CN119364417B - A method for calculating the maximum multipath delay based on propagation path length within the line-of-sight range at sea - Google Patents
A method for calculating the maximum multipath delay based on propagation path length within the line-of-sight range at seaInfo
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- CN119364417B CN119364417B CN202411506729.6A CN202411506729A CN119364417B CN 119364417 B CN119364417 B CN 119364417B CN 202411506729 A CN202411506729 A CN 202411506729A CN 119364417 B CN119364417 B CN 119364417B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W24/00—Supervisory, monitoring or testing arrangements
- H04W24/08—Testing, supervising or monitoring using real traffic
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
- H04W4/30—Services specially adapted for particular environments, situations or purposes
- H04W4/40—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P]
- H04W4/46—Services specially adapted for particular environments, situations or purposes for vehicles, e.g. vehicle-to-pedestrians [V2P] for vehicle-to-vehicle communication [V2V]
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Abstract
The invention discloses a maximum multipath time delay calculation method based on propagation path length in an offshore apparent distance range. When the electric wave communicated between the first ship and the second ship propagates through the direct path, the direct path length of the electric wave propagation in the offshore visual range 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 invention solves the technical problems that in the existing offshore line-of-sight communication scene, as the signal of the transmitting end reaches the receiving end through the direct path and the plurality of reflection paths, and the lengths of the paths are different, the time for the signal to reach the receiving end is different, thereby generating multipath time delay, and the larger multipath time delay causes at least inter-interference, so that the signal quality of the receiving end is reduced, the error rate is increased, and the system performance is further reduced.
Description
Technical Field
The invention relates to the technical field of offshore wireless communication, in particular to a maximum multipath time delay calculation method based on propagation path length in an offshore line-of-sight range.
Background
Multipath delay refers to the difference in delay caused by the signal passing through different propagation paths from the transmitting end to the receiving end. In an offshore line-of-sight communication scenario, a signal from a transmitting end arrives at a receiving end through a direct path and a plurality of reflection paths, and the lengths of the paths are different, so that the time for the signal to arrive at the receiving end is different, thereby generating multipath time delay.
The larger multipath time delay can cause at least inter-interference, so that the signal quality of a receiving end is reduced, the error rate is increased, the system performance is further reduced, and the influence is particularly remarkable in high-speed data transmission application. Therefore, in the waveform design of the offshore line-of-sight communication system, the maximum multipath time delay in the line-of-sight range needs to be calculated in advance, and corresponding technologies such as channel equalization, orthogonal frequency division multiplexing and the like are further adopted to reduce the influence of multipath by combining the calculation results, so that the performance of the communication system is improved.
In practical systems (such as communication systems and global satellite navigation systems), channel estimation is currently the main method for acquiring multipath delay. The method comprises the steps of firstly, estimating channel characteristics by sending a predefined pilot signal as a reference signal, comparing the predefined pilot signal with a known pilot signal by a receiving end after receiving the predefined pilot signal, estimating impulse response of a channel by utilizing least square or least mean square error algorithm and the like, and extracting delay information of different paths by further analysis. However, the use of pilot signals adds additional transmission overhead. In addition, the existing method for calculating the multipath time delay in the offshore apparent distance calculates the length of the reflection path in an enumeration mode according to the number of reflection points of the electric wave on the sea surface, however, in the offshore apparent distance communication scene, the number of reflection points of the electric wave on the sea surface is larger, which obviously increases the calculation complexity and cannot be well adapted to the rapid change of the channel caused by the movement of the ship.
Disclosure of Invention
The embodiment of the invention provides a maximum multipath time delay calculation method based on propagation path length in an offshore line-of-sight range, which at least solves the technical problems that in the existing offshore line-of-sight communication scene, as a signal of a transmitting end reaches a receiving end through a direct path and a plurality of reflection paths, the lengths of the paths are different, so that the time for the signal to reach the receiving end is different, thereby generating multipath time delay, and the larger multipath time delay causes at least inter-path interference, so that the signal quality of the receiving end is reduced, the error rate is increased, and the system performance is further reduced.
