Method for predicting path loss inside ship
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a path loss prediction method in a ship.
Background
The communication industry of China is continuously strengthening the strength of the communication industry, and through the investment of a large amount of scientific research expenses and the use of manpower and material resources, the communication industry of China has occupied an important position internationally. The fifth generation mobile communication technology (5G) is a leading technology hit by the global technology revolution, and the transmission speed thereof is much higher than that of the current 4G network. The emergence of 5G also means that the global mobile communication industry is upgraded again, reliable signal coverage can be realized for military scenes by virtue of the characteristics of large bandwidth, high reliability, low time delay and the like, and the 5G network coverage of the military industry becomes an important subject of 5G network construction in China.
Talkback scheduling inside ships is an extremely important application function in military scenarios. In order to ensure the signal coverage quality inside the ship, accurate network deployment is required. Generally, a network planner uses a path loss model to predict the coverage of indoor wireless signals, so as to determine the number and deployment positions of APs. Therefore, a precise indoor path loss model can save a large amount of manpower, material resources and time, and the network planning efficiency is improved. As a special indoor scene, the ship island still has the characteristic of the sealing property of the indoor scene, so that the research on the path loss model of the ship island starts from a classical path loss model. At present, three common classical indoor path loss models are One-Slope, Keenan-Motley and COST231-Multi-Wall, and the specific theoretical calculation formula is as follows:
(1)One-Slope Model
L=L0+10nlog10d (1)
in the formula: l is the path loss value, in dB; l is0Is a loss reference value of unit distance and is closely related to a propagation environment; n is a path loss exponent, typically taken to be 2, depending on the indoor environment; d is the distance between the transceivers, in m. The One Slope model is simple and visual, can quickly predict the signal propagation characteristic, and has a good prediction effect on a scene with a simple structure. But the model does not take into account the transmission loss, multipath effects and shadowing effects caused by a complex indoor environment on the signal. Therefore, the One Slope is only suitable for free space or indoor non-occlusion scenes, and the model has larger prediction error in indoor scenes with complex structures.
(2)Keenan-Motley Model
In the formula: l is the path loss value, in dB; n is a path loss index, and is generally 2; l is0Is a loss reference value per unit distance; l is a radical of an alcoholwjIs a wall attenuation factor; n is a radical ofwjThe number of walls; l isfiIs a floor decay factor; n is a radical offiThe number of floors; d is the distance between the transceivers, in m.The Keenan-Motley model predicts path loss by taking into account spatial losses between transceivers and adding to the transmission attenuation of walls and floors. Compared with an One Slope, Keenan-Motley greatly improves the prediction accuracy of the path loss model in a complex indoor scene. But it considers the penetration loss as the product of the wall number and the wall loss reference value only and does not consider the influence of multipath effect and shadow effect. Even if the factor that the single transmission attenuation value is reduced as the number of the penetration obstacles is increased is not considered, all the wall losses take the same value, and therefore, the precision is limited.
(3)COST231-Multi-Wall Model
In the formula: l is the path loss value in dB; l is0Is a loss reference value per unit distance; n is a path loss exponent; d is the distance between transceivers, in m; k is a radical ofwjIs the w-th blocking wall with the type i; l iswjIs the transmission attenuation value of the w-th blocking wall with the type i; kfIs the number of floors; l isfIs the transmission attenuation value of the floor. Compared with the Keenan-Motley model, the COST231-Multi-Wall model further considers the problem that the signal single transmission attenuation value is correspondingly reduced along with the increase of the number of the penetration obstacles, so that the prediction accuracy of the model is further improved. The model is widely applied to path loss prediction of complex indoor scenes.
Therefore, the One-Slope model is only suitable for simple and non-shielding indoor scenes, and for complex indoor scenes such as ship islands, the accuracy is often unsatisfactory due to the fact that the influence of walls is not considered. And the Keenan-Motley model considers the influence of the wall and the floor, so that the accuracy is greatly improved. The COST231-Multi-Wall model considers the problem that as the number of penetration obstacles increases, the single transmission attenuation value of the signal decreases correspondingly, and is therefore the most accurate model in indoor path loss prediction. However, the Keenan-Motley model and the COST231-Multi-Wall model require a good understanding of the structure of the scene, i.e., the type of Wall sequentially passing between the transceivers and the corresponding penetration loss.
