ATM-based transport architecture for multiservices wirelesspersonal communication networks

This paper presents an ATM-based transport architecture for next-generation multiservices personal communication networks (PCN). Such “multimedia capable” integrated services wireless networks are motivated by an anticipated demand for wireless extensions to future broadband networks. An ATM compatible wireless network concept capable of supporting a mix of broadband ISDN services including constant bit-rate (CBR), variable bit-rate (VBR), and packet data transport is explored from an architectural viewpoint. The proposed system uses a hierarchical ATM switching network for interconnection of PCN microcells, each of which is serviced by high-speed, shared-access radio links based on ATM-compatible cell, relay principles. Design issues related to the physical (modulation), media access control (MAC), and data-link layers of the ATM-based radio link are discussed, and preliminary technical approaches are identified in each case. An example multiservice dynamic reservation (MDR) TDMA media access protocol is then considered in further detail, and simulation results are presented for an example voice/data scenario with a proportion of time-critical (i.e., multimedia) packet data. Time-of-expiry (TOE) based queue service disciplines are also investigated as a mechanism for improving the quality-of-service (QoS) in this scenario     

Effect of personal mobility management in mobile communication networks

Personal mobility (PM) is one of the key issues in realizing a personal communications service (PCS) in emerging third-generation mobile communication networks such as IMT-2000. It can be realized through the universal personal telecommunication (UPT) service. Two PM management schemes are proposed to manage PM information related to UPT users for incoming call (incall) registration/deregistration, incall registration reset by a mobile terminal (MT) owner, and incall delivery to UPT users in mobile communication networks based on the location information managed by the user's home network. The relative cost, i.e., the ratio of cost per unit time for supporting both terminal mobility (TM) and PM management to that of TM management, is derived, and the effect of PM management is analyzed from the aspects of update or query cost, signaling delivery cost, and processing cost. These results can be utilized in the implementation of PM management in IMT-2000.     

Topology-based tracking strategies for personal communication networks

This paper explores tracking strategies for mobile users in personal communication networks which are based on thetopology of the cells. We introduce the notion oftopology-based strategies in a very general form. In particular, the known paging areas, overlapping paging areas, reporting centers, and distance-based strategies are covered by this notion. We then compare two topology-based strategies with the time-based strategy on the line and mesh cell topology.     

Optimal dynamic mobility management for PCS networks

We study a dynamic mobility management scheme: the movement-based location update scheme. An analytical model is applied to formulate the costs of location update and paging in the movement-based location update scheme. The problem of minimizing the total cost is formulated as an optimization problem that finds the optimal threshold in the movement-based location update scheme. We prove that the total cost function is a convex function of the threshold. Based on the structure of the optimal solution, an efficient algorithm is proposed to find the optimal threshold directly. Furthermore, the proposed algorithm is applied to study the effects of changing important parameters of mobility and calling patterns numerically     

Tree-based object tracking without mobility statistics in wireless sensor networks

Object tracking in wireless sensor networks is to track mobile objects by scattered sensors. These sensors are typically organized into a tree to deliver report messages upon detecting object’s move. Existing tree construction algorithms all require a mobility profile that characterizes the movement statistics of the target object. Mobility profiles are generally obtained based on historical running traces. The contribution of this work is twofold. We first show that the problem of finding an optimal message report tree that requires the least amount of report messages is NP-hard. We then propose analytic estimates of mobility profiles based on Markov-chain model. This profiling replaces an otherwise experimental process that generates and analyzes running traces. Simulation results show that the analytic profiling works well and can replace costly statistical profiling without noticeable performance degradation.     

Host mobility key management in dynamic secure group communication

The key management has a fundamental role in securing group communications taking place over vast and unprotected networks. It is concerned with the distribution and update of the keying materials whenever any changes occur in the group membership. Wireless mobile environments enable members to move freely within the networks, which causes more difficulty to design efficient and scalable key management protocols. This is partly because both member location dynamic and group membership dynamic must be managed concurrently, which may lead to significant rekeying overhead. This paper presents a hierarchical group key management scheme taking the mobility of members into consideration intended for wireless mobile environments. The proposed scheme supports the mobility of members across wireless mobile environments while remaining in the group session with minimum rekeying transmission overhead. Furthermore, the proposed scheme alleviates 1-affect-n phenomenon, single point of failure, and signaling load caused by moving members at the core network. Simulation results shows that the scheme surpasses other existing efforts in terms of communication overhead and affected members. The security requirements studies also show the backward and forward secrecy is preserved in the proposed scheme even though the members move between areas.     

