Mobile-Fi无线接入技术研究

在3G系统全面铺开的时候,一种新出台的无线通信标准却有可能对它的前景构成威胁,这就是Mobile-Fi,即IEEE 802．20标准,也称移动宽带无线接入(MBWA)标准。文章首先对最近提出的移动无线宽带接入标准Mobile-Fi作了介绍,并与Wi-Fi、WiMAX、3G、4G等进行了比较,分析了其发展所面临的挑战。     

B3G无线通信中合作网络的一种新型无线接入方案

The paper discusses the signifi cance and development foreground of co-operation among heterogeneous networks in composite radio context for B3G wireless communications. The concept of composite reconfigurable wireless network is introduced in the paper, and the development of future wireless communication systems is also discussed. The basic confi guration framework of the network interoperation is given, and the functions of important parts are analyzed. A management platform for co-operation between WLAN...     

Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks

The traffic-adaptive medium access protocol (TRAMA) is introduced for energy-efficient collision-free channel access in wireless sensor networks. TRAMA reduces energy consumption by ensuring that unicast and broadcast transmissions incur no collisions, and by allowing nodes to assume a low-power, idle state whenever they are not transmitting or receiving. TRAMA assumes that time is slotted and uses a distributed election scheme based on information about traffic at each node to determine which node can transmit at a particular time slot. Using traffic information, TRAMA avoids assigning time slots to nodes with no traffic to send, and also allows nodes to determine when they can switch off to idle mode and not listen to the channel. TRAMA is shown to be fair and correct, in that no idle node is an intended receiver and no receiver suffers collisions. An analytical model to quantify the performance of TRAMA is presented and the results are verified by simulation. The performance of TRAMA is evaluated through extensive simulations using both synthetic- as well as sensor-network scenarios. The results indicate that TRAMA outperforms contention-based protocols (CSMA, 802.11 and S-MAC) and also static scheduled-access protocols (NAMA) with significant energy savings. This work was supported in part by the NSF-NGI grant number ANI-9813724 and by the Jack Baskin Chair of Computer Engineering at UCSC. Venkatesh Rajendran received the B.E. degree in Electronics and Communication Engineering from the Anna University in 2001, and M.S. in Computer Engineering from the University of California, Santa Cruz (UCSC) in 2003. He is currently working towards his Ph.D at UCSC. He is a graduate student researcher at the Inter-networking Research Lab (INRG). His research interests are in wireless communication system design, energy-aware media access control protocols for wireless ad hoc networks, smart sensor networks, reliable multi-casting, wireless multi-carrier communications, digital signal processing, adaptive modulation, and smart antenna systems. Katia Obraczka received the B.S. and M.S. degrees in electrical and computer engineering from the Federal University of Rio de Janeiro, Brazil, and the M.S. and Ph.D. degrees in computer science from the University of Southern California (USC). She is an Assistant Professor of Computer Engineering at the University of California, Santa Cruz. Before joining UCSC, she held a research scientist position at USC's Information Sciences Institute and a research faculty appointment at USC's Computer Science Department. Her research interests include computer networks, more specifically, network protocol design and evaluation in wire-line as well as wireless (in particular, multi-hop ad hoc) networks, distributed systems, and Internet information systems. J.J. Garcia-Luna-Aceves received the M.S. and Ph.D. degrees in electrical engineering from the University of Hawaii, Honolulu, HI, in 1980 and 1983, respectively. He is the Baskin Professor of Computer Engineering at the University of California, Santa Cruz (UCSC). Dr. Garcia-Luna-Aceves directs the Computer Communication Research Group (CCRG), which is part of the Information Technologies Institute of the Baskin School of Engineering at UCSC. He has been a Visiting Professor at Sun Laboratories and a consultant on protocol design for Nokia. Prior to joining UCSC in 1993, he was a Center Director at SRI International (SRI) in Menlo Park, California. Dr. Garcia-Luna-Aceves has published a book and more than 250 refereed papers and three U.S patents, and has directed more than 18 Ph.D. theses at UCSC. He has been Program Co-Chair of ACM MobiHoc 2002 and ACM Mobicom 2000; Chair of the ACM SIG Multimedia; General Chair of ACM Multimedia '93 and ACM SIGCOMM '88; and Program Chair of IEEE MULTIMEDIA '92, ACM SIGCOMM '87, and ACM SIGCOMM '86. He has served in the IEEE Internet Technology Award Committee, the IEEE Richard W. Hamming Medal Committee, and the National Research Council Panel on Digitization and Communications Science of the Army Research Laboratory Technical Assessment Board. HE has been on the editorial boards of the IEEE/ACM Transactions on Networking, the Multimedia Systems Journal, and the Journal of High Speed Networks. He received the SRI International Exceptional-Achievement Award in 1985 and 1989, and is a senior member of the IEEE.     

