A method for calculating the maximum multipath delay based on propagation path length within the line-of-sight range at sea

Abstract

The present invention discloses a method for calculating the maximum multipath delay based on the propagation path length within the line-of-sight range at sea. The method comprises the following steps: when the radio waves for communication between a first ship and a second ship are propagated via a direct path, the direct path length of the radio waves propagating within the line-of-sight range at sea is obtained based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship. The present invention solves the technical problem in existing line-of-sight communication scenarios at sea, in which the signal from the transmitting end reaches the receiving end via a direct path and multiple reflection paths, and the length of each path is different, resulting in different arrival times of the signal at the receiving end, thereby generating multipath delay. Larger multipath delays will cause inter-symbol interference, resulting in a decrease in the signal quality at the receiving end, an increase in the bit error rate, and further degradation of system performance.

Description

Technical Field

[0001] The present invention relates to the technical field of maritime wireless communications, and in particular to a method for calculating a maximum multipath delay based on a propagation path length within a line-of-sight range at sea. Background Art

[0002] Multipath delay refers to the difference in signal delay caused by different propagation paths from the transmitter to the receiver. In line-of-sight communications at sea, the signal from the transmitter reaches the receiver via a direct path and multiple reflected paths. Each path is of varying length, resulting in different arrival times, thus causing multipath delay.

[0003] Large multipath delays can cause intersymbol interference (ISI), leading to reduced signal quality at the receiving end and increased bit error rates, further degrading system performance. This impact is particularly significant in high-speed data transmission applications. Therefore, in the waveform design of maritime line-of-sight communication systems, it is necessary to pre-calculate the maximum multipath delay within the line-of-sight range. Based on the calculated results, appropriate technologies such as channel equalization and orthogonal frequency division multiplexing can be used to reduce the impact of multipath and improve communication system performance.

[0004] In practical systems (such as communications and global satellite navigation systems), channel estimation is currently the primary method for obtaining multipath delay. This method first estimates channel characteristics by sending a predefined pilot signal as a reference signal. Upon receiving the predefined pilot signal, the receiver compares it with the known pilot signal. The channel impulse response is then estimated using algorithms such as least squares or minimum mean square error (LMSE). Further analysis extracts delay information for different paths. However, the use of pilot signals adds additional transmission overhead. Furthermore, existing methods for calculating multipath delay within line of sight at sea use an enumeration approach to calculate the reflection path length based on the number of reflection points on the sea surface. However, in line-of-sight communications at sea, the large number of reflection points significantly increases computational complexity and does not adapt well to rapid channel changes caused by ship movement. Summary of the Invention

[0005] An embodiment of the present invention provides a method for calculating the maximum multipath delay based on the propagation path length within the line-of-sight range at sea, so as to at least solve the technical problem in existing line-of-sight communication scenarios at sea, in which the transmitting end signal reaches the receiving end through a direct path and multiple reflection paths, and the length of each path is different, resulting in different signal arrival times at the receiving end, thereby generating multipath delay. Large multipath delay will cause inter-symbol interference, resulting in a decrease in signal quality at the receiving end, an increase in the bit error rate, and further deterioration of system performance.

[0006] According to one aspect of an embodiment of the present invention, a method for calculating a maximum multipath delay based on a propagation path length within line-of-sight at sea is provided. The method may include: when radio waves used for communication between a first ship and a second ship propagate via a direct path, determining the direct path length of the radio waves propagating within line-of-sight at sea based on the height of a transmitting antenna, the height of a receiving antenna, and the distance between the first ship and the second ship; when radio waves used for communication between the first ship and the second ship propagate via a reflection path, determining the target reflection path length of the radio waves propagating within line-of-sight at sea based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and a reflection point of the radio waves on the sea surface, and the distance between the reflection point of the radio waves on the sea surface and the second ship; and determining the maximum multipath delay within line-of-sight at sea based on the target reflection path length, the direct path length, and the propagation speed of the radio waves within line-of-sight at sea. Determining the maximum multipath delay within line-of-sight at sea is used to set the symbol interval to 1.5-2 times the maximum multipath delay when designing a line-of-sight communication system at sea.

[0007] Optionally, the expression for obtaining the direct path length of radio wave propagation within the line-of-sight range at sea based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship is:

[0008] (1)

[0009] in, Direct path length, is the height of the transmitting antenna, is the height of the receiving antenna, is the distance between the first ship and the second ship.

