Research On Analysis And Provisioning Of Latency And Reliability In Wireless Communications Systems

In 5G/B5 G wireless communications networks,the burgeoning services of different scenarios are emerging,which demand personalized reliability guarantee.The reliability with the latency constraint,which is the probability that the latency is lower than the latency threshold,has received extensive attention as an important indicator to measure network performance.It can guide network control and affect user experience.The issue of statistical latency reliability provisioning must be faced for mature 5G/B5 G networks.Reasonable bandwidth allocation is the necessary and sufficient condition for reliability guarantee.Under the millisecond-level latency constraint,the provisioning of strict reliability demands the large bandwidth.The precise estimation and abstraction of bandwidth requirement determines the efficient resource allocation.In the packet switching mode,the emerging services desire end-to-end(E2E)latency reliability provisioning.The bottleneck is how to decouple the relation between the statistical E2 E latency reliability requirement and the service demands of each node in the tandem system,so as to harmonize the wireless access node and multiple core network nodes for the ultimate E2 E reliability guarantee.An accurate analysis framework of network latency reliability is vital for mapping statistical reliability requirement to the bandwidth demand and guiding resource allocation.The latency performance of the wireless access network subjects to the bursty random characteristics of the traffic,the fading characteristics of the wireless channel,and the complex access mechanisms of the access node.The latency performance of the core network depends on the service capability of function nodes and the forwarding mechanisms of networking nodes.Network latency is the product of highly coupled random processes with complex and heterogeneous properties.The existing Qo S(Quality of Service)framework has mathematical barriers,and it is difficult to provide an accurate latency performance analysis method.The conservative estimations of arrival,service envelope curves,and flow approximation treatments lead to loose theoretical upper bounds of latency unreliability.And for the complex network scenarios,rarely researches have focused on the accurate analysis and guarantee of E2 E latency reliability so far.We devote to explore the novel theory of network latency performance analysis.Based on martingale theory and Lyapunov theory and so on,we study the methods of statistical latency reliability guarantee with martingale frameworks and research new algorithms.For the services with the E2 E latency reliability requirement,a groundbreaking reliability analysis framework regard to E2 E latency is proposed.Bandwidth abstraction and E2 E network slice customization are researched innovatively.For the queuing system with aggregate traffic arrival,considering the heterogeneity and bursty arrival characteristics among flows,we study a precise analysis method of latency unreliability for the aggregate traffic based on supermartingale theory and stopping time theory.For the tactile services with the closed-loop latency reliability requirement,an analysis framework of closed-loop latency reliability is proposed leveraging martingale construction.A bandwidth abstraction and service rate instantiation scheme is designed.The main contributions of this work are as follows.(1)To guarantee the E2 E latency reliability of services,we propose a martingale-based analysis framework of E2 E latency reliability for a tandem queuing system,where services provided by wireless nodes and networking nodes are heterogeneous.The Wald martingales of the arrival process and service processes are constructed.A martingale parameter,named as tandem service descriptor,is proposed to characterize the synergy of tandem heterogeneous services for a specific arrival flow.It solves the problem of inability to measure the service capacity of the tandem queuing system.We evaluate the allowed maximum average arrival rate of the E2 E traffic and the demanded minimum average service rate of each node in the martingale domain.Based on it,the arrival bias and service bias are defined,which enable to capture the statistical properties of non-stationary accumulated arrivals and accumulated service processes respectively relying on Doob maximum inequality.The complementary cumulative distribution function of E2 E latency is obtained with the aiding of moment generating function.The bandwidth abstraction and E2 E slice customization algorithm is designed based on the martingale framework for the first time.Packet duplication and hot-backup transmission pattern is adopted for network reliability enhancement.For the parallel transmission system consisting of multiple E2 E links,a reliability decomposition and bandwidth abstraction(RD-BA)algorithm is proposed,which decomposes the E2 E latency reliability requirement and defines the reliability target of each E2 E link.Bandwidth abstraction facilitates to map the E2 E reliability provisioning as the desired bandwidth of each involved node.In the wireless access network slice instantiation,a long-term stochastic optimization problem subject to abstracted bandwidth is formulated,and is transformed to mathematically tractable forms by Lyapunov Drift and Penalty framework.Through user scheduling and power allocation in small time scale,statistical reliability provisioning is achieved.In the core network slice instantiation,the service rates of the networking nodes are determined,where the high forwarding probability is provided for the E2 E traffic.Simulation results verify the effectiveness of the E2 E slice customization strategy proposed in this paper.(2)For a queuing system with aggregate arrivals and a single service,a precise martingale-based analysis framework of latency reliability is proposed.The aggregate flows with homogeneous reliability requirements and heterogeneous arrival characteristics are considered.To highlight the burstiness,heterogeneity and batch arrival features,a novel model,MMMP-4(Four-state Markov Modulated Multinomial Process)is proposed to describe the interweaved and mixed arrival behaviour of two flows.The data service flow is modeled as an IMP(Interrupted Multinomial Process),which depicts the sporadic arrival and discontinuity of packets.Based on supermartingale theory,the arrival martingale of Markov modulated arrival processes is constructed.The corresponding complex martingale parameters are determined.Based on the multiplicative property of independent supermartingale processes,the backlog martingale is defined,which achieves the modeling of buffer behaviour in the queuing system with aggregate traffic.The particular event where the queuing length exceeds the threshold is regarded as a stopping event.Leveraging the stopping time theory of martingale,we derive the queue overflow probability and latency violation probability of aggregate traffic.From the perspective of martingales,the latency unreliability of aggregate traffic is analyzed precisely.The simulation results show that the latency performance of the system is very sensitive to the burstiness of aggregate traffic.(3)For the tactile services with the closed-loop latency reliability requirement,we study the analysis method of closed-loop latency performance in the martingale domain novelty,and design the algorithm of reliability guarantee.Based on martingale theory,a backlog martingale process is constructed for the downlink queuing system by considering the burtiness of tactile services.The martingale parameters are determined.A stopping time event that considers uplink and downlink jointly is defined,which can reflect the correlation between uplink and downlink latency under the closed-loop latency threshold constraint.And the uplink latency is combined into the analysis of the downlink queuing system,which enables the performance evaluation of closed-loop latency.Renting stopping time theory,a tight latency unreliability bound of downlink is derived,which can be regarded as the analysis of the closed-loop latency unreliability.Subject to the closed-loop latency reliability requirement,an algorithm of downlink bandwidth abstraction and service rate instantiation is designed innovatively.Considering the complex features of the tactile traffic and the dynamic effect of uplink latency,we achieve the mapping of the statistical closed-loop latency reliability requirement to the downlink demanded bandwidth.Under the abstracted bandwidth constraint,RRHs(Remote Radio Heads)are activated dynamically so that the demanded service rate can be provisioned to meet the closed-loop latency reliability requirement.The tactile slice customization is achieved.Simulation results verify that the bandwidth abstraction and service rate instantiation algorithm proposed in this paper can guarantee the closed-loop latency reliability.