WLAN接入GPRS核心网的认证机制

无线局域网和移动运营商网络结合起来，利用现有GPRS核心网强大的管理功能和漫游能力，可以拓展无线局域网的业务范围。这一方案中，只有控制信息被传输到移动核心网，而用户数据直接通过IP骨干网传输，这样可以极大地缓解无线数据业务对移动核心网的负荷。如何利用IP机制将移动用户认证信令从终端传到GPRS核心网是设计的难点。本着重分析认证机制及其相关协议。     

Municipalities as a Driver for Wireless Broadband Access

Municipalities can form a driving force behind the deployment of new telecom infrastructure. While a telecom operator focuses on direct (financial) profits, a municipality is mainly interested in the social benefits for its inhabitants. In this paper, we evaluate a wireless municipality network from both a technical and an economic point of view. WiFi and WiMAX are considered as the most suited technologies for this purpose. A detailed techno-economic study has been performed including forecasting of the user adoption, dimensioning of the wireless network and modelling the related costs and revenues. The trade-off between installing a high number of relatively cheap WiFi access points, and a smaller number of more expensive WiMAX base stations for delivering full coverage is investigated in several scenarios.

面向普适计算的动态多级安全访问控制方案

提出一种面向普适计算的动态多级安全访问控制新方案,形式化描述了访问控制的构成要素,定义了动态访问控制策略,最后给出了授权实现算法.方案既保证了授权的动态性,又增强了访问控制的安全性,更适合于普适计算环境.     

无线Ad Hoc网络中基于业务感知的多信道MAC协议(英文)

Existing multi-channel Medium Access Control (MAC) protocols have been demonstrated to significantly increase wireless network performance compared to single channel MAC protocols. Traditionally, the channelization structure in IEEE 802.11 based wireless networks is pre-configured, and the entire available spectrum is divided into subchannels and equal channel widths. In contrast, this paper presents a Traffic-Aware Channelization MAC (TAC-MAC) protocol for wireless ad hoc networks, where each node is equipped with a single half duplex transceiver. TAC-MAC works in a distributed, fine-grai-ned manner, which dynamically divides variable-width subchannels and allocates subchannel width based on the Orthogonal Frequency Division Multiplexing (OFDM) technique according to the traffic demands of nodes. Simulations show that the TAC-MAC can significantly improve network throughput and reduce packet delay compared with both fixed-width multi-channel MAC and single channel 802.11 protocols, which illustrates a new paradigm for high-efficient multi-channel MAC design in wireless ad hoc networks.     

Performance Analysis for a New Medium Access Control Protocol in Wireless LANs

One fundamental issue in high-speed wireless local area networks (LANs) is to develop efficient medium access control (MAC) protocols. In this paper, we focus on the performance improvement in both MAC layer and transport layer by using a novel medium access control protocol for high-speed wireless LANs deploying carrier sense multiple access/collision avoidance (CSMA/CA). We first present a recently proposed distributed contention-based MAC protocol utilizing a Fast Collision Resolution (FCR) algorithm and show that the proposed FCR algorithm provides high throughput and low latency while improving the fairness performance. The performance of the FCR algorithm is compared with that of the IEEE 802.11 MAC algorithm via extensive simulation studies on both MAC layer and transport layer. The results show that the FCR algorithm achieves a significantly higher efficiency than the IEEE 802.11 MAC and can significantly improve transport layer performance.     

新无线接入技术NR-MIMO赋形研究

5G-NR为一种新的接入技术,以满足广泛的需求,包括增强的移动带宽、大规模机器式通信、超可靠和低时延通信等。新的无线接入技术能支持高达100GHz的宽频率范围。但对于6GHz以上的高频通信,存在着明显的路径损耗和穿透损耗。解决这一问题的其中一个解决方案是部署大型天线阵列以获得高波束赋形增益。因此,研究包括模拟/数字/混合波束形成在内的各种波束赋形的增强型大规模MIMO在内的新型无线电接口的多天线方案是十分必要的。     

A Combined Forward Error Control and Multiple Access Protocol for Wireless Voice/Data Integration

