Maximum multipath time delay calculation method based on propagation path length in maritime sight distance range

Abstract

The invention discloses a maximum multipath time delay calculation method based on propagation path length in an offshore sight distance range. The method comprises the following steps: when an electric wave for communication between a first ship and a second ship is propagated through a direct path, obtaining the length of the direct path for propagation of the electric wave within a seaborne sight distance range 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. The method solves the problems that in an existing marine sight distance communication scene, due to the fact that signals of a transmitting end reach a receiving end through a direct path and multiple reflection paths, the lengths of all the paths are different, the time for the signals to reach the receiving end is different, multi-path time delay is generated, large multi-path time delay will cause inter-symbol interference, and the communication performance is poor. The signal quality of a receiving end is reduced, the bit error rate is increased, and the system performance is further reduced.

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 maritime line-of-sight range. Background Art

[0002] Multipath delay refers to the delay difference caused by the signal passing through different propagation paths from the transmitter to the receiver. In the maritime line-of-sight communication scenario, since the transmitter signal reaches the receiver through a direct path and multiple reflection paths, and the length of each path is different, the signal arrives at the receiver at different times, resulting in multipath delay.

[0003] Large multipath delay 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 degraded system performance, which is particularly significant in high-speed data transmission applications. Therefore, in the waveform design of the maritime line-of-sight communication system, it is necessary to calculate the maximum multipath delay within the line-of-sight range in advance, and further adopt corresponding technologies such as channel equalization and orthogonal frequency division multiplexing based on the calculation results to reduce the impact of multipath and improve the performance of the communication system.

[0004] In practical systems (such as communication systems and global satellite navigation systems), channel estimation is currently the main method for obtaining multipath delay. This method first estimates the channel characteristics by sending a predefined pilot signal as a reference signal; after receiving the predefined pilot signal, the receiver will compare it with the known pilot signal; then the impulse response of the channel is estimated using algorithms such as least squares or minimum mean square error, and the delay information of different paths is extracted through further analysis. However, the use of pilot signals adds additional transmission overhead. In addition, the existing method for calculating multipath delay within the line of sight at sea is to calculate the length of the reflection path by enumeration based on the number of reflection points of the radio wave on the sea surface. However, in the line-of-sight communication scenario at sea, the number of reflection points of the radio wave on the sea surface is large, which will significantly increase the calculation complexity and cannot adapt well to the rapid changes in the channel caused by the movement of the ship. Summary of the invention

[0005] The 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 that in the existing line-of-sight communication scenario at sea, the signal from the transmitting end reaches the receiving end through a direct path and multiple reflection paths, and the length of each path is different, resulting in different times for the signal to arrive at the receiving end, thereby generating multipath delay. A large multipath delay 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 reducing the system performance.

[0006] According to one aspect of 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 at sea is provided. The method may include: when the radio waves for communication between the first ship and the second ship are propagated through a direct path, 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 direct path length of the radio waves propagating within the line of sight at sea is obtained; when the radio waves for communication between the first ship and the second ship are propagated through a reflection path, 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, the target reflection path length of the radio waves propagating within the line of sight at sea is determined; based on the target reflection path length, the direct path length and the propagation speed of the radio waves within the line of sight at sea, the maximum multipath delay within the line of sight at sea is obtained, wherein determining the maximum multipath delay within the line of sight at sea is used to set the symbol interval to 1.5-2 times of the maximum multipath delay when designing the 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: (1) 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.

[0008] Optionally, determining the target reflection path length of radio wave propagation within the sea line of sight range 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: 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 wave on the sea surface, and the distance between the reflection point of the radio wave on the sea surface and the second ship, the initial reflection path length of the radio wave propagation within the line of sight at sea is determined, wherein 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 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 value points of the first-order derivative of the initial reflection path length; the two extreme value points are processed to obtain the target extreme value point, wherein the target extreme value 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 reflection point of the radio wave on the sea surface in the expression for determining the initial reflection path length is replaced by the target extreme value point, and the distance between the reflection point of the radio wave on the sea surface and the second ship is replaced by the target extreme value point, to obtain the target reflection path length of the radio wave propagation within the line of sight range at sea.

[0009] Optionally, the expressions for the two extreme points of the first-order derivative of the initial reflection path length are: (3) (4) 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.

[0010] Optionally, the distance between the first ship and the reflection point of the radio wave 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 reflection point of the radio wave on the sea surface and the second ship is replaced by the target extreme point, and the expression for the target reflection path length of the radio wave propagation within the line of sight range at sea is obtained as follows: (5) is the target reflection path length.

[0011] Optionally, based on the target reflection path length, the direct path length and the propagation speed of radio waves within the sea line-of-sight range, the expression for the maximum multipath delay within the sea line-of-sight range is obtained as follows: (6) 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 range at sea.