For a military ship island scene, when a specific ship island structure cannot be obtained and the wireless signal coverage in the ship island structure needs to be predicted, a Keenan-Motley model and a COST231-Multi-Wall model cannot be well applied. In view of the above, a path loss prediction model inside a ship is needed to predict the wireless signal coverage inside the ship under the above circumstances.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for predicting a path loss inside a ship, which can predict the path loss more easily and with accuracy guaranteed, and greatly improve the prediction efficiency.
A path loss prediction method in a ship comprises the following steps:
s1: dividing the interior of a ship into an LOS area, an NLOS area and a ship island head-tail area according to the actual position of the transmitter in the interior of the ship;
s2: for the LOS area inside the ship, the calculation method of the path LOSs L is as follows:
L=L0+10n log10 d+Xσ
wherein L is0Is a loss reference value per unit distance, n is a path loss exponent, d is a distance between the receiver and the transmitter, XσThe mean value is 0, and the root mean square error is a Gaussian random variable;
s3: for the NLOS region inside the ship, the path loss PL is calculated as follows:
wherein, i is 1,2, …, M is the number of the wall body penetrated by the transmitting signal of the transmitter, J represents the material class number of the wall body penetrated by the transmitting signal, and J is 1,2, …, J is the total wall body material class penetrated by the transmitting signal currentlyThe number of the first and second groups is,
the transmission coefficient, L, corresponding to the ith block wall with the material class number j
trans_ijThe transmission loss value corresponding to the ith blocking wall body with the material class number j;
s4: for the warship island head-tail area, the calculation method of the path loss L is as follows:
wherein r is 1,2, …, N
0,N
0The number of the walls which are required to be penetrated by the transmitting signals of the transmitter when the transmitting signals reach the head and tail areas of the warship island is the minimum,
the transmission coefficient corresponding to the r-th block wall with the material class number j, L
trans_rjThe transmission loss value corresponding to the r-th wall with the material class number j.
Further still, said L0、n、XσThe determination is performed using a non-linear least squares method.
Further, said L0、n、XσThe values of (A) are as follows:
when the transmitter is located in the room and the door of the room is in the open state, L0=40.62、n=1.789、σ=5.51;
When the transmitter is located in the room and the door of the room is closed, L0=41.98、n=0.755、σ=5.26;
L when the transmitter is in the corridor and the room door is open0=40.76、n=1.706、σ=5.61;
L when the transmitter is in the corridor and the room door is closed0=40.37、n=1.51、σ=5.55。
Further, the method for determining the number M of walls through which the transmission signal of the transmitter passes includes:
wherein the transmitter is in the room, d02 times the sum of the corridor width and the distance of the transmitter to the corridor when the transmitter is in the corridor, d0The average width of a room in the warship island; m is a unit of1~mkIs d<d0The number of walls through which the transmitted signal may pass, p1~pkRespectively for the transmission signal to pass through m1~mkProbability corresponding to the wall blockage; theta is an included angle between a connecting line of the transmitter and the receiver and the central axis of the corridor; a is1~a4Are model coefficients determined according to a least squares method.
Further, when the transmitter is located in the room and the door of the room is in the open state, a1=0.2743,a2=-1.796,a3=0.28,a40.7147, when the transmitter is in the room and the door of the room is closed, a1=0.2817,a2=-1.599,a3=0.2919,a40.7196, when the transmitter is in the corridor and the room door is open, a1=0.1873,a2=-1.383,a3=0.3112,a40.8861, when the transmitter is in the corridor and the room door is closed, a1=0.2204,a2=-1.669,a3=0.4144,a4=0.7021。
Further, when d<d0When the signal is transmitted, the maximum value of the wall number which can be penetrated by the transmitting signal is 4, and m is made1=1、m2=2、m3=3、m4=4;
When the transmitter is in the room and the door of the room is in the open state
While the transmission signal passes through m
1The probability of blocking the wall is 94.05 percent and the wall penetrates through m
2The probability of blocking the wall is 5.95 percent and the wall penetrates through m
3And m
4The probability of blocking the wall is 0;
when the transmitter is in the room and the door of the room is in the open state
While the transmission signal passes through m
1The probability of blocking the wall is 42.79 percent and the wall penetrates through m
2The probability of blocking the wall is 41.54 percent and the wall penetrates through m
3The probability of blocking the wall is 15.67 percent and the wall penetrates through m
4The probability of blocking the wall is 0;
when the transmitter is located in the room and the door of the room is closed and
while the transmission signal passes through m
1The probability of blocking the wall is 92.76 percent and the wall penetrates through m
2The probability of blocking the wall is 7.24 percent and the wall penetrates through m
3And m
4The probability of blocking the wall is 0;
when the transmitter is located in the room and the door of the room is closed and
