Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Recent improvements in vehicular ad hoc networks are accelerating the realization of intelligent transportation system (ITS), which not only provides road safety and driving efficiency, but also enables infotainment services. Since data dissemination plays an important part in ITS, recent studies have found caching as a promising way to promote the efficiency of data dissemination against rapid variation of network topology. In this paper, we focus on the scenario of roadside unit (RSU) caching, where multiple content providers (CPs) aim to improve the data dissemination of their own contents by utilizing the storages of RSUs. To deal with the competition among multiple CPs for limited caching facilities, we propose a multi-object auction-based solution, which is sub-optimal and efficient to be carried out. A caching-specific handoff decision mechanism is also adopted to take advantages of the overlap of RSUs. Simulation results show that our solution leads to a satisfactory outcome. <s> BIB001 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Vehicular networks enable an efficient communication with the aim of improving data dissemination among vehicles. However, a growing number of vehicles expect to conduct data dissemination through road side facilities which cause an increment of network load. To address the issue, this letter applies fog computing technologies for enhancing vehicular network that is planned as a layered network architecture. Moreover, two dynamic scheduling algorithms are proposed on the fog computing scheme for the data scheduling in vehicular networks. These algorithms can dynamically adapt a changeable network environment and benefit in efficiency. For performance analysis, a compositional formal method, named performance evaluation process algebra, is applied to model scheduling algorithm in a fog-based vehicular network. <s> BIB002 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Distributed reputation systems can be used to foster cooperation between nodes in decentralized and self-managed systems due to the nonexistence of a central entity. In this paper, a Robust and Distributed Reputation System for Delay-Tolerant Networks (REPSYS) is proposed. REPSYS is robust because despite taking into account first- and second-hand information, it is resilient against false accusations and praise, and distributed, as the decision to interact with another node depends entirely on each node. Simulation results show that the system is capable, while evaluating each node's participation in the network, to detect on the fly nodes that do not accept messages from other nodes and that disseminate false information even while colluding with others, and while evaluating how honest is each node in the reputation system, to classify correctly nodes in most cases. <s> BIB003 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Motivated by message delivery in vehicular ad hoc networks, we study distributed data replication algorithms for information delivery in a special completely connected network. To improve the efficiency of data dissemination, the number of message copies that can be spread is controlled and a distributed randomized data replication algorithm is proposed. The key idea is to let the data carrier distribute the data dissemination tasks to multiple nodes to speed up the dissemination process. We show how the network converges and prove that the network can enter into a balanced status in a small number of stages. Most of the theoretical results described in this paper are to study the complexity of network convergence. Simulation results show that the proposed algorithm can disseminate data to a specific area with low delay. <s> BIB004 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Efficient content distribution is a critical challenge in vehicular networks (VANETs). This is due to the characteristics of vehicular networks, such as high mobility, dynamic topologies, short-lived links and intermittent connectivity between vehicles. Recently, information-centric networking (ICN) has been proposed to VANET scenarios for improving content delivery of infotainmentapplications. However, ICN in VANETs suffers from the Interest transmission broadcast problem, which results in a waste of resources and diminishes the performance of VANETs' applications. In this paper, we propose the link stability-based Interest forwarding for content request (LISIC) protocol, in order to tackle the Interest broadcast storm problem during a content search in information-centric VANETs. The proposed protocol controls Interesttransmission by prioritizing neighboring vehicles with more stable links with the current sender. Simulation results show that the proposed protocol improves the content delivery rate by 40% while decreases the Interest packet transmissions by 26%, in scenario of a low number of content producers in the network. <s> BIB005 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> By analogy with Internet of things, Internet of vehicles (IoV) that enables ubiquitous information exchange and content