Dynamic Channel Allocation for Real-Time Connections in Highway Macrocellular Networks

The wide deployment of multimedia services in third generation wireless networks will require handoff designs that can simultaneously reduce the blocking probability of handoff requests and decrease the handoff delay. Reducing the handoff blocking probability is needed to prevent frequent call dropping of real-time VBR/VCR connections and decreasing the delay associated with handoff is needed to prevent QoS degradation for multimedia traffic. In this paper, we present a channel assignment/reassignment scheme for highway cellular networks that achieves both requirements. The scheme can be used to deliver real-time data to a large segment of global highways, namely, highways in which the radio channels used in a given cell cannot be simultaneously used in the two neighboring cells to its left and to its right. The scheme possesses the desirable features of real-time algorithms: the execution time per handoff request has a constant time complexity, the number of transmitted messages per request is small, and the space overhead is also O(1). The scheme uses a non-compact initial assignment of nominal channels to neighboring cells and utilizes a set of pointers in each base station to implement an efficient channel assignment and reassignment strategy. The resulting approach greatly simplifies the selection process and avoids the expensive computation and message exchanges typically needed by dynamic channel allocation schemes. The low communication overhead of the scheme can be further reduced via control thresholds. Performance simulation results show that the scheme achieves low blocking probability and is therefore suitable for handling handoffs of real-time connections in highway cellular networks.     

A New Dynamic Channel Allocation Scheme for Microcellular Systems

1IntroductionThetremendousgrowthofthemobileuserpopulahonrequiresefficientreuseofscarceradiospectrUmallocatedtomobilecommunications.InmobilenetWorks,co-channelinterferencecausedbyfrequencyreuseisthemostrestrainingfactorontheoverallsystemcapacity.Inthecurrentcellularsystems,themainideabehindchannelallocationistomakeuseofradiopropagationpathlosscharacteristicsinordertondnindzethecaacer-tointerferenceratio(CIR)andhencetoincreasetheradiospecmimreuseefficiency.MicrocellularsystemshaveshowngreatPO…     

智能天线系统中基于载干比的动态信道分配

智能天线系统实现了同道在同小区的重用,其空域波束分配可以有效抑制同道干扰;信道分配可以充分结合其他信道资源。在Matlab系统级仿真中,充分利用定时器的特性,真实地建立移动台和基站之间在线服务的多线程通信仿真模型,对载频、时隙和码字中任一种或多种结合在空域位置形成的信道,提出基于载干比测量的动态信道分配策略,并对其进行了仿真研究和性能分析。仿真结果与理论分析吻合,同时得到一些有意义的参数。     

An Adaptive and Fault-Tolerant Channel Set Allocation Algorithm for Microcell/Macrocell Cellular Networks

Microcell/macrocell architectures are generally deployed in current cellular networks, and involve allocating each cell to a preliminary channel set to support the communications of mobile subscribers. However, cellular networks suffer risks of base transceiver station (BTS) service failure and traffic load variation among BTSs. Both of these conditions impact traffic-carrying capacity and mobile subscriber satisfaction. This investigation presents a dynamic channel set allocation algorithm for ensuring continuous optimization of overall traffic-carrying capacity. This algorithm can tolerate BTSs failure and also resolve the traffic-adaptive problem. Additionally, analytical and simulation results are presented to demonstrate the efficiency of the algorithm.Chyi-Ren Dow was born in 1962. He received the B.S. and M.S. degrees in information engineering from National Chiao Tung University, Taiwan, in 1984 and 1988, respectively, and the M.S. and Ph.D. degrees in computer science from the University of Pittsburgh, U.S.A., in 1992 and 1994, respectively. Currently, he is a Professor in the Department of Information Engineering, Feng Chia University, Taiwan. His research interests include mobile ad-hoc networks, network agents, learning technologies, and embedded systems.Jong-Shin Chen was born in 1972. He received the B.Sc. and Ph.D. degrees in engineering from Feng Chia University, Taiwan, in 1996 and 2003, respectively. His research interests include mobile computing, wireless communications, capacity planning, and systems.Yi-Hsung Li was born in 1979. He received his B.S. degree and M.S. degree in information engineering from Feng Chia University, Taiwan, in 2001 and 2003. He is currently a graduate student for the Ph.D. degree in the Department of Information Engineering and Computer, Feng Chia University, Taiwan. His research interests include personal communications, mobile computing, learning technologies, and network agents.     

