Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> In content-oriented networking, content files are typically cached in network nodes, and hence how to cache content files is crucial for the efficient content delivery and cache storage utilization. In this paper, we propose a content caching scheme, WAVE, in which the number of chunks to be cached is adjusted based on the popularity of the content. In WAVE, an upstream node recommends the number of chunks to be cached at its downstream node, which is exponentially increased as the request count increases. Simulation results reveal that the average hop count of content delivery of WAVE is lower than other schemes, and the inter-ISP traffic volume of WAVE is the second lowest (CDN is the lowest). Also, WAVE achieves higher cache hit ratio and fewer frequent cache replacements than other on-demand caching strategies. <s> BIB001 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> New communication protocols, as WiFi Direct, are now available to enable efficient Device-to-Device (D2D) communications in wireless networks based on portable devices. At the same time, new network paradigms, as Content-Centric-Networking (CCN), allow a communication focused on the content and not its location within the network, enabling a flexible location for the content, which can be cached in the nodes across the network. In such context, we consider a multi-hop wireless network adopting CCN-like cooperative caching, in which each user terminal acts also as a caching node. We propose an interest-based insertion policy for the caching, based on the concept of “social-distance” borrowed by online recommendation systems, to improve the performance of the overall network of caches; the main idea is to store only the contents which appear to be of interest for the local user. We show that our proposed scheme outperforms other well-known insertion policies, that are oblivious of such social-distance, in terms of cache hit probability and access delays. <s> BIB002 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Recent years have seen a tremendous growth in the volume of video traffic in mobile settings. In this paper, we present the design of a mobile video-centric proxy cache, named iProxy, that offers improved performance in terms of both hit rates and streaming quality. Our thesis in designing iProxy is that we need to elevate the traditional view of caching from "data" to "information" in order to optimally meet the stringent requirements of video streaming in mobile settings. iProxy relies on recent advances on information-bound references (IBRs) to collapse multiple related cache entries into a single one, improving hitrate while lowering storage costs. iProxy incorporates a novel dynamic linear rate adaptation scheme to ensure high stream quality in face of channel diversity and device heterogeneity. Our evaluation of iProxy using realistic traffic traces shows that it can improve hitrate, but we need to use novel information-aware replacement policies for optimal performance. We show that our linear encoder can adapt well to changes in bandwidth, and yield better bit rates, lower buffering and lower start up delays than state-of-the-art schemes. <s> BIB003 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> In this paper, the problem of content-aware user clustering and content caching in wireless small cell networks is studied. In particular, a service delay minimization problem is formulated, aiming at optimally caching contents at the small cell base stations (SCBSs). To solve the optimization problem, we decouple it into two interrelated subproblems. First, a clustering algorithm is proposed grouping users with similar content popularity to associate similar users to the same SCBS, when possible. Second, a reinforcement learning algorithm is proposed to enable each SCBS to learn the popularity distribution of contents requested by its group of users and optimize its caching strategy accordingly. Simulation results show that by correlating the different popularity patterns of different users, the proposed scheme is able to minimize the service delay by %42 and 27%, while achieving a higher offloading gain of up to 280% and 90%, respectively, compared to random caching and unclustered learning schemes. <s> BIB004 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Small cells constitute a promising solution for managing the mobile data growth that has overwhelmed network operators. Local caching of popular content items at the small cell base stations (SBSs) has been proposed to decrease the costly transmissions from the macrocell base stations without requiring high capacity backhaul links for connecting the SBSs with the core network. However, the caching policy design is a challenging problem especially if one considers realistic parameters such as the bandwidth capacity constraints of the SBSs that can be reached in congested urban areas. We consider such a scenario and formulate the joint routing and caching problem aiming to maximize the fraction of content requests served locally by the deployed SBSs. This is an NP-hard problem and, hence, we cannot obtain an optimal solution. Thus, we present a novel reduction to a variant of the facility location problem, which allows us to exploit the rich literature of it, to establish algorithms with approximation guarantees for our problem. Although the reduction does not ensure tight enough bounds in general, extensive numerical results reveal a near-optimal performance that is even up to 38% better compared to conventional caching schemes using realistic system settings. <s> BIB005 