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The Journal of China Universities of Posts and Telecommunications 2011年第3期18卷 1-7页

作者： chen dan ji hong li xi College of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

Cooperative relaying is emerging as an effective technology to fulfill requirements on high data rate coverage in next-generation cellular networks, like long term evolution-advanced （LTE-Advanced）. In this paper, we propose a distributed joint relay node （RN） selection and power allocation scheme over multihop relaying cellular networks toward LTE-Advanced, taking both the wireless channel state and RNs＇ residual energy into consideration. We formulate the multihop relaying cellular network as a restless bandit system. The first-order finite-state Markov chain is used to characterize the time-varying channel and residual energy state transitions. With this stochastic optimization formulation, the optimal policy has indexability property that dramatically reduces the computational complexity. Simulation results demonstrate that the proposed scheme can efficiently enhance the expected system reward, compared with other existing algorithms.

关键词： cooperative relaying LTE-Advanced relay selection power allocation residual energy restless bandit

Optimal joint relay selection and resource allocation with QoS constraints in multiuser OFDM-based cellular networks

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High Technology Letters 2011年第3期17卷 305-310页

作者： chen dan ji hong li xi Luo Changqing Beijing University of Posts and Telecommunications Beijing 100876 P. R. China

This paper investigates the relay selection and resource allocation problem in multiuser orthogonal frequency division multiplexing （OFDM） based cooperative cellular networks, in which user nodes could relay information for each other using the decode-and-forward （DF） protocol to achieve spatial diversity gain. Specifically, the paper proposes an optimal joint relay selection and resource allocation （0RSRA） algorithm whose objective is to maximize system total achievable data rate with the constraints of each user＇ s individual quality of service （QoS） requirement and transmission power. Due to being a mixed binary integer programming （MBIP） problem, a novel two-level Lagrangian dual-primal decomposition and subgradient projection approach is proposed to not only select the appropriate cooperative relay nodes, but also allocate subcarries and power optimally. Simulation re- suits demonstrate that our proposed scheme can efficiently enhance overall system data rate and guarantee each user＇ s QoS requirement. Meanwhile, the fairness among users can be improved dramatically.

关键词： cooperative diversity relay selection resource allocation Lagrangian dual-primal decomposition

QoS-guaranteed multi-relay selection and power allocation optimization in cooperative systems

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The Journal of China Universities of Posts and Telecommunications 2010年第6期17卷 25-31页

作者： chen dan,ji hong,li xi,li Yi College of Information and Communication Engineering,Beijing University of Posts and Telecommunications,Beijing 100876,China College of Information and Communication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

This paper investigates the relay selection and power allocation problem in multi-user based cooperative networks,where intermediate relay nodes help source forward information to destination using decode-and-forward （DF） relaying protocol. Specifically,we propose a novel multi-relay nodes selection strategy taking both instantaneous channel state information （I-CSI） and residual energy into consideration,by which ＇emergence＇ diversity gain can be achieved and the imbalance of resource utilization can be overcome. Besides,using Largangian dual-primal decomposition and subgradient projection approach,an optimal power allocation algorithm at source and cooperative relay nodes is presented with the constraints of each user＇s individual quality of service （QoS） requirements and system total transmit power. Theoretical analysis and simulation results demonstrate that the proposed scheme can significantly improve energy efficiency,while guaranteeing a good balance between achievable data rate and average network lifetime with relatively low implementation complexity.

关键词： cooperative diversity relay selection resource allocation Lagrangian dual-primal decomposition subgradient projection

Load-adaptive frequency reuse scheme for inter-cell interference coordination in relay networks

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The Journal of China Universities of Posts and Telecommunications 2010年第5期17卷 38-43页

作者： chen Mu-qiong ji hong li xi School of Information and Telecommunication Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

Cellular relay networks adopting orthogonal frequency division multiple （OFDM） technology has been widely accepted for next generation wireless communication due to its advantage in enlarging coverage scale as well as improving data *** order to improve the performance of user equipments （UEs） near the cell edge,especially to avoid the interference from inter-cell and intra cell,an enhanced soft frequency reuse scheme is adopted in this paper to assure inter-cell interference coordination （ICIC）.Compared with traditional frequency allocation work,the proposed scheme is interference-aware and load-adaptive,which dynamically assigns available frequency among UEs under certain schedule method in variable traffic load condition and mitigates interference using information provided by interference *** can improve signal-to-interference plus noise ratio （SINR） of the UE in each sub channel thus enable the system achieve better throughput and blocking probability *** results prove that the proposed scheme may achieve desirable performance on throughput,blocking probability and spectral utilization in the sector under different traffic load compared with other schemes.