[0012] Beneficial effects of the present invention: 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 can quickly calculate the maximum multipath delay of ship communications within the line-of-sight range at sea 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. 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-code interference, the symbol interval Must be greater than the maximum multipath delay Therefore, the symbol interval is set to 1.5-2 times of the maximum multipath delay, reserving enough time for the channel to make the energy of the previous symbol 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

[0013] 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: Figure 1 is a flow chart of a method for calculating the maximum multipath delay based on the propagation path length within the sea line-of-sight range according to an embodiment of the present invention; Figure 2 This is a scene diagram of a method for calculating a maximum multipath delay based on a propagation path length within a line-of-sight range at sea according to an embodiment of the present invention; Figure 3 is a schematic diagram of 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 is a 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 5 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 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 It is a schematic diagram of the 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

[0014] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0015] It should be noted that the terms "first", "second", etc. in the specification 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 can be 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 that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0016] Example 1 According to an embodiment of the present invention, a method for calculating the maximum multipath delay based on the propagation path length within the sea line-of-sight range 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.

[0017] Figure 1 is a flow chart of a method for calculating the maximum multipath delay based on the propagation path length within the sea line-of-sight range according to an embodiment of the present invention. Figure 1 As shown, the method may include the following steps: Step S101, when the radio waves for communication between the first ship and the second ship are propagated through a direct path, the direct path length of the radio waves propagating 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.

[0018] In the technical solution provided in the above step S101 of the present invention, Figure 2is a scene diagram of a method for calculating the maximum multipath delay based on the propagation path length within the sea line of sight 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 figure is the straight-line distance d, and the height of the transmitting antenna is , the receiving antenna height is , the distance between the first ship and the second ship is , that is Figure 2 The sight distance , that is, BD, can be calculated from the longitude and latitude 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): (7) in, It is the maximum distance of radio wave propagation within the line of sight at sea, measured in meters.

[0019] Step S102, when the radio waves for communication between the first ship and the second ship are propagated through a reflection path, 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, the target reflection path length of the radio waves propagating within the line of sight at sea is determined.

[0020] 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 The AC and CF paths in the figure are used for propagation. AC and CF represent the distance between the transmitting antenna and the 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 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 reflection point of the radio wave 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 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, the target reflection path length of the radio wave propagation within the sea line of sight range is calculated.

[0021] Step S103, based on the target reflection path length, the direct path length and the propagation speed of radio waves within the sea line-of-sight range, obtain the maximum multipath delay within the sea line-of-sight range, wherein determining the maximum multipath delay within the sea line-of-sight range is used to set the code element interval to 1.5-2 times the maximum multipath delay when designing the sea line-of-sight communication system.

[0022] 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 sea line of sight range are calculated to obtain the maximum multipath delay within the sea line of sight range ( ), where, 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 of the maximum multipath delay, which reserves enough time for the channel to make the energy of the previous symbol decay to a negligible level, thereby effectively avoiding inter-symbol interference.

[0023] The above method of this embodiment is further introduced below.

[0024] As an optional implementation manner, in step S101, the expression for obtaining the direct path length of radio wave propagation within the sea line-of-sight range 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) 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.

[0025] As an optional implementation manner, step S102, 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 wave on the sea surface, and the distance between the reflection point of the radio wave on the sea surface and the second ship, determines the target reflection path length of the radio wave propagation within the line of sight at sea, including: 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 wave on the sea surface, and the distance between the reflection point of the radio wave on the sea surface and the second ship, determines the initial reflection path length of the radio wave propagation within the line of sight at sea, wherein 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 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 value points of the first-order derivative of the initial reflection path length; the two extreme value points are processed to obtain the target extreme value point, wherein the target extreme value 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 reflection point of the radio wave on the sea surface in the expression for determining the initial reflection path length is replaced by the target extreme value point, and the distance between the reflection point of the radio wave on the sea surface and the second ship is replaced by the target extreme value point, to obtain the target reflection path length of the radio wave propagation within the line of sight range at sea.

[0026] In this embodiment, the expression for determining the initial reflection path length is based on The expression for solving the first-order derivative is: (8) in, The expression for determining the initial reflection path length is based on Solve the first-order derivative; Let the first-order derivative be equal to zero. The steps are as follows: make have (9) Squaring both sides and sorting them gives: (10) Further rearrangement of formula (10) yields: (11) like , both sides of formula (11) do not hold; otherwise, both sides are divided by , can be obtained (12) The formula (12) is further simplified as follows.

[0027] set up (13), then (14) Substituting formula (14) into formula (11), formula (11) becomes

[0028] therefore, ,Will Substitution (Formula (14)) to obtain (15), we can get the following two extreme points: (3) (4) The two extreme points are processed, including: taking the second-order derivative of the length of the reflection path of radio wave propagation, and obtaining (16) in, It is the second derivative of the reflection path length of radio wave propagation.

[0029] According to the actual scenario of maritime line-of-sight communication, the steps to determine the type of extreme point are as follows: Transmitting antenna height of maritime line-of-sight communication system Height to receiving antenna Generally no more than 50m, much less than and Therefore, for any , are established, and , so is a maximum value point.