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Information-Centric Networking (ICN) has a great potential to better support the content distribution over the future Internet. Meanwhile, users with mobile devices will also access ICN, introducing a new challenge to ICN providers to handle such mobile content requests. In this paper, a mobility and popularity-based caching strategy is proposed to increase the cache hit rate through WiFi while people are moving from one WiFi hotspot to another. It thus lowers the network traffic from the local ICN to the outside Internet. Specifically, a precise derivation on the content request rate is provided based on the content popularity and user mobility. A novel caching strategy is further developed based on this derivation for both the mobility-oblivious and mobility-aware scenarios. We evaluate different caching strategies with a trace-driven simulation and our new approach can achieve a 33.84% reduction on the network traffic when compared with the caching strategies only considering the content popularity. <s> BIB006 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> The demand for rich multimedia services over mobile networks has been soaring at a tremendous pace over recent years. However, due to the centralized architecture of current cellular networks, the wireless link capacity as well as the bandwidth of the radio access networks and the backhaul network cannot practically cope with the explosive growth in mobile traffic. Recently, we have observed the emergence of promising mobile content caching and delivery techniques, by which popular contents are cached in the intermediate servers (or middleboxes, gateways, or routers) so that demands from users for the same content can be accommodated easily without duplicate transmissions from remote servers; hence, redundant traffic can be significantly eliminated. In this article, we first study techniques related to caching in current mobile networks, and discuss potential techniques for caching in 5G mobile networks, including evolved packet core network caching and radio access network caching. A novel edge caching scheme based on the concept of content-centric networking or information-centric networking is proposed. Using trace-driven simulations, we evaluate the performance of the proposed scheme and validate the various advantages of the utilization of caching content in 5G mobile networks. Furthermore, we conclude the article by exploring new relevant opportunities and challenges. <s> BIB007 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> A mobile opportunistic social network (MOSN) is a new type of delay tolerant network (DTN), in which the mobile users contact each other opportunistically. While cooperative caching in the Internet has been studied extensively, cooperative caching in MOSNs is a considerably different and challenging problem due to the probabilistic nature of contact among the mobile users in MOSNs. In order to reduce the total access delay, we let the mobile users cooperatively cache these data items in their limited buffer space. We balance between selfishness (caching the data items according to its own preference) and unselfishness (helping other nodes to cache). The friends with higher contact frequency may share similar interests, hence, caching the data items for friend users can lead to some benefit. In this paper, we present a hierarchical cooperative caching scheme, which divides the buffer space into three components: self, friends, and strangers. In the self component, mobile users cache the data items according to their preference. In the friends component, mobile users help their friends to cache some data items. In the strangers component, mobile users randomly cache the remaining data items. We formally analyze the access delay of the proposed scheme. The effectiveness of our approach is verified through extensive real world trace-driven simulations. <s> BIB008 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Abstract The rapid growth of wireless data networks has introduced unprecedented traffic that far exceeds the deployment of cellular infrastructures. Caching has been a common approach for coping with the increased amount of traffic. In this paper we propose an in-network cache assisted eNodeB caching mechanism for 4G LTE Networks. The idea is to cache content objects at eNodeBs 1 and leverage in-network caches to improve eNodeB caching. We model the cost structure from both bandwidth and delay viewpoints and show that eNoodeB caching is noticeably beneficial. We propose a framework in which eNodeBs can use the information from in-network caches to improve caching performance. We formulate the problem of maximizing delay reduction and prove that the problem is NP-complete. We provide a 2-competitive offline algorithm and a practical online algorithm to solve the problem. We conduct trace-driven simulations and experiment under both synthetic and real network topologies. Results show that our approach can significantly save bandwidth for mobile operators and reduce delays for end users. <s> BIB009 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Wireless ad hoc networks (WAHNs) consist of autonomous nodes cooperating with each other to transmit/receive data over multiple-hops in the network. Caching is a useful mechanism to leverage this cooperation. Nodes with cached content can satisfy requests from other nodes, thus helping reduce network traffic and energy consumption, and improve latency. With the proliferation of wireless devices on the Internet and the proposal of a future Internet with emphasis on in-network caching, improvements in caching can significantly