[0010] Optionally, determining a target reflection path length for radio wave propagation within a line-of-sight range at sea based on a height of a transmitting antenna, a height of a receiving antenna, a distance between the first ship and a reflection point of the radio wave on the sea surface, and a distance between the reflection point of the radio wave on the sea surface and the second ship includes:

[0011] Based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the radio wave reflection point on the sea surface, and the distance between the radio wave reflection point on the sea surface and the second ship, the initial reflection path length of the radio wave propagation within the line of sight range at sea is determined. The expression for determining the initial reflection path length is:

[0012] (2)

[0013] in, is the initial reflection path length, is the distance between the first ship and the reflection point of the radio wave on the sea surface, is the distance between the wave reflection point on the sea surface and the second ship; the expression for determining the initial reflection path length is based on The first-order derivative is solved and set equal to zero to obtain two extreme points of the first-order derivative of the initial reflection path length; the two extreme points are processed to obtain a target extreme point, where the target extreme point is determined by the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship; the distance between the first ship and the radio wave reflection point on the sea surface in the expression for determining the initial reflection path length is replaced with the target extreme point, and the distance between the radio wave reflection point on the sea surface and the second ship is replaced with the target extreme point, to obtain the target reflection path length for radio wave propagation within the line-of-sight range at sea.

[0014] Optionally, the expressions for the two extreme points of the first-order derivative of the initial reflection path length are:

[0015] (3)

[0016] (4)

[0017] in, is the first extreme point relative to the distance between the first ship and the reflection point of the radio wave on the sea surface, It is the second extreme point relative to the distance between the first ship and the point where the radio wave is reflected on the sea surface.

[0018] Optionally, the distance between the first ship and the radio wave reflection point on the sea surface in the expression for determining the initial reflection path length is replaced by the target extreme point, and the distance between the radio wave reflection point on the sea surface and the second ship is replaced by the target extreme point. The expression for the target reflection path length of radio wave propagation within the line-of-sight range at sea is obtained as follows:

[0019] (5)

[0020] is the target reflection path length.

[0021] Optionally, based on the target reflection path length, the direct path length, and the propagation speed of radio waves within the line-of-sight range at sea, the expression for the maximum multipath delay within the line-of-sight range at sea is obtained as follows:

[0022] (6)

[0023] in, is the maximum multipath delay within the line-of-sight range at sea, It is the propagation speed of radio waves within the line of sight at sea.

[0024] Beneficial effects of the present invention:

[0025] The present invention proposes a method for calculating the maximum multipath delay based on the propagation path length within the line-of-sight range at sea. This method only requires substituting the three parameters of the transmitting antenna height, the receiving antenna height, and the distance between ships into the derived analytical expression of the maximum multipath delay, so that the maximum multipath delay of ship communications within the line-of-sight range at sea can be quickly calculated. Therefore, this method effectively reduces the additional transmission overhead and complexity required to obtain the maximum multipath delay within the line-of-sight range at sea, thereby being able to adapt to the rapid changes in the line-of-sight channel at sea caused by the movement of ships. The calculation results can also guide the waveform design of the line-of-sight communication system for ships at sea. When designing the line-of-sight communication system at sea, in order to avoid inter-symbol interference, the symbol interval Must be greater than the maximum multipath delay Therefore, the symbol interval is set to 1.5-2 times the maximum multipath delay, reserving enough time for the channel to allow the energy of the previous symbol to decay to a negligible level, thereby effectively avoiding inter-symbol interference, ultimately reducing the bit error rate and improving the performance of the maritime line-of-sight communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0027] Figure 1 is a flow chart of a method for calculating the maximum multipath delay based on the propagation path length within the maritime line-of-sight range according to an embodiment of the present invention;

[0028] Figure 2 This is a scenario diagram of a method for calculating the maximum multipath delay based on the propagation path length within a line-of-sight range at sea according to an embodiment of the present invention;

[0029] Figure 3 Schematic diagram of the maximum distance of radio wave propagation within the sea line-of-sight range determined by different transmitting and receiving antenna heights according to an embodiment of the present invention;

[0030] Figure 4 Schematic diagram of maximum multipath delay at the limit distance of radio wave propagation within the sea line-of-sight range determined by different transmitting and receiving antenna heights according to an embodiment of the present invention;

[0031] Figure 5 2 is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 5 meters according to an embodiment of the present invention;

[0032] Figure 6 is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 15 meters according to an embodiment of the present invention;

[0033] Figure 7 2. This is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 25 meters according to an embodiment of the present invention;

[0034] Figure 8 This is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 35 meters according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described 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 making creative efforts should fall within the scope of protection of the present invention.

