A dynamic pilot allocation method in ship-to-shore VDE communication

Abstract

The present invention belongs to the field of wireless communication technology, and specifically relates to a dynamic pilot allocation method in ship-shore VDE communication, which includes the following steps: the shore station of the port numbers the ships entering the port in chronological order; using the dynamic pilot allocation algorithm, the shore station sequentially allocates pilots to the numbered ships, and dynamically adjusts the pilot allocation according to the changes of the ships entering and leaving the port; at the beginning of each frame, the shore station sends the dynamic pilot allocation result of the previous step to the ship, and the ship uses the pilot according to the pilot allocation result. Compared with the existing pilot allocation method, this method can dynamically allocate and adjust the pilot according to the changes of the ships entering and leaving the port, and the system implementation complexity is low, thereby reducing the channel estimation interference between ships and improving the data transmission quality of ship-shore communication.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology, and in particular relates to a dynamic pilot allocation method in ship-to-shore VDE communication. Background Art

[0002] The Very High Frequency Data Exchange System (VHF Data Exchange System, VDES) is a maritime communication system developed on the basis of the original Automatic Identification System (AIS). It comprehensively improves the communication capabilities between ships, shore stations and satellites, and provides ships with navigation safety and richer data communication services.

[0003] In the VDES system, when a ship approaches a shore port and enters the communication range of the port shore station, the ship is said to have entered the port and is a ship in the port. A large amount of data information needs to be exchanged between the ship in the port and the port shore station. In order to meet the high-quality data transmission requirements, accurate channel estimation is required to support it. In the VDE (VHF Data Exchange) communication from the ship to the shore station, each ship inserts a pilot in each transmitted data frame, and the shore station first extracts the pilot receiving signal in the received data frame. Since the shore station knows the transmitted pilot of each ship, it can restore the channel state information from each ship to the shore station, that is, the channel estimation. The channel estimation result is used to restore the data information in the data frame. Therefore, the more accurate the channel estimation, the more accurate the restored data information, and the higher the data transmission quality of the ship-to-shore communication.

[0004] In addition, the length of the data frame is limited, so the length of the pilot is limited, which makes the number of available mutually orthogonal pilots limited. With the development of the maritime transportation industry, the number of ships in shore ports is increasing. When the number of ships in the port exceeds the number of available orthogonal pilots, it is inevitable that multiple ships in the port need to use the same pilot at the same time. Ships using the same pilot will interfere with each other during channel estimation, reducing the accuracy of each other's channel estimation, thereby affecting the data transmission quality of ship-to-shore communication and further affecting navigation safety.

[0005] In existing recommendations (such as IALA G1139), the pilot frequency allocation of the shore station to the ships in the port adopts a fixed pilot frequency allocation based on the order of the ships, such as ships s1, s2, ..., s N Use pilots λ1,λ2,…,λ M ,λ1,λ2,…,λ M ,…, that is, using the Mcyclic multiplexing, where N>M. This fixed pilot allocation method does not consider the channel estimation interference between ships using the same pilot, and whether such interference will cause the mean square error of the channel estimation of the ship to exceed the threshold value, which may seriously affect the data transmission quality; and does not consider the dynamic changes of ships leaving and new ships entering the shore port over time. Therefore, this fixed pilot allocation method cannot track the dynamic changes of the port ships and make adjustments when there are a large number of ships in the port and there are changes in the number of ships entering and leaving the port. It is easy to have inaccurate channel estimation and low data transmission quality in ship-to-shore communication. Patent CN112152766A provides a pilot allocation method based on cell division in a mobile communication system. At the beginning of the design, it did not consider the situation where new users join or leave. When a new user joins, it is necessary to readjust the pilots of other users (users with large pilot pollution) except the new user, and the system implementation is highly complex.

[0006] Finding a pilot allocation method that can track the changes of ships entering and leaving the port and has low system implementation complexity is an urgent problem that needs to be solved and is also the key to improving the quality of data transmission in ship-to-shore communications. Summary of the invention

[0007] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a dynamic pilot allocation method in ship-to-shore VDE communication, which can dynamically allocate and adjust the pilot according to the changes of ships entering and leaving the port and has low system implementation complexity, thereby reducing channel estimation interference between ships and improving the data transmission quality of ship-to-shore communication.