improve network response while reducing network load. In this paper, we present a holistic caching framework, Split-Cache, which enables a network node to account for the frequency of requests of data items and their presence in the network, and to leverage a split-cache (one part caches popular items and the other caches less popular items) to make caching and cache-eviction decisions. We performed exhaustive simulations to compare Split-Cache with the state-of-the-art: Split-Cache improved the cache request resolution time on an average by 30% (and as high as 72%), and required 15% less average traffic for resolving requests-large savings when considering large number of requests. <s> BIB010 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> High-quality multimedia streaming services in Vehicular Ad-hoc Networks (VANETs) are severely hindered by intermittent host connectivity issues. The Information Centric Networking (ICN) paradigm could help solving this issue thanks to its new networking primitives driven by content names rather than host addresses. This unique feature, in fact, enables native support to mobility, in-network caching, nomadic networking, multicast, and efficient content dissemination. In this paper, we focus on exploring the potential social cooperation among vehicles in highways. An ICN-based COoperative Caching solution, namely ICoC, is proposed to improve the quality of experience (QoE) of multimedia streaming services. In particular, ICoC leverages two novel social cooperation schemes, namely partner-assisted and courier-assisted, to enhance information-centric caching. To validate its effectiveness, extensive ns-3 simulations have been executed, showing that ICoC achieves a considerable improvement in terms of start-up delay and playback freezing with respect to a state-of-the-art solution based on probabilistic caching. <s> BIB011 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Due to the exponentially increasing demands for multimedia services over recent years, the growing network traffic load becomes a severe concern for the mobile network operators (MNOs). However, the wireless link capacity, the radio access networks, and MNOs' backhaul networks cannot deal with the traffic load effectively. To solve this problem, content caching is regarded as an effective emerging technique to reduce the duplicated transmissions of the content downloads demanded by mobile users and improve users' quality of service (QoS). Therefore, in this paper, we mainly focus on the cooperative cell caching for future mobile networks, where each cell (e.g., base station) can cache popular contents for improving QoS especially on the overall delay performance of users. The task is formulated as a problem of minimizing the expected overall user delay of accessing the demanded contents. Instead of rewriting it as a non-linear and non-convex problem based on an approximate transformation, we convert it to a linear programming problem by using a novel equivalent transformation. To solve the problem, rather than using the existing branchand-bound (BNB) method, which suffers from exponential-time and exponential-space complexity, we propose a new distributed suboptimal algorithm, which has polynomial-time and linearspace complexity. Numerical evaluation results demonstrate that our proposed cooperative cell caching framework can reduce the expected overall delay significantly. <s> BIB012 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Heterogeneous cellular networks (HCN) with embedded small cells are considered, where multiple mobile users wish to download network content of different popularity. By caching data into the small-cell base stations (SBS), we will design distributed caching optimization algorithms via belief propagation (BP) for minimizing the downloading latency. First, we derive the delay-minimization objective function (OF) and formulate an optimization problem. Then we develop a framework for modeling the underlying HCN topology with the aid of a factor graph. Furthermore, distributed BP algorithm is proposed based on the network's factor graph. Next, we prove that a fixed point of convergence exists for our distributed BP algorithm. In order to reduce the complexity of the BP, we propose a heuristic BP algorithm. Furthermore, we evaluate the average downloading performance of our HCN for different numbers and locations of the base stations (BS) and mobile users (MU), with the aid of stochastic geometry theory. By modeling the nodes distributions using a Poisson point process, we develop the expressions of the average factor graph degree distribution, as well as an upper bound of the outage probability for random caching schemes. We also improve the performance of random caching. Our simulations show that (1) the proposed distributed BP algorithm has a near-optimal delay performance, approaching that of the high-complexity exhaustive search method, (2) the modified BP offers a good delay performance at a low communication complexity, (3) both the average degree distribution and the outage upper bound analysis relying on stochastic geometry match well with our Monte-Carlo simulations, and (4) the optimization based on the upper bound provides both a better outage and a better delay performance than the benchmarks. <s> BIB013 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Future mobile communications face enormous challenges as traditional voice services are replaced with increasing mobile multimedia services. To address the vast data traffic volume and the requirement of user Quality of Experience (QoE) in the next generation mobile networks, it is imperative