[0036] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0037] Example 1

[0038] According to an embodiment of the present invention, a method for calculating the maximum multipath delay based on the propagation path length within the line-of-sight range at sea is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system comprising at least one set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0039] Figure 1 FIG. 1 is a flow chart of a method for calculating the maximum multipath delay based on the propagation path length within the maritime line-of-sight range according to an embodiment of the present invention. Figure 1 As shown, the method may include the following steps:

[0040] Step S101: When radio waves used for communication between a first ship and a second ship are propagated via a direct path, the length of the direct path for radio wave propagation within the line of sight at sea is obtained based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship.

[0041] In the technical solution provided in the above step S101 of the present invention, Figure 2 This is a scenario diagram of a method for calculating the maximum multipath delay based on the propagation path length within the maritime line-of-sight range according to an embodiment of the present invention. If the radio waves for communication between the first ship and the second ship are propagated through a direct path, that is, Figure 2 AF in the equation is the straight-line distance d, and the transmitting antenna height is , the receiving antenna height is , the distance between the first ship and the second ship is , that is Figure 2 Sight distance , that is, BD, can be calculated from the latitude and longitude coordinates of the two ships, in meters, satisfying , the maximum distance of radio wave propagation within the line of sight at sea It is calculated based on the height of the transmitting and receiving antennas of the marine ship communication system, for example, formula (7):

[0042] (7)

[0043] in, It is the maximum distance of radio wave propagation within the line of sight at sea, measured in meters.

[0044] Step S102, when the radio waves for communication between the first ship and the second ship are propagated through a reflection path, the target reflection path length of the radio waves propagating within the line of sight at sea is determined based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the reflection point of the radio waves on the sea surface, and the distance between the reflection point of the radio waves on the sea surface and the second ship.

[0045] In the technical solution provided in step S102 of the present invention, if the radio waves for communication between the first ship and the second ship are propagated through a reflection path, that is, Figure 2 AC and CF are the paths of propagation, AC and CF are the distances between the transmitting antenna and the reflection point of the radio wave on the sea surface, and CF are the distances between the reflection point of the radio wave on the sea surface and the receiving antenna, respectively. The height of the transmitting antenna is , the receiving antenna height is , the distance between the first ship and the reflection point of the radio wave on the sea surface is BC ( ), the distance CD between the radio wave reflection point on the sea surface and the second ship ( ), the reflection point is C; according to the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the radio wave reflection point on the sea surface, and the distance between the radio wave reflection point on the sea surface and the second ship, the target reflection path length of the radio wave propagation within the sea line of sight range is calculated.

[0046] Step S103, based on the target reflection path length, the direct path length, and the propagation speed of radio waves within the line-of-sight range at sea, obtain the maximum multipath delay within the line-of-sight range at sea, wherein determining the maximum multipath delay within the line-of-sight range at sea is used to set the code element interval to 1.5-2 times the maximum multipath delay when designing the line-of-sight communication system at sea.

[0047] In the technical solution provided in step S103 of the present invention, the target reflection path length, the direct path length, and the propagation speed of radio waves within the line-of-sight range at sea are calculated to obtain the maximum multipath delay within the line-of-sight range at sea ( ), in which, in order to avoid inter-code interference when designing a maritime line-of-sight communication system, the symbol interval Must be greater than the maximum multipath delay Therefore, the symbol interval is set to 1.5-2 times the maximum multipath delay, which reserves enough time for the channel to allow the energy of the previous symbol to decay to a negligible level, thereby effectively avoiding inter-symbol interference.

[0048] The above method of this embodiment is further introduced below.

[0049] As an optional embodiment, in step S101, the expression for obtaining the direct path length of radio wave propagation within the line-of-sight range at sea based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship is:

[0050] (1)

[0051] in, is the direct path length, is the height of the transmitting antenna, is the height of the receiving antenna, is the distance between the first ship and the second ship.