According to an aspect of the embodiment of the invention, a maximum multipath delay calculation method based on propagation path length in an offshore line-of-sight range is provided. The method includes the steps of obtaining a direct path length of electric wave propagation in an offshore line of sight 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 when electric waves communicated between the first ship and the second ship are propagated through a direct path, determining a target reflection path length of electric wave propagation in the offshore 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 an electric wave at a sea surface reflection point and the distance between the electric wave at the sea surface reflection point and the second ship when electric waves communicated between the first ship and the second ship are propagated through a reflection path, and obtaining a maximum multipath time delay in the offshore line of sight range based on the target reflection path length, the direct path length and the propagation speed of electric waves in the offshore line of sight range, wherein the maximum multipath time delay in the offshore line of sight range is 1.5-2 times of a maximum multipath time delay for setting a symbol interval when the offshore line of sight communication system is designed.
Optionally, the expression for obtaining the direct path length of the electric wave propagation in the offshore apparent distance 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)
Wherein, the Direct path length,Is the height of the transmitting antenna,Is the height of the receiving antenna,Is the distance between the first vessel and the second vessel.
Optionally, determining the target reflection path length of the electric wave propagation in the offshore line of sight based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first vessel and the electric wave at the sea surface reflection point, and the distance between the electric wave at the sea surface reflection point and the second vessel includes:
determining an initial reflection path length of electric wave propagation in an offshore apparent distance range based on the height of a transmitting antenna, the height of a receiving antenna, the distance between a first ship and an electric wave at a sea surface reflection point and the distance between the electric wave at the sea surface reflection point and a second ship, wherein the expression for determining the initial reflection path length is as follows:
(2)
Wherein, the For the initial reflection path length,For the distance between the first vessel and the wave at the sea surface reflection point,For the distance of the wave between the sea surface reflection point and the second vessel, the expression for determining the initial reflection path length is based onThe method comprises the steps of solving a first derivative, enabling the first derivative to be equal to zero, obtaining two extreme points of the first 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 the height of a transmitting antenna, the height of a receiving antenna and the distance between a first ship and a second ship, and replacing the distance between the first ship and an electric wave in an expression for determining the initial reflection path length and the sea surface reflection point with the target extreme point and replacing the distance between the electric wave and the sea surface reflection point and the second ship with the target extreme point to obtain the target reflection path length of electric wave propagation in the sea apparent distance range.
Alternatively, the expression of the two extreme points of the first derivative of the initial reflection path length is:
(3)
(4)
Wherein, the Is the first extreme point of the distance between the sea surface reflection point with respect to the first vessel and the electric wave,Is a second extreme point with respect to the distance between the first vessel and the wave at the sea surface reflection point.
Optionally, replacing a distance between the first ship and the electric wave at the sea surface reflection point in the expression for determining the initial reflection path length with a target extremum point, and replacing a distance between the electric wave at the sea surface reflection point and the second ship with a target extremum point, so as to obtain an expression for obtaining a target reflection path length of electric wave propagation in the offshore line-of-sight range, wherein the expression comprises:
(5)
For the target reflection path length.
Optionally, based on the target reflection path length, the direct path length and the propagation speed of the electric wave in the offshore line of sight, the expression for obtaining the maximum multipath time delay in the offshore line of sight is:
(6)
Wherein, the For maximum multipath delay in the offshore line-of-sight range,Is the propagation velocity of the electric wave in the offshore line-of-sight range.
The invention has the beneficial effects that:
The invention provides a maximum multipath time delay calculation method based on propagation path length in an offshore apparent distance range, which can be used for rapidly calculating the maximum multipath time delay of ship communication in the offshore apparent distance range by substituting three parameters of transmitting antenna height, receiving antenna height and ship-to-ship distance into a derived maximum multipath time delay analytical expression. Therefore, the method effectively reduces the extra transmission cost and complexity required for acquiring the maximum multipath time delay in the offshore apparent distance range, thereby being capable of adapting to the rapid change of the offshore apparent distance channel caused by the ship movement, and the calculation result can also guide the waveform design of the offshore ship apparent distance communication system, and in order to avoid inter-code crosstalk when the offshore apparent distance communication system is designed, the code element interval is reduced Must be greater than the maximum multipath delayTherefore, the code element interval is set to be 1.5-2 times of the maximum multipath time delay, and enough time is reserved for the channel to enable the energy of the previous code element to be attenuated to a negligible degree, so that the inter-code crosstalk is effectively avoided, the error rate is finally reduced, and the performance of the offshore visual range communication system is improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:
FIG. 1 is a flow chart of a method for maximum multipath delay calculation based on propagation path length over an offshore line of sight in accordance with an embodiment of the present invention;
FIG. 2 is a scenario diagram of a maximum multipath delay calculation method based on propagation path length in the offshore line of sight according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of wave propagation limit distances in the offshore line of sight determined by different transmit and receive antenna heights in accordance with an embodiment of the present invention;
FIG. 4 is a schematic diagram of maximum multipath delay at wave propagation limit distances in the offshore line of sight range determined by different transmit and receive antenna heights according to an embodiment of the present invention;
fig. 5 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 5 meters according to an embodiment of the present invention;
fig. 6 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 15 meters according to an embodiment of the present invention;
Fig. 7 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 25 meters according to an embodiment of the present invention;
fig. 8 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 35 meters according to an embodiment of the present invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, a technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in which it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, shall fall within the scope of the invention.