Failure restoration of mobility databases for personal communication networks

This paper studies failure restoration of mobility databases for personal communication networks (specifically, VLRs and HLRs). We model the VLR restoration with and without checkpointing. The optimal VLR checkpointing interval is derived to balance the checkpointing cost against the paging cost. We also model GSM periodic location updating (location confirmation) to quantify the relationship between the location confirmation frequency and the number of lost calls. The HLR failure restoration procedures for IS-41 and GSM are described. We show the number of lost calls in a HLR failure. Both the procedures in IS-41 and GSM cannot identify the VLRs that need to be accessed by the HLR after a failure. An algorithm is proposed to identify the VLRs, which can be used to aggressively restore a HLR after its failure.     

Joint mobility tracking and handoff in cellular networks via sequential Monte Carlo filtering

We consider the application of sequential Monte Carlo (SMC) methodology to the problem of joint mobility tracking and handoff detection in cellular wireless communication networks. Both mobility tracking and handoff detection are based on the measurements of pilot signal strengths from certain base stations. The dynamics of the system under consideration are described by a nonlinear state-space model. Mobility tracking involves an online estimation of the location and velocity of the mobile, whereas handoff detection involves an online prediction of the pilot signal strength at some future time instants. The optimal solutions to both problems are prohibitively complex due to the nonlinear nature of the system. The SMC methods are therefore employed to track the probabilistic dynamics of the system and to make the corresponding estimates and predictions. Both hard handoff and soft handoff are considered and three novel locally optimal (LO) handoff schemes are developed based on different criteria. It is seen that under the SMC framework, optimal mobility tracking and handoff detection can be implemented naturally in a joint fashion, and significant improvement is achieved over existing methods, in terms of both the tracking accuracy and the trade-off between service quality and resource utilization during handoff.     

面向多波束卫星通信网络的步进跟踪方法

面向多波束覆盖的卫星通信网络,为解决相控阵用户终端位置姿态信息无法获取时程序跟踪卫星失效的问题,提出了一种步进扫描跟踪方法。在该方法中,终端仅需比较单个波束的信标接收能量即可判断波束指向,从而降低跟踪时延。在此基础上,为满足终端在动中通场景下的业务通信需求,进一步研究动态条件下的跟踪方法,并讨论跟踪时延的影响因素。实验结果表明,当终端位置姿态变化较小时,所提方法的跟踪性能接近程序跟踪。     

基于迭代学习控制的潜望式激光通信终端系统的动态跟踪设计

为提高潜望式激光通信终端伺服系统的动态跟踪性能,针对基于永磁同步电机的二维伺服转台的控制系统进行了设计。通过采取空间矢量控制方法实现电机的解耦控制,建立控制模型并完成了各控制回路的设计。针对动目标跟踪设计了迭代学习控制方法以提高通信终端的动态跟踪性能,并对控制系统的速度阶跃响应进行测试,分析通信终端系统的低速平稳性。最后,搭建了4.62 km激光通信的动态跟踪实验,利用六自由度转台模拟平台抖动,为动态跟踪验证实验创造外部平台扰动条件。实验结果表明:通信终端系统速度阶跃响应的稳态误差为±0.02 (°)/s,表明伺服系统速度回路具有较快的动态响应特性和较高的稳态精度,在最大加速度为0.219 (°)/s2的正弦波扰动条件,二维伺服转台的动态粗跟踪精度可以达到62 μrad,粗精复合跟踪精度优于2 μrad,验证了通信终端伺服系统的有效性及其动态跟踪性能,为进一步提高终端系统的跟踪精度奠定基础。     

船载卫通站跟踪与通信极化分离设计

大口径船载卫通站一般采用单脉冲跟踪方式,需要高次模耦合出的差信号与通信网络输出的和信号经和差网络合成后输出误差信号用作解调跟踪。这种方式要求通信与跟踪极化方式需相同,限制了卫通站的使用,分析了馈源网络的基本结构以及单脉冲跟踪的工作原理,提出通信低噪采用2∶1低噪冗余控制系统代替1∶1冗余控制系统,可以实现通信极化与跟踪极化的分离,从而实现固定跟踪A极化信标,通信根据需要灵活选择A极化或B极化转发器,提高了船载卫通站使用的灵活性。     