[0052] As an optional embodiment, step S102, determining a target reflection path length of radio wave propagation within the line of sight at sea based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the radio wave reflection point on the sea surface, and the distance between the radio wave reflection point on the sea surface and the second ship, includes determining an initial reflection path length of radio wave propagation within the line of sight at sea based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the radio wave reflection point on the sea surface, and the distance between the radio wave reflection point on the sea surface and the second ship, wherein an expression for determining the initial reflection path length is:

[0053] (2)

[0054] in, is the initial reflection path length, is the distance between the first ship and the reflection point of the radio wave on the sea surface, is the distance between the wave reflection point on the sea surface and the second ship; the expression for determining the initial reflection path length is based on The first-order derivative is solved and set equal to zero to obtain two extreme points of the first-order derivative of the initial reflection path length; the two extreme points are processed to obtain a target extreme point, where the target extreme point is determined by the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship; the distance between the first ship and the radio wave reflection point on the sea surface in the expression for determining the initial reflection path length is replaced with the target extreme point, and the distance between the radio wave reflection point on the sea surface and the second ship is replaced with the target extreme point, to obtain the target reflection path length for radio wave propagation within the line-of-sight range at sea.

[0055] In this embodiment, the expression for determining the initial reflection path length is based on The expression for solving the first-order derivative is:

[0056] (8)

[0057] in, The expression for determining the initial reflection path length is based on Solve the first-order derivative;

[0058] Let the first-order derivative be equal to zero. The steps are as follows:

[0059] make have (9)

[0060] Squaring both sides and sorting them gives:

[0061] (10)

[0062] Further sorting out formula (10) yields:

[0063] (11)

[0064] like , both sides of formula (11) do not hold; otherwise, divide both sides by , we can get

[0065] (12)

[0066] The formula (12) is further simplified below.

[0067] set up (13), then (14)

[0068] Substituting formula (14) into formula (11), formula (11) becomes

[0069] therefore, ,Will Substitution (Formula (14)) to obtain (15), we can get the following two extreme points:

[0070] (3)

[0071] (4)

[0072] The two extreme points are processed, including: taking the second-order derivative of the length of the reflection path of the radio wave propagation, and obtaining

[0073] (16)

[0074] in, It is the second derivative of the reflection path length of radio wave propagation.

[0075] According to the actual scenario of maritime line-of-sight communication, the steps to determine the extreme point type are as follows:

[0076] Transmitting antenna height of maritime line-of-sight communication system Height from receiving antenna Generally no more than 50m, much less than and Therefore, for any , are established, and , so is a maximum point.

[0077] also, Needs to be satisfied ,Right now .

[0078] because and If both are positive numbers, then Only needs to meet the following requirements to establish , however, this is consistent with the assumption Contradictory, therefore is not an extreme point, so is the target extreme point.

[0079] As an optional embodiment, the expressions of the two extreme points of the first-order derivative of the initial reflection path length are:

[0080] (3)

[0081] (4)

[0082] in, is the first extreme point relative to the distance between the first ship and the reflection point of the radio wave on the sea surface, is the second extreme point relative to the distance between the first ship and the point where the radio wave is reflected on the sea surface.

[0083] As an optional embodiment, the distance between the first ship and the radio wave reflection point on the sea surface in the expression for determining the initial reflection path length is replaced with the target extreme point, and the distance between the radio wave reflection point on the sea surface and the second ship is replaced with the target extreme point. The expression for the target reflection path length of radio wave propagation within the line-of-sight range at sea is obtained as follows:

[0084] (5)

[0085] is the target reflection path length.

[0086] In this embodiment, the distance between the first ship and the radio wave reflection point on the sea surface in Formula 2 is replaced by the target extreme point, and the distance between the radio wave reflection point on the sea surface and the second ship is replaced by the target extreme point to obtain the target reflection path length of the radio wave propagation within the line of sight range at sea.

[0087] As an optional embodiment, in step S103, based on the target reflection path length, the direct path length, and the propagation speed of radio waves within the line-of-sight range at sea, an expression for the maximum multipath delay within the line-of-sight range at sea is obtained:

[0088] (6)

[0089] in, is the maximum multipath delay within the line-of-sight range at sea, It is the propagation speed of radio waves within the line of sight at sea.

[0090] In this embodiment, the target reflection path length, the direct path length, and the propagation speed of radio waves within the line-of-sight range at sea are substituted into formula (6) to obtain the maximum multipath delay within the line-of-sight range at sea. According to formula 6, it can be seen that the maximum multipath delay within the line-of-sight range at sea can be obtained based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship.

[0091] Experimental part:

[0092] When the height of the transmitting and receiving antennas are both 5m, the maximum distance of radio wave propagation within the line of sight at sea is 18.4252km. Similarly, when the height range of the transmitting and receiving antennas is set to 5m to 35m with a step size of 5m, the calculation results of the maximum distance of radio wave propagation within the line of sight at sea are as follows: Figure 3 shown. Figure 3 Schematic diagram of the maximum distance of radio wave propagation within the sea line of sight determined by different transmitting and receiving antenna heights according to an embodiment of the present invention. Figure 3 It can be seen that the maximum distance of radio wave propagation within the line of sight at sea increases with the increase of the height of the transmitting and receiving antennas, and the curves of the maximum distance of radio wave propagation within the line of sight at sea corresponding to different receiving antenna heights are almost parallel.