[0008] The solution of the present invention to solve the above technical problems is:

[0009] A method for dynamic pilot allocation in ship-to-shore VDE communications, the method comprising the following steps:

[0010] Step 1: The port's shore station numbers the ships entering the port in chronological order

[0011] Assume that the port has a shore station, denoted as d; the shore station numbers the N ships entering the port in the order of their time of entry into the port as 1, 2, ..., N, and denoted as s1, s2, ..., s N ; Suppose there are M available mutually orthogonal pilots, denoted as λ1,λ2,…,λ M For ports with dense ships, the number of ships is usually greater than the number of pilots, that is, N is greater than M, and the number of ships N will change as the ships enter and leave the port. Therefore, multiple ships will need to use the same pilot at the same time. m The ships are grouped into set D m, where m∈{1,2,…,M}; ships belonging to the same set will interfere with each other during channel estimation, resulting in inaccurate channel estimation; let ship s n The mean square error of channel estimation is recorded as Where n∈{1,2,…,N}; the threshold of the mean square error of channel estimation is denoted by E max , E max is a certain value;

[0012] Step 2: Using the dynamic pilot allocation algorithm, the shore station allocates pilots to the numbered ships in turn, and dynamically adjusts the pilot allocation according to the changes in the ships entering and leaving the port.

[0013] The dynamic pilot allocation algorithm is as follows:

[0014] 1) Let n = 1;

[0015] 2) Let m = 1;

[0016] 3) Order s n ∈D m , that is, the ship n Using pilot λ m ;

[0017] 4) Let l = 1;

[0018] 5) Determine whether s l ∈D m ;

[0019] 51) If s l ∈D m , then recalculate the ship s l The mean square error of channel estimation is Determine whether

[0020] 511) If Then jump to sub-step 6);

[0021] 512) If Then m=m+1, determine whether m≤M; if m≤M, return to step 3); if m>M, then s n Do not allocate pilots for the time being, recalculate the mean square error of channel estimation for all ships in the port, and wait for the next frame to arrive before s n Allocate pilots and jump to sub-step 8);

[0022] 52) If Then jump to sub-step 6);

[0023] 6) l=l+1, determine whether l≤N; if l≤N, return to sub-step 5); if l>N, jump to sub-step 7);

[0024] 7) Order s n ∈D m , that is, s n Using pilot λ m , recalculate the channel estimation mean square error of all ships in the port, and jump to sub-step 8);

[0025] 8) n = n + 1, determine whether n ≤ N; if n ≤ N, return to sub-step 2); if n > N, then n = n - 1, jump to sub-step 9);

[0026] 9) Whether there are any ships leaving the port;

[0027] 91) If a ship leaves, release the pilot used by the departing ship, recalculate the mean square error of channel estimation for all ships in the port, and jump to sub-step 10);

[0028] 92) If no ship has left, jump to sub-step 10);

[0029] 10) Determine whether there are new ships entering the port;

[0030] 101) If no new ship enters the port, continue to wait until the next frame arrives and return to step 9);

[0031] 102) If a new ship enters the port, then N = N + 1, n = n + 1, determine whether n ≤ N; if n ≤ N, return to step 2); if n > N, the algorithm ends;

[0032] Step 3: At the beginning of each frame, the shore station sends the dynamic pilot allocation result of step 2 to the ship, and the ship uses the pilot according to the pilot allocation result.

[0033] The present invention discloses a method for dynamic pilot allocation in ship-shore VDE communication, which has the following beneficial effects compared with the prior art:

[0034] Compared with the existing fixed pilot allocation method, this method adds the dynamic allocation adjustment of pilots according to the departure or joining of ships, focusing on how pilot allocation tracks the dynamic changes of port ships. When a ship leaves, the pilots of the leaving ship are released and reallocated; when a ship joins, the channel state of the joining ship is considered to allocate available pilots to it, thereby realizing the dynamic allocation adjustment of pilots, reducing the channel estimation error of each ship, and improving the data transmission quality of ship-to-shore communication, which is also of great significance for ensuring navigation safety. Secondly, compared with the existing adjustable pilot allocation method, when a new user joins, it is necessary to readjust the pilots of other users (users with large pilot pollution) except the newly joined user. The pilot allocation method in this application is a pilot allocation for all users, without cell division and pilot set allocation of cells. When a new user joins, after calculating the pilot pollution of all users, it is only necessary to select a suitable pilot for the newly joined user, and it does not involve the pilot adjustment of other users except the newly joined user. In this way, when implemented in an actual system, the system implementation complexity of the method of this application is low. Thirdly, by releasing the pilots that have left the ship and then reallocating them, it is possible to dynamically allocate the pilots on demand and improve the utilization rate of the pilots. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a general flow chart of a dynamic pilot allocation method in ship-to-shore VDE communication disclosed by the present invention;

[0036] Figure 2 A schematic diagram of a system model of a dynamic pilot allocation method in ship-to-shore VDE communication disclosed in the present invention;

[0037] Figure 3 A flow chart of a dynamic pilot allocation algorithm in a dynamic pilot allocation method in ship-to-shore VDE communication disclosed in the present invention;

[0038] Figure 4 A simulation result diagram of the mean square error of channel estimation in a dynamic pilot allocation method in ship-to-shore VDE communication disclosed in the present invention; DETAILED DESCRIPTION

[0039] The present invention will be further explained below in conjunction with the accompanying drawings.