while the transmission signal passes through m
1The probability of blocking the wall is 32.74 percent and the wall penetrates through m
2The probability of blocking the wall is 48.93 percent and the wall penetrates through m
3The probability of blocking the wall is 18.34 percent and the wall penetrates through the hole m
4The probability of blocking the wall is 0;
when the transmitter is in the corridor and the room door is open and d<d0While the transmission signal passes through m1The probability of blocking the wall is 63.64 percent and the wall penetrates through m2The probability of blocking the wall is 25.64 percent and the wall penetrates through m3The probability of blocking the wall is 8.86 percent and the wall penetrates through m4The probability of blocking the wall is 1.62%;
when the transmitter is in the corridor and the room door is closed and d<d0While the transmission signal passes through m1The probability of blocking the wall is 59.18 percent and the wall penetrates through m2The probability of blocking the wall is 29.63 percent and the wall penetrates through m3The probability of blocking the wall is 9.50 percent and the wall penetrates through m4The probability of blocking the wall is 1.69%.
Further, the probability P (X ═ j) that the material class number j of the ith wall body through which the transmission signal passes is:
wherein S isjThe total area of the wall with the material class number j in the ship is shown, and S is the total area of the ship.
Has the advantages that:
1. the invention provides a method for predicting path LOSs in a ship, which comprises the steps that a user firstly divides the interior of the ship into an LOS (local area of service) area, an NLOS (non-line-of-service) area and a ship island head-tail area according to the actual position of a transmitter in the interior of the ship, then a path LOSs model of the LOS area in a ship island scene, a path LOSs model of the NLOS area in the ship island scene and a path LOSs model of a head-tail cabin in the ship island scene are given out, the path LOSs is predicted more simply while the accuracy is ensured, meanwhile, the problem that the conventional model cannot represent the multipath effect and the shadow effect is solved, the dependence of path LOSs prediction on a scene structure is reduced, and the prediction efficiency is greatly improved.
2. The invention provides a method for predicting path LOSs in a ship, which is characterized in that for an LOS area, a large amount of independent original data and a nonlinear least square principle are utilized, the influence of a multipath effect is considered, and a path LOSs index and a LOSs reference value of a unit distance are corrected; meanwhile, the method introduces Gaussian random variables to characterize shadow fading, and improves the accuracy of the model under the condition of ensuring the simplicity of the model.
3. The invention provides a method for predicting path loss inside a ship, for an NLOS region, a user does not need to provide a specific scene model and the type and sequence of wall materials specifically passing through each transceiving path, the number of wall bodies passing through is obtained according to a statistical and fitting mode, meanwhile, the probability of penetration of each wall body type is determined according to an area ratio, and the wireless signal coverage inside the ship can be effectively predicted under the condition that a specific ship island structure cannot be obtained.
4. The invention provides a method for predicting path loss in a ship, which is a solution provided separately for ship island head and tail cabins with obviously different structures, and greatly considers the influence of scene characteristics on signal propagation, unlike the prior model in which only one mode is adopted for predicting the path loss in one scene.
Drawings
FIG. 1 is a flow chart of an embodiment of the present invention;
FIG. 2 is a ship internal structure;
FIG. 3 is a diagram of a received power simulation of a transmitter in a room with a door closed;
FIG. 4 is a graph of a received power simulation of a transmitter in a room and in a door open state;
FIG. 5 is a graph of a received power simulation of a transmitter in a hallway and in a closed door state;
fig. 6 is a diagram of a simulation of the received power of a transmitter in a hallway and in a door open state.
Detailed Description
In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.
The invention provides a prediction method for the indoor path loss of a ship island, which obtains a large amount of original data according to an actual ship island scene and a high-performance ray tracking technology. When the transmitting antenna is installed in a room or a corridor, the door opening/closing state is studied. And fitting the path LOSs under the four conditions to respectively obtain path LOSs models of an LOS area (non-occlusion area) and an NLOS area (occlusion area). The user firstly defines the LOS area and the NLOS area in the whole ship according to the project requirement and the relative position of the transceiver, and the path LOSs model provided by the invention can be applied to predict the radio signal coverage in the ship. The invention mainly depends on the internal structure characteristics of a typical ship island scene, and the structures of the head and tail cabins of the ship island are different from the middle position, so that the head and tail cabins are independently considered in the model.