Teletraffic analysis and mobility modeling of PCS networks

Channel holding time is of primary importance in teletraffic analysis of PCS networks. This quantity depends on user's mobility which can be characterized by the cell residence time. We show that when the cell residence time is not exponentially distributed, the channel holding time is not exponentially distributed either, a fact also confirmed by available field data. In order to capture the essence of PCS network behaviour, including the characterization of channel holding time, a correct mobility model is therefore necessary. The new model must be good enough to fit field data, while at the same time resulting in a tractable queueing system. We propose a new mobility model, called the hyper-Erlang distribution model, which is consistent with these requirements. Under the new realistic operational assumption of this model, in which the cell residence time is generally distributed, we derive analytical results for the channel holding time distribution, which are readily applicable to the hyper-Erlang distribution models. Using the derived analytical results we demonstrate how the distribution of the cell residence time affects the channel holding time distribution. The results presented in this paper can provide guidelines for field data processing in PCS network design and performance evaluation     

Real-time mobility tracking algorithms for cellular networks based on Kalman filtering

We propose two algorithms for real-time tracking of the location and dynamic motion of a mobile station in a cellular network using the pilot signal strengths from neighboring base stations. The underlying mobility model is based on a dynamic linear system driven by a discrete command process that determines the mobile station's acceleration. The command process is modeled as a semi-Markov process over a finite set of acceleration levels. The first algorithm consists of an averaging filter for processing pilot signal, strength measurements and two Kalman filters, one to estimate the discrete command process and the other to estimate the mobility state. The second algorithm employs a single Kalman filter without prefiltering and is able to track a mobile station even when a limited set of pilot signal measurements is available. Both of the proposed tracking algorithms can be used to predict future mobility behavior, which can be, useful in resource allocation applications. Our numerical results show that the proposed tracking algorithms perform accurately over a wide range of mobility parameter values.     

Active tracking: Locating mobile users in personal communication service networks

The problem of tracking mobile users in Personal Communication Service (PCS) networks is discussed. We propose a novel approach for reducing the wireless cost of tracking users. The basic idea is to use nonutilized system resources for initiating queries about the location of mobile users, in addition to the process of user registration. Queries are applied at each cell, independently of the other cells, whenever the load on the local control channel drops below a predefined threshold. Our study focuses on two issues: (1) proposing the initiated queries approach and an algorithm for its application, and (2) studying and quantifying the value of location information and evaluating the parameters affecting it. Our analysis shows that the expected benefit due to location knowledge in a Markovian motion model depends, among other things, on the determinant of the transition matrix and on the variability of the location distribution function. The active tracking approach, as opposed to other dynamic strategies, does not require any modification of user equipment. The importance of this property is in its practicality: An implementation of a new registration strategy in current systems would require a modification of the users equipment. Moreover, the proposed method can be easily implemented in addition to any known tracking strategy, to reduce further the tracking cost. The performance of the active tracking method is evaluated under two registration strategies: The geographicbased strategy, currently used in cellular networks, and the profilebased strategy, suggested elsewhere. Under both strategies, it significantly reduces the tracking cost.     

一种长时延网络中移动节点间的时间同步算法

长时延网络的同步对于提升网络传输效率,增加网络吞吐量具有重要意义。现有用于长时延网络典型时间同步协议有TSHL,Tri-Message等,这些同步协议都是针对传播时延保持稳定或者保持短时稳定的长时延网络,但在实际情况中,有时传播时延会发生变化,如节点间相对位移的变化,如何在这样的长时延网络中进行时间同步也是一个值得研究的问题,文中提出了一种运用于长时延网络中移动节点间的时间同步算法,利用节点间多次的信息交互计算出传播时延变化的速率,然后对时延变化进行估算来进行时间偏移的补偿以达到时间同步。     

A new analytic framework for dynamic mobility management of PCS networks

This paper presents a new analytic framework for dynamic location management of PCS networks. Based on the theory of hexagonal cellular patterns, a novel two-dimensional Markov walk model with six states is proposed to characterize the dynamic behavior of the intercell movements for a mobile station. We discover a broad class of isotropic processes having an identical uniform steady-state distribution of the six directions, but distinct circulant transition probability matrices. Six special isotropic processes exhibiting IID, directional, turning, ping-pong, h-spin, and t-spin mobility patterns are identified for performance comparison. We also generalize the selective paging strategy by introducing the concept of probabilistic selective paging (PSP) to reduce the paging cost. A unified analysis using recursive computations is carried out to compute the exact probability distribution for the number of per-call location updates. We calculate the location profile with respect to an incoming call and derive an exact expression of the average paging cost for PSP. With its ability to distinguish subtle performance variations and unveil new features of various dynamic location management schemes, our analytic framework is demonstrated to provide more precise and insightful results than conventional analysis.     

