Dynamic Channel Assignment with Flexible Reuse Partitioning in Cellular Systems

In cellular communications, one of the main research issues is how to achieve optimum system capacity with limited frequency spectrum. For many years, researchers have proposed and studied many dynamic channel assignment (DCA) schemes to increase the capacity of cellular systems. Another proposed technique, Reuse Partitioning (RP), is used to achieve higher capacity by reducing the overall reuse distance. In convention, when RP is exploited in network-based DCA, a portion of channels will be assigned permanently to each partitioned region. However, the number of channels assigned to each region may not be~optimum due to factors like the uneven and time-varying traffics. In this paper, a new network-based DCA scheme is proposed with the flexible use of RP technique, named as flexible dynamic reuse partitioning with interference information (FDRP-WI). In this scheme, channels are open to all incoming calls and no channel pre-allocation for each region is required. As long as the channel assignment satisfies the co-channel interference constraints, any user from any region can use any channel. The scheme aims to minimize the effect of assigned channels on the availability of channels for use in the interfering cells and to reduce overall reuse distance. Both FDRP-WI with stationary users and mobile users are investigated. Simulation results have confirmed the effectiveness of FDRP-WI scheme. In the case with stationary users, FDRP-WI exhibits outstanding performance in improving the system capacity under both uniform and non-uniform traffic distributions. Under the uniform traffic case, the scheme can provide over 100% capacity improvement as compared to conventional fixed channel assignment scheme with 70 system channels at 1% blocking probability. In the case with mobile users, the impact of mobility on the new call probability, P _b, and the call dropping probability, P _d, is evaluated. The effect on system capacity of reserving some channels for handoff calls is first studied. Then, we propose a new handoff scheme, called “Reverse Overflow” (RO), to improve the utilization of channels with smaller reuse distances under mobile environment. Simulation results show that, with RO handoff, the system capacity of FDRP-WI is effectively improved at the expense of higher handoff rates in the cellular system.     

Some Effects on Channel Occupancy of Limiting the Number of Available Servers in Small Cell Mobile Radio Systems Using Dynamic Channel Assignment

The performance of large scale multicell mobile radio systems using dynamic channel assignment and having limitations on the number of servers available in each coverage cell was investigated by computer simulation. At low system blocking the traffic carried is determined solely by the server limitations while at higher blocking the traffic carried is determined by channel limitations.     

TDD-CDMA系统的动态信道分配算法

TDD-CDMA系统由于上下行业务量的不对称,因此会产生严重的小区间干扰,需要使用动态信道分配算法(DCA)来适应上下行业务量的动态不平衡.文中提出了一种基于平均功率值的DCA算法.它通过采用平均功率控制的算法对功率进行处理,以提高信道利用率;并避免基站间的相互干扰来改善系统性能,从而提高系统容量.仿真结果表明,提出的算法能够显著地改善系统指标,达到优化效果.     

A Scheduling Algorithm with Dynamic Priority Assignment for WCDMA Systems

In third generation WCDMA systems, shared channels allow many users to jointly utilize a single Orthogonal Variable Spreading Factor (OVSF) code. In this paper, we propose a Scheduling Algorithm with Dynamic Priority Assignment (DPA) which is designed for the Downlink-Shared channel (DSCH) of 3G WCDMA systems and operates within a cross layer framework. The DPA scheduler has low computational complexity and is able to provide QoS differentiation among traffic flows based on their delay sensitivity. Through the cross layer framework, DPA takes into account the variations of the wireless channel, and exploits processing gain to improve transmission quality and enable service provisioning when possible. Additionally, by providing a guaranteed rate per traffic flow at each scheduling period, DPA can offer a deterministic delay bound to each connection when transmissions are reliable. Stochastic delay guarantees under transmission power limitations are also provided when the traffic flows are identical. Simulation results show that DPA outperforms Feasible Earliest Due Date (FEDD), a variation of EDD for wireless environments.     