to develop efficient content distribution technique, aiming at significantly reducing redundant data transmissions and improving content delivery performance. On the other hand, cloud computing as a new content-centric paradigm is exploited to fulfil the multimedia requirements by provisioning data and computing resources on demand. In this paper, we propose a cooperative caching framework which implements State based Content Distribution (SCD) algorithm for future mobile networks. In our proposed framework, cloud service providers deploy a plurality of cloudlets in the network forming a Distributed Cloud Service Networks (DCSN). We formulate a content distribution optimization model, and data contents are distributed in local cloudlets according to the optimal solution to minimize redundant content transmissions. We use simulation experiments to validate the effectiveness of our proposed framework. Numerical results show that the proposed framework can significantly improve content cache hit rate, reduce content delivery latency and outbound traffic volume in comparison with known existing caching strategies. <s> BIB014 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Hash-routing is a well-known technique used in server-cluster environments to direct content requests to the responsible servers hosting the requested content. In this work, we look at hash-routing from a different angle and apply the technique to Information-Centric Networking (ICN) environments, where in-network content caches serve as temporary storage for content. In particular, edge-domain routers re-direct requests to in-network caches, more often than not off the shortest path, according to the hash-assignment function. Although the benefits of this off-path in-network caching scheme are significant (e.g., high cache hit rate with minimal co-ordination overhead), the basic scheme comes with disadvantages. That is, in case of very large domains the off-path detour of requests might increase latency to prohibitive levels. In order to deal with extensive detour delays, we investigate nodal/domain clustering techniques, according to which large domains are split in clusters, which in turn apply hash-routing in the subset of nodes of each cluster. We model and evaluate the behaviour of nodal clustering and report significant improvement in delivery latency, which comes at the cost of a slight decrease in cache hit rates (i.e., up to 50% improvement in delivery latency for less than 10% decrease in cache hit rate compared to the original hash-routing scheme applied in the whole domain). <s> BIB015 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> D2D offloading reduces the load of cellular network by asking mobile nodes to download content directly from storage of neighboring helpers via short range links. In this paper, we introduce a novel storage assignment scheme that can enhance storage utilization for D2D networks that have different types of storage nodes. Unlike traditional D2D systems that only use storage as static content cache, our scheme uses on-demand relaying to enhance storage utilization. Our on-demand relaying scheme replicates rare content when it is requested. Therefore, the proposed scheme can greatly increase the amount of content supported by the offloading system. We develop a convex optimization based algorithm to find the optimal storage assignment tradeoff between static caching and on-demand relaying. Numerical results and real-world trace-driven simulations show that our algorithm can achieve 30% reduction in offloading failure rate compared to static schemes. <s> BIB016 </s> Information-centric mobile caching network frameworks and caching optimization: a survey <s> User Centric Optimization based on caching networks <s> Recent explosive growth in computing and wireless communication technologies has led to an increasing interest in mobile ad hoc networks (MANET). Among the many challenges for MANET designers and users, data availability is a critical issue. Caching is considered as an effective solution for the availability problem. Although cooperative caching improves the data access by reducing access latency and bandwidth usage in MANETs, it still suffers from several hurdles and technical problems. This paper introduces a new cooperative caching strategy for MANETs, which is called Administrative Cluster-Based Cooperative Caching (ACCC). ACCC keeps at most two copies of the cached data items in each cluster. Moreover, it develops a new administrative module, which perfectly controls the caching process. ACCC is a cluster-based caching strategy, hence, it divides the network into a set of overlapping clusters. Each cluster is managed by a Cluster Manager (CM) as well as a Cluster Backup (CB). ACCC has several salient features that other techniques do not have such as: (i) the integration between CM and CB besides the integration among all the caching modules improves the data availability within the cluster, (ii) ACCC; maximizes the caching hit ratio, reduces access delay, and saves the battery power of network nodes. ACCC is simulated using Java Caching System JCS2 with the efficient platform Java Enterprise Edition EE8 using a client/server model. Experimental results have shown that ACCC outperforms recent cluster-based caching strategies as it introduces higher cache hit ratio as well as better data availability. <s> BIB017