sharing among vehicles with little or no human intervention is a key enabler for the intelligent transportation industry. In this paper, we study how to combine both the physical and social layer information for realizing rapid content dissemination in device-to-device vehicle-to-vehicle (D2D-V2V)-based IoV networks. In the physical layer, headway distance of vehicles is modeled as a Wiener process, and the connection probability of D2D-V2V links is estimated by employing the Kolmogorov equation. In the social layer, the social relationship tightness that represents content selection similarities is obtained by Bayesian nonparametric learning based on real-world social big data, which are collected from the largest Chinese microblogging service Sina Weibo and the largest Chinese video-sharing site Youku. Then, a price-rising-based iterative matching algorithm is proposed to solve the formulated joint peer discovery, power control, and channel selection problem under various quality-of-service requirements. Finally, numerical results demonstrate the effectiveness and superiority of the proposed algorithm from the perspectives of weighted sum rate and matching satisfaction gains. <s> BIB006 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> In this article, a robust and distributed incentive scheme for collaborative caching and dissemination in content-centric cellular-based vehicular delay-tolerant networks (REPSYS) is proposed. REPSYS is robust because despite taking into account first- and second-hand information, it is resilient against false accusations and praise, and distributed, as the decision to interact with another node depends entirely on each node. The performance evaluation shows that REPSYS is capable, while evaluating each node's participation in the network, of correctly classifying nodes in most cases. In addition, it reveals that there are trade-offs in REPSYS, for example, to reduce detection time of nodes that neither cache nor disseminate other nodes' data, one may sacrifice the system's resilience against false accusations and praise, or even, by penalizing nodes that do not disseminate data, one may temporarily isolate nodes that could contribute to data dissemination. <s> BIB007 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Driven by the evolutionary development of automobile industry and cellular technologies, dependable vehicular connectivity has become essential to realize future intelligent transportation systems (ITS). In this paper, we investigate how to achieve dependable content distribution in device-to-device (D2D)-based cooperative vehicular networks by combining big data-based vehicle trajectory prediction with coalition formation game-based resource allocation. First, vehicle trajectory is predicted based on global positioning system and geographic information system data, which is critical for finding reliable and long-lasting vehicle connections. Then, the determination of content distribution groups with different lifetimes is formulated as a coalition formation game. We model the utility function based on the minimization of average network delay, which is transferable to the individual payoff of each coalition member according to its contribution. The merge and split process is implemented iteratively based on preference relations, and the final partition is proved to converge to a Nash-stable equilibrium. Finally, we evaluate the proposed algorithm based on real-world map and realistic vehicular traffic. Numerical results demonstrate that the proposed algorithm can achieve superior performance in terms of average network delay and content distribution efficiency compared with the other heuristic schemes. <s> BIB008 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Due to the dynamically changing topology of Internet of Vehicles (IoV), it is a challenging issue to achieve efficient data dissemination in IoV. This paper considers strongly connected IoV with a number of heterogenous vehicular nodes to disseminate information and studies distributed replication-based data dissemination algorithms to improve the performance of data dissemination. Accordingly, two data replication algorithms, a deterministic algorithm and a distributed randomised algorithm, are proposed. In the proposed algorithms, the number of message copies spread in the network is limited and the network will be balanced after a series of average operations among the nodes. The number of communication stages needed for network balance shows the complexity of network convergence as well as network convergence speed. It is proved that the network can achieve a balanced status after a finite number of communication stages. Meanwhile, the upper and lower bounds of the time complexity are derived when the distributed randomised algorithm is applied. Detailed mathematical results show that the network can be balanced quickly in complete graph; thus highly efficient data dissemination can be guaranteed in dense IoV. Simulation results present that the proposed randomised algorithm outperforms the present schemes in terms of transmissions and dissemination