[0030] also, Needs to be satisfied ,Right now .

[0031] because and If both are positive numbers, then Only needs to meet the following requirements to be established: , however, this is consistent with the assumption Contradictory, therefore is not an extreme point, so is the target extreme point.

[0032] As an optional embodiment, the expressions of the two extreme points of the first-order derivative of the initial reflection path length are: (3) (4) 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.

[0033] As an optional implementation mode, the distance between the first ship and the reflection point of the radio wave 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 reflection point of the radio wave on the sea surface and the second ship is replaced by the target extreme point, and the expression for the target reflection path length of the radio wave propagation within the line of sight range at sea is obtained as follows: (5) is the target reflection path length.

[0034] 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.

[0035] As an optional implementation manner, in step S103, based on the target reflection path length, the direct path length and the propagation speed of radio waves within the sea line-of-sight range, the expression of the maximum multipath delay within the sea line-of-sight range is obtained as follows: (6) 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 range at sea.

[0036] In this embodiment, the target reflection path length, the direct path length and the propagation speed of radio waves within the sea line of sight range are substituted into formula (6) to obtain the maximum multipath delay within the sea line of sight range. According to formula 6, it can be seen that the maximum multipath delay within the sea line of sight range can be obtained according to the height of the transmitting antenna, the height of the receiving antenna and the distance between the first ship and the second ship.

[0037] Experimental part: 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, the range of the transmitting and receiving antenna heights is set to 5m to 35m with a step length 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 limit 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 limit 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 limit distance of radio wave propagation within the line of sight at sea corresponding to different receiving antenna heights are almost parallel.

[0038] The formula for determining the maximum multipath delay within the sea line of sight range also applies to of the situation, in which 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 limit distance of radio wave propagation within the line of sight at sea. Similarly, the height range of the transmitting and receiving antennas is set to 5m to 35m with a step length of 5m. The maximum multipath delay calculation results at the limit distance of radio wave propagation within the line of sight 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 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 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.

[0039] 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.

[0040] Figure 5 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 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 increases The maximum multipath delay in the line of sight range gradually increases, and the maximum multipath delay in the line of sight range gradually decreases; in the range of 1km-5km, the maximum multipath delay decreases sharply; beyond 5km, the downward trend tends to be gentle. This shows that the difference between the length of the reflection path of radio wave propagation between ships in the line of sight range and the length of the direct path of radio wave propagation also decreases with the increase of the distance between the two ships, and in the range of 1km-5km, the difference between the two decreases rapidly.

[0041] In an embodiment of the present invention, when the radio waves for communication between the first ship and the second ship are propagated through 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; 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 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 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; based on the target reflection path length, the direct path length and the propagation speed of the radio waves within the line-of-sight range at sea, the maximum multipath delay within the line-of-sight range at sea is obtained, wherein 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 reflection paths, and the length of each path is different, resulting in different times for the signal to arrive at the receiving end, thus generating multipath delay. A larger multipath delay will cause inter-code interference, resulting in a decrease in the signal quality at the receiving end, an increase in the bit error rate, and further degradation 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 of 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.

[0042] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0043] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0044] 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 schematic. For example, the division of units can be a logical function division. There may be other division methods in actual implementation. For example, 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.

[0045] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

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 the radio waves for communication between the first ship and the second ship are propagated through 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; When the radio waves for communication between the first ship and the second ship are propagated through a reflection path, 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, determining the target reflection path length of the radio waves propagating within the line of sight at sea; Based on the target reflection path length, the direct path length and the propagation speed of radio waves within the sea line-of-sight range, the maximum multipath delay within the sea line-of-sight range is obtained, wherein the maximum multipath delay within the sea line-of-sight range is determined to set the code element interval to 1.5-2 times the maximum multipath delay when designing the sea line-of-sight communication system.

2. The method according to claim 1, characterized in that The expression for obtaining the direct path length of radio wave propagation within the sea line-of-sight range 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) 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.

3. The method according to claim 1, characterized in that The method of determining the target reflection path length of radio wave propagation within the sea line of sight range 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 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, the initial reflection path length of the radio wave propagation within the line of sight at sea is determined, wherein 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 reflection point of the radio wave 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 two extreme points of the first-order derivative of the initial reflection path length; Processing the two extreme value points to obtain a target extreme value point, wherein the target extreme value 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 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, so as to obtain the target reflection path length of radio wave propagation within the line of sight range at sea.

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, 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.

5. The method according to claim 3, characterized in that: The distance between the first ship and the reflection point of the radio wave 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 reflection point of the radio wave on the sea surface and the second ship is replaced by the target extreme point, and the expression for the target reflection path length of the radio wave propagation within the line of sight at sea is obtained as follows: （5） is the target reflection path length.

6. The method according to claim 1, characterized in that The expression for the maximum multipath delay within the sea line-of-sight range is obtained based on the target reflection path length, the direct path length and the propagation speed of the radio wave within the sea line-of-sight range: (6) 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 range at sea.

7. 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.

8. 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.

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

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