It should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above-described drawings are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
Example 1
According to an embodiment of the present invention, there is provided a method of calculating a maximum multipath delay based on propagation path length over an offshore line of sight, it being noted that the steps shown in the flowchart of the drawings may be performed 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 performed in an order different from that shown herein.
Fig. 1 is a flowchart of a method for calculating a maximum multipath delay based on propagation path length in an offshore line of sight according to an embodiment of the present invention, as shown in fig. 1, the method may include the steps of:
In step S101, when the radio wave for communication between the first vessel and the second vessel propagates through the direct path, the direct path length of the radio wave propagation in the offshore line-of-sight range is obtained based on the height of the transmitting antenna, the height of the receiving antenna, and the distance between the first vessel and the second vessel.
In the solution provided in the step S101 of the present invention, fig. 2 is a scene diagram of a method for calculating maximum multipath delay based on propagation path length in the offshore line of sight according to an embodiment of the present invention, if the electric wave for communication between the first vessel and the second vessel propagates through the direct path, that is, AF in fig. 2, that is, straight distance d, the transmitting antenna height isThe receiving antenna has a height ofThe distance between the first ship and the second ship isI.e. line of sight distance in fig. 2Namely BD, can be calculated from longitude and latitude coordinates of two ships, and the unit is meter, thereby meeting the requirements ofWave propagation limit distance in offshore apparent distance rangeCalculated from the transmit and receive antenna heights of the marine vessel communication system, for example, equation (7):
(7)
Wherein, the The wave propagation limit distance in meters is the wave propagation limit distance in the offshore apparent distance range.
In step S102, when the electric wave for communication between the first vessel and the second vessel propagates through the reflection path, a target reflection path length for propagation of the electric wave in the offshore line of sight is determined based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first vessel and the electric wave at the sea surface reflection point, and the distance between the electric wave at the sea surface reflection point and the second vessel.
In the technical solution provided in the above step S102 of the present invention, if the electric wave for communication between the first vessel and the second vessel propagates through the reflection path, that is, the AC and CF paths in fig. 2 propagate, where AC and CF respectively represent the distance between the transmitting antenna and the electric wave at the sea surface reflection point and the distance between the electric wave at the sea surface reflection point and the receiving antenna, the transmitting antenna has a height ofThe receiving antenna has a height ofThe distance between the first ship and the electric wave at the sea surface reflection point is BC #) Distance CD between sea surface reflection point and second ship) And calculating the target reflection path length of the electric wave propagation in the offshore apparent distance range according to the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the electric wave at the sea surface reflection point and the distance between the electric wave at the sea surface reflection point and the second ship.
And step S103, obtaining the maximum multipath time delay in the offshore apparent distance range based on the target reflection path length, the direct path length and the propagation speed of the electric wave in the offshore apparent distance range, wherein the maximum multipath time delay in the offshore apparent distance range is determined to be 1.5-2 times of the maximum multipath time delay when the offshore apparent distance communication system is designed.
In the technical scheme provided in the step S103, the propagation speed of the electric wave in the offshore apparent distance range, which is calculated by the target reflection path length, the direct path length and the propagation speed of the electric wave in the offshore apparent distance range, is obtained to obtain the maximum multipath time delay in the offshore apparent distance range) Wherein, in designing the offshore line-of-sight communication system, in order to avoid inter-code crosstalk, symbol spacingMust be greater than the maximum multipath delay. Therefore, the symbol interval is set to 1.5-2 times of the maximum multipath delay, and enough time is reserved for the channel so that the energy of the previous symbol decays to a negligible extent, thereby effectively avoiding inter-symbol interference.
The above-described method of this embodiment is further described below.
As an optional embodiment, step S101, the expression for obtaining the direct path length of the electric wave propagation in the offshore line of sight 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)
Wherein, the 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 vessel and the second vessel.
