Rong Chai

Optimal joint utility based load balancing algorithm for heterogeneous wireless networks

The rapid development of mobile broadband services with continuously increasing traffic volumes has resulted in a number of challenges, including ubiquitous network coverage, high bandwidth, and reliable services for reasonable price, etc. To address these challenges, evolved packet system (EPS) is proposed as the evolution of the packet core network. While resource management and load balancing issues in EPS are discussed in 3GPP standardization, relatively few research works consider mechanism design for load information monitoring and evaluation. Furthermore, even though some load balancing algorithms have been proposed for integrated networks, the load balancing scheme design which achieves the optimization of joint system performance has not been extensively studied. In this paper, an inter-access system anchor based load balancing mechanism is introduced which performs load monitoring and evaluation for access gateways and networks, and an optimal load balancing algorithm is proposed for heterogeneous integrated networks. To characterize the performance of integrated networks, the concept of utility function is introduced and the comprehensive performance of integrated networks which support both single type service and multimedia service is modeled mathematically. Applying vertical handoff as an efficient mechanism for achieving load balancing, the optimal number of handoff users is obtained through solving the optimization problem. Numerical results demonstrate that load balancing between access networks can be achieved, and the optimal number of handoff users corresponding to the maximal joint network utility can be obtained.

An optimal IASA load balancing scheme in heterogeneous wireless networks

The mobile broadband revolution with its rapidly increasing traffic volumes has resulted in a number of challenges, including ubiquitous network coverage, high bandwidth, and reliable services for reasonable price, etc‥ To address these challenges, the Evolved Packet System is proposed as the evolution of the packet core network. While resource management and load balancing issue in Evolved Packet System (EPS) is mentioned in standard, relatively little discussions focus on the scheme design for load information monitoring and evaluation. Furthermore, as the system utility is one of the major considerations for system service provider, how to design the load balancing algorithm to maximize the joint system utility in the integration scenario of multiple access gateways and heterogeneous access networks is an important issue worthy of study. In this paper, an IASA load balancing mechanism is proposed which performs load status monitoring and evaluation for access gateways and heterogeneous networks and an optimal load balancing algorithm to maximize the joint utility of integrated heterogeneous networks is also proposed. The system utilities of access networks are modeled mathematically and the optimal handoff user number is obtained through solving the optimization problem. Numerical results demonstrate the network utility varying with the number of users in it, and the optimal handoff user number can be obtained corresponding to the maximum of the joint network utility.

Work in progress paper: Utility based clustering algorithm for VANET

Clustering is expected to be one of the most efficient and promising solutions for data transmission in Vehicular Ad hoc NETworks (VANET). The particular characteristics of VANET, including highly dynamic network topology, unstable transmission channel, and various service requirements, pose challenges and difficulties on clustering algorithm design. In this paper, a clustering algorithm based on utility function is proposed for VANET. The utility function of vehicles is formulated which jointly considers current state of vehicles characterized by the vehicle degree, relative velocity and position between adjacent vehicles, and long-term transmission performance of vehicles, defined as credit history function, which is characterized by the average available bandwidth, queue length and the duration for being a cluster head (CH) in a past period. The process of cluster forming is presented, and the vehicles with large utility function are selected as CHs successively. Numerical simulations demonstrate that comparing to previously proposed algorithms, the proposed algorithm offers better performance in terms of packet delivery rate, average transmission delay and total throughput.

Energy consumption optimization based joint routing and flow allocation algorithm for software defined networking

Software-defined networking (SDN) is expected to dramatically simplify network control processes, enable the convenient deployment of sophisticated networking functions, and support user applications with guaranteed quality of service (QoS). To achieve data packet transmission between two non-adjacent switches in SDN, an efficient route selection algorithm should be designed. In this paper, we consider the data transmission of multiple user flows over SDN. Under the assumption that flow splits at intermediate switches are allowed, we jointly study the route selection and flow allocation problem. To stress the problem of resource competition among various user flows, we apply network virtualization technology and propose a virtual network architecture based on the design of an optimal joint route selection and flow allocation algorithm. Jointly considering the transmission performance of multiple user flows and stressing the importance of energy consumption at transmission links and switches, we formulate the total energy consumption of user flows and design an optimization problem that minimizes the energy consumption, subject to data transmission and service requirement constraints of the flows. Because the formulated optimization problem is an NP-complete problem that cannot be conveniently solved, we transform it into a minimum-cost commodity flow problem and solve the problem by using an N-algorithm. Numerical results demonstrate the effectiveness of the proposed algorithm.

Energy efficient joint subchannel selection and resource allocation for heterogeneous CRNs

Cognitive radio networks (CRNs) are expected to improve spectrum utilization significantly by allowing secondary users (SUs) to opportunistically access the licensed spectrum of primary users (PUs). In a CRN scenario consisting of multiple heterogeneously integrated CRNs, the SUs with multiple interfaces may have to conduct spectrum handoff to target subchannels. Jointly considering the interruption delay and the transmission performance of the handoff SUs on target subchannels, the subchannel selection and resource allocation optimization problem which maximizes the energy efficiency of all the interrupted SUs under the quality of service (QoS) constraints is formulated and solved through applying iterative algorithm and Lagrange dual method. Numerical results demonstrate the efficiency of the proposed scheme.

