中国移动传输建设的切入点——无线接入

本文首先介绍了无线接入的特点,然后从覆盖范围、系统容量、业务能力、适应范围等方面比较了3．5GHz固定无线接入与LMDS无线接入的区别。文章指出,3．5GHz固定无线接入适合于业务发展初期进行宽范围的一般覆盖,从而上提供业务;而LMDS适合于业务量集中的小范围热点地区覆盖,从点上提供业务。     

宽带无线接入技术的现状及发展

宽带无线接入已成为接入领域的热点，本文从宽带无线接入技术的产生，介绍了宽带无线接入技术的现状，比较了几种技术的特点及市场定位，并分析了宽带无线接入技术未来的发展前景。     

面向应用的短距离无线通信系统信道接入机制

自组方式短距离无线通信具有设备简单、使用方便及成本低等特点,因此成为研究和应用的热点,其信道接入是关键技术之一。针对短距离无线通信系统在现实应用中的信道接入问题,论述了两种信道接入机制———轮询方式和竞争方式。从工作原理、性能、优缺点等方面对这两种机制进行了比较,以系统成本、复杂度、性能指标等为参数分析了各自的应用。分析表明,两种信道接入机制各有特点,适合不同的条件,是实用的自组方式的无线接入方式。     

三种技术支持无线城市

WiFi主要用于办公室、家庭、酒店以及热点地区的短距离分布式网络接入。相对于有线接入技术,WiFi的突出优势在于：接入方式不受网络信息点位置的限制,网络覆盖范围相对广泛且易于扩展;传输速度很快,预计可以达到500Mbps;不需要投入资金进行布线及开沟挖槽,节省了大量成本,简化了安装程序,缩短了建设周期。     

繁华的宽带无线接入技术

2004年，宽带无线接入技术继续呈现热点不断的繁荣局面，不时有新技术引起业界的瞩目，无线接入技术继续沿宽带化和多样化的方向前进。2005年，这一趋势将得到延续，同时宽带无线接入移动性的研究将进一步加强，而技术本身的应用研究也将受到业界的关注。以下，将重点就一些热点和即将成为热点的无线接入技术进行点析。     

支持多媒体业务的接入控制技术研究进展

如何保障不同类型的多媒体业务在通信过程中的通信服务质量(QoS),是目前接入控制技术中一项热点研究问题。通过对近十几年间相关文献的整理和分析,对支持多媒体业务的接入控制技术的研究进展进行综述,具体内容包括多媒体业务类型的设计、支持多媒体业务的接入控制协议、多信道分配策略等方面,并提出了支持多媒体业务的接入控制技术未来的研究方向。     

宽带无线接入技术的现状及发展

宽带无线接入已成为接入领域的热点。本文从宽带无线接入技术的产生,介绍了宽带无线接入技术的现状,比较了几种技术的特点及市场定位,并分析了宽带无线接入技术未来的发展前景。     

基于DVB-RCS和WiMAX的卫星宽带无线接入体系设计

卫星宽带通信已成为目前研究的热点.现有的DVB-RCS卫星无线接入标准以物理层规范为主,尚未构成完整的卫星宽带无线接人体系.本文基于DVB-RCS技术,针对卫星宽带无线接入的需求和特点,结合地面WiMAX宽带无线接入技术,给出了卫星宽带无线接人体系的功能架构设计,并具体分析了各主要功能的设计与实现方法.     

IEEE802系列宽带无线接入标准简介

随着Intemet、和数据通信产业的迅速发展，宽带无线接入（BWA）成为当前通信业界的讨论热点。本文结合最新的技术发展状况，重点介绍IEEES02系列宽带无线接入标准，并从覆盖范围、工作频率、移动性等六个方面对进行比较。     

LTE随机接入过程的探讨

从触发条件、前导、主要步骤和分类对随机接入过程进行了详细探讨。     

Understanding and Predicting Data Hotspots in Cellular Networks

The unprecedented growth in mobile data usage is posing significant challenges to cellular operators. One key challenge is how to provide quality of service to subscribers when their residing cell is experiencing a significant amount of traffic, i.e. becoming a traffic hotspot. In this paper, we perform an empirical study on data hotspots in today’s cellular networks using a 9-week cellular dataset with 734K+ users and 5327 cell sites. Our analysis examines in details static and dynamic characteristics, predictability, and causes of data hotspots, and their correlation with call hotspots. We show that using standard machine learning methods, future hotspots can be accurately predicted from past observations. We believe the understanding of these key issues will lead to more efficient and responsive resource management and thus better QoS provision in cellular networks. To the best of our knowledge, our work is the first to empirically characterize traffic hotspots in today’s cellular networks.     

Enabling location‐based services in wireless LAN hotspots

The wide deployment of IEEE 802.11 Wireless LAN (WLAN) makes possible application services developed in WLAN hotspots. Owing to the small cell size in WLAN hotspots, it is practical to develop location‐based services with the awareness of the WLAN access points (APs) that mobile devices currently access. In this paper, we propose an effective location determination technique using the inherent SNMP support in WLAN APs. It is shown that the current location of a mobile device can be determined from the SNMP traps sent by APs. Since the SNMP‐based approach doesn't need any particular software or hardware in mobile devices, location‐based services can be widely deployed, especially in public WLAN hotspots. To further enable location‐based services through the WWW, this paper also considers the location determination of a mobile device from its IP address, retrieved in a WWW environment. In addition, we propose a web service framework for location‐based services in WLAN hotspots. Thus, location‐based services can be developed in a standard way. Copyright © 2005 John Wiley & Sons, Ltd.     