The Effect of Fiber Non-Linearity on Two Dispersion Compensation Schemes

1introductionTheintroductionofErbium-dopedfiberamplifier(EDFA)hasbroughthigh-capacityopticalnetWorksoperatingaround1550urn.Theultimatetransmissionlimitationsarenowchirp,chromaticdispersion,fibernon-linearityandnoisefromEDFAs.Sincethemajorityoftoday'sinstalledfiberisdesignedtooperatearound1310urn,greateffortsaremadetocommerciallyexploitandupgradethembydispersioncompensation.ChirpedBraggfibergratingsusedasdispersioncompensatorshavereceivedconsiderableattentionlatelybecauseoftheirlow-inseFti…     

Integrating Distributed Channel Allocation and Adaptive Handoff Management for QoS-Sensitive Cellular Networks

Next generation high-speed cellular networks are expected to support multimedia applications, which require QoS provisions. Since frequency spectrum is the most expensive resource in wireless networks, it is a challenge to support QoS using limited frequency spectrum. In the literature, two orthogonal approaches are used to address the bandwidth utilization issue and the QoS provision issue; that is, channel allocation schemes have been proposed to improve bandwidth efficiency, whereas handoff management schemes, based on bandwidth reservation, have been proposed to guarantee a low connection dropping rate. However, little effort has been taken to address both issues together. In this paper, we integrate distributed channel allocation and adaptive handoff management to provide QoS guarantees and efficiently utilize the bandwidth. First, we present a complete distributed distributed channel allocation algorithm and propose techniques to reduce its message complexity and intra-handoff overhead. Second, we integrate the proposed distributed channel allocation algorithm with an adaptive handoff management scheme to provide QoS guarantees and efficiently utilize the bandwidth. Detailed simulation experiments are carried out to evaluate the proposed methodology. Compared to previous schemes, our scheme can significantly reduce the message complexity and intra-handoff overhead. Moreover, the proposed scheme can improve the bandwidth utilization while providing QoS guarantees.     

Dynamic Bandwidth Allocation in WDM Passive Star Networks with Asymmetric Traffic

When asymmetric traffic is offered to a WDM passive star network, the offered bandwidth must be allocated is such a way that each station takes a portion of the available bandwidth proportional to its needs. When the traffic characteristics are fixed and a priori known, then, the bandwidth allocation scheme can be based on these characteristics. Unfortunately, the traffic characteristics are often unknown and time-variable. In this paper, a dynamic bandwidth allocation scheme is presented, which is based on the network feedback information in order to be capable of adapting to the changing traffic characteristics. According to the proposed scheme, a set of learning automata processes the network feedback information and dynamically allocates the available bandwidth to the stations according to their needs.     

On the Capacity Enhancement of a Cellular CDMA Channel with Asymmetrical Bandwidth Allocation

Capacity enhancement of cellular CDMA is analyzed using an asymmetrical-bandwidth-allocation approach. Cellular CDMA systems with and without successive interference cancellation are considered. The main source of interference is interuser interference and, in particular, a 9-cell configuration is employed to account for interference from surrounding cells. By transferring more bandwidth or, equivalently, processing gain from the forward link to the reverse link, we have effectively balanced their performance and raised the overall capacity of the cellular system. The optimum bandwidth allocation is easily obtained from the performance curves of both links. For a typical cellular CDMA with a bit error rate of 10-³, the capacity gain of this approach is about 40%. If successive interference cancellation is employed and both links have the same quality, then both links should have equal bandwidth. However, in a situation where imperfect power control occurs, our studies indicate that using interference cancellation alone achieves a 25% increase in capacity, while enhancement with an asymmetrical bandwidth allocation overlay raises this gain to 68%.     