As shown in fig. 1, is a flow chart of an embodiment of the present invention, which specifically includes the following steps:
s1: according to the actual position of the transmitter in the ship, the interior of the ship is divided into an LOS area, an NLOS area and ship island head and tail areas.
S2: for the LOS area inside the ship, the calculation method of the path LOSs L is as follows:
L=L0+10n log10 d+Xσ
wherein L is0Is the loss reference value per unit distance, in dB; n is the path loss exponent, d is the distance between the receiver and the transmitter, in m; xσThe values are Gaussian random variables with the mean value of 0 and the root mean square error of sigma.
It should be noted that, the path LOSs calculation model derivation process in the LOS region is as follows:
for the LOS area in the ship, the scene structure is simple because the shielding does not exist between the transceivers in the area. Therefore, the model fully considers the influence of multipath effect and shadow effect on the basis of the One-Slope model. Based on formula (1), a large amount of independent raw data including path loss L and distance d obtained by using a high-performance ray tracing technology is added with a shadow fading obeying a lognormal distribution, and a functional relation existing between the path loss L and the distance d is set:
wherein L is0,n,XσThe method is characterized in that the method utilizes a nonlinear least square principle and takes the least square sum of errors as a criterion to calculate the optimal estimation value of the parameter according to the original data (path loss L and distance d) collected in advance, so as to obtain the optimal functional relation between the path loss L and the distance d.
That is to say, the invention is based on the One-Slope model and according to two common installation positions of the internal transmitter of the ship: the method comprises the following steps of correcting a path LOSs index and a LOSs reference value of a unit distance by respectively adopting a door opening and closing state at the top of a room and a corridor wall, and representing a shadow effect by adopting a Gaussian random variable, so as to obtain a general path LOSs model of an LOS area as follows:
L=L0+10n log1o d+Xσ (5)
each undetermined parameter L of the model in four cases0,n,XσAs shown in the following table:
TABLE 1
S3: for the NLOS region inside the ship, the path loss PL is calculated as follows:
wherein i represents the number of the wall body through which the transmission path passes, i is 1,2, …, M is the number of the wall body through which the transmission signal of the transmitter passes, the calculation method is shown in formula (8), J represents the material class number of the wall body through which the transmission signal passes, is related to the occupied area ratio of each type of the wall body and is input by a user, and J is 1,2, …, J is the total number of the material classes of the wall body through which the transmission signal currently passes,
the transmission coefficient corresponding to the ith blocking wall body with the material class number j is 0.79 in the scene; l is
trans_ijAnd the unit of the transmission loss value corresponding to the ith blocking wall body with the material class number j is dB, and the transmission loss value is input by a user.
It should be noted that, in the NLOS region, the penetration loss caused by the occlusion between the transceivers also needs to be taken into consideration. The penetration loss caused by each occlusion between transceivers is therefore superimposed in this model. Meanwhile, the model introduces the transmission coefficient of the material
The power of the attenuation increases with the number of the penetrating shelters, so as to solve the problem that the single transmission attenuation value of the signal decreases correspondingly with the increase of the number of the penetrating shelters.
In addition, because the penetration loss caused by the signal penetrating different materials is different, and the penetration loss value is also related to the penetration sequence, the path loss model for characterizing the NLOS region needs to determine the wall type of each penetration path. In the model, the probability of the wall type j penetrating each time is obtained according to the area proportion occupied by various materials of the scene input by a user, and the statistical prediction is sequentially carried out on the wall type j penetrating each time, wherein the probability calculation mode is as follows:
wherein S is
jThe total area of the wall with the material class number j in the ship is shown, and S is the total area of the ship. j. S
jAnd S, the user is required to define and input, and for a naval vessel scene with a simple structure, the identification can be carried out according to the existence of two materials, namely a wall body and a watertight door,
can be identified by the ratio of the area of the wall or door of a single room to the total area of the room.
