Performance Analysis And Interference Cancellation In Wireless Cache-Enabled Stochastic Networks

In regard to the network service type,content-centric services(e.g.,multimedia transmission)rather than connection-centric services(e.g.,voice communication)contribute to the majority of the current and future network traffic.The content-centric services are characterized by diversity,agglomeration and convergence.Therefore,the traditional “End-to-End” communication mode leads to serious redundant transmission of contents in the network nowadays.In regard to the wireless network topology,one widely regarded as the cornerstone technology is ultra-dense node deployment.The current and future wireless networks are characterized by high-density,randomness and heterogeneity.Interference and wired backhaul bottleneck are key limitations on wireless networks.The content-aware wireless caching exploiting the characteristics of multimedia services can release the burden of wired backhaul and mitigate the over-the-air traffic,promoting the deep integration of ICT.The paper is dedicated to answering the following questions 1)How much performance improvement actually can be reaped via the caching technology in the stochastic network,2)How to combine caching with traditional interference management techniques in the stochastic network,3)How to design a universal scheme of coded caching and information transmission for the stochastic network with dynamic traffic.The main work and contributions can be summarized as follows,Firstly,a content-centric transmission protocol in a three-tier stochastic and heterogeneous network(HetNet)is proposed for the problem of high load and redundant content transmission.The traffic offloading via caching is evaluated,and the network performance,e.g.,throughput gain,is analyzed.Compared with previous works considering static network topology and ideal assumptions,the paper is the first that models the topology of wireless cache-enabled network with Poisson Point Processes(PPPs)of stochastic geometric theory.It reveals the influence of randomness of network node locations,randomness of node density,randomness of channels,and randomness of content requests on the performance of wireless cache-enabled network.Based on the requested content and the associated network layer,users in the stochastic network are classified into different classes,and the traffic offloading probability via caching is obtained.From the perspective of user,the average transmission rates and the outage probabilities of different classes of users are then theoretically analyzed.Furthermore,from the perspective of network,the throughput gain,transmission delay,and maximum allowable traffic of the HetNet are investigated.Moreover,impacts of some key network characteristics,e.g.,caching space,node densities and content popularity,on the system performance are elaborated.Secondly,aiming at the problem of interference management in wireless stochastic networks,the paper proposes an interference cancellation mechanism based on caching at receivers,evaluates and optimizes the proposed mechanism to improve the performance in terms of packet loss rate(PLR),and solves the problem of modeling of cell load in a stochastic network with dynamic traffic.Compared with previous works where caching is for traffic offloading,the paper is the first proposes the mechanism of reconstructing and cancelling the interference in unicast transmission by exploiting both the cached side information at receiver and the interference channel state information(ICSI).Compared with previous works which use stochastic geometric theory and yet assume that cells are always fully loaded,the paper considers the dynamics of network traffic.Probabilities of full-,free-,and modest-load cells are elaborated,based on which a more accurate interference model is established.Furthermore,the influences of the content placement strategy,the ICSI,caching space,content popularity,user request rate,etc.,on the PLR are analyzed.The content placement strategy in decentralized caching network is optimized to reap both the traffic offloading gain and the interference cancellation gain.Thirdly,for the problem of concurrent interference of multi-user superposition transmission(MUST)in the stochastic network,we propose,analyze and optimize the joint scheme of cache-assisted interference cancellation(CAIC)and successive interference cancellation(SIC)at users.The spectrum efficiency(SE)and the area spectrum efficiency(ASE)are improved.The paper is the first that proposes the joint interference cancellation scheme of CAIC and SIC for multi-user superposition transmission.The average successful transmission probability is analyzed from the user's point of view,and the optimization issues of power allocation and base station density are established from the perspective of network to improve the average SE and the average ASE.In addition,the corresponding necessary condition is provided so that the average successful transmission probability of each user exceeds a specified threshold,and the SE is optimized under this condition.At the same time,the problem of maximizing the minimum average transmission probability of users is considered to ensure fairness among users.Finally,for the problem of how to apply the existing coded caching to the large-scale stochastic network with multicast and dynamic traffic,the inter-group coded caching and multicast transmission mechanism is proposed,analyzed and optimized,yielding the improvement of the network throughput per unit area.The paper is the first to design the transmission mechanism of inter-group coded caching and the inter-group multicast for a large-scale stochastic network with dynamic traffic.Grouping in the user dimension,the inter-group coded caching is proposed.The content library is grouped in the information dimension,and the dynamically arrived user requests are divided into different request queues according to the different sub-libraries in which the desired contents belong to.Inter-group superimposed multicast is performed at the base station via each subchannel for the request queues of different user groups.The inter-and intra-cell interference are modeled,based on which the average successful probability for the user to recover its requested packet based on the cached packets and the multicast message is analyzed.Moreover,the upper and lower bounds of the average successful probability are obtained when both inter-and intra-group multicast are performed.