Abstract
To solve the problem of the missing data of radiator during the aerial war, and to address the problem that traditional algorithms rely on prior knowledge and specialized systems too much, an algorithm for radiator threat evaluation with missing data based on improved Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) has been proposed. The null estimation algorithm based on Induced Ordered Weighted Averaging (IOWA) is adopted to calculate the aggregate value for predicting missing data. The attribute reduction is realized by using the Rough Sets (RS) theory, and the attribute weights are reasonably allocated with the theory of Shapley. Threat degrees can be achieved through quantization and ranking of radiators by constructing a TOPSIS decision space. Experiment results show that this algorithm can solve the incompleteness of radiator threat evaluation, and the ranking result is in line with the actual situation. Moreover, the proposed algorithm is highly automated and does not rely on prior knowledge and expert systems.
Introduction
Radiator threat evaluation is an important research topic within the field of Electronic Countermeasures (ECM) [1]. The accuracy of radiator threat evaluation indirectly affects the outcome of the war. As the types and operation modes of radiator become ever more complex and the anti-jamming capability of targets develops, radiator threat evaluation faces great challenges.
At present, a wealth of research accomplishments have been made in the field of target threat evaluation. Bayesian Network Image was introduced to intuitively describe the reasoning process of target threat evaluation, and fuzzy relation in threat evaluation is clearly expressed through a directed acyclic graph [2, 3]. Evidence theory was used to deal with uncertain problems, and combat intentions and equipment capability of air combat targets were deeply considered to realize threat evaluation [4]. Information entropy, radar perception network, and cognitive mapping were combined with fuzzy sets theory to solve the uncertain decision problems in threat evaluation [5–7]. XU et al. regarded target threat evaluation as a multi-attribute decision problem, and constructed an air combat target threat evaluation model based on the improved Intuitionistic Fuzzy Sets (IFS).
The above researches rely on prior knowledge and expert system support, which may not have applied to all cases. To address this challenge, Zhang et al. used intuitionistic fuzzy entropy to determine attribute weights and evaluated the target threat through a multi-criteria decision model based on VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) algorithm [10]. Zhang et al. introduced the TOPSIS algorithm, which has been widely used in various fields to calculate the nearness degrees of each target and obtained the threat degrees of targets by comparing them [11–19]. To improve the reliability of an evaluation model, a radiator threat evaluation algorithm based on Shapley-TOPSIS was proposed, which could assign attribute weights objectively [20].
The processed data of the above research were complete. However, within the actual operational process, the radiator information system for detection and collection was usually incomplete. For the problem of target threat evaluation with missing data, ZHANG et al. introduced an improved tolerance relation rough set algorithm to build a complete set of decision rules extracting model [21]. However, the algorithm could only divide the radiator into several categories according to the threat degrees and was unable to distinguish the threat degree in detail for the targets in the categories. In addition, SUN et al. proposed a threat evaluation method based on dynamic Bayesian Networks of constraint parameter learning, and the AR(p) model was used to predict the missing data on the time series [22]. This method needed the support from target data in multiple historical moments, difficult to obtain the data in actual combat. Therefore, the method has some limitations. To achieve the detailed ranking of the radiator threat degree in the case of missing data and expand application scope, effectively overcoming the problem of incomplete data, we combine the IOWA operator [23–28] with Shapley-TOPSIS algorithm. Then, a radiator threat evaluation model with missing data based on improved TOPSIS is constructed. The proposed algorithm can deal with incomplete information systems and has the value of the military promotion.
Null estimation algorithm based on IOWA
The null estimation algorithm based on IOWA considers both the correlation between objects and attributes and can adjust the weight vector according to different backgrounds, which can effectively make up the missing data of the object.
(ω1, ω2, ⋯ ω
p
) is the weight vector of OWA pairs, which is determined by the following function:
Among them,
The processing principle of null estimation algorithm based on IOWA: For the missing attribute, only one null value can be predicted for each iteration. If the value of the correlation attribute of the missing attribute changes during the iteration, the missing data of the attribute can be predicted through the next iteration.