Meanwhile, the determination of the number M of the penetrated walls is determined by combining statistics and fitting. The internal structure of the vessel is shown in fig. 2 and is generally composed of corridors and rooms on both sides. By observing its structure, it can be seen that wall loss is not incurred in a certain range near the transmitter because the wall is not penetrated, and the number of wall penetrations outside this range is related to the angle and the transceiver distance.
For the above characteristics, the characterization of the number M of the penetrating walls in the formula (6) in the model is as follows:
when the transmitter is in the room, d02 times the sum of the corridor width and the distance from the transmitter to the corridor; when the transmitter is in the corridor, d0The average width of a room in the warship island; wherein when d<d0In the process, the statistical analysis is carried out on the original data (the installation positions of the transmitter and the receiver, the distance d and the corresponding number of the penetrated walls) collected in advance to obtain the number m of the penetrated walls1~mkCorresponding probability p1~pkAnd determining the number M of the penetrated walls according to a linear weighted average method. In addition, in d<d0When the signal is transmitted, the maximum value of the wall number which can be penetrated by the transmitting signal is 4, and m is made1=1、m2=2、m3=3、m44, m under the following four scenarios1~m4Is taken to be the value and corresponding probability p1~p4As shown in table 2 below:
TABLE 2
It can be found from the original data that when d ≧ d0In time, the correlation between the number of penetrating walls and the angle and the transceiver distance is improved, so that a functional relation exists between the number of penetrating walls M and the angle theta and the transceiver distance d:
M=ω(θ,d,a1,a2,a3,…am) (9)
wherein a is1,a2,a3,…amFor undetermined parameters in a theoretical functional formula, according to two common installation positions of a ship internal transmitter: four kinds of door opening and closing states are adopted on the top of the room and the walls of the corridor respectivelyThe situation was studied. By means of the Curve Fitting Tool in Matlab, the optimal estimation value of the parameter is calculated according to the original data by using the nonlinear least square method principle and the minimum sum of the squares of the errors as the criterion, so that the condition that d is more than or equal to d is obtained0The optimal functional relationship between the number M of time-through walls, the angle theta and the transceiver distance d is as follows:
M=a1d-a2θ2+a3dθ2+a4 (10)
wherein the model parameter a1,a2,a3,a4The values of (a) are shown in table 3:
TABLE 3
S4: for the warship island head-tail area, the calculation method of the path loss L is as follows:
wherein d is the distance between the transceivers, the unit is m, and the d is input by the user; r represents the number of the wall body penetrated by the transmission path, and r is 1,2, …, N
0,N
0The minimum value of the number of walls which are penetrated by a transmitting signal of a transmitter and reach the head and tail areas of the ship island,
the transmission coefficient corresponding to the r-th blocking wall body with the material class number j is taken as 0.79 in the scene; l is a radical of an alcohol
trans_rjAnd the unit of the transmission loss value corresponding to the r-th wall body with the material class number j is dB, and the r-th wall body is input by a user.
It should be noted that the model is proposed mainly by the internal structural characteristics of the ship island, and the structures of the head and tail cabins of the ship island are different from the middle position, so that the head and tail cabins are considered separately in the model.
Therefore, for each pair of transceivers in the ship, an LOS area, an NLOS area and a ship island head-tail area are defined firstly, and the path LOSs model is applied to calculate to obtain a path LOSs result under a single link. And comparing the path loss values of the plurality of communication links at the same position to obtain the minimum value, namely the path loss value of the position under the multilink, and predicting the wireless signal after setting the transmitting power according to the minimum value.
For a certain naval vessel scene, the path loss model provided by the patent is applied for prediction, the transmitting power is set to be 0dBm, and four conditions are respectively obtained: the power receiving conditions of the transmitter in the room and in the door closing state, the transmitter in the room and in the door opening state, the transmitter in the corridor and in the door closing state, and the transmitter in the corridor and in the door opening state are shown in fig. 1 to 4; therefore, in the LOS area, the method can predict the path LOSs more simply while ensuring the accuracy, and simultaneously solve the problem that the prior model can not represent the multipath effect and the shadow effect; for the NLOS area, since a specific ship internal structure cannot be obtained in the application scene, it is necessary to start from a typical ship island structure, predict the type and quantity of the shielding material inside the ship by combining the geometric attributes of the scene, and obtain the corresponding path loss after considering the wall influence.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it will be understood by those skilled in the art that various changes and modifications may be made herein without departing from the spirit and scope of the invention as defined in the appended claims.