[0093] The formula for determining the maximum multipath delay within the sea line of sight range is also applicable to situations, in which This is a special case. When the height of the transmitting and receiving antennas are both 5m, the maximum multipath delay is 0.00904558176747135ns at the extreme distance of radio wave propagation within the line of sight range at sea. Similarly, when the height range of the transmitting and receiving antennas is set to 5m to 35m with a step size of 5m, the maximum multipath delay calculation results at the extreme distance of radio wave propagation within the line of sight range at sea are as follows: Figure 4 As shown, Figure 4 Schematic diagram of the maximum multipath delay at the limit distance of radio wave propagation within the sea line of sight range determined by different transmitting and receiving antenna heights according to an embodiment of the present invention, Figure 4 It can be seen that within the limit distance of radio wave propagation within the line of sight range at sea, the maximum multipath delay increases with the increase of the height of the transmitting and receiving antennas, and at the same transmitting antenna height, the maximum multipath delay gradually increases with the increase of the receiving antenna height. The distance between two ships within the line of sight range does not exceed the limit distance of radio wave propagation, so Figure 4 The maximum multipath delay at the extreme distance of radio wave propagation within the line-of-sight range at sea calculated in is a special case.

[0094] The distance between two ships within the visual range is a fixed value, satisfying .when Gradually increase from 1km to hour, Figures 5 to 8 The maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights under a fixed transmitting antenna height is given.

[0095] Figure 5 2 is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 5 meters according to an embodiment of the present invention; Figure 6 is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 15 meters according to an embodiment of the present invention; Figure 7 2. This is a schematic diagram of maximum multipath delay within the line-of-sight range corresponding to different receiving antenna heights when the transmitting antenna height is 25 meters according to an embodiment of the present invention; Figure 8 : is a schematic diagram of the maximum multipath delay within the line of sight corresponding to different receiving antenna heights when the transmitting antenna height is 35 meters according to an embodiment of the present invention, Figures 5 to 8 As can be seen from the figure, as the distance between the two ships The maximum multipath delay decreases gradually within the line-of-sight range. Within the 1km-5km range, the maximum multipath delay decreases sharply; beyond 5km, the downward trend flattens. This indicates that the difference between the length of the reflected path and the length of the direct path of radio wave propagation between ships within line of sight also decreases with increasing distance between the two ships, and the difference decreases rapidly within the 1km-5km range.

[0096] In an embodiment of the present invention, when radio waves for communication between a first ship and a second ship propagate via a direct path, a direct path length of radio wave propagation within the line-of-sight range at sea is obtained based on the height of a transmitting antenna, the height of a receiving antenna, and the distance between the first ship and the second ship. When radio waves for communication between the first ship and the second ship propagate via a reflected path, a target reflection path length of radio wave propagation within the line-of-sight range at sea is determined based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and a reflection point of the radio wave on the sea surface, and the distance between the reflection point of the radio wave on the sea surface and the second ship. Based on the target reflection path length, the direct path length, and the propagation speed of radio waves within the line-of-sight range at sea, a maximum multipath delay within the line-of-sight range at sea is obtained. Determining the maximum multipath delay within the line-of-sight range at sea is used to set the symbol interval to 1.5 of the maximum multipath delay when designing a line-of-sight communication system at sea. -2 times, which solves the technical problem that in the existing maritime line-of-sight communication scenario, the signal from the transmitting end reaches the receiving end through a direct path and multiple reflected paths, and the length of each path is different, resulting in different times for the signal to reach the receiving end, thus generating multipath delay. A large multipath delay will cause inter-code interference, resulting in a decrease in the signal quality of the receiving end, an increase in the bit error rate, and further deterioration of the system performance. By substituting the three parameters of the transmitting antenna height, the receiving antenna height and the distance between ships into the derived analytical expression of the maximum multipath delay, the maximum multipath delay of ship communications within the maritime line-of-sight range can be quickly calculated. This method effectively reduces the additional transmission overhead and complexity required to obtain the maximum multipath delay within the maritime line-of-sight range, thereby being able to adapt to the rapid changes in the maritime line-of-sight channel caused by the movement of ships. The calculation results can also guide the waveform design of the maritime ship line-of-sight communication system. In order to avoid inter-code interference, the symbol interval Must be greater than the maximum multipath delay Therefore, the symbol interval is set to 1.5-2 times the maximum multipath delay, reserving enough time for the channel to allow the energy of the previous symbol to decay to a negligible level, thereby effectively avoiding inter-symbol interference, ultimately reducing the bit error rate and improving the performance of the maritime line-of-sight communication system.