As an alternative embodiment, step S102, determining the target reflection path length of the wave propagation in the offshore line of sight based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first vessel and the wave at the sea surface reflection point, and the distance between the wave at the sea surface reflection point and the second vessel, includes determining the initial reflection path length of the wave propagation in the offshore line of sight based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first vessel and the wave at the sea surface reflection point, and the distance between the wave at the sea surface reflection point and the second vessel, wherein the expression for determining the initial reflection path length is:
(2)
Wherein, the For the initial reflection path length,For the distance between the first vessel and the wave at the sea surface reflection point,For the distance of the wave between the sea surface reflection point and the second vessel, the expression for determining the initial reflection path length is based onThe method comprises the steps of solving a first derivative, enabling the first derivative to be equal to zero, obtaining two extreme points of the first 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 the height of a transmitting antenna, the height of a receiving antenna and the distance between a first ship and a second ship, and replacing the distance between the first ship and an electric wave in an expression for determining the initial reflection path length and the sea surface reflection point with the target extreme point and replacing the distance between the electric wave and the sea surface reflection point and the second ship with the target extreme point to obtain the target reflection path length of electric wave propagation in the sea apparent distance range.
In this embodiment, the expression for determining the initial reflection path length is based onThe expression for solving the first derivative is:
(8)
Wherein, the The expression for determining the initial reflection path length is based onSolving a first derivative;
Let the first derivative equal zero, the steps are as follows:
Order the Has the following components(9)
Two sides are squared and arranged simultaneously to obtain:
(10)
Further finishing of equation (10) may result:
(11)
If it is The formula (11) is not true on both sides, otherwise, both sides are divided byCan be obtained
(12)
Equation (12) is further simplified below.
Is provided with(13) Then(14)
Substituting equation (14) into equation (11), equation (11) becomes
Thus, the first and second substrates are bonded together,Will beSubstitute for returnThe expression of (formula (14)) yields(15) The following two extreme points can be obtained:
(3)
(4)
the two extreme points are processed by obtaining the second derivative of the wave propagation reflection path length
(16)
Wherein, the Is the second derivative of the path length of the wave propagation reflection.
Based on offshore line-of-sight communication reality the scene judges the type of the extreme point, the method comprises the following steps:
transmitting antenna height for offshore line-of-sight communication system Height with receiving antennaGenerally not more than 50m, much smaller thanAnd. Thus, for any one,All are true, andTherefore, it isIs a maximum point.
In addition, in the case of the optical fiber,Needs to meet the requirements ofI.e.。
Due toAndAll are positive numbers, thenIs established only byHowever, this is consistent with the assumption thatContradictory, thusIs not an extreme point, and therefore,Is the target extreme point.
As an alternative embodiment, the expression of the two extreme points of the first derivative of the initial reflection path length is:
(3)
(4)
Wherein, the Is the first extreme point of the distance between the sea surface reflection point with respect to the first vessel and the electric wave,Is a second extreme point with respect to the distance between the first vessel and the wave at the sea surface reflection point.
As an alternative embodiment, the distance between the first ship and the electric wave at the sea surface reflection point in the expression for determining the initial reflection path length is replaced by a target extremum point, and the distance between the electric wave at the sea surface reflection point and the second ship is replaced by a target extremum point, so that the expression for obtaining the target reflection path length of electric wave propagation in the offshore line of sight range is as follows:
(5)
For the target reflection path length.
In this embodiment, the distance between the first vessel and the electric wave at the sea surface reflection point in equation 2 is replaced with a target extremum point, and the distance between the electric wave at the sea surface reflection point and the second vessel is replaced with a target extremum point, so as to obtain the target reflection path length of the electric wave propagation in the offshore line of sight.
As an optional embodiment, step S103, based on the target reflection path length, the direct path length, and the propagation speed of the electric wave in the offshore line of sight, obtains an expression of the maximum multipath delay in the offshore line of sight as follows:
(6)
Wherein, the For maximum multipath delay in the offshore line-of-sight range,Is the propagation velocity of the electric wave in the offshore line-of-sight range.
In this embodiment, the target reflection path length, the direct path length and the propagation speed of the electric wave in the offshore line of sight range are substituted into the formula (6), so as to obtain the maximum multipath time delay in the offshore line of sight range, and as can be seen according to the formula 6, the maximum multipath time delay in the offshore 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.
