Zijie Zheng

Game theoretic approaches for wireless proactive caching

Recently proposed wireless proactive caching has opened up a promising avenue for reducing the redundant traffic load of the future wireless network. In addition to infrastructure updating, caching schemes for different wireless caching scenarios are also essential problems of concern. Along with the benefits brought by proactive caching, the cost of proactive caching should also be taken into account, since caching schemes can be influenced by different interest relevant parties in wireless networks. In this article, we discuss several typical caching scenarios and apply corresponding game theoretical models to illustrate how the selfishness of different parties may influence the overall wireless proactive caching. Efficient caching strategies can be designed by carefully considering the relations and interactions among these parties by using game theory. We also outline possible future research directions in this emerging area.

Resource Allocation in Wireless Powered Relay Networks: A Bargaining Game Approach

Information and power transfer in mobile relay networks have recently emerged simultaneously, where the relay can harvest the radio frequency (RF) energy and then use this energy for data forwarding and system operation. Most of the previous works do not consider that the relay may have its own objectives, such as using the harvested energy for its own transmission instead of maximizing transmission of the network. Therefore, in this paper, we propose a Nash bargaining approach to balance the information transmission efficiency of source–destination pairs and the harvested energy of the relay in a wireless powered relay network with multiple source–destination pairs and one relay. We analyze and prove that the Nash bargaining problem has several desirable properties such as the discreteness and quasi-concavity, when it is decomposed into three subproblems: the energy transmission power optimization, the power control for data transmission, and the time division between energy transmission and data transmission. Based on the theoretical analysis, we propose an alternating power control and time-division algorithm to find a suboptimal solution. Simulation results clearly show and demonstrate the properties of the problem and the convergence of our algorithm.

Social-aware multi-file dissemination in Device-to-Device overlay networks

Multi-File dissemination through wireless communication has attracted considerable attentions in recent years, especially when Device-to-Device (D2D) communication is developed to support peer-to-peer file transmission. To decrease the total delay, the authors in proposed a cluster-based D2D network in which files are transmitted from the BS to several cluster-heads, and then shared inside each cluster through D2D communication. Distributed caching is another option to enhance the transmission rate by precaching files to users, with which mobile users with the same interest can share files directly through D2D communication. However, most of the current studies on D2D-based file sharing schemes typically assume that all users are separated in non-overlapping communities that each user can only select one sort of files, and ignore the social relations among mobile users. When considering heterogeneous but overlapping interests of users, how to utilize social ties for multi-file sharing with minimum delay is still a challenging problem. To this end, we propose a graph based social aware algorithm in which cellular links and D2D links are established according to social ties and social contributions of users for efficient multi-file dissemination.

Caching as a Service: Small-Cell Caching Mechanism Design for Service Providers

Wireless network virtualization has been well recognized as a way to improve the flexibility of wireless networks by decoupling the functionality of the system and implementing infrastructure and spectrum as services. Recent studies have shown that caching provides a better performance to serve the content requests from mobile users. In this paper, we propose that caching can be applied as a service in mobile networks, i.e., different service providers (SPs) cache their contents in the storage of wireless facilities that are owned by mobile network operators. Specifically, we focus on the scenario of small-cell networks, where cache-enabled small-cell base stations are the facilities to cache contents. To deal with the competition for storage among multiple SPs, we design a mechanism based on multi-object auctions, where the time-dependent feature of system parameters and the frequency of content replacement are both taken into account. Simulation results show that our solution leads to a satisfactory outcome.