Processing flow of the null estimation algorithm based on IOWA.
The processing flow of the null estimation algorithm based on IOWA is shown in Fig. 1.
The specific steps are as follows: For the first iteration, the correlation attributes of the attributes with missing data are determined. Firstly, the attributes with missing data and incomplete information systems are selected. The information contained in complete data-sets is fully utilized to calculate the correlation function values of each attribute and the remaining attributes, respectively. Then, the values of the correlation functions are compared, and the attribute corresponding to the maximum value is its correlation attribute. OWA pairs are calculated. After obtaining all correlation attributes through Step 1, for each attribute with missing data, the corresponding objects when both attribute values are complete are listed in combination with its correlation attribute, and then the attribute values of correlation attributes are listed in accordance with the principle from large to small in order to form OWA pairs. The data-set is completed. The parameter values of the weight calculation formula are determined based on practical situations, and the weights of OWA pairs are reasonably allocated. Then, the OWA pairs and weights are combined to calculate the aggregate value, which is used for replacing the null value. Finally, the first iteration is completed. If there are attributes with missing data after the first iteration, the next iteration according to Step 1-Step 3, is undertaken until the data of the system is complete.
The basic principle of the TOPSIS algorithm is to construct an evaluation space through positive samples and negative samples based on the standardized sample evaluation matrix. The object to be evaluated can be regarded as a point in the evaluation space and the evaluation result is provided through calculating the relative “distance” (Euclidean distance) between objects and positive and negative ideal solution.
At present, radiator threat evaluation is mainly carried out by analyzing radiator pulse parameters and platform situation. The specific steps of the evaluation algorithm based on TOPSIS are as follows.
Many algorithms have emerged during the radiator threat evaluation process, including expert assignment, Analytic Hierarchy Process (AHP), IFS, etc. These algorithms have defects, which may include excessive subjectivity, having an overly dependence on prior knowledge, or being highly complex, so this work introduces Shapley value dominance relation rough set to optimize attribute weight allocation.
Where, S k is a collection consisting of all subsets which include s k , and S′ is one of the subsets which include s k . S′ ∖ s k represents that s k is removed from S′. And the Shapley value of attribute s k represents the contribution of s k to the information loss of attribute subset.
Through the above analysis, we combine the amount of information and Shapley value to quantify the importance of attribute to decision making, and the weights of attributes are obtained using the following formula.

Processing flow of the proposed model.
The processing flow of the algorithm of radiator threat evaluation with missing data based on improved TOPSIS is shown in Fig. 2.
The specific steps of the model are as follows: We complete the radiator data through the null estimation algorithm based on IOWA. Given the attribute with missing data in the radiator signal pulse, the correlation function is calculated to determine the correlation attribute, and then the OWA pairs composed of non-null values of the two attributes are listed. Combined with the weight vector, the aggregate value is obtained to complete the missing data. We construct an evaluation matrix. After that the incompleteness of the information system is solved through Step1, the initial evaluation matrix is constructed according to the radiator attribute parameters, and the difference of dimensions of different attributes is eliminated by distinguishing the benefit-type index and the cost-type index, so as to obtain the standardized evaluation matrix. We assign attribute weights based on the Shapley value dominance relation algorithm. According to the evaluation matrix constructed by Step 2, the dominant relationship between radiator attributes is analyzed by rough set theory, with the attribute set reduced. Then, based on the principle of the attribute’s contribution to the total information loss, the Shapley value of each attribute is calculated, and the attribute weight vector of the radiator is obtained after normalization processing. We calculate the threat degrees of radiators. Combining the evaluation matrix of Step 2 and the attribute weight vector of Step3, the TOPSIS model decision space is constructed to generate positive and negative solutions, and the relative “distance” between each evaluation object and the ideal solution is calculated to obtain the relative ranking of threat degree.
Experiment
To verify the validity of the algorithm and model across this work, radiator data in Ref. [29] are introduced, as shown in Table 1. s1, s2, s3, s4, s5, s6, s7 respectively represent platform height (/km), platform approach speed (/Ma), platform distance (/km), angle of attack (/°), signal radio frequency (/GHz), signal pulse repetition frequency (/KHz), and signal pulse width (/μs).