delay. <s> BIB009 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> In future vehicular networks, to satisfy the ever-increasing capacity requirements, ultrahigh-speed directional millimeter-wave (mmWave) communications will be used as vehicle-to-vehicle (V2V) links to disseminate large-volume contents. However, the conventional IP-based routing protocol is inefficient for content disseminations in high-mobility and dynamic vehicular environments. Furthermore, the vehicle association also has a significant effect on the content dissemination performance. The content segment diversity, defined as the difference of desired content segments between content requesters and content repliers, is a key consideration during vehicle associations. The relative velocity between vehicles, which highly influences the link stability, should also been taken into account. The beam management, such as the beamwidth control, determines the link quality and, therefore, the final content dissemination rate. Based on the above observations, to improve the content dissemination performance, we propose an information-centric network (ICN)-based mmWave vehicular framework together with a decentralized vehicle association algorithm to realize low-latency content disseminations. In the framework, by using the ICN protocol, contents are cached and retrieved at the edge of the network, thereby reducing the content retrieval latency. To enhance the content dissemination rate, the vehicle association algorithm, which jointly considers the content segment diversity, the relative velocity between vehicles, and the transceiver’s beamwidths, is operated in every vehicle. Considering the blindness of directional mmWave links, a common control channel operating at low frequency bands with omni-directional coverage is used to share the information related to vehicle associations. The simulation results demonstrate that the proposed algorithm can improve the content dissemination efficiency and reduce the content retrieval latency. <s> BIB010 </s> Computation Offloading and Content Caching Delivery in Vehicular Edge Computing: A Survey <s> A. Homogeneous Edge Nodes <s> Abstract The information-centric networking (ICN) paradigm has gained increasing attention as a solution for boosting content delivery in vehicular network applications. The content-naming oriented search and in-network data caching procedures of ICN can improve content delivery by avoiding the need to determine and maintain end-to-end routing paths in vehicular networks, which is challenging due to the mobility of vehicles, and intermittent and short-lived connections between them. However, the use of the ICN paradigm in vehicular networks aggravates the broadcast storm problem, and constantly suffers from breaks in the reverse path used for content discovery and delivery. In this paper, we propose the location-based and information-centric (LoICen) architecture to improve the content request procedure and reduce the broadcast storm problem in intelligent vehicular networks. In the LoICen architecture, vehicles opportunistically obtain the location information of the vehicles that might have desired content in their cache. This location information is used whenever possible to improve content search and discovery by directing Interest packets to the area where the content may be located, mitigating the broadcast storm problem by selecting only the most suitable neighboring vehicle at each hop to continue forwarding the Interest packet, and improving content delivery by selecting more stable paths. Simulation results show that the LoICen architecture outperformed related work in terms of content delivery ratio, while reducing the delay for the content delivery and the number of transmissions of Interest packets for content search. <s> BIB011
Homegeneous cache is defined for a single type of edge node, e.g., vehicle and RSU, that caches and shares the contents. In this paper, we broadly categorised homogeneous caching appraoches into two groups, which are noncooperative and cooperative homogenenous caching. Fig. 7 : Content caching and delivery 1) Non-cooperative caching: In the non-cooperative caching, each edge node stored and disseminated the content without relying on other homogeneous edge nodes. The authors in BIB001 explored a handoff decision between two RSUs for the caching service, as their model. A multi-object auction was presented in solving the RSU-caching problem with the objective was to maximise the total amount of downloaded data BIB001 . The advantages of the work are that a cachinghandoff mechanism and handoff delay are considered. The results demonstrated that the cached-enabled RSUs were fully utilised when the vehicle density was moderate. It is interesting to discover that the increase of data block size can reduce the total downloaded segmented data due to the wasted space of unallocated data block, and the reduction is critical for the unsegmented data. However, the study was conducted for a low mobility of 20 m/s. Meanwhile, a joint peer discovery, power control, and channel selection problem was formulated in maximising the