Dynamic Flow Model for Borrowing Channel Assignment Scheme in Cellular Mobile System

A mathematical model that predicts the dynamic flows in cellular mobile networks that allocate channels using the Borrowing Channel Assignment (BCA) scheme is described in this paper. Two types of handoff procedures – the prioritized and non-prioritized schemes – will be considered in the model. Discrete event simulations were performed and the results were found to be comparable to the results obtained using the mathematical model. Application to comparative study of the dynamic behaviours of the BCA and the Fixed Channel Assignment (FCA) schemes is also presented.     

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.     

蜂窝移动网中基于MMPP业务输入模型的系统性能分析

文章针对现有的以Poisson过程作为输入业务流模型分析系统性能的不足,提出采用马尔可夫调制泊松过程(MMPP)作为输入业务流来分析系统的呼叫阻塞率和掉话率.数值和仿真结果表明,MMPP能够较好的对蜂窝移动网中的业务输入流近似建摸,它考虑了业务流本身的相关特性和突发特性,可以更加准确的用于分析系统性能.     

Performance Evaluation of a Virtual Queuing – Channel Allocation Scheme for Microcellular Networks

This paper deals with the performance evaluation of a novel distributed channel allocation scheme that attains a high resource reuse in cellular networks. A suitable interference model has been envisaged. Resources are nominally assigned to cells with Fixed Channel Allocation (FCA), according to a given reuse distance. Whenever a channel demand from a mobile user does not find a free nominal resource in a cell, a channel is temporarily borrowed violating the reuse distance constraint, provided that the co-channel interference level is acceptable. As soon as a nominal channel becomes available in this cell, the borrowed resource is released (virtual queuing). The performance of the proposed channel allocation scheme has been evaluated considering both uniform and non-uniform traffic patterns. A performance analysis approach has been also developed and validated by simulations. Comparisons with the classical FCA scheme and other dynamic and borrowing channel allocation strategies have permitted to highlight the good performance of the proposed technique.     

TD-SCDMA系统多业务动态信道分配算法研究

在基于的第三代移动通信中,由于业务的多样性,使得原有的只考虑到语音业务的信道分配无法满足TD-SCDMA系统需要,在信道资源分配上需要使用动态信道分配。为了适应多业务资源管理,该文在已有的DCA研究成果基础上,对DCA各个执行阶段进行了分析和阐述,并对移动边界策略和双门限带宽预留的多业务算法做了介绍和分析,分析结果表明这些策略能更好的适应于语音和数据的业务系统。     

Predictive Dynamic Channel Allocation Scheme for Improving Power Saving and Mobility in BWA Networks

The radio spectrum of IEEE 802.16 medium access control (MAC) protocol ranges from 2–66 GHz, which is one of potential solutions for broadband wireless access (BWA) or beyond third generation (B3G)/4G networks. The maximum transmission range can reach about 48 km. However, with the property of radio propagation, the maximum transmission distance is proportioned inversely to the frequency the mobile subscriber station (MSS) carries. According to this property, the channel allocation can be based on how far the distance between the MSS and the base station (BS) in a macrocell. Therefore, this paper first proposes a new concept of channel allocation model for BWA system and investigates the relations between the signal propagation and the distance as well as propose a signal-aware dynamic channel allocation (SDCA) scheme for dynamic channel allocation (DCA) in BWA networks (BWANs). The SDCA enables the BS to allocate appropriate channels to MSSs according to the received signal-to-noise ratio (SNR) value from the MSSs. Besides, according to the frequency, the SDCA can estimate a minimum power for MSS to communicate. The SDCA not only increases the capacity of the system but saves the overall power consumption of the system well. We also present a new out-of-service prevention scheme for supporting mobility in the system. Simulation results show that the proposed SDCA can achieve the channel utilization (throughput) by up to 94.4% when the spectrum ranges from 2–11 GHz.