使用Proxy Server的Intranet中应用服务器通信的实现

Intranet的应用服务器除了提供企业内部应用以外,还允许被外部Intranet主机访问以实现对外信息发布交流,使用ProxyServer是目前常用的安全、有效的方法。本文对使用ProxyServer的Intranet,分析了应用服务器之间可能存在的几种通信,并论述了利用MicrosoftProxyServer2．0实现这些通信的方法。     

分布式系统中基于鉴别服务器的鉴别式通信

本文介绍分布式系统中鉴别服务器的基本概念及利用它实现实体间鉴别式通信(包括鉴别式交互通信、鉴别式单向通信和签名通信等)的基本原理与方法,针对私有密钥系统和公开密钥系统分别进行论述。     

Approximate Analysis for Dynamic Channel Assignment in Large Systems with Cellular Structure

Two approximate methods for analysis of large-scale probems using dynamic channel assignment and a cellular structure are described. Such problems arise in the areas of mobile radio telephony and in multibeam satellite systems. The grade of service of individual zones is considered in detail. The problem is analyzed in terms of the carried erlang load rather than in terms of the system states. These methods are shown to be of a much lower order of difficulty than available methods.     

WCDMA系统的信道码分配策略

第三代移动通信系统WCDMA支持多业务、多QoS的传输,能更好地利用信道码的分配策略。3GPPWCD-MA标准采用的正交可变长扩频码(OVSF)支持变速率业务,举例说明了一种可行的信道码动态分配方案。     

A Network-Based Dynamic Channel Assignment Scheme for TDMA Cellular Systems

Network-based dynamic channel assignment (DCA) schemes can be used to increase the capacity of TDMA cellular systems. In this paper, a new distributed network-based DCA scheme, known as DCA with interference information, DCA-WI, is proposed and its performance is studied. In this scheme, a base station (BS) assigns a channel in such a way as to minimize the effect on the availability of channels for use in its interfering cells. To accomplish this, each BS maintains an interference information table which contains information about the local cell and its interfering cells. DCA-WI does not require system-wide information. Channel reassignment for new and completed calls are used to further reduce the call blocking probability. Simulation results show that DCA-WI provides a lower call blocking probability compared to other existing schemes in both uniform and nonuniform traffic distributions.     

服务器个数随机可变的轮询系统分析

前人关于轮询系统的大量研究均以服务器无故障为前提。本文提出了一种容许服务器个数随机可变的多服务器轮询模型。同时考虑排队延迟与服务器故障／修复的影响，获得了顾客等待时间的平均值公式。     

Comments on "Approximate Analysis for Dynamic Channel Assignment in Large Systems with Cellular Structure"

Correction and discussion of results appearing in a recent paper are presented in this correspondence.     

Dynamic Flow Model for Borrowing Channel Ordering Assignment Scheme in Cellular Mobile Systems

A mathematical model that predicts the dynamic flows in cellularmobile networks that allocate channels using the Borrowing ChannelOrdering Assignment (BCO) scheme is described in this paper. Two types ofhandoff procedures – the prioritized and non-prioritized schemes –will be considered in the model. Discrete event simulations wereperformed and the results were found to be comparable to the resultsobtained using the mathematical model. Application to comparative studyof the dynamic behaviours of the BCO, the simple borrowing channel assignment(BCA) and the Fixed Channel Assignment (FCA) schemes is also presented.     

Pushing Dependent Data in Clients–Providers–Servers Systems

In satellite and wireless networks and in advanced traffic information systems in which the up-link bandwidth is very limited, a server broadcasts data files in a round-robin manner. The data files are provided by different providers and are accessed by many clients. The providers are independent and therefore files may share information. The clients who access these files may have different patterns of access. Some clients may wish to access more than one file at a time in any order, some clients may access one file out of of several files, and some clients may wish to access a second file only after accessing another file. The goal of the server is to order the files in a way that minimizes the access time of the clients given some a-priori knowledge of their access patterns. This paper introduces a clients–providers–servers model that better represents certain environments than the traditional clients–servers model. Then, we show that a random order of the data files performs well, independent of the specific access pattern. Our main technical contribution is de-randomizing the procedure that is based on selecting a random order. The resulting algorithm is a polynomial-time deterministic algorithm that finds an order with the same performance bounds as those of the random order.     

