the functional relationship being in the form of: the unit time crossing frequency being equal to the effective Doppler frequency multiplied by an exponential function with a natural constant as a base, and the exponent of the exponential function being a negative value of the square of the hysteresis threshold divided by the square of twice the intra-period standard deviation; S5, combining the handover trigger holding time and the upper limit of false triggering probability, substituting into the monotonic relationship to form an equation constraint, and solving the hysteresis threshold through the equation constraint to perform adaptive handover based on the hysteresis threshold, comprising: calculating an intra-period false triggering probability based on the monotonic relationship, and the calculation method being: one minus an exponential function with a natural constant as a base, the product of the unit time crossing frequency and the handover trigger holding time as an exponent, and the negative value of the exponential function; letting the intra-period false triggering probability be equal to the upper limit of false triggering probability to form the equation constraint; solving the hysteresis threshold, comprising: representing the hysteresis threshold as a product of the intra-period standard deviation and the square root of twice the natural logarithm through equation transformation, and the real number of the natural logarithm being the product of the effective Doppler frequency and the handover trigger holding time divided by the negative value of the natural logarithm of one minus the upper limit of false triggering probability; taking the hysteresis threshold obtained and the handover trigger holding time as a handover trigger parameter together, and performing frequency adaptive handover according to the handover trigger parameter in the target time period.

2. The frequency adaptive handoff method in a distributed wireless network of claim 1, wherein, acquiring a wireless signal quality parameter of a service frequency band and a wireless signal quality parameter of an adjacent frequency band, calculating a cross-frequency signal quality difference sequence, and calculating an intra-period standard deviation based on a statistical characteristic of the cross-frequency signal quality difference sequence, comprising: acquiring the wireless signal quality parameter of the service frequency band and the wireless signal quality parameter of the adjacent frequency band at each sampling moment in the target time period respectively; wherein the sampling intervals of adjacent sampling moments are all equal; The cross-band signal quality difference at the i-th sampling moment is calculated by subtracting the wireless signal quality parameter of the service band from the wireless signal quality parameter of the adjacent band at the i-th sampling moment; A cross-band signal quality difference sequence is formed based on the cross-band signal quality difference at each sampling moment; The standard deviation of the cross-band signal quality difference sequence within the target time period is calculated as the intra-period standard deviation.

3. The frequency adaptive handoff method in a distributed wireless network of claim 2, wherein, The terminal position at the start moment and the terminal position at the end moment of the target time period are obtained, and the average moving speed of the terminal within the target time period is calculated according to the length of the target time period, including: The start moment and the end moment of the target time period are determined; The start position and the end position of the terminal at the start moment and the end moment are obtained respectively; The straight-line distance between the end position and the start position is taken as the displacement distance within the target time period; The ratio of the displacement distance to the length of the target time period is taken as the average moving speed.

4. The frequency adaptive handoff method in a distributed wireless network of claim 3, wherein, The larger value between the center frequency of the service band and the center frequency of the adjacent band is selected as the dominant frequency, and the effective Doppler frequency reflecting the time-varying characteristics of the wireless signal is calculated according to the dominant frequency and the average moving speed, including: The center frequency of the service band and the center frequency of the adjacent band are obtained; The larger center frequency between the center frequency of the service band and the center frequency of the adjacent band is taken as the dominant frequency; The effective Doppler frequency is calculated by dividing the product of the average moving speed and the dominant frequency by the speed of light constant.

Images