Analysis of cost and quality of service of time-based dynamic mobility management in wireless networks

A key observation of a time-based location management scheme (TBLMS) is that the simple paging method (i.e., the fastest paging method) does not guarantee to find a mobile terminal, no matter how small the location update cycle is and how big the radius of a paging area (PA) is. Therefore, in addition to cost analysis and optimization, there is one extra issue to deal with in a TBLMS, i.e., the quality of service (QoS), which is the probability that a mobile terminal can be found in the current PA. The main contributions of the paper are as follows. First, based on our previous results on random walks among rings of cell structures, we analyze the location distribution of a mobile terminal in a PA and the reachability of a mobile terminal in a PA when a phone call arrives, where the inter-call time and the cell residence time can have an arbitrary probability distribution. Second, using results from renewal processes, we analyze the cost of dynamic mobility management in a TBLMS, where the inter-call time and the cell residence time can have an arbitrary probability distribution. Third, we develop a method to find a TBLMS which has the best combination of the location update cycle and the radius of a PA with the minimum cost of mobility management, while still satisfying the required QoS.     

Design and analysis of synchronous dynamic frequency hopping code division multiple access communication system

An optical dynamic frequency hopping code division multiple access communication system is proposed. In this system, an electrically controlled tunable optical filter (TOF) is used to encode the modulated broadband light source. The code depends on the function set to the controller. Two-dimensional code, named functional code, is also proposed based of shifted sine function. The function defines the dynamic coding pattern of the central wavelength of the transmitted narrowband optical signal. Thus, the system will allow for an easy reconfiguration of the transmitter without the need for sophisticated encoder. At the receiver, a synchronized TOF with the same function is used as a decoder. The system is modeled and analyzed taking into account the multiple access interference, phase induced intensity noise, and thermal noise. The performance of this system is shown to be better compared with a fast frequency hopping system and a spectral amplitude coding system that uses either a Hadamard code, a modified quadratic congruence code (MQC), or a modified frequency hopping code (MFH).     

Teletraffic analysis of hierarchical cellular communication networks

The sustained increase of users and the request for advanced multimedia services are amongst the key motivations for designing new high-capacity cellular telecommunication systems. The proposals that are being pursued by several studies and field implementations consider hierarchical architectures and dynamic resource allocation. A hierarchical cellular communication network is analyzed, taking user mobility into account and exploiting dynamic channel-allocation schemes. In particular, a finite number of users has been considered, moving at different speeds in a geographical region covered by a finite number of cells structured in two hierarchical levels: micro- and macrocells. For such a system, mobility and traffic models have been developed, both based on queueing networks analyzing maximum packing (MP), a dynamic channel-allocation scheme. The obtained results, validated by simulation experiments, allow the evaluation of main system-performance parameters in terms of new-call and handoff blocking probabilities, and forced-termination probability as a function of load and system parameters.     

光电跟踪设备中光纤通信系统设计

为实现高数据传输率、强抗干扰性和超低误码率的目标,采用光纤通信技术传输高帧频、高分辨力的数字图像数据。本设计针对Cameralink接口红外图像数据源,设计了一种基于现场可编程门阵列(FPGA)控制的自适应分辨率和帧频的光纤收发系统,采用了低成本SPARTAN6器件XC6SLX45、串并转换芯片组DS90UB903/904、小型化单模小封装可插拔(SFP)单纤双向收发光模块,实现了双路图像光纤收发功能。其中FPGA接收Cameralink接口图像数据,进行图像转换处理,再通过内部集成电路(I2C)总线控制串并转芯片组实现自适应图像串行化和解串功能,并驱动光模块实现光电转换。本设计实现了分辨率640×512、帧频100 Hz红外图像数据的发送和接收功能,并通过了各项环境试验,已应用于实际型号项目中。