TD—SCDMA的动态信道分配

TD－SCDMA是由中国提出并被ITU所接受的第三代移动通信标准，是第三代移动通信系统（UMTS）和IMT2000国际电信标准大家庭中的重要成员。 一、 TD－SCDMA的特点TD－SCDMA的移动无线系统是针对所有无线环境下对称和非对称的3G业务所设计的，它运行在不成对的射频频谱上，适用于TDD模式下的TDMA操作系统。TD－SCDMA的先进设计支持每射频载波上灵活的时域上／下行链路的转换，从而更加能够适应于不同3G业务中不同的上／下链路关系。传输方向的时域自适应资源分配可取得独立于对称业务负载关系的频谱分配的最佳利用率，因此，…     

Modified Packing Algorithm for Dynamic Energy-Saving in Cloud Computing Servers

Since the raising of the cloud computing, the applications of web service have been extended rapidly. However, the data centers of cloud computing also cause the problem of power consumption and the resources usually have not been used effectively. Decreasing the power consumption and enhancing resource utilization become main issues in cloud computing environment. In this paper, we propose a method, called MBFDP (modified best fit decreasing packing), to decrease power consumption and enhance resource utilization of cloud computing servers. From the results of experiments, the proposed solution can reduce power consumption effectively and enhance the utilization of resources of servers.     

Modified Packing Algorithm for Dynamic Energy-Saving in Cloud Computing Servers

Since the raising of the cloud computing, the applications of web service have been extended rapidly. However, the data centers of cloud computing also cause the problem of power consumption and the resources usually have not been used effectively. Decreasing the power consumption and enhancing resource utilization become main issues in cloud computing environment. In this paper, we propose a method, called MBFDP (modified best fit decreasing packing), to decrease power consumption and enhance resource utilization of cloud computing servers. From the results of experiments, the proposed solution can reduce power consumption effectively and enhance the utilization of resources of servers. 1     

Dynamic Address Assignment in Broadcast Networks

In this paper we consider the problem of dynamically assigning addresses to stations attached to a broadcast network. We present a distributed protocol which guarantees that a new station will eventually be assigned an address if one is free, and furthermore, that no two stations on the network will have the same address. We show how the protocol can be simplified in certain specific environments.     

基于认知的协作系统中继分配算法

随着无线移动通信系统的飞速发展,无线通信网络能耗急剧增加,基于中继协作技术的绿色无线通信研究受到众多研究者的关注.针对基于认知的中继协作系统,提出了一种以最大主系统能效为目标的中继分配算法.该算法在不影响主系统性能基础上,对主系统请求次系统用户作为中继转发数据,且共享主用户频谱进行了简要介绍.算法中次系统通过最大权重匹配方法为主系统分配中继（次用户）,在满足主系统能效最大化的同时,实现了次系统与主系统的频谱共享.对算法进行仿真验证,提出的算法能获得较高的主系统能效,同时提高了整个系统的频谱利用率.     

视频流点播Dynamic Batched Patching算法研究

本文提出了一个新的视频流点播传输策略,用以解决现有传输策略中存在的系统资源利用率低,QoS较差等问题.该策略的思想是服务器根据用户请求到达时刻,按动态批处理的方式来接纳并服务请求用户,每组用户必须同时从一个或两个信道接收视频内容.文中对本策略的性能进行了理论推导与定量分析,并与现有传输策略作了性能比较,最后采用仿真实验对前面的理论分析与比较进行了验证.理论分析及实验结果表明该策略是一个简单高效的传输策略,适合任意规模的点播应用.     

Dynamic Allocation of Servers to Jobs in a Grid Hosting Environment

As computational resources become available for use over the Internet, a requirement has emerged to reconfigure servers to an optimal allocation to cope with an unpredictable flow of incoming jobs. This paper describes an architecture that allows the dynamic reconfiguration of servers to process incoming jobs by switching servers between conceptual pools. The system makes use of heuristic policies to make close-to-optimal switching decisions. A prototype system which builds on existing resource management software has been developed to demonstrate some of the concepts described.