TD—SCDMA小区初搜方法研究

TD-SCDMA系统作为我国第一个被国际电联所采纳的标准，得到了我国政府的高度重视。在TD—SCDMA系统中，小区初始搜索是一个非常关键的过程。本文基于TD—SCDMA规范对小区初始搜索过程的原理和实现方法进行了分析。[编者按]     

WCDMA终端小区搜索过程详解

不同的移动通信制式采用了不同的终端小区搜索过程，而移动终端的网络搜索能力和时长将直接影响用户的感知。本文就从技术角度来解析WCDMA终端的网络搜索过程，对终端小区搜索过程使用的各种码、信道结构、同步过程等进行了详细描述。     

基于马尔可夫过程的水下运动目标启发式搜索

在搜索海域存在障碍的情况下,该文将启发式搜索算法应用于对水下运动目标的搜索,研究了基于马尔可夫过程的运动目标启发式搜索算法。建立了马尔可夫水下运动目标规避模型、搜索器启发式搜索过程模型和马尔可夫水下运动目标的搜索概率模型。该算法由已知的目标先验位置分布信息不断地对目标的运动位置进行估计、更新,以获得精确的目标后验分布,再利用启发函数得到下一步的最佳搜索节点。仿真分析表明:在对水下运动目标搜索时,搜索器能有效地规避障碍,提高搜索效率,有助于研究水下目标的优化搜索。     

WCDMA终端网络搜索过程剖析

移动终端的网络搜索能力是评价终端质量的一项重要指标。WCDMA终端的网络搜索包括PLMN选择和小区搜索两个子过程。对第一个子过程。具体介绍了PLMN的分类、PLMN的自动和手动选择方式。对第二个子过程。具体介绍了小区的分类、小区搜索过程和小区选择的信号质量要求。     

反舰导弹搜捕过程仿真及应用

搜捕过程是影响反舰导弹作战效能的主要因素之一。对反舰导弹搜捕过程进行了仿真,分析了反舰导弹搜捕过程中的4个仿真模型:方位搜索模型、距离搜索模型、捕捉判断模型和自控终点位置模型,给出了在冲淡式干扰条件下反舰导弹的突防概率,对反舰导弹的使用及舰艇的反导抗击具有一定的参考价值。     

移动搜索技术与业务发展研究

分析了移动搜索业务的定义和特点，介绍了移动搜索业务的分类，并对移动搜索业务的系统结构和搜索引擎系统技术进行了研究，然后对移动搜索业务发展的商业模式和现状进行了探讨。     

网络信息搜索技术的研究进展

搜索技术可以分为以分类目录为主的搜索引擎、以网页全文检索为主的搜索引擎和新兴的搜索技术。其中，对称搜索技术是当今搜索技术的代表，本文从对称搜索技术的优越性、对称性、对称搜索引擎的收录范围以及对称搜索技术在商业中的应用三个方面对其进行了介绍。Google是互联网信息搜索技术的代表，文章重点介绍了Google中的对称搜索技术以及Google进行高速搜索的关键一索引，从中可以了解到Coogle取胜的原因。     

声音

移动搜索简单、快速、直接，所需信息信手拈来。2004年10月8日，Google在美国推出了基于短信（SMS）的移动搜索业务，引起业界的广泛关注。随后，其竞争对手也纷纷跟进，搜索逐渐由Web浏览转向移动终端，五花八门的移动搜索，如雨后春笋不断涌现。今年更是移动搜索的“大年”。随着3G的部署，移动搜索将迅速窜红，对传统搜索发起强有力的挑战。在互联网业占尽优势的搜索巨头正积极与移动运营商牵手，抢占市场先机。各大手机厂商也对移动搜索表现出浓厚兴趣。     