关键词： relay frequency reuse interference coordination resource allocation

Dynamic hierarchical collaborative caching scheme in ultra-dense networks

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The Journal of China Universities of Posts and Telecommunications 2021年第1期28卷 78-86页

作者： chen jianing li xi ji hong Zhang Heli Key Laboralory of Univensal Wireless Communications Bejing University of Posts and TelecommunieationsBejing 100876China School of Information and Communieation Engineering Beijing Universily of Posts and TelecommunicationsBeijing 100876China

Pushing popular contents to the edge of the network can meet the growing demand for data traffic, reduce latency and relieve the pressure of the backhaul. However, considering the limited storage space of the base stations, it is impossible to cache all the contents, especially in ultra-dense network(UDN). Furthermore, the uneven distribution of mobile users results in load imbalance among small base stations(SBSs) in both time and space, which also affects the caching strategy. To overcome these shortcoming, the impact of the changing load imbalance in UDN was investigated, and then a dynamic hierarchical collaborative caching(DHCC) scheme was proposed to optimize latency and caching hit rate. The storage of the SBS is logically divided into the independent caching layer and the collaborative caching layer. The independent caching layer caches the most popular contents for local users’ interest, and the collaborative caching layer caches contents as much as possible for the benefit of content diversity in the region. Different SBSs have respective storage space layer division ratios, according to their real-time traffic load. For SBSs with heavy load, the independent caching layers are allocated with more space. Otherwise, the collaborative caching layers could store more contents with larger space. The simulation results show that, DHCC improved both transmission latency and hit rate compared with existing caching schemes.

关键词： ultra-dense network(UDN) load imbalance caching

Handover improvement based on cost function and user fairness for cellular relay enhanced LTE networks

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High Technology Letters 2011年第3期17卷 299-304页

作者： chen Muqiong ji hong li xi Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 P. R. China

In order to optimize handover target selection and achieve better handover performance in cellular relay networks under the long term evolution （LTE） system, a novel handover measurement and decision scheme based on cost function is proposed in the paper. The relay-enhanced network provides user equipment （UE） multiple handover choices from neighbor base stations or relays. This may result in different overhead, resource utility and traffic load which attaches importance to proper handover schemes. Compared with traditional handover measurement and decision schemes, the proposed scheme adopts reference signal receiving quality （RSRQ） in the measurement stage and uses a modified signal cost function considering signal overhead in different handover types and expected long-term throughput of UE. Besides, UE fairness and sector resource utilization are taken into account as well. Theory analysis and simulation results prove that the proposed scheme can enhance cell throughput, decrease handover delay and signal overhead, and improve UE fairness.

关键词： handover relay cost function fairness

Multi-path routing based on load-balance for cognitive packet networks

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The Journal of China Universities of Posts and Telecommunications 2011年第5期18卷 71-75页

作者： chen liang ji hong li Yi li xi College of Information and Commumieation Engineering Beijing University of Posts and Telecommunications Beijing 100876 China

Quality of service （QoS） routing algorithms have been hardly discussed in the scientific community, most previous work on QoS routing concentrates on the performance of the single route. Cognitive packet network （CPN） has been designed for providing QoS routing. In this paper, to balance the loads among networks, we present a multi-path routing algorithm based on load-balance （MPRLB）, which is carried out in two steps. The algorithm with low computational complexity is firstly applied to establish multi path routing for each source and destination node pairs （SD-pair） nodes in the network. Then, we propose the hopfield neural network algorithm, which is applied to improve the efficiency of the flow deviation method for fast flow allocation among the links of the network based on load balance. Extensive simulation results demonstrate that the proposed scheme significantly improves the performance compared with the existing scheme that ignores load balancing.

关键词： hopfield neural network CPN multi-path routing

Load-balance cell association for improving network capacity in heterogeneous cellular networks

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The Journal of China Universities of Posts and Telecommunications 2014年第3期21卷 56-61,70页

作者： chen Lei li xi ji hong liU Gang School of Telecommunication Engineering Beijing University of Posts and Telecommunications

Heterogeneous cellular networks improve the spectrum efficiency and coverage of wireless communication networks by deploying low power base station （BS） overlapping the conventional macro cell. But due to the disparity between the transmit powers of the macro BS and the low power BS, cell association strategy developed for the conventional homogeneous networks may lead to a highly unbalanced traffic loading with most of the traffic concentrated on the macro BS. In this paper, we propose a load-balance cell association scheme for heterogeneous cellular network aiming to maximize the network capacity. By relaxing the association constraints, we can get the upper bound of optimal solution and convert the primal problem into a convex optimization problem. Furthermore we propose a Lagrange multipliers based distributed algorithm by using Lagrange dual theory to solve the convex optimization, which converges to an optimal solution with a theoretical performance guarantee. With the proposed algorithm, mobile terminals （MTs） need to jointly consider their traffic type, received signal-to-interference-noise-ratios （SINRs） from BSs, and the load of BSs when they choose server BS. Simulation results show that the load balance between macro and pico BS is achieved and network capacity is improved significantly by our proposed cell association algorithm.