Data of radiators
Data of radiators
To improve the validity and reliability of the experimental results and verify the universality of the algorithm in this paper, three groups of experiments are set up in this section, in which partial radiator’s information is randomly removed in Table 1 respectively.
Partial information in Table 1 is randomly removed to obtain incomplete radiator data as shown in Table 2.
Incomplete data of radiators (experiment 1)
The first iteration. For attribute s1, OWA pairs are obtained according to Definition 3 as follows, which is the basis for generating the aggregate values.
Then, according to Equation (3), the weights of OWA pairs are determined as follows.
Finally, the aggregate value is obtained according to Equation (2) and it is used as the predicted value of the missing data of attribute s1.
Similarly, the predicted values of attributes s2, s6, s7 are 1.5, 20, and 1.4, respectively. Because the correlation attribute s1 of the attribute s4 has changed, the prediction of the missing value of s4 goes through a second iteration.
The second iteration. The aggregate value of the attribute s4 is 11.2 through the same steps above.
After the above processing, we get the complete radiator data in Table 3.
Complete data of radiators after been processed by the proposed algorithm (experiment 1)
The evaluation matrix is constructed based on Table 3.
To eliminate the difference of attribute dimension and unit, based on the analysis of the attributes above, the benefit-type indexes and the cost-type indexes are processed according to Equation (5) and Equation (6) respectively. According to Ref. [29], platform height, platform distance, angle of attack and signal pulse width are cost-type indexes, namely, the greater the values of these indexes, the lower the threat degree of the radiator. Moreover, platform approach speed, signal radio frequency and signal pulse repetition frequency are benefit-type indexes, namely, the greater the values of these indexes, the higher the threat degree of the radiator. Then, we obtain the standardized evaluation matrix as follows.
The missing data in the incomplete information system are completed and the standardized evaluation matrix is constructed above. We mainly assign attribute weights in this step.
At first, based on the evaluation matrix B, the identity matrix is generated as follows (in Table 4) according to definition 7.
Identity matrix (experiment 1)
All non-empty elements contain, {s6}, {s1, s4}, {s5, s6}, {s5, s7}, {s1, s2, s4}, {s5, s6, s7}, {s1, s2, s3, s4}, {s3, s5, s6, s7}, {s1, s2, s3, s4, s6}, {s1, s2, s3, s4, s7}, {s2, s3, s5, s6, s7}, {s1, s2, s3, s4, s5, s6}, {s1, s2, s3, s4, s5, s7}, {s1, s2, s3, s4, s5, s6, s7}. According to definition 8, the reduction set is V = {s4, s6, s7}, and the evaluation matrix after reduction is as follows:
Then, the amount of information of s4, s6, s7 can be calculated as Equation (14), and the Shapley values of s4, s6, s7 can be calculated as Equation (18).
Finally, according to Equation (19), the attribute weights are calculated as follows.
Following this, the decision environment is built. According to Equation (8) and Equation (9), positive and negative ideal solutions are generated.
After that, the relative “distance” between the radiator and positive and negative ideal solutions can be calculated as Equation (10) and Equation (11) respectively.
Finally, we obtain the nearness degrees of radiators as follows, according to Equation (12).
According to the nearness degrees, the threat degree ranking result of the five radiators is x1 > x6 > x4 > x3 > x2 > x5, which is consistent with the result obtained in Ref. [29] based on complete data.
To further verify the effectiveness and reliability of the proposed algorithm, the incomplete radiator data in Table 5 are processed based on the proposed algorithm.
Incomplete data of radiators (experiment 2)
According to the step1-step3 in experiment 1, the ranking result of the radiator threat degree is x1 > x6 > x4 > x3 > x2 > x5, which is consistent with the result obtained in Ref. [29] based on complete data.
In experiment 3, the incomplete radiator data in Table 6 are processed based on the proposed algorithm similarly.
