Although machine learning methods are not extensively utilized to predict the reliability of vehicular communications, there are many studies on other applications of these methods in VANETs. Some of the applied DL and machine learning methods are reviewed in this section.
A traffic flow prediction approach was presented in [15] based on DL; this method considered spatial and temporal correlations. The researchers determined traffic flow features using stacked auto-encoders. Moreover, a greedy layer-wise unsupervised learning algorithm was applied to improve the prediction performance through fine-tuning.
The proposed intrusion detection solution in [16] used Deep Neural Networks (DNNs). The training for feature extraction was performed using in-vehicle network packets to detect normal and hacking packets.
In [17], the authors proposed an ANN-based clustering algorithm based on the mobility and reliability of vehicles. The reliability, speed, and distance between the vehicles were considered for clustering, which increased stability and connectivity while decreasing bandwidth and delay.
In [18], the authors used a Deep Q-Network (DQN) to learn from the characteristics of the vehicles located in a roadside unit range to provide road safety, an acceptable level of Quality of Service (QoS), and lengthen the roadside unit's battery lifetime.
A method for misbehavior detection using ANN models was provided in [19]. The authors derived features showing the status of misbehavior, the environment, and communication to detect misbehavior data, and feed-forward and back-propagation algorithms were used for misbehavior classification.
A stereo vision-based method was presented in [20] for obstacle detection in VANETs in an urban environment. The utilized model was a Deep-Stacked Auto-encoder (DSA), with the k-nearest neighbor classifier using three real-life datasets.
The proposed DQN model in [21] handled speed, overtaking, and lane change decisions by training the vehicles.
A resource allocation mechanism for vehicle-to-vehicle communications was presented in [22]. This method was based on Deep Reinforcement Learning (DRL) to find the optimal spectrum and power for message transmissions between vehicles.
In [23], the authors studied the application of the Convolutional Neural Network (CNN) model for traffic control and optimal route assignment for vehicular communication. The proposed model was evaluated using various parameters, including delay, throughput, packet delivery ratio, and network load.
A clustering-based reliable routing was presented in [24]. In the proposed solution, clustering was performed using the Simulated Annealing (SA) algorithm, and a neural network was used to select the cluster's head.
A machine learning-based method for driving habit prediction was presented in [25] for stable clustering. The authors classified vehicles into two alignments using a naive Bayes classifier with different factors, such as relative speed, vehicle type, and the number of traffic violations. When combined with clustering design, the method was effective for stable clustering.
In [26], the authors found the optimum size of the Contention Window (CW) in VANETs using three Artificial Neural Network (ANN) algorithms, namely the particle swarm optimization, differential evolution algorithm, and artificial bee colony algorithm.
The method proposed in [27] was a hybrid SVM-based method for detecting Distributed Denial-of-Service (DDoS) attacks on VANETs. The SVM methods considered features like collisions, packet drop, and jitter under normal conditions and DDoS attacks.
Since network traffic prediction allows Intelligent Transport Systems (ITS) for proactive response to events before they happen, an LSTM DL model was purposed in [28] for VANETs traffic prediction. They evaluated the model based on RMSE and Mean Absolute Percentage Error (MAPE).
Intrusion detection was performed in [29] using a combination of auto-encoder networks and Recurrent Neural Networks (RNN).
The method described in [30] was also an Intrusion Detection System (IDS) for VANETs using DL, in which the researchers used the Deep Belief Network (DBN) algorithm for learning.
A machine learning-based hybrid intrusion detection model in VANETs was presented in [31]. The model had two components: it detected known attacks using RF classification, and it filtered dishonest nodes using coresets-based clustering.
An optimized method for VANET clustering inspired by whales' nature was described in [32]. This method optimized the number of clusters, hence, resource requirements reduction. Also, it increased the cluster lifetime.
The framework proposed in [33] was a model for trust management of the internet of vehicles. It was based on context-based cognition and a Bayesian machine learning model.