Experimental part:
when the heights of the transmitting antenna and the receiving antenna are 5m, the wave propagation limit distance in the offshore visual range is 18.4252km, and similarly, the height range of the transmitting antenna and the receiving antenna is set to be 5m to 35m, the step length is 5m, and the wave propagation limit distance in the offshore visual range is calculated as shown in fig. 3. Fig. 3 is a schematic diagram showing the wave propagation limit distance in the offshore line of sight determined by the heights of the transmitting and receiving antennas according to an embodiment of the present invention, it can be seen from fig. 3 that the wave propagation limit distance in the offshore line of sight increases with the increase of the heights of the transmitting and receiving antennas, and the wave propagation limit distance curves in the offshore line of sight corresponding to the heights of the different receiving antennas are nearly parallel.
The equation for determining the maximum multipath delay in the offshore line-of-sight range is also applicableIn the case of (1), in whichIs a special case. When the heights of the transmitting and receiving antennas are 5m, the maximum multipath time delay is 0.00904558176747135ns under the wave propagation limit distance in the offshore line of sight, the height range of the transmitting and receiving antennas is set to be 5m to 35m, the step length is 5m, the calculation result of the maximum multipath time delay under the wave propagation limit distance in the offshore line of sight is shown in fig. 4, fig. 4 is a schematic diagram of the maximum multipath time delay under the wave propagation limit distance in the offshore line of sight determined by different transmitting and receiving antenna heights according to the embodiment of the invention, and as can be seen from fig. 4, the maximum multipath time delay increases with the increase of the transmitting and receiving antenna heights under the same transmitting antenna height. The distance between two vessels in the line of sight does not exceed the limit distance of propagation of the electric wave, and thus the maximum multipath delay at the limit distance of propagation of the electric wave in the offshore line of sight calculated in fig. 4 is a special case.
Distance between two vessels in line of sightIs a fixed value, satisfy. When (when)Gradually increase from 1km toFig. 5 to 8 show the maximum multipath delays in the range of view corresponding to different receiving antenna heights at a fixed transmitting antenna height.
Fig. 5 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 5m according to an embodiment of the present invention, fig. 6 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 15 m according to an embodiment of the present invention, fig. 7 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 25m according to an embodiment of the present invention, fig. 8 is a schematic diagram of maximum multipath delay in a range of view corresponding to different receiving antenna heights when the transmitting antenna height is 35 m according to an embodiment of the present invention, and as can be seen from fig. 5 to 8, the distance between two vessels is as a function of the distance between two vesselsThe maximum multipath time delay is gradually increased in the range of the viewing distance, the maximum multipath time delay is gradually reduced in the range of 1km-5km, and the descending trend is gradually gentle beyond 5 km. This shows that the difference between the wave propagation reflection path length and the wave propagation direct path length between vessels in the line of sight range also decreases as the distance between the two vessels increases, and the difference between them rapidly decreases in the range of 1km to 5 km.
In the embodiment of the invention, when the electric wave communicated between the first ship and the second ship is transmitted through the direct path, the direct path length of the electric wave transmission in the offshore visual range 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 electric wave for communication between the first ship and the second ship propagates through the reflection path, the target reflection path length of the electric wave propagation in the offshore visual range is determined based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the electric wave at the sea surface reflection point and the distance between the electric wave at the sea surface reflection point and the second ship, and the maximum multipath time delay in the offshore visual range is obtained based on the target reflection path length, the direct path length and the propagation speed of the electric wave in the offshore visual range, wherein the maximum multipath time delay in the offshore visual range is determined to be 1.5-2 times of the maximum multipath time delay when the offshore visual range communication system is designed, the problems that the signal of the transmitting end reaches the receiving end through the direct path and a plurality of reflection paths in the existing offshore visual range communication scene, the time delay is different when the signal reaches the receiving end, the multipath time delay is generated, the maximum multipath time delay causes the signal quality of the receiving end to be reduced, the system performance is further reduced, the problem that the three-dimensional time delay of the transmitting end can be calculated to reach the maximum multipath time delay of the ship in the receiving antenna in the marine visual range can be calculated, the method effectively reduces the extra transmission cost and complexity required by acquiring the maximum multipath time delay in the offshore apparent distance range, thereby being capable of adapting to the rapid change of the offshore apparent distance channel caused by the ship movement, and the calculation result can also guide the waveform design of the offshore ship apparent distance communication system, so as to avoid inter-code crosstalk, and the code element intervalMust be greater than the maximum multipath delayTherefore, the code element interval is set to be 1.5-2 times of the maximum multipath time delay, and enough time is reserved for the channel to enable the energy of the previous code element to be attenuated to a negligible degree, so that the inter-code crosstalk is effectively avoided, the error rate is finally reduced, and the technical effect of the performance of the offshore line-of-sight communication system is improved.