通信侦察中信号的搜索与截获

讨论了通信侦察中信号的搜索与截获问题，重点讨论了对信号的频率搜索截获和提高搜索速度的方法。并给出了各种接收机对信号频率搜索截获的性能。     

移动搜索业务在信息化社会转型中的现状及创新发展策略研究

在向信息化社会转型的过程中，移动信息化起到举足轻重的作用，手机上网用户增长迅猛，极大地促进了移动搜索业务的发展，移动搜索能够满足用户个性化、隐私性的要求。本文分析了我国移动搜索业务现状和存在的问题，提出了我国移动搜索业务的创新发展策略，并对移动搜索服务在信息化社会转型中的发展进行了一定的探索。     

Modelling and performance of packet synchronization in A data communications system

This paper deals with some problems of packet synchronization in a slotted packet-radio communications system. The problems considered are bit-synchronization and unique word detection for bursty systems. The necessary overhead for synchronization purposes is dimensioned for applications in land-mobile satellite communication systems. The performance of synchronization is evaluated using hardware measurement equipment, including a commercial bit-synchronizer. Using these results, the performance loss of communication systems due to packet synchronization effects can be estimated. This is done for the additive white Gaussian noise channel and the class of land-mobile satellite channels.     

Media Synchronization and QoS Packet Scheduling Algorithms for Wireless Systems

Wireless multimedia synchronization is concerned with distributed multimedia packets such as video, audio, text and graphics being played-out onto the mobile clients via a base station (BS) that services the mobile client with the multimedia packets. Our focus is on improving the Quality of Service (QoS) of the mobile client's on-time-arrival of distributed multimedia packets through network multimedia synchronization. We describe a media synchronization scheme for wireless networks, and we investigate the multimedia packet scheduling algorithms at the base station to accomplish our goal. In this paper, we extend the media synchronization algorithm by investigating four packet scheduling algorithms: First-In-First-Out (FIFO), Highest-Priority-First (PQ), Weighted Fair-Queuing (WFQ) and Round-Robin (RR). We analyze the effect of the four packet scheduling algorithms in terms of multimedia packet delivery time and the delay between concurrent multimedia data streams. We show that the play-out of multimedia units on the mobile clients by the base station plays an important role in enhancing the mobile client's quality of service in terms of intra-stream synchronization and inter-stream synchronization. Our results show that the Round-Robin (RR) packet scheduling algorithm is, by far, the best of the four packet scheduling algorithms in terms of mobile client buffer usage. We analyze the four packet scheduling algorithms and make a correlation between play-out of multimedia packets, by the base station, onto the mobile clients and wireless network multimedia synchronization. We clarify the meaning of buffer usage, buffer overflow, buffer underflow, message complexity and multimedia packet delay in terms of synchronization between distributed multimedia servers, base stations and mobile clients.     

PTP技术分析与应用

在通信系统全网IP化的大背景下,分组网络作为统一承载网将面临新的同步需求问题。传统的同步技术精度较低,无法满足新应用对高精度同步的需求。IEEE 1588标准精密时间同步协议(PTP)的提出,成为一种有效解决高精度同步问题的方案。首先分析了PTP技术的同步原理,接着通过综合比较当今几种常用的同步技术的特点得出PTP技术的优势,最后提出了应用方案,并分析了实施过程和部署灵活性。PTP技术可方便灵活地应用于分组网络中,同步精度可达亚微秒级,将成为GPS的有效替代。     

Efficient Media Synchronization Mechanism for SVC Video Transport over IP Networks

The scalable extension of H.264, known as scalable video coding (SVC) has been the main focus of the Joint Video Team's work and was finalized at the end of 2007. Synchronization between media is an important aspect in the design of a scalable video streaming system. This paper proposes an efficient media synchronization mechanism for SVC video transport over IP networks. To support synchronization between video and audio bitstreams transported over IP networks, a real‐time transport protocol/RTP control protocol (RTP/RTCP) suite is usually employed. To provide an efficient mechanism for media synchronization between SVC video and audio, we suggest an efficient RTP packetization mode for inter‐layer synchronization within SVC video and propose a computationally efficient RTCP packet processing method for inter‐media synchronization. By adopting the computationally simple RTCP packet processing, we do not need to process every RTCP sender report packet for inter‐media synchronization. We demonstrate the effectiveness of the proposed mechanism by comparing its performance with that of the conventional method.     