Real-Time Profiling of Fine-Grained Air Quality Index Distribution Using UAV Sensing

Given significant air pollution problems, air quality index (AQI) monitoring has recently received increasing attention. In this paper, we design a mobile AQI monitoring system boarded on the unmanned-aerial-vehicles, called ARMS, to efficiently build fine-grained AQI maps in real-time. Specifically, we first propose the Gaussian plume model on the basis of the neural network (GPM-NN), to physically characterize the particle dispersion in the air. Based on GPM-NN, we propose a battery efficient and adaptive monitoring algorithm to monitor AQI at the selected locations and construct an accurate AQI map with the sensed data. The proposed adaptive monitoring algorithm is evaluated in two typical scenarios, a 2-D open space like a roadside park, and a 3-D space like a courtyard inside a building. The experimental results demonstrate that our system can provide higher prediction accuracy of AQI with GPM-NN than other existing models, while greatly reducing the power consumption with the adaptive monitoring algorithm.

Poster: Roadside Unit Caching Mechanism for Multi-Service Providers

Roadside units (RSUs) with caching abilities are becoming an important part for the future transportation system, enabling both Internet accesses and local caching services for vehicular users. In this paper, we address the caching problem which involves the coexistence of multiple service providers who intend to cache their own contents into the RSUs by competitions to improve the data disseminations. And we propose a mechanism based on multi-object auctions, which can achieve a sub-optimal outcome. Simulation results also show the effectiveness of our solution.

Hybrid cooperation for machine-to-machine data collection in hierarchical smart building networks

Machine-to-machine (M2M) communication plays an important role in various kinds of intelligent networks. In this study, a hybrid cooperation scheme for data collection in hierarchical smart building networks (SBN) is proposed under the framework of M2M communications. The hierarchical network structure means that the data collection process is carried out via multi-layer communications. In the first layer, smart metres organise themselves into clusters and send information to the cluster-heads. Then all cluster-heads forward the received information to the base station automatically in the second layer. In particular, the roles of cluster-head can be acted by either fixed nodes or user terminals in the building, and this endow a hybrid cooperation mode to the data collection process. To construct the network structure and utilise the resources efficiently, the authors first provide some theoretical analysis on the influence of network structure and bandwidth constraints. Then a distributed scheme for joint structure formation and subband allocation is proposed based on coalitional game theory. Furthermore, for the feasibility of this scheme in practical applications, some improvements of the proposed scheme have also been made at last. The advantages of the proposed scheme are verified by simulation results.

Roadside Unit Caching: Auction-Based Storage Allocation for Multiple Content Providers

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.

Resource allocation in wireless powered relay networks through a nash bargaining game

Simultaneously information and power transfer in mobile relay networks have recently emerged, where relays can harvest the radio frequency (RF) energy and then use this energy for data forwarding and system operation. However, most of the previous works do not consider that relays may have their own objectives, such as harvesting more residual energy for maximizing its own data transmission instead of reaching a single goal of the network. Therefore, in this paper, we propose a Nash bargaining approach to balance the information transmission efficiency of source-to-destination pairs and the residual harvested energy of relays. We theoretically analyze and prove that this Nash bargaining problem has several desirable properties such as the quasi-concavity when it is decomposed into three sub-problems: energy harvesting power optimization, time division between information transmission and energy harvesting, and the power control for information transmission. Based on the theoretical analysis, we propose an alternating power control and time division scheme to find a sub-optimal solution. Simulation results clearly show and demonstrate the properties of the problem and the convergence of our algorithm.

Efficient resource optimization for heterogeneous smart-building networks

Smart meters aided by wireless communications have been widely used to collect the information of the electrical appliances. In this paper, we consider a two-layer heterogeneous smart building network, consisting of a number of cluster-organized smart meters, and a base station (BS). The communication takes two phase: 1) periodical data collection via cluster heads in the first layer, and 2) data transmission from the cluster heads to the BS in the second layer. But, due to the irregular topology of smart meter networks and various types of data traffic of electrical appliances, the data aggregation to the heads and associated spectrum allocation become quite challenging. To solve these problems, we first analyze the relationship between the system performance and the cost of network construction. By using coalition formation game theory, we propose a practical strategy in optimizing channel allocation and cluster-heads deployment. The proposed algorithms are verified through computer simulations.