sum of weighted transmission rate subject to the physical-social score and the spectrum efficiency for matching the vehicles, i.e., V-TX and V-RX. BIB006 . When multiple content providers assigned with the same spectrum resource or content consumer that can be solved using a price rising strategy and yet merely for V2V edge solution. For edge server caching, two dynamic queuing theory-based scheduling schemes were proposed based on a probabilistic function of sending a job to a server by computing the ratio of mean response time at a server to the transient response time, and another scheduling considered a queue length of the server BIB002 . A formal compositional method called Performance Evaluation Process Algebra was used to model the scheduling algorithms in a fog-based vehicular network. Because of the consistent queue length, the algorithm based on mean response time and transient response time outperformed in an unstable vehicular server system. However, the work is only investigated for edge servers and the detailed VEC architecture is not well-discussed. 2) Cooperative caching: In the cooperative caching, the same kind of edge nodes cooperatively cache and disseminate the contents in any means. A Robust and Distributed Reputation System (REPSYS) BIB003 , BIB007 consists of three different modules, namely, the reputation module (reputation collection and evaluation modules), the trust module, and the decision module based on Bayesian classification. The nodes monitored and evaluated the neighbouring nodes' behaviours with regards to the reputation rating and trust rating besides the recommendation of other nodes for the cooperation BIB003 . The work is then extended to an incentive mechanism for vehicles caching and disseminating data in content-centric cellular-based vehicular delay-tolerant networks BIB007 . The system achieved a high percentage for the misbehaving nodes detection, but the bottleneck required long detection time. On the other hand, the classification of vehicles can also be in terms of vehicles types and storage capabilities BIB009 . Data dissemination in the dense Internet of Vehicles (IoV) can be abstracted as a complete graph using graph theory BIB009 , BIB004 . Two replication-based algorithms; a deterministic algorithm and a distributed randomised algorithm, were designed under heterogeneous vehicular networks occupied with different types of vehicles with varying capabilities of storage. Interestingly, the proposed randomised algorithm improved the delivery ratio up to 80% and the latency below 1.5 ms due to the various capabilities of vehicles. Another cooperative caching, BIB010 assumed that the contents are cached in vehicles' storage, and a novel ICNbased mmWave vehicular framework is proposed, which is illustrated in Figure 8 . A decentralised vehicle association algorithm called Adaptive-beamwidth Weighted Association Fig. 8 : ICN-based mmWave vehicular framework BIB010 Scheme (ABWAS) was efficiently developed to match between vehicles by maximising the content dissemination efficiency, which jointly optimised the content dissemination rate and the number of retrieval content segments. A vehicle with higher dissemination rate can support maximum transmitted content segments within the beam coherence time. Therefore, the content retrieval latency is low. The reason is that ABWAS adjusted the vehicles with their associated beamwidths in retrieving more content segments at higher transmission rate despite that high overheads. On the other hand, the formulated joint peer discovery, spectrum allocation, and route selection optimisation problem was solved using a big data integrated coalition formation game approach via D2D-V2V multihop content distribution BIB008 . In particular, the V-RX that received the content can also cache and hence served other adjacent vehicles. The utility function proposed is to minimise the average network delay, which considered as the individual pay for each coalition member. The technique can serve approximately 90% of vehicles on the area and achieve the average network delay below 3 ms with the increasing number of resource blocks (RBs). Despite that, Interest Packet transmissions were introduced BIB011 in the proposed location-based, and information-centric (LoICen) architecture which consisted of three components, namely content request, content-location management, and content delivery. The redundant data transmission problem was solved by the vehicles' Pending Interest Table ( PIT) prior to the Interest packet arrival. The data can be sent either based on location or agnostic search, i.e., link stability-based Interest forwarding (LISIC) protocol BIB005 , to identify the vehicle that cached the required content. LoICen outperformed in terms of content delivery ratio, delay, and overhead due to the locationspecific mechanism. However, the specific component that handled the LoICen is not mentioned and this is probably a BS or a coordinator server. All the previously mentioned cooperative caching methods suffer a serious limitation of only vehicles as caching nodes, i.e., V2V and not other edge nodes involved.