A Dynamic Frequency Reuse Method between Self-Organizing Cells of a VDES System

Abstract

The present invention belongs to the field of wireless communication technology, and particularly relates to a method for dynamic frequency reuse between self-organizing cells of a VDES system. The method includes the following steps: establishing a self-organizing cell model and performing frequency reuse grouping on the self-organizing cells; using a dynamic frequency reuse algorithm to dynamically adjust the grouping attribution of the self-organizing cells with a small average signal-to-interference-plus-noise ratio; and performing frequency reuse between the self-organizing cells according to the adjustment result of the grouping attribution of the self-organizing cells. Compared with the existing random frequency reuse method between self-organizing cells, the present invention increases the dynamic adjustment of frequency reuse for the self-organizing cells with large interference. Each adjustment reduces the interference for the self-organizing cells with large interference under the condition of little impact on other self-organizing cells. Therefore, the method of the present invention can dynamically adjust the frequency reuse between the self-organizing cells and reduce the communication interference between ships.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to a method for dynamic frequency reuse between self-organizing cells of a VDES system. Background Art

[0002] In order to meet the growing maritime communication needs, the International Association of Lighthouse Authorities (IALA) has proposed the VHF Data Exchange System (VDES). Compared with the original Automatic Identification System (AIS) for ships, the VDES system can comprehensively improve the data communication capabilities of maritime ships and provide information services such as navigation, collision avoidance, weather forecasting, search and rescue for ships.

[0003] In the VDES system, ships in close proximity will form self-organizing cells for data communication in a self-organizing manner. The "IALA G1139 Standard" recommendation has given the available communication frequency bands between ship and ship in the VDES system. Since the frequency range for maritime communication is limited, the number of available communication frequency bands is also limited. Although the use of frequency bands can be distinguished within a self-organizing cell, there will inevitably be repeated use of frequency bands between self-organizing cells, that is, frequency reuse. In existing recommendations (such as the "IALA G1139 Standard"), ships within a self-organizing cell use the communication frequency band in a mutually competitive manner, without considering whether it is necessary to coordinate the repeated use of communication frequency bands between self-organizing cells. That is to say, a random frequency reuse method is adopted between self-organizing cells. However, with the prosperous development of the maritime transportation industry, the number of maritime ships is increasing, and the number of self-organizing cells is also increasing. Especially in some large ports, self-organizing cells are dense. If this random frequency reuse method between self-organizing cells is used in ports or on the sea where self-organizing cells are dense, ships in adjacent self-organizing cells will reuse the same communication frequency band, and thus there will be significant communication interference between ships using the same frequency band, reducing the received signal-to-interference-plus-noise ratio of the ships, seriously affecting the transmission quality of the signal, and further affecting navigation safety.

[0004] Therefore, in areas where self-organizing cells are dense, how to coordinate the repeated use of communication frequency bands between self-organizing cells and reduce communication interference between ships is an important problem that needs to be solved currently. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the technical problem to be solved by the present invention is to provide a method for dynamic frequency reuse between self-organizing cells of a VDES system, which can dynamically adjust the frequency reuse between self-organizing cells and reduce the communication interference between ships.

[0006] The solution of the present invention to the above technical problem is as follows:

[0007] A method for dynamic frequency reuse between self-organizing cells of a VDES system, the method comprising the following steps:

[0008] Step 1: Establish a self-organizing cell model and perform frequency reuse grouping on the self-organizing cells

[0009] Suppose there are N ships in Q self-organizing cells, and the numbers of the self-organizing cells are 1, 2,..., Q respectively. Suppose there are l i ships in the i-th self-organizing cell, i ∈ {1, 2,..., Q}, then The average signal-to-interference-plus-noise ratio of all ships in the i-th self-organizing cell is denoted as γ i , and the minimum signal-to-interference-plus-noise ratio threshold is denoted as γ min , and γ min is equal to a fixed value; all available communication frequency bands are classified into M non-overlapping frequency band sets φ1, φ2,..., φ M , and each self-organizing cell selects one of the frequency band sets φ1, φ2,..., φ M and uses the selected frequency band set for data communication; since Q is much larger than M in practice, when Q self-organizing cells use M frequency band sets, there will be a situation where multiple self-organizing cells reuse the same frequency band set, that is, frequency reuse; suppose the self-organizing cells using the φ m frequency band set belong to the φ m grouping, where m ∈ {1, 2,..., M}, then the Q self-organizing cells can be classified into the M groupings of φ1, φ2,..., φ M ; if the i-th cell belongs to the φ m grouping, it is denoted as i ∈ φ m ; the initial frequency allocation is to randomly classify the Q self-organizing cells into the above-mentioned M groupings;