[0097] The serial numbers of the above embodiments of the present invention are for description only and do not represent the advantages or disadvantages of the embodiments.

[0098] In the above embodiments of the present invention, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only exemplary. For example, the division of units can be a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0100] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple units. Some or all of the units may be selected to achieve the purpose of the present embodiment according to actual needs.

Claims

1. A method for calculating the maximum multipath delay based on the propagation path length within the line-of-sight range at sea, characterized in that: include: When radio waves used for communication between the first ship and the second ship propagate via a direct path, the length of the direct path for radio wave propagation within line-of-sight at sea is obtained based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship. When radio waves used for communication between the first ship and the second ship propagate via a reflection path, determining a target reflection path length for radio wave propagation within line of sight at sea based on the height of a transmitting antenna, the height of a receiving antenna, the distance between the first ship and a point where the radio waves are reflected on the sea surface, and the distance between the point where the radio waves are reflected on the sea surface and the second ship; Based on the target reflection path length, direct path length, and the propagation speed of radio waves within the line-of-sight range at sea, the maximum multipath delay within the line-of-sight range at sea is obtained, and its expression is: (6) in, is the maximum multipath delay within the line-of-sight range at sea, is the propagation speed of radio waves within the line of sight at sea, is the first extreme point relative to the distance between the first ship and the reflection point of the radio wave on the sea surface, is the target reflection path length, is the direct path length, is the height of the transmitting antenna, is the height of the receiving antenna, is the distance between the first ship and the second ship; Among them, determining the maximum multipath delay within the maritime line-of-sight range is used to set the code element interval to 1.5-2 times the maximum multipath delay when designing the maritime line-of-sight communication system.

2. The method according to claim 1, characterized in that The expression for the direct path length of radio wave propagation within the line-of-sight range at sea, obtained based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first ship and the second ship, is: (1)。 3. The method according to claim 2, characterized in that The determining of the target reflection path length of radio wave propagation within the line-of-sight range at sea based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the radio wave reflection point on the sea surface, and the distance between the radio wave reflection point on the sea surface and the second ship comprises: Based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the radio wave reflection point on the sea surface, and the distance between the radio wave reflection point on the sea surface and the second ship, the initial reflection path length of the radio wave propagation within the line of sight range at sea is determined. The expression for determining the initial reflection path length is: (2) in, is the initial reflection path length, is the distance between the first ship and the reflection point of the radio wave on the sea surface, is the distance between the point where the radio wave is reflected on the sea surface and the second ship; The expression for determining the initial reflection path length is based on Solve the first-order derivative and set it equal to zero to obtain the two extreme points of the first-order derivative of the initial reflection path length; processing the two extreme points to obtain a target extreme point, wherein the target extreme point is determined by a height of a transmitting antenna, a height of a receiving antenna, and a distance between the first ship and the second ship; The target reflection path length for radio wave propagation within the line of sight at sea is obtained by replacing the distance between the first ship and the radio wave reflection point on the sea surface and the distance between the radio wave reflection point on the sea surface and the second ship in the expression for determining the initial reflection path length with the target extreme point.

4. The method according to claim 3, characterized in that The expressions of the two extreme points of the first-order derivative of the initial reflection path length are: （3） （4） in, It is the second extreme point relative to the distance between the first ship and the point where the radio wave is reflected on the sea surface.

5. The method according to claim 4, characterized in that The expression for determining the initial reflection path length is obtained by replacing the distance between the first ship and the radio wave reflection point on the sea surface with the target extreme point, and replacing the distance between the radio wave reflection point on the sea surface and the second ship with the target extreme point. The expression for the target reflection path length of radio wave propagation within the line-of-sight range at sea is: （5）。 6. A computer system, characterized in that include: One or more processors, and a computer-readable storage medium for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors are enabled to implement the method of claim 1.

7. A computer-readable storage medium, characterized in that Computer-executable instructions are stored, and when the instructions are executed, they are used to implement the method of claim 1.

8. A computer program product, characterized in that The invention comprises computer executable instructions, which are used to implement the method of claim 1 when the instructions are executed.

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