[0040] Example 1

[0041] like Figures 1 to 3 As shown, a method for dynamic pilot allocation in ship-to-shore VDE communication disclosed in the present invention includes the following steps:

[0042] Step 1: The port's shore station numbers the ships entering the port in chronological order

[0043] like Figure 2 As shown, the port has a shore station, denoted as d; the shore station numbers the N ships entering the port in the order of their time of entry into the port as 1, 2, ..., N, and denoted as s1, s2, ..., s N ; Suppose there are M available mutually orthogonal pilots, denoted as λ1,λ2,…,λ M For ports with dense ships, the number of ships is usually greater than the number of pilots, that is, N is greater than M, and the number of ships N will change as the ships enter and leave the port. Therefore, multiple ships will need to use the same pilot at the same time. m The ships are grouped into set D m , where m∈{1,2,…,M}; ships belonging to the same set will interfere with each other during channel estimation, resulting in inaccurate channel estimation; let ship s n The mean square error of channel estimation is recorded as Where n∈{1,2,…,N}; the threshold of the mean square error of channel estimation is denoted by E max , E max is a certain value;

[0044] Step 2: Using the dynamic pilot allocation algorithm, the shore station allocates pilots to the numbered ships in turn, and dynamically adjusts the pilot allocation according to the changes in the ships entering and leaving the port. The flowchart of the dynamic pilot allocation algorithm is shown in the figure. Figure 3 As shown, the specific steps are as follows:

[0045] 1) Let n = 1;

[0046] 2) Let m = 1;

[0047] 3) Order s n ∈D m , that is, the ship n Using pilot λ m ;

[0048] 4) Let l = 1;

[0049] 5) Determine whether s l ∈D m ;

[0050] 51) If s l ∈D m , then recalculate the ship s l The mean square error of channel estimation is Determine whether

[0051] 511) If Then jump to sub-step 6);

[0052] 512) If Then m=m+1, determine whether m≤M; if m≤M, return to step 3); if m>M, then s n Do not allocate pilots for the time being, recalculate the mean square error of channel estimation for all ships in the port, and wait for the next frame to arrive before s n Allocate pilots and jump to sub-step 8);

[0053] 52) If Then jump to sub-step 6);

[0054] 6) l=l+1, determine whether l≤N; if l≤N, return to sub-step 5); if l>N, jump to sub-step 7);

[0055] 7) Order s n ∈D m , that is, s n Using pilot λ m , recalculate the channel estimation mean square error of all ships in the port, and jump to sub-step 8);

[0056] 8) n = n + 1, determine whether n ≤ N; if n ≤ N, return to sub-step 2); if n > N, then n = n - 1, jump to sub-step 9);

[0057] 9) Whether there are any ships leaving the port;

[0058] 91) If a ship leaves, release the pilot used by the departing ship, recalculate the mean square error of channel estimation for all ships in the port, and jump to sub-step 10);

[0059] 92) If no ship has left, jump to sub-step 10);

[0060] 10) Determine whether there are new ships entering the port;

[0061] 101) If no new ship enters the port, continue to wait until the next frame arrives and return to step 9);

[0062] 102) If a new ship enters the port, then N = N + 1, n = n + 1, determine whether n ≤ N; if n ≤ N, return to step 2); if n > N, the algorithm ends;

[0063] Step 3: At the beginning of each frame, the shore station sends the dynamic pilot allocation result of step 2 to the ship, and the ship uses the pilot according to the pilot allocation result.

[0064] Example 2 (Experimental Example)

[0065] This embodiment is a simulation experiment, which compares the dynamic pilot allocation method disclosed in the present invention with the existing fixed pilot allocation method to illustrate its feasibility and effectiveness.

[0066] During the simulation, it is assumed that all channels are Rayleigh channels and obey circularly symmetric complex Gaussian distribution. The channels are independent of each other. The communication range of the port shore station is a semicircle with a radius of 500 meters. After entering the port, the ships obey a uniform distribution in the port. The pilot transmission power of the ships is 6kW, the noise variance is 1, and the number of available mutually orthogonal pilots is M=50.