In user centric optimization based on mobile caching networks, access delay, caching hit rate and caching failure probability are often chosen as significant metrics for optimization. The metric of delay is discussed using optimization theory in BIB015 BIB012 BIB004 BIB013 BIB014 and game theory in  . Minimizing caching failure probability or maximizing caching hit rate are formulated in  BIB005 BIB016 BIB006  . From the perspective of simulation, tracebased simulation is used to evaluate user experience delay in BIB007 BIB008 BIB009 , and discrete event-driven simulators are adopted to evaluate caching hit rate in BIB010 BIB002 BIB001 . In BIB012 , minimization of the expected sum user delay is addressed in mobile cellular network with cooperative cell caching strategies. The round-trip time is defined as user delay for obtaining a required content by a mobile user via the MNO networks. To solve the optimization problem, an equivalent transformation is provided which converts the problem into a linear programming optimization problem. A distributed suboptimal method is also presented which has polynomial-time and linearspace complexity to solve the problem based on the equivalent transformation. Jiang et al. propose a caching architecture where several local caches of distributed cloudlets work in a cooperative way to realize content sharing based on Distributed Cloud Service Network architecture BIB014 . The cooperative cloudlets which could be co-located with BSs form a cooperative caching domain in a region. The authors use content state which is determined by content requests, editorial updates and new arrivals to formulate a State based Content Distribution (SCD) framework. The optimization objective is to minimize the average total content delivery latency for all users in a cooperative caching domain to obtain content services. Software tools are used to solve the nonlinear integer 0-1 programing problem, and then the overall SCD algorithm for content distribution is proposed. Numerical results show that the proposed framework significantly improves content cache hit rate and reduces content delivery latency. A joint user clustering and caching scheme for wireless heterogeneous networks is presented which small-cell users have different preferences over different content types in BIB004 . Service delay experienced by UE to retrieve the requested content from BS is defined as the ratio between content size and downlink transmission rate from base station (MBS or SBSs) to user, and the caching optimization problem is formulated to minimize the total delay by finding the optimal caching strategy. To solve the problem in a decentralized manner, the problem is decoupled into two subproblems. Firstly, a clustering algorithm is proposed by grouping users into clusters based on their content request similarities. Secondly, a reinforcement learning algorithm based on the distributed regret learning approach is presented to minimize the delay within a specific SBS. The proposed algorithm outperforms random caching and learning without clustering schemes in terms of lower service delay due to the edge caching strategy which more popular contents are provided close to small cell UEs. In BIB013 , a distributed caching optimization algorithm based on belief propagation (BP) is designed for minimizing the downloading latency. The definition of delay of downloading a file in BIB013 is similar to service delay in BIB004 . A file placement matrix is used to minimize the average delay of downloading a file. In the BP algorithm, the factor graph is established based on the underlying HCN topology. The vertex set consists of factor nodes and variable nodes, and each factor node is related to a mobile user and each variable node is related to an SBS. The expressions of the average factor graph degree distribution and an upper bound of the outage probability for random caching schemes are derived. A heuristic BP algorithm is also proposed in order to reduce the complexity of the BP algorithm. In BIB015 , hash-routing and domain clustering techniques are applied to ICN environment of arbitrary topology, which aims to reduce the retrieval latency of ICN. In the network, when a request arrives, an edge router calculates the hash of the content identifier and forwards it to the responsible cache in the domain. The latency for the retrieval of content is formulated, which is pertinent to the caching capability of the domain, the efficiency of the used hash function and the size of the domain. To handle the retrieval delay, nodal/domain clustering techniques are investigated, including k-split clustering and k-medoids clustering. By partitioning the domain into clusters/sub-domains based on a hybrid similarity metric which captures the topological distance and the pairwise Euclidean distance of the content popularity at each node of the network, and then using hashrouting in the subset of nodes of each cluster, the average retrieval latency of a content is reduced while keeping a large cache hit ratio. In BIB016 , a joint caching assignment is addressed in a hybrid network based on cellular network and D2D. Seeds and relays are helpers to contribute their caches as content caches and allow other nodes to download content from them through D2D links. Seeds are those stable content caches which serve for all requests to a given content. The system allocates a certain number of seeds for each piece of content to ensure the availability of content. Relays are temporary caches allocated to a specific request, which are selected according to the information of the given request to enhance storage utility. The content cached in relays may dynamically change due to arrival or completion of relaying requests. The problem is then formulated to jointly optimize the cache assigned to seeds and relays so that the overall offloading failure probability is minimized for contents with different