A joint utility optimization based virtual AP and network slice selection scheme for SDWNs

The proliferation of mobile demands and increasingly multifarious services pose challenges to both the radio access networks (RANs) and the core network (CN). Unfortunately, the traditional networks can hardly meet the increasing requirements. Software-defined network (SDN) and network virtualization (NV) are considered as innovative paradigms to stress these problems. By extending SDN to wireless networks, software-defined wireless network (SDWN) consisting of both RANs and CN can be obtained. In this paper, the RANs and CN of SDWN are virtualized to virtual access points (VAPs) and network slices respectively based on NV technology. Considering the system scenario that a SDWN consists of overlapping RANs, an optimal joint VAP and network slice selection scheme is proposed. To characterize the complicated transmission performance of VAPs and network slices, the concepts of utility function and network calculus are introduced, and the joint utility of VAPs and network slices is formulated based on which the optimal VAP and network slice combination corresponding to the maximal joint utility can be selected. The simulation results demonstrate the efficiency of the proposed scheme.

Energy efficiency optimization based joint relay selection and resource allocation for SWIPT relay networks

In this paper, a joint relay selection and resource allocation scheme is proposed for simultaneous wireless information and power transfer (SWIPT) relay networks with multiple Source nodes (SNs) and Destination nodes (DNs) pairs and energy harvesting Relay nodes (RNs). The transmit power, subchannel, power splitting ratio allocation for SNs/RNs and the relay selection scheme strategy are jointly optimized to maximize the total energy efficiency of all the SNs and RNs. The optimization problem is transformed equivalently into two subproblems, i.e., transmit power and power splitting ratio optimization subproblem of one SN-RN-DN path and the optimal relay and subchannel allocation subproblem. By applying iterative algorithm and Lagrange dual method, the optimal relay selection and resource allocation strategy are obtained. Simulation results demonstrate the efficiency of the proposed scheme.

An improved cross-layer RSU/mobile relay selection scheme in VANET

In Vehicular Ad hoc Network (VANET), the communication modes, i.e., vehicle to vehicle, vehicle to infrastructure, and hybrid communication are expected to be supported. In the case that the communication link between a vehicle and the infrastructure is inaccessible, both the fixed and mobile relay can be employed in VANET for supporting vehicular multi-hop accessing. In this paper, a cross-layer based RSU/mobile relay station (RS) selection scheme for VANET is proposed which jointly considers multiple metrics from multiple protocol layers, including the link status, bandwidth and delay characteristics of access RS and user service requirements, and simple additive weighting (SAW) method is applied to evaluate the performance of candidate RSs. Simulation results demonstrate that comparing to previous algorithms, the novel algorithm offers better average throughput performance.

A resource characteristic and user QoS oriented bandwidth and power allocation algorithm for heterogeneous networks

AbstractHeterogeneous networks (HetNets) composed of macrocells and small cells are expected to improve the transmission performance of users significantly. Designing efficient resource allocation schemes, specifically, bandwidth allocation and power allocation schemes for HetNets is of particular importance for it may affect user quality of service (QoS) and network performance severely. In this paper, we consider the resource allocation problem of a HetNet composed of a macrocell and a number of femtocells and propose a resource characteristic and user QoS oriented bandwidth and power allocation algorithm for the femto base stations (FBSs) which share spectrum with the macro base station. By taking into account the service requirements of the femto user equipments (FUEs) and the bandwidth resource characteristics of the network, various bandwidth resource allocation schemes are proposed. Particularly, in the case of slightly insufficient bandwidth resource, we propose a bankruptcy game based bandwidth resource allocation algorithm for the FBSs, and solve the bandwidth allocation problem by means of Shapley value method. To stress the tradeoff between data rate and power consumption, we examine the energy efficiency of the FBSs and formulate the power allocation problem as a multi-objective optimization problem with the objectives of maximizing the energy efficiency of all the FBSs. The optimal power allocation strategy can be obtained by solving the optimization problem via ideal point method and generic algorithm. Simulation results demonstrate the efficiency of the proposed algorithm.

End-to-End Transmission Performance Optimization Based Routing Selection Algorithm for Software Defined Networking

Software-defined networking (SDN) is a new networking paradigm enabling innovation through decoupling control plane from data plane and providing programmability for network application development. Specific research focus has been placed to achieve route optimal selection in SDN scenario. In this paper, we study the problem of route selection for a user flow in a SDN scenario consisting of a number of switches and propose an end-to-end transmission performance optimization based routing selection algorithm. We jointly consider the characteristics of user flow and service capability of the network, and formulate the arrival curve of user flow and the service curve of switches by applying Network Calculus theory. The transmission performance of user flow, defined as effective bandwidth is evaluated and the route offering the maximum effective bandwidth is selected as the optimal route. Numerical results demonstrate the effectiveness of the proposed algorithm.