关键词： heterogeneous cellular networks load balance cell association Lagrange dual problem

A Creative Approach to Reducing Ambiguity in Scenario-based Software Architecture Analysis

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International Journal of Automation and computing 2019年第2期16卷 248-260页

作者： xi-Wen Wu chen li Xuan Wang hong-ji Yang Department of Computer Science and Engineering Shanghai Jiao Tong University Department of Computing Imperial College London Center for Creative Computing Bath Spa University

In software engineering, a scenario describes an anticipated usage of a software system. As scenarios are useful to understand the requirements and functionalities of a software system, the scenario-based analysis is widely used in various tasks, especially in the design stage of software architectures. Although researchers have proposed various scenario-based approaches to analyse software architecture, there are still limitations in this research field, and a key limitation is that scenarios are typically not formally defined and thus may contain ambiguities. As these ambiguities may lead to defects, it is desirable to reduce them as many as possible. In order to reduce ambiguity in scenario-based software architecture analysis, this paper introduces a creative computing approach to scenario-based software requirements analysis. Our work expands this idea in three directions. Firstly, we extend an architecture description language(ADL)-based language – Breeze/ADL to model the software architecture. Secondly, we use a creative rule – combinational rule(CR) to combine the vector clock algorithm for reducing the ambiguities in modelling scenarios. Then, another creative rule – transformational rule(TR) is employed to help to transform our Breeze/ADL model to a popular model – unified modelling language(UML) model. We implement our approach as a plugin of Breeze, and illustrate a running example of modelling a poetry to music system in our case *** results show the proposed creative approach is able to reduce ambiguities of the software architecture in practice.

关键词： Creative computing vector clock algorithm scenario-based analysis of software architecture sequence diagram Breeze/ architecture description language (ADL)

Honokiol:a promising small molecular weight natural agent for the growth inhibition of oral squamous cell carcinoma cells

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International Journal of Oral Science 2011年第1期3卷 34-42页

作者： xi-rui chen Rui Lu hong-xia dan Ga liao Min Zhou xiao-yu li Ning ji Pharmacology and Toxicology Program Faculty of Art and Science University of Toronto Ontario Canada State Key Laboratory of Oral Diseases West China School of Stomatology Sichuan University Chengdu 610041 China

Honokiol （HNK） is a small organic molecule purified from magnolia species and has demonstrated anticancer activities in a variety of cancer cell lines; however, its effect on oral squamous cell carcinoma （OSCC） cells is unknown. We investigated the antitumor activities of HNK on OSCC ceils in vitro for the first time. The inhibitory effects of HNK on the growth and proliferation of OSCC cells were demonstrated via in vitro 3-（4,5-dimethyl thiazol-2-yl）-2,5-diphenyltetrazolium bromide （MTT） and propidium iodide （PI） assays, and the apoptotic cells were investigated by the observation of morphological changes and detection of DNA fragmentation via PI, TdT-mediated dUTP-biotin nick end labeling （TUNEL）, and DNA ladder assays, as well as flow cytometry assay. The results showed that HNK inhibited the growth and proliferation of OSCC cells in vitro in a time and dose-dependent manner. The inhibitory effect was associated with the cell apoptosis induced by HNK, evidenced by the morphological features of apoptotic cells, TUNEL-positive cells and a degradation of chromosomal DNA into small internucleosomal fragments. The study also demonstrated here that the inhibition or apoptosis mediated by 15 μ***-1 or 20 μ***-1 of HNK were more stronger compared with those of 20 μg-mL-1 5-fluorouracil （5-Fu, the control） applied to OSCC cells, when the ratio of OSCC cell numbers were measured between the treatment of different concentrations of HNK to the 5-Fu treatment for 48 h. HNK is a promising compound that can be potentially used as a novel treatment agent for human OSCC.

关键词： honokiol oral squamous cell carcinoma anticancer apoptosis