request rates. The results show that the static system can only offload a constant amount of contents while in the relaying case, the amount of contents increases with the number of helpers. In the case where subscribers have less than 10 friends, the relay system can support 10 times more contents than the static caching system. In  , a heuristic cache management scheme for energy efficiency of ICN in wireless content dissemination is addressed. In the system, A receiver-driven chunkbased ICN enabled with the edge caching of infrastructural mobile networks is considered, where the contents are identified and stored as uniquely identifiable chunks (segments). These chunks are transported at chunk level with built-in network storage for caching. An energy consumption model and reward structure is proposed, and the caching replacement problem is formulated as the maximization of the reward, which the expected reward of caching an item in a single of AP (i.e. AP 0 ) is the expected avoidance of energy consumption for fetching the item from any of the network nodes other than AP 0 minus the cost of having and fetching that chunk locally in AP 0 . In order to reduce the complexity of solving the problem, a greedy heuristic algorithm called energy aware caching for wireless ICN (ENACI) is presented for cache management which incorporates energy reward, popularity, TTL and delay (namely chunk loss due to delay sensitivity). The performance and low-complexity of ENACI is evaluated compared to the LRU algorithm. In  , the optimization of caching networks is investigated by considering a real network and a virtual network based on an Online Social Network, in which the real network consists of a set of UEs, SBSs, Service Provider Servers (SPSs), radio links which connect UEs to SBSs and backhaul links which connect SBSs to SPSs. Through the Online Social Network, UEs can communicate and share information with their friends. A SPS decides to cache a video in a number of SBSs originating from different SPSs, therefore the matching of SPSs to SBSs is needed. The caching problem is formulated as a many-to-many matching game between small base stations and service providers' servers in order to offer the smallest download time for end-users. A new matching algorithm is proposed and it can reach a pairwise stable outcome. The satisfaction of requests by the small base stations can reach up to three times of that comparing to a random caching policy, and the experienced delay by the end-users is reduced significantly since a set of videos are cached at the SBSs and user requests are satisfied mostly from SBSs instead of SPSs. In  , a proactive caching algorithm called PropCaching (proactive popularity caching) is presented to maximize the satisfaction ratio under resource constraints. In the caching system, a central scheduler is designed to collect statistics on the popularity of requested files in small cell networks and a set of small cells are deployed with high capacity storage units and limited capacity backhaul links. The satisfaction ratio is defined as the ratio of the satisfied requests over the total requests. Since not all requested files can be cached due to storage constraints, the PropCaching algorithm chooses to store the files with the highest popularities until the storage capacity of small cells are achieved. The results show that PropCaching outperforms random caching in most cases. In BIB005 , the optimal caching policy is introduced in the cellular networks enhanced with backhaul-constrained SBSs. Supposing that user requests are unsplittable which implies that each request is entirely satisfied by a base station, the joint routing and caching policy for unsplittable requests is then formulated as an NP-hard problem which minimizes the requests routed to the MBS (maximize the fraction of content requests served locally by the deployed SBSs). A novel reduction to a variant of the facility location problem is presented which enables the derivation of a set of polynomial time algorithms with approximation guarantees. The proposed scheme outperforms typical greedy algorithms up to 38%. In BIB006 , a mobility and popularity-based caching strategy named MPCS is proposed to increase cache hit rate through Wi-Fi when users are moving from one Wi-Fi hotspot to another. The system model is an ICN composed of multiple sites/clusters which are able to cache popular contents, and centralized servers provide a full source of requested contents from the outside network. Mobility-aware caching policy is presented which takes user mobility into account. Content request rate considering user mobility on the content popularity at different ICN sites is derived, and integer linear programming problems are formed to maximize total cache hit rate in any site for mobility-aware caching scheme. In  , an optimization problem is addressed which aims to determine the optimum caching probability for each content in order to minimize the average caching failure probability in a mobile content delivery network supporting D2D. Mobile devices are designed as caching severs (caching-sever device: CSD), which can provide user devices in the proximity with some contents that they request via D2D communication in order to reduce the traffic load of backbone network. A low-complexity solution approach called optimum dual-solution searching algorithm is proposed to solve the optimization problem with limited storage of mobile CSDs. The results show that the optimal caching policy is caching those less popular contents with some given probabilities while caching more popular contents with a higher probability. Besides analytical