Different strategies for error control are investigated, in conjunction with a MAC-level protocol, operating in a multimedia noisy cellular environment, where a base station co-ordinates mobile users within each cell. The channel multiplexing structure is based on Time Division (TDM), and the slots in each frame are dynamically assigned to the users and their service classes. The access rights are decided by an algorithm, namely, the Independent Stations Algorithm (ISA), at the cell base station, which broadcasts this information to the users. Each single mobile station is associated a bit error probability, which changes with time in a random fashion. Bit error probabilities are estimated and the protection level of the Forward Error Correction (FEC) code is dynamically adapted to the new conditions. The performance of the scheme is analyzed by simulation in the presence of mixed voice and data traffic, and with different error handling techniques (FEC and Automatic Retransmission Request (ARQ)).     

异构无线网络业务接入多目标优化控制算法

提出了一种应用于异构无线网络环境的基于多目标优化的业务接入控制算法.该算法以业务占用总资源最少、业务阻塞率最低和网络间负载最均衡为目标建立了多目标优化控制模型,采用高斯和戒上型组合隶属函数将多目标问题模糊化,利用最大化满意度指标法将多目标问题转化为单目标问题,并通过遗传算法求得最优解.仿真结果表明,所提算法能在兼顾各网络资源高效利用的同时,保证业务接入的可靠性,并相对于参考算法有效降低了业务阻塞率.     

HYPERFLOW: An Efficient Error Control Protocol for Wireless Broadband Access Networks

The subject of this paper is the design and evaluation of an efficient errorcontrol scheme for indoor cellular wireless broadband access networks, whichcan be considered as the wireless extension of a fixed quality-of-serviceoriented network (e.g., based on the ATM- (asynchronous transfer mode-)protocol). In order to improve the high and time-variant probability of transmissionerrors, a novel error control scheme is developed. The protocol calledHYPERFLOW (Hybrid Partial sElective Repeat ARQ with Flow control) representsan efficient combination of a selective repeat and a Go-Back-N ARQ- (automaticrepeat request-) scheme while keeping the implementation complexity withinlimits. Additionally, it features a flow control mechanism which prevents the channel from being blocked by a user with momentarily hightransmission error probability and thus considerably increases the totalsystem throughput. Furthermore, the HYPERFLOW-protocol is combined with anadaptive forward error control code. The resulting type II hybrid ARQ-schemeis based on the principle of incremental redundancy with redundant symbolsbeing sent only when they are required.A realistic model for the fluctuations of the transmission quality is used forthe performance evaluation of the HYPERFLOW-protocol. It turns out that the adaptive FEC-based error correction scheme can considerably improve thesystem performance.The mean transmission delay, for instance, can be reduced by a factor of upto 10 when the FEC-scheme is properly applied.     

无线车联网WAVE车-车通信中的一种路由算法实现

车载网络WAVE中车与车之间能够通信靠的是移动过程中车与车之间建立起来的网络连接，路由是实现网络连接的一个关键问题。基于行车速度与距离的快速多跳路由算法FMHR是以中间车辆与目标车辆之间通信时间值最小为策略来选择信息传递的下一跳。提出的保持最大通信时间KMCT路由算法与FMHR不同，KMCT 是以中间车辆与发送信息车辆之间通信时间的最大值为策略来选择信息传递的下一跳，实验结果表明，当车辆速度较高时，KMCT性能要优于FMHR。     

Virtual Cellular Network: A New Wireless Communications Architecture with Multiple Access Ports

A virtual cellular network (VCN) is proposed to provide wireless random access for bursty multimedia traffic to a fixed backbone infrastructure. A VCN does not use a conventional cellular frequency reuse concept. In a VCN, each terminal sends packets using the entire system bandwidth while any nearby port can pick up the signal. Then, the ports relay the packets to the port server (PS) over a fixed (wired) network. Ports can be simple radio receivers as they do not have to support the same functionality as conventional cellular base stations. The performance is investigated in terms of probability of capture, throughput and delay. Both our analysis and simulation show that despite its simplicity this network has a larger user capacity than conventional cellular reuse patterns.     