[0010] Step 2: Use the dynamic frequency reuse algorithm to dynamically adjust the grouping belonging of the self-organizing cells with a small average signal-to-interference-plus-noise ratio; the dynamic frequency reuse algorithm is specifically as follows:

[0011] 1) Let i = 1;

[0012] 2) Judge whether γ i ≥γ min is satisfied. If γ i ≥γ min, jump to sub-step 3); if γ i <γ min , jump to sub-step 4);

[0013] 3) Let i = i + 1, and determine whether i ≤ Q is satisfied; if i ≤ Q, return to sub-step 2); if i > Q, jump to sub-step 9);

[0014] 4) Let m = 1;

[0015] 5) Assume i ∈ φ m , for all l ∈ {1, 2,..., Q}, recalculate γ l ;

[0016] 6) Let j = 1;

[0017] 7) Determine whether j ∈ φ m ;

[0018] 71) If j ∈ φ m , determine whether γ j ≥γ min ;

[0019] 711) If γ j ≥γ min , jump to sub-step 7111);

[0020] 7111) Let j = j + 1, and determine whether j ≤ Q is satisfied; if j ≤ Q, return to sub-step 7); if j > Q, jump to sub-step 8);

[0021] 712) If γ j <γ min , m = m + 1, and determine whether m ≤ M is satisfied; if m ≤ M, return to sub-step 5); if m > M, return to sub-step 3);

[0022] 72) If jump to sub-step 7111);

[0023] 8) Let i ∈ φ m , for all l ∈ {1, 2,..., Q}, recalculate γ l , return to sub-step 3);

[0024] 9) Determine whether for all l ∈ {1, 2,..., Q}, γ l ≥γ min ;

[0025] 91) If for all l ∈ {1, 2,..., Q}, γ l ≥γ min cannot be satisfied simultaneously, then return to sub-step 1);

[0026] 92) If for all l ∈ {1, 2, …, Q}, γ can be satisfied simultaneously l ≥γ min , then the dynamic adjustment of the pilot reuse of all self-organizing cells is completed, and the algorithm ends;

[0027] Step 3: Perform frequency reuse between self-organizing cells according to the adjustment result of the grouping attribution of self-organizing cells

[0028] Perform frequency reuse between self-organizing cells according to the adjustment result of the grouping attribution of self-organizing cells, that is, the self-organizing cells belonging to the φ m group reuse the frequency band set φ m , where m ∈ {1, 2, …, M}.

[0029] The present invention discloses a method for dynamic frequency reuse between self-organizing cells of a VDES system. Compared with the prior art, it has the following beneficial effects:

[0030] Compared with the existing random frequency reuse method between self-organizing cells, the method of the present invention first calculates the average signal-to-interference-plus-noise ratio of each self-organizing cell, and then dynamically adjusts the grouping attribution (frequency reuse) of the self-organizing cells with small average signal-to-interference-plus-noise ratio (large interference). Before each adjustment, it is necessary to judge whether the adjustment conditions are met: if adjusted, the average signal-to-interference-plus-noise ratio of the self-organizing cells using the same frequency band should be greater than the minimum signal-to-interference-plus-noise ratio threshold; only when the conditions are met can the adjustment be carried out. Therefore, each adjustment is carried out on the premise of having little impact on other self-organizing cells, and this dynamic adjustment can also reduce the interference of the self-organizing cells with large interference. Therefore, the communication interference between ships can be reduced, which is of great significance for ensuring the communication quality between ships and guaranteeing the navigation safety of ships. Brief Description of the Drawings

[0031] Figure 1 is the overall flowchart of a method for dynamic frequency reuse between self-organizing cells of a VDES system disclosed by the present invention;

[0032] Figure 2 is a schematic diagram of a ship self-organizing cell model in a method for dynamic frequency reuse between self-organizing cells of a VDES system disclosed by the present invention;

[0033] Figure 3 is the flowchart of a dynamic frequency reuse algorithm in a method for dynamic frequency reuse between self-organizing cells of a VDES system disclosed by the present invention;

[0034] Figure 4 is the average received signal-to-interference-plus-noise ratio result graph of a simulation experiment of a method for dynamic frequency reuse between self-organizing cells of a VDES system disclosed by the present invention; Detailed implementation manners

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] Embodiment 1

[0037] As Figure 1 shown, a method for dynamic frequency reuse between self-organizing cells of a VDES system disclosed by the present invention includes the following steps:

[0038] Step 1: Establish a self-organizing cell model and group the self-organizing cells for frequency reuse

[0039] Suppose there are N ships in Q self-organizing cells. As Figure 2 shown, the numbers of the self-organizing cells are 1, 2,..., Q respectively. Suppose there are li ships in the i-th self-organizing cell, i ∈ {1, 2,..., Q}, then The average signal-to-interference-plus-noise ratio of all ships in the i-th self-organizing cell is denoted as γ i , and the minimum signal-to-interference-plus-noise ratio threshold is denoted as γ min , and γ min is equal to a fixed value; all available communication frequency bands are classified into M non-overlapping frequency band sets φ1, φ2,..., φ M , and each self-organizing cell selects one of the frequency band sets φ1, φ2,..., φ M and uses the selected frequency band set for data communication; since Q is much larger than M in practice, when Q self-organizing cells use M frequency band sets, there will be a situation where multiple self-organizing cells reuse the same frequency band set, that is, frequency reuse; suppose the self-organizing cells using the φ m frequency band set belong to the φ m group, where m ∈ {1, 2,..., M}, then the Q self-organizing cells can be classified into the M groups of φ1, φ2,..., φ M ; if the i-th cell belongs to the φ m group, it is denoted as i ∈ φ m ; the initial frequency allocation is to randomly classify the Q self-organizing cells into the above-mentioned M groups;

[0040] Step 2: Use the dynamic frequency reuse algorithm to dynamically adjust the group membership of the self-organizing cells with a small average signal-to-interference-plus-noise ratio; the flow chart of the dynamic frequency reuse algorithm is as Figure 3 shown, and the specific steps are as follows:

[0041] 1) Let i = 1;

[0042] 2) Judge whether γ i ≥γ min is satisfied. If γ i ≥γmin , jump to sub-step 3); if γ i < γ min , jump to sub-step 4);

[0043] 3) Let i = i + 1, and determine whether i ≤ Q is satisfied; if i ≤ Q, return to sub-step 2); if i > Q, jump to sub-step 9);

[0044] 4) Let m = 1;

[0045] 5) Assume i ∈ φ m , for all l ∈ {1, 2,..., Q}, recalculate γ l ;

[0046] 6) Let j = 1;

[0047] 7) Determine whether j ∈ φ m ;

[0048] 71) If j ∈ φ m , determine whether γ j ≥ γ min ;

[0049] 711) If γ j ≥ γ min , jump to sub-step 7111);

[0050] 7111) Let j = j + 1, and determine whether j ≤ Q is satisfied; if j ≤ Q, return to sub-step 7); if j > Q, jump to sub-step 8);

[0051] 712) If γ j < γ min , m = m + 1, and determine whether m ≤ M is satisfied; if m ≤ M, return to sub-step 5); if m > M, return to sub-step 3);

[0052] 72) If jump to sub-step 7111);

[0053] 8) Let i ∈ φ m , for all l ∈ {1, 2,..., Q}, recalculate γ l , and return to sub-step 3);

[0054] 9) Determine whether for all l ∈ {1, 2,..., Q}, γ l ≥ γ min ;

[0055] 91) If for all l ∈ {1, 2,..., Q}, γ l ≥ γ min cannot be satisfied simultaneously, then return to sub-step 1);

[0056] 92) If for all l ∈ {1, 2,..., Q}, γ l ≥ γ min can be satisfied simultaneously, then the dynamic adjustment of the pilot reuse for all self-organizing cells is completed and the algorithm ends;

[0057] Step 3: Perform frequency reuse between self-organizing cells according to the adjustment result of the grouping attribution of self-organizing cells

[0058] Perform frequency reuse between self-organizing cells according to the adjustment result of the grouping attribution of self-organizing cells, that is, the self-organizing cells belonging to the φ m group reuse the frequency band set φ m , where m ∈ {1, 2,..., M}.

[0059] Embodiment 2 (Experimental Example)

[0060] This embodiment is a simulation experiment, comparing the dynamic frequency reuse method of the present invention with the existing random frequency reuse method to illustrate its feasibility and effectiveness.

[0061] During the simulation, the channel is set as a Rayleigh channel, all channels follow a circularly symmetric complex Gaussian distribution, the channels are independent of each other, the radius of the self-organizing cell is 200 meters, the ships are uniformly distributed within the self-organizing cell, the transmission power of the ships is 3 kW, the noise variance is 1, and the number of frequency band sets is M = 3.

[0062] Figure 4 The "random frequency reuse" in Figure 4 is the existing random frequency reuse method between self-organizing cells, and the "dynamic frequency reuse" is the dynamic frequency reuse method between self-organizing cells disclosed in the present invention.