modeling, simulation are used to verify the performance optimization for the proposed caching policies or frameworks. Discrete event-driven simulator is used in BIB010 BIB002 BIB011 BIB001 , and trace-based simulation is performed in BIB007 BIB008 BIB003 BIB009 . In BIB010 , a holistic caching framework called SplitCache is presented and evaluated in multi-hop wireless network, in which cache C is splitted into two parts C1 and C2 for popular and less popular items. Cacheeviction decisions are made for C1 and C2 respectively. Split-Cache is evaluated by NS-2 simulator compared with other two replacement policies. The results show that Split-Cache provides higher request satisfaction ratio and less query-solving time both in static and mobile scenarios. In BIB002 , an interest-based caching insertion policy is proposed based on the concept of social-distance. The main idea is to store only those contents which appear to be of interest for local users. A simulator is developed in Omnet++ to evaluate the performance of the proposed interest-based caching policy, which has superior performance on cache hit probability and access delay (hops to retrieve the contents) compared with no-cache, probability-cache and all-cache policies. In BIB001 , a popularity-based and collaborative caching scheme called WAVE is proposed in content-oriented networks. A discrete event-driven simulator GT-ITM is used to evaluate the cache hit ratio of the caching scheme. In BIB007 , several caching techniques are evaluated including no caching, EPC caching, RAN caching, EPC + RAN caching and CCN-based caching. CCN-based caching exhibits best on the performance of user content access delay. In BIB008 , a hierarchical cooperative caching scheme is presented in a mobile opportunistic social network. The cache of the mobile users is divided into three hierarchical components: self, friends, and strangers. Access delay and successful ratio are evaluated. The results show that the proposed caching scheme performs better compared to the performance of random cache, selfish cache and unselfish cache policies. In BIB017 , a cluster-based cooperative caching strategy called ACCC is proposed for MANETs. A new administrative module is developed in ACCC to control the caching process. The network is divided into a set of overlapping clusters, and each cluster is managed by a Cluster Manager as well as a ClusterBackup. By using Java Caching System JCS2 with platform Java Enterprise EditionEE8 and client/server model, ACCC is simulated and experimental results show that it outperforms recent cluster-based caching strategies as it introduces higher cache hit ratio as well as better data availability. Based on the highway VANET scenario by using ad hoc Wi-Fi 802.11a, two social cooperation schemes are presented in BIB011 to maximize video playback quality without excessive startup delay and minimize the playback freezing ratio, one is the partner-assisted cooperation caching scheme which is based on cooperative video segment caching among neighbor vehicles, the other is the courier-assisted cooperation scheme which aims to enlarge the searching range of each Interest among vehicles in different lanes and enhance distributing the Interest packets along the road so as to promote content discovery. Extensive simulations have been executed by NS3, and a considerable improvement in terms of start-up delay and playback freezing is evaluated compared with probabilistic caching. In BIB003 , a mobile video-centric proxy cache named iProxy is designed in cellular network for mobile video providers, and an Info-aware Cache Replacement policy called LFU-based IBR-score is provided and evaluated. Information-bound references (IBRs) is used to map multiple URLs to one IBR value (associates with a single video file) in order to collapse multiple related cache entries into a single one. The cache replacement policy depends on the IBR scores. The optimization metrics are chosen as buffering, bit rate, and start up delay. The evaluation of iProxy design relies on two sets of real traffic traces, one is the Web video data set, and the other is collected over the University of Wisconsin's Wireless Network. The results show that iProxy with information-centric replacement policies can improve video start time (by up to 13 s), buffering rates and average bit rates (by 16%). In BIB009 , an in-network cache assisted eNodeB caching mechanism called InCan is presented for 4G LTE Networks, which aims to cache content objects at eNodeBs, save bandwidth for mobile operators and reduce delay for end users. InCan adopts a loosely collaborative approach between eNodeBs and routers rather than the full collaboration in traditional hierarchical caching systems. The cost structure considering both bandwidth and delay is modeled, and a framework is proposed in which eNodeBs can use the information from innetwork caches to improve caching performance. The problem is then formulated to maximize delay reduction and it is a NP-complete problem. A 2-competitive offline algorithm and a practical online algorithm are provided to solve the problem. By trace-driven simulations and experiments under both synthetic and real network topologies, the mechanism is evaluated and the results show that the proposed approach can significantly save bandwidth for mobile operators and reduce delay for end users. From all the issues surveyed above, optimization of information-centric mobile caching networks can be classified by optimization goal, network architecture, optimization objective and research method. Table 4 gives a summary of the optimization on informationcentric mobile caching networks.