The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
In the foregoing embodiments of the present invention, the descriptions of the embodiments are emphasized, and for a portion of this disclosure that is not described in detail in this embodiment, reference is made to the related descriptions of other embodiments.
In the several embodiments provided in the present application, it should be understood that the disclosed technology may be implemented in other manners. The above-described embodiments of the apparatus are merely exemplary, and the division of units may be a logic function division, and there may be another division manner in actual implementation, for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some interfaces, units or modules, or may be in electrical or other forms.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
Claims (8)
1. A method for calculating a maximum multipath delay based on propagation path length over an offshore line of sight, comprising:
When the electric wave communicated between the first ship and the second ship is transmitted through the direct path, the direct path length of the electric wave transmission in the offshore apparent distance range 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 electric wave communicated between the first ship and the second ship propagates through the reflection path, determining a target reflection path length of the electric wave propagation in the offshore apparent distance range based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first ship and the electric wave at the sea surface reflection point and the distance between the electric wave at the sea surface reflection point and the second ship;
based on the target reflection path length, the direct path length and the propagation speed of the electric wave in the offshore apparent distance range, the maximum multipath time delay in the offshore apparent distance range is obtained, and the expression is as follows:
(6)
Wherein, the For maximum multipath delay in the offshore line-of-sight range,Is the propagation speed of the electric wave in the offshore visual range,A first extreme point which is the distance between the first ship and the wave reflection point 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 vessel and the second vessel;
wherein the maximum multipath delay in the offshore line of sight range is determined to be 1.5-2 times the maximum multipath delay for setting the symbol interval when designing the offshore line of sight communication system.
2. The method of claim 1, wherein the expression for obtaining the direct path length of the wave propagation in the offshore line of sight based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first vessel and the second vessel is:
(1)。
3. The method of claim 2, wherein determining the target reflection path length for the wave propagation within the offshore line of sight based on the height of the transmitting antenna, the height of the receiving antenna, the distance between the first vessel and the wave at the sea surface reflection point, the distance between the wave at the sea surface reflection point and the second vessel, comprises:
determining an initial reflection path length of electric wave propagation in an offshore apparent distance range based on the height of a transmitting antenna, the height of a receiving antenna, the distance between a first ship and an electric wave at a sea surface reflection point and the distance between the electric wave at the sea surface reflection point and a second ship, wherein the expression for determining the initial reflection path length is as follows:
(2)
Wherein, the For the initial reflection path length,For the distance between the first vessel and the wave at the sea surface reflection point,The distance between the sea surface reflection point and the second ship is the electric wave;
the expression for determining the initial reflection path length is based on Solving a first derivative, and enabling the first derivative to be equal to zero to obtain two extreme points of the first 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 the height of the transmitting antenna, the height of the receiving antenna and the distance between the first ship and the second ship;
And replacing the distance between the first ship and the electric wave in the expression for determining the initial reflection path length with a target extreme point, and replacing the distance between the electric wave in the sea surface reflection point and the second ship with a target extreme point, so as to obtain the target reflection path length of electric wave propagation in the sea apparent distance range.
4. A method according to claim 3, wherein the expression for the two extreme points of the first derivative of the initial reflection path length is:
(3)
(4)
Wherein, the Is a second extreme point with respect to the distance between the first vessel and the wave at the sea surface reflection point.
5. The method of claim 4, wherein the replacing the distance between the first vessel and the wave at the sea surface reflection point in the expression for determining the initial reflection path length with the target extremum point and the replacing the distance between the wave at the sea surface reflection point and the second vessel with the target extremum point, the expression for obtaining the target reflection path length of the wave propagation in the sea line of sight is:
(5)。
6. a computer system comprising one or more processors, a computer-readable storage medium storing one or more programs, wherein the one or more programs, when executed by the one or more processors, cause the one or more processors to implement the method of claim 1.
7. A computer readable storage medium, characterized by storing computer executable instructions that, when executed, are adapted to implement the method of claim 1.
8. A computer program product comprising computer executable instructions which, when executed, are adapted to implement the method of claim 1.
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