Integrated Optimal Cell Site Selection and Frequency Allocation for Cellular Radio Networks

Two major planning problems are encountered when designing a cellular radio network. The initial question is where to locate the base transmitter stations such that full coverage is achieved at low interference. This is relevant for frequency division (FDMA) as well as code division multiple access (CDMA) technology. If the locations of base stations are given, then for an FDMA-system frequencies have to be assigned such that there is a sufficient number of channels per cell available at a low total interference level. Since cell site selection and frequency allocation have mutual influences on each other, the ultimate goal is to deal with both problems in a single design step. The main intention of this paper is to model the above planning issues as linear integer programs, and to discuss solution methods for the corresponding NP-hard problems. According to their increasing complexity we proceed from channel allocation via cell site selection to an integrated single setup.     

Modeling and Analysis of Broadband Cellular Networks with Multimedia Connections

As mobile networking is moving towards the direction of providing high-speed multimedia services, the presence of connections that do not generate traffic at constant rate is becoming reality in wireless environment. For preliminary network design purposes analytical models are necessary that examine the performance or wireless networks with such connections. In this paper an analytical method is presented to calculate call-level system parameters of cellular networks with multimedia connections. The method is based on an approximate recursive calculation. The accuracy of the approximation is verified by computer simulations. The derivation of the distributions of user describing time variables and two simple admission control policies are also presented and investigated.     

LED交通灯的光通信系统信道建模与分析

LED交通灯作为智能交通系统中的光通信媒介具有广泛的应用前景。只有对LED交通灯的通信传播信道特征有充分了解才能确保所设计的可见光通信系统具备令人满意的性能,而构建信道模型则是一种花费比较小且较为灵活的替代手段。采用微分元素表征方案构建直射链路和一次路面反射链路的信道模型,分析了典型天气条件、接收机位置、传输距离和不同路面反射对通信系统传输特性的影响。仿真结果表明：信道建模时应忽略沥青和积水路面漫反射对通信的影响,考虑冰和积雪路面漫反射对信号接收的影响;汽车距离光源表面越近,接收信号越强;同时验证了接收机安装在汽车顶部接收信号的效果最佳。     

Impact of Power Control Strategy and Cell Classification on Hierarchical Cellular System's Reverse Link

1IntroductionRecelltly,theCDMAtechniquehasdrawntheattentionfrommanyresearchersforitsapplicationinglobalPersonnelmobilesystemsl'1'l'].UsingCDMAscheme,combiningmacrocellwithmicrocellhierarchicalsystemsmayprovidehighcapacityradioaccesstOthecellularsystem.InCDMAsystem,themoStimpo~problemissaidtobeaso-called"near-farproblem"I'l'I'I,generally,thisproblemcanbeovercomebyintroducingtheperfecttransmitterPOwercontrol(TPC).TheTPCiscomprisedofreverselinkandfonvardlinkTPCS.Butinpracticalsystems…     

WCDMA网络中的多媒体流量特性及流量模型分析

以WCDMA为例,分析了3G移动通信网络的网络流量特性,给出了网络流量模型,进而给出了3G移动通信网络的合成流量与系统存储容量之间的函数关系。     

Queue Analysis and Multiplexing of Heavy-tailed Traffic in Wireless Packet Data Networks

Recent research based on traffic measurements shows that Internet traffic flows have a fractal nature (i.e., self-similarity property), which causes an underestimation of network engineering parameters when using the conventional Poisson model. Preliminary field measurements demonstrate that packet data traffic in wireless communications also exhibits self-similarity. In this paper, we investigate the queuing behavior of self-similar traffic flows for data applications in a packet-switching single-server wireless network. The traffic is generated by an on–off source with heavy-tailed on periods and exponentially distributed off periods. We extend previous analysis of a relation among the asymptotic distribution of loss probability, traffic specifications, and transmission rate for a wireline system to a wireless system, taking into account wireless propagation channel characteristics. We also investigate the multiplexing of heavy-tailed traffic flows with a finite buffer for the downlink transmission of a wireless network. Computer simulation results demonstrate that assumptions made in the theoretical analysis are reasonable and the derived relationships are accurate.