The presented method in [34] was an integrated algorithm for misbehavior detection. It was a combination of CNN and LSTM models to reconstruct the location information and an SVM as a binary classification method to check to compromise a vehicle. They used the VeReMi dataset to evaluate the performance of their algorithm.
A stable cluster head selection was presented in [35] using DL spectrum sensing. In the research, a classification problem was designed using Long Short-Term Memory (LSTM) for spectrum sensing.
Anomaly detection of VANETs communications and classification of abnormal behaviors were performed in [36] using DL neural network and LSTM model. They used the VeReMi [37] dataset to detect abnormal behaviors on roads and classify the types of location anomalies.
In [38], a machine learning model was proposed to improve the IDSs performance for preventing attacks in VANET using RF and a posterior detection based on coresets. Their goal was improving the detection accuracy and increasing the detection efficiency.
An RL model was proposed in [39] for routing to have a more stable communication system and increase communication reliability in VANETs. A complex objective space with geo-positioning information of vehicles, propagation signal strength, and environmental path loss with obstacles was created to train the model and get the best route based on route stability and hop count.
The proposed system in [40] was an effective IDS using Adaptive Neuro-Fuzzy Inference System (ANFIS) and CNN. The system was an intelligent IDS using soft computing techniques to detect both known and unknown attacks.
Attack classification in VANETs was performed in [41] using a hybrid optimization-based Deep Maxout Network (DMN). The DMN was used for attack classification, and a hybrid optimization algorithm was designed to select the cluster head, perform routing, and teach the DMN.
The novel proposed method in [42] predicted node mobility in ad hoc networks. An RNN-based method comprising a single feed-forward layer was used for more precise and realistic mobility predictions by depicting interactions and connections between nodes.
The proposed approach in [43] was a secure and intelligent message-forwarding strategy based on DRL. The key supporting elements of the model were reasonably designed, and the model's sufficient training was carried out by DQNs.
Table 1 summarizes the applications of machine learning and DL in VANETs. Based on the table DL model was not used previously for the reliability of vehicular networks, which is used in this paper for CR-VANETs' reliability prediction.
Table 1
Different applications of machine learning algorithms for VANETs
Reference | Algorithm | Application |
Lv (2015) [15] | DL | Traffic flow prediction |
Kang (2016) [16] | DNN | Intrusion detection |
Marzak (2016) [17] | ANN method | Clustering |
Atallah (2017) [18] | DQN | Safety and QoS |
Ghaleb (2017) [19] | ANN method | Misbehavior detection |
Dairi (2018) [20] | DSA | Obstacle detection |
Hoel (2018) [21] | DQN | Lane change decisions |
Ye (2018) [22] | RL | Resource allocation |
Jindal (2018) [23] | CNN | Traffic control and routing |
Bagherlou (2018) [24] | SA and NN | Clustering |
Liu (2019) [25] | Naïve bayes classifier | Classification and clustering |
Karabulut (2019) [26] | ANN | Finding the optimum size of CW |
Adhikary (2020) [27] | SVM | DDoS attack detection |
Abdellah (2020) [28] | LSTM | Traffic prediction |
Li (2020) [29] | RNN | Intrusion detection |
Vitalkar (2020) [30] | DBN | Intrusion detection |
Bangui (2021) [31] | RF | Intrusion detection |
Husnain (2021) [32] | Whale's nature-inspired | Clustering |
Rehman (2021) [33] | Bayesian learning | Trust management |
Hsu (2021) [34] | CNN, LSTM, SVM | Misbehavior detection |
Kareem (2022) [35] | LSTM | Spectrum sensing |
Xiangyu (2022) [36] | LSTM | Anomaly detection |
Bangui (2022) [38] | RF | Intrusion detection |
Teixeira (2022) [39] | RL | Routing |
Karthiga (2022) [40] | ANFIS and CNN | Intrusion detection |
Kaur (2022) [41] | DMN | Attack detection |
Yeruva (2023) [42] | RNN | Mobility forecasting |
Liu (2023) [43] | DRN and DQN | Secure message forwarding |
Proposed Method | DL | CR-VANETs' reliability estimation |