[0067] Figure 4 The “fixed pilot allocation” in the description is an existing fixed pilot allocation method, and the “dynamic pilot allocation” is a dynamic pilot allocation method disclosed in the present invention. Figure 4 The horizontal axis is the number N of ships entering the port, and the vertical axis is the average value of the mean square error of channel estimation for all ships in the port.

[0068] from Figure 4 It can be seen that as the number of ships entering the port increases, the average channel estimation mean square error of "dynamic pilot allocation" and "fixed pilot allocation" increases. This is because the more ships enter the port, the more ships reuse the same pilot, the greater the interference of channel estimation, so the average channel estimation mean square error increases. "Dynamic pilot allocation" is obviously better than "fixed pilot allocation", and as the number of ships entering the port increases, the average channel estimation mean square error of "dynamic pilot allocation" increases more slowly than that of "fixed pilot allocation". This shows that compared with "fixed pilot allocation", "dynamic pilot allocation" adds dynamic allocation adjustment of pilots according to changes in ships entering and leaving the port, thereby reducing channel estimation interference between ships. The more accurate the channel estimation, the higher the data transmission quality of ship-to-shore communication.

[0069] In summary, compared with the existing pilot allocation method, the dynamic pilot allocation method in ship-to-shore VDE communication disclosed in the present invention can dynamically adjust the pilot allocation according to the changes of ships entering and leaving the port, and the system implementation complexity is low, thereby reducing channel estimation interference between ships and improving the data transmission quality of ship-to-shore communication.

Claims

1. A method for dynamic pilot allocation in ship-to-shore VDE communications, the method comprising the following steps: Step 1: The port's shore station numbers the ships entering the port in chronological order Assume that the port has a shore station, denoted as d; the shore station numbers the N ships entering the port in the order of their time of entry into the port as 1, 2, ..., N, and denoted as s1, s2, ..., s N ; Suppose there are M available mutually orthogonal pilots, denoted as λ1,λ2,…,λ M ; For ports with dense ships, the number of ships is usually greater than the number of pilots, that is, N is greater than M, and the number of ships N will change as the ships enter and leave the port. Therefore, multiple ships will need to use the same pilot at the same time. m The ships are grouped into set D m , where m∈{1,2,…,M}; ships belonging to the same set will interfere with each other during channel estimation, resulting in inaccurate channel estimation; let ship s n The mean square error of channel estimation is recorded as Where n∈{1,2,…,N}; the threshold of the mean square error of channel estimation is denoted by E max , E max is a certain value; Step 2: Using the dynamic pilot allocation algorithm, the shore station allocates pilots to the numbered ships in turn, and dynamically adjusts the pilot allocation according to the changes in the ships entering and leaving the port. The dynamic pilot allocation algorithm is as follows: 1) Let n = 1; 2) Let m = 1; 3) Let s n ∈D m , that is, the ship s n Using pilot λ m ; 4) Let l = 1; 5) Determine whether s l ∈D m ; 51) If s l ∈D m , then recalculate the ship s l The mean square error of channel estimation is Determine whether 511) If Then jump to sub-step 6); 512) If Then m=m+1, determine whether m≤M; if m≤M, return to step 3); if m>M, then s n Do not allocate pilots for the time being, recalculate the mean square error of channel estimation for all ships in the port, and wait for the next frame to arrive before s n Allocate pilots and jump to sub-step 8); 52) If Then jump to sub-step 6); 6) l=l+1, determine whether l≤N; if l≤N, return to sub-step 5); if l>N, jump to sub-step 7); 7) Order s n ∈D m , that is, s n Using pilot λ m , recalculate the channel estimation mean square error of all ships in the port, and jump to sub-step 8); 8) n = n + 1, determine whether n ≤ N; if n ≤ N, return to sub-step 2); if n > N, then n = n - 1, jump to sub-step 9); 9) Whether there are any ships leaving the port; 91) If a ship leaves, release the pilot used by the leaving ship, recalculate the mean square error of the channel estimation for all ships in the port, and jump to sub-step 10); 92) If no ship has left, jump to sub-step 10); 10) Determine whether there are new ships entering the port; 101) If no new ship enters the port, continue to wait until the next frame arrives and return to step 9); 102) If a new ship enters the port, then N = N + 1, n = n + 1, determine whether n ≤ N; if n ≤ N, return to step 2); if n > N, the algorithm ends; Step 3: At the beginning of each frame, the shore station sends the dynamic pilot allocation result of step 2 to the ship, and the ship uses the pilot according to the pilot allocation result.

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