[0063] From Figure 4 it can be seen that as the number of self-organizing cells increases, the average received signal-to-interference-plus-noise ratio of both "dynamic frequency reuse" and "random frequency reuse" decreases. This is because as the number of self-organizing cells increases, the number of ships using the same frequency band repeatedly increases, and the communication interference increases, so the average received signal-to-interference-plus-noise ratio decreases. "Dynamic frequency reuse" is significantly better than "random frequency reuse", and compared with "random frequency reuse", the decreasing trend of "dynamic frequency reuse" is much slower; this shows that compared with "random frequency reuse", "dynamic frequency reuse" increases the dynamic adjustment of frequency reuse, and the adjustment process is to reduce communication interference.

[0064] In summary, compared with the existing random frequency reuse method, the dynamic frequency reuse method between self-organizing cells of a VDES system disclosed by the present invention can dynamically adjust the frequency reuse between self-organizing cells and reduce the communication interference between ships.

Claims

1. A dynamic frequency reuse method between self-organizing cells of a VDES system, the method comprising the following steps: Step 1: Establish a self-organizing cell model and perform frequency reuse grouping on the self-organizing cells Suppose there are N ships in Q self-organizing cells. The numbers of the self-organizing cells are 1, 2, …, Q. Let there be l i ships in the i-th self-organizing cell, where i ∈ {1, 2, …, Q}. Then the average signal-to-interference-plus-noise ratio of all ships in the i-th self-organizing cell is denoted as γ i , and the minimum signal-to-interference-plus-noise ratio threshold is denoted as γ min , and γ min is equal to a fixed value. All available communication frequency bands are grouped into M non-overlapping frequency band sets φ1, φ2, …, φ M . Each self-organizing cell selects one of the frequency band sets φ1, φ2, …, φ M and uses the selected frequency band set for data communication. Since Q is much larger than M in practice, when Q self-organizing cells use M frequency band sets, there will be a situation where multiple self-organizing cells reuse the same frequency band set, that is, frequency reuse. Let the self-organizing cells using the φ m frequency band set belong to the φ m group, where m ∈ {1, 2, …, M}. Then the Q self-organizing cells are grouped into the M groups φ1, φ2, …, φ M . If the i-th cell belongs to φ m for grouping, it is denoted as i ∈ φ m ; The initial frequency allocation is to randomly assign Q self-organizing cells to the M groups mentioned above; Step 2: Use the dynamic frequency reuse algorithm to dynamically adjust the grouping attribution of the self-organizing cells with a small average signal-to-interference-plus-noise ratio; the dynamic frequency reuse algorithm is as follows: 1) Let i = 1; 2) Determine whether γ i ≥γ min , if γ i ≥γ min , jump to step 3); if γ i <γ min , jump to step 4); 3) i = i + 1, and determine whether i ≤ Q; If i ≤ Q, return to step 2); If i > Q, jump to step 9) 4) Let m = 1; 5) Assume that i ∈ φ m For all l ∈ {1, 2, …, Q}, recalculate γ l 6) Let j = 1; 7) Determine whether j ∈ φ m 71) If j ∈ φ m , determine whether γ j ≥ γ min 711) If γ j ≥ γ min , jump to step 7111) 7111) Let j = j + 1, and determine whether j ≤ Q; if j ≤ Q, return to step 7); if j > Q, jump to step 8) 712) If γ j <γ min , m = m + 1, and determine whether m ≤ M; if m ≤ M, return to step 5); if m > M, return to step 3) 72) If Jump to step 7111) 8) Let \(i\in\varphi\) m For all \(l\in\{1,2,\ldots,Q\}\), recalculate \(\gamma\) l Return to step 3) 9) Determine whether, for all l ∈ {1, 2, …, Q}, γ can be satisfied simultaneously l ≥ γ min 91) If for all l ∈ {1, 2, …, Q}, γ l ≥ γ min cannot be satisfied simultaneously, then return to step 1); 92) If for all l ∈ {1, 2, …, Q}, it can be simultaneously satisfied that γ l ≥ γ min , then the dynamic adjustment of all self-organizing cell pilot multiplexing is completed, and the algorithm ends; Step 3: Perform frequency reuse between self-organizing cells according to the adjustment result of the grouping attribution of the self-organizing cells According to the adjustment result of the grouping attribution of self-organizing cells, frequency reuse among self-organizing cells is performed, that is, the self-organizing cells belonging to φ m The self-organizing cells in the group reuse the frequency band set φ m , where m ∈ {1, 2, …, M}.

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