Techniques for Packet Voice Synchronization

Packet switching has been proposed as an effective technology for integrating voice and data in a single network. An important aspect of packet-switched voice is the reconstruction of a continuous stream of speech from the set of packets that arrive at the destination terminal, each of which may encounter a different amount of buffering delay in the packet network. The magnitude of the variation in delay may range from a few milliseconds in a local area network to hundreds of milliseconds in a long-haul packet voice and data network. This paper discusses several aspects of the packet voice synchronization problem, and techniques that can be used to address it. These techniques estimate in some way the delay encountered by each packet and use the delay estimate to determine how speech is reconstructed. The delay estimates produced by these techniques can be used in managing the flow of information in the packet network to improve overall performance. Interactions of packet voice synchronization techniques with other network design issues are also discussed.     

Distributed slot synchronization (DSS): a network-wide slotsynchronization technique for packet-switched optical networks

Distributed slot synchronization (DSS) is a network-wide packet synchronization technique which coordinates node transmissions so that packets arrive aligned to one another at a reference point in the network, independent of propagation delays. DSS was developed for use in the contention resolution with delay-lines (CORD) project, a DARPA-funded 2.5 Gb/s/λ, wavelength division multiplexer (WDM) optical packet-switched network testbed. In this implementation, it was experimentally demonstrated that the DSS system, operating with 80 MHz control logic, achieves a packet arrival jitter of less than 13 ns with 12 km node spacings. DSS was also shown to be robust against noise and node failure or fiber breaks. The technique is data rate and format independent and can be used in other star, extended ring, or tree-and-branch network architectures for metropolitan area network (MAN) and access applications     

A multimedia synchronization model and its implementation intransport protocols

An implementation of a synchronization mechanism in transport protocol to support multimedia applications over a packet or cell switched network is proposed. In designing such a mechanism for practical use, ease of implementation and capability of handling random delay of packets are two key issues for success. Since the random delay of packet or cell switched networks makes synchronization among media more complicated after the transmission across the network, a model which considers the random transmission delay is hence required to specify the temporal relationship among media. Therefore, a real-time synchronization model is presented to satisfy this requirement in the paper. Based on the proposed synchronization model, a transport protocol, namely the multimedia synchronization transport protocol (MSTP), is designed and implemented. We have implemented a prototype system using the MSTP protocol and built a simulation system for the wide area network (WAN) environment in order to evaluate the performance of the MSTP protocol     

Multimedia synchronization protocols for broadband integratedservices

Protocols to provide synchronization of data elements with arbitrary temporal relationships of both stream and non-stream broadband traffic types are proposed. It is specified that the provision of a synchronization function be performed within a packet switched network, and, accordingly, a two-level communication architecture is presented. The lower level, called the network synchronization protocol (NSP), provides the ability to establish and maintain individual connections with specified synchronization characteristics. The upper level, the application synchronization protocol (ASP), supports an integrated synchronization service for multimedia applications. The ASP identifies the temporal relationships among an application's data objects and manages the synchronization of arriving data for playout. The proposed NSP and ASP are mapped to the session and application layers of the open-systems-interconnection (OSI) reference model, respectively     

Maximum likelihood synchronization for OFDM using a pilot symbol:algorithms

The design of a pilot symbol for orthogonal frequency-division multiplexing packet detection and synchronization is presented. Algorithms are described for packet detection and for synchronization using maximum likelihood estimation of channel frequency offset, phase offset for coherent detection, and subsample timing offset. The efficacy of the detection and synchronization algorithms is demonstrated experimentally     

分组网络同步技术的标准化进展

介绍了基于分组网络的频率同步标准和时间同步标准的发展历程,分析了分组频率与时间同步标准的最新进展,最后对分组同步标准今后的发展方向进行了阐述。