Bus-driven floorplanning with thermal consideration

As the increasing number of buses in multi-core SoC designs, bus planning problems become a dominant factor in determining the chip performance. To cope with these issues, it is desirable to consider them in the early floorplanning stage. Recently, many bus-driven floorplanners have been proposed in the literature. However, these proposed algorithms only consider the bus planning problem without the thermal effect. As a result, there are hotspots, which result in high chip temperature, on the chip. In this paper, a thermal-driven bus-driven floorplanning algorithm is proposed to separate hotspots during the perturbation stage and to keep buses away from hotspots during the routing stage. To avoid time-consuming thermal simulations, the superposition of thermal profiles, which are the thermal distribution of each module, is adopted to efficiently estimate the module temperature. Compared with the state-of-the-art bus-driven floorplanner, experimental results demonstrate that the proposed algorithm can effectively separate hotspots and reduce the chip temperature.     

A fuzzy logic approach to detect hotspots with NOAA/AVHRR image using multi-channel information fusion technique

This paper proposes a novel approach to detect hotspots using NOAA advanced very high resolution radiometer (AVHRR) for the Jharia, Jharkhand (India) region. Jharia coalfield in Jharkhand is the richest coal bearing area in India that contains a large number of mine fires which have been burning for several decades. In this paper, a fuzzy based methodology has been applied for the determination of hotspots to Jharia AVHRR images based on a theoretical model that establishes relationship among AVHRR channel 4, channel 5 and different vegetation indices. The algorithm consists of four stages: data preprocessing, multi-channel information fusion, hotspot detection using fuzzy logic approach and validation of result. The most commonly used existing algorithms like contextual algorithms, multi-thresholding, entropy based thresholding, and genetic algorithms have limitation that they need some mathematical model for training in order to get the required result. The employed fuzzy logic approach overcomes this requirement and in addition, it is flexible, tolerant of imprecise data and is based on natural language. The results were compared with the results obtained by ground survey and a good agreement has been obtained between observed and predicted hotspots.     

室内定位技术应用、研究现状及展望

通过对室内定位技术的典型应用场景进行介绍,归纳总结了现有室内定位技术的基本原理和实施方案,并对未来室内通信技术可能的研究热点进行了展望。     

PTN应用现状及展望浅析

PTN技术已在本地或城域传送网中获得大量应用,本文从PTN的测试、现网应用、热点问题及发展等几个方面进行了分析。     

Repeaters for hotspot capacity in DS-CDMA networks

Currently, wireless operators around the world are building code-division multiple-access (CDMA) based radio access networks and big efforts are made to find the most cost effective way to do so. In this paper, the novel use of repeaters in a direct-sequence CDMA (DS-CDMA) system such as UMTS to improve capacity in areas with hotspots (small areas with increased traffic volume) is studied through static Monte Carlo simulations. The performance of the repeaters is shown to be sensitive to tuning of the repeater gain. With correct tuning, the simulations show that the repeaters are very beneficial for the downlink, which is the capacity-limiting link. When repeaters covering the hotspots are introduced, the system is thus seen to tolerate more hotspot traffic. For a scenario in which the hotspots are located close to the cell border, the system tolerates approximately twice as high hotspot traffic load. For hotspots located halfway between the base station and the cell border, the system tolerates approximately 80% more hotspot traffic load. Also in the uplink, more hotspot traffic is tolerated when repeaters are introduced. The effect is smaller than for the downlink, however. The results indicate that repeaters are well suited to increase capacity of a WCDMA /UMTS system in hotspot areas.     

An Efficient Contextual Algorithm to Detect Subsurface Fires With NOAA/AVHRR Data

This paper deals with the potential application of National Oceanic and Atmospheric Administration (NOAA)/Advanced Very High Resolution Radiometer (AVHRR) data to detect subsurface fire (subsurface hotspots) by proposing an efficient contextual algorithm. Most of the solutions proposed to date are mainly focused on the problem of surface fires, and very few research works have been performed to develop techniques for the subsurface fire problem. Although few algorithms based on the fixed-thresholding approach have been proposed for subsurface hotspot detection, however, for each application, thresholds have to be specifically tuned to cope with unique environmental conditions. The main objective of this paper is to develop an instrument-independent adaptive method by which direct threshold or multithreshold can be avoided. The proposed contextual algorithm is very helpful to monitor subsurface hotspots with operational satellite data, such as the Jharia region of India, without making any region-specific guess in thresholding. Novelty of the proposed work lies in the fact that once the algorithmic model is developed for the particular region of interest after optimizing the model parameters, there is no need to optimize those parameters again for further satellite images. Hence, the developed model can be used for optimized automated detection and monitoring of subsurface hotspots for future images of the particular region of interest. The algorithm is adaptive in nature and uses vegetation index and different NOAA/AVHRR channel's statistics to detect hotspots in the region of interest. The performance of the algorithm is assessed in terms of sensitivity and specificity and compared with other well-known thresholding techniques such as Otsu's thresholding, entropy-based thresholding, and existing contextual algorithm proposed by Flasse and Ceccato. The proposed algorithm is found to give better hotspot detection accuracy with lesser false alarm rate.     

电子货币的关键技术及其研究进展

电子货币由于具有匿名等特性,一直是电子支付工具研究的热点之一。本文描述了这一研究热点的基本概念,归纳其主要特性和研究中应用的关键技术,最后介绍它的研究进展。