Incomplete data of radiators (experiment 3)
According to the processing steps in experiment 1, the ranking result of the radiator threat degree is x1 > x6 > x4 > x3 > x2 > x5, which is consistent with the result obtained in Ref. [29] based on complete data.
In experiment 4, the incomplete radiator data in Table 7 are processed based on the proposed algorithm similarly.
Incomplete data of radiators (experiment 4)
According to the processing steps in experiment 1, the ranking result of the radiator threat degree is x1 > x6 > x3 > x4 > x2 > x5, which is inconsistent with the result obtained in Ref. [29] based on the complete data. In the light of the ranking result, the threat degree of radiator x3 is higher than that of radiator x4, which is reverse with the actual situation.
In experiment 5, the incomplete radiator data in Table 8 are processed based on the proposed algorithm similarly.
Incomplete data of radiators (experiment 5)
According to the processing steps in experiment 1, the ranking result of the radiator threat degree is x6 > x3 > x1 > x4 > x2 > x5, which is inconsistent with the result obtained in Ref. [29] based on complete data. In the light of the ranking result, the threat degrees of radiator x3 and x6 are higher than that of radiator x1. But actually, the threat degree of radiator x1 is the highest one.
In experiment 6, the incomplete radiator data in Table 9 are processed based on the proposed algorithm similarly.
Incomplete data of radiators (experiment 6)
According to the processing steps in experiment 1, the ranking result of the radiator threat degree is x4 > x1 > x6 > x5 > x3 > x2, which is inconsistent with the result obtained in Ref. [29] based on the complete data. In the light of the ranking result, the threat degree of radiator x4 is higher than that of radiator x1, and the threat degree of radiator x5 is higher than that of radiator x3 and x2. But actually, the threat degrees of radiator x1 and x5 are the highest one and the lowest one respectively.
It can be demonstrated that the proposed algorithm eliminates incompleteness and achieves threat degree evaluation. In this work, the algorithm effectively realizes the threat evaluation of radiators with missing data, and the ranking results of threat degree in the first three groups (experiment 1-experiment 3) are consistent with the actual situation. However, the ranking results of threat degree in the last three groups (experiment 4-experiment 6) are inconsistent with the actual situation. As can be seen from the experiments, the proposed algorithm works effectively when the number of missing values is 5 or 6, and the performance of it degrades when the number of missing values is 8, 10 or 12. The reason for the above phenomenon is that the amount of information for the rest radiator data is scant and then the missing data cannot be predicted accurately when the number of missing values is 8, 10 or 12, but it can be predicted with some accuracy when the number of missing values is 5 or 6. In other words, when the number of missing values is too large, the reliability and availability of the algorithm will descend gradually with the increasing of the number of missing values.
In considering the actual demands of radiator threat evaluation under incomplete conditions, an evaluation algorithm based on improved TOPSIS is proposed. Firstly, we introduce the null estimation algorithm based on IOWA to comprehensively analyze the relationship between correlation attributes and to obtain the predicted values of the missing data. Then, the attribute set is reduced, and the weights are given based on the algorithm of Shapley Value Dominance Relation Rough Set, which can objectively measure the influence degrees of each attribute to the radiator threat evaluation process. Finally, the ranking result is obtained through the TOPSIS algorithm. Compared with the ICW-RCM evaluation algorithm in Ref. [29], the algorithm in this work is highly automated and does not rely on prior knowledge and expert systems. Furthermore, the model in this work makes up the limitations of radiator threat evaluation in the absence of data and can be applied to military practices.
In future work, weapon configuration information of the radiator platform should be considered in the research of radiator threat evaluation to improve the rationality of the model, and how to select a reasonable evaluation index is significant with the developing trend of multi-aircraft cooperative operation. In addition, due to changes in the combat situation and the tasks of the combatants involved, the threat degrees of the radiators are constantly changing, so it is necessary to consider the threat evaluation under dynamic variable parameters. Furthermore, the applicability of threat evaluation model needs to be improved to tackle the huge amount of missing values.
Footnotes
Acknowledgment
Here, Yuheng Xu expressed his heartfelt thanks to Siyi Cheng and all friends who contributed to this work.