4G/5G协同无线网工程建设方案

如何处理好4G/5G在资源上的矛盾,解决好二者之间的协同,是当前无线网规划与工程建设面临的新课题。首先结合中国移动5G 2.6 GHz频率使用策略,提出面向4G/5G协同的工程建设方案,随后聚焦4G/5G天面协同,以中国移动现网多制式多频段天馈现状为出发点,提出“最佳三副、最少两副”的天面目标形态建议,并针对原有4 G D频段天馈调整、5G天馈建设给出分场景工程建设方案。     

针对3G上网用户的无线网络加速系统

随着3G上网业务的不断发展,越来越多的用户使用3G网络移动上网,这样会导致无线资源紧张,影响用户的使用体验,同时也给移动网络带来了沉重的负担。针对这一问题开发了针对3G移动上网用户Web应用的无线网络加速系统,该系统使用缓存和数据压缩技术,可以通过单向透明或者双向透明2种无客户端的方式部署在移动数据网到互联网的出口位置,以便于产品的推广使用。对该系统进行的现网测试包括单用户测试和现网流量测试两个部分,测试结果表明,使用无线网络加速系统大幅度减少移动上网用户的Web页面打开时间,从而提高了用户体验;同时使用该系统后,对于移动用户的Web应用产生的流量,在网络出口一侧和无线接入网一侧,能实现16%以上的流量节省。     

A Hybrid Adaptive Wireless Channel Access Protocol for Multimedia Personal Communication Systems

This paper proposes a new medium access protocol (MAC) protocol for futurewireless multimedia personal communication systems, denoted hybrid andadaptive multiple access control (HAMAC) protocol. The HAMAC protocolintegrates fixed assignment TDMA protocol, reservation-based protocols, andcontention-based protocols into a single wireless network so as tosimultaneously and efficiently support various classes of traffic such asconstant-bit-rate (CBR), variable-bit-rate (VBR), and available-bit-rate (ABR)traffic. In particular, the HAMAC protocol uses a novel preservationslot technique to overcome the packet contention overhead in packetreservation multiple access (PRMA) like protocols, while keeping mostisochronous service features of TDMA protocols to serve voice and CBR trafficstreams. A preservation slot is a very short slot which is used torepresent a CBR connection when the traffic in the CBR connection is in asilent period in which there is no meaningful data to transmit. Due to thevery short length of the preservation slot, it only takes minimalportion of the bandwidth pre-allocated to the CBR connection, so that theremaining bandwidth can be freed for other connections to use. When the CBRsource becomes active again, the preservation slot is replaced bynormal data slots without any reservation operation, extra delay, orsignificant bandwidth loss. Consequently, the guaranteed service andsimplified signaling features of TDMA protocols, together with the adaptivebandwidth allocation features of PRMA-like protocols, are both realized in theHAMAC protocol. We have analyzed the performance of the HAMAC protocol usingextensive simulations. The results show that the HAMAC protocol can achievevery low loss rates for various multimedia traffic with stringent quality ofservice (QoS) requirements and outperforms state-of-the-art PRMA-likeprotocols. As a result, the HAMAC protocol appears to be a good candidate forfuture generation multimedia personal communication systems.     

Efficient Access Control for Wireless Sensor Data

Although very developed in many sectors (databases, filesystems), access control schemes are still somewhat elusive when it comes to wireless sensor networks. However, it is clear that many WSN systems—such as healthcare and automotive ones—need a controlled access to data that sensor nodes produce, given its high sensitivity. Enforcing access control in wireless sensor networks is a particularly difficult task due to the limited computational capacity of wireless sensor nodes. In this paper we present a full-fledged access control scheme for wireless sensor data. We enforce access control through data encryption, thus embedding access control in sensor data units. We also propose a lightweight key generation mechanism, based on cryptographic hash functions, that allows for hierarchical key derivation. The suggested protocol only relies on simple operations, does not require interactions between nodes and data consumers and has minimal storage requirements.

A New OFDM System Based on Lifting Wavelet Transform for Wireless Channel

1 Introduction The high-bit-rate and large capacity transmission be-comes more and more i mportant in future generationmobile communication systems . OFDMis an efficienttechnology for wireless datatransmission[1].It has beenadoptedinseveral wireless standards such as Digital Au-dio Broadcasting (DAB)[2], Digital Video Broadcasting(DVB-T) ,andis a potential candidatefor fourth-gener-ation (4G) mobile wireless communication systems .The advantages of OFDM[3 ~4]include robustness a-gains…     

一种分层多跳无线网中的移动性管理策略

该文介绍一种分层多跳无线网与其他骨干网络互连情况下的网络层移动性管理方案。它使用了包含逻辑家乡代理的宏移动性管理和将位置管理与路由和寻呼机制结合起来的微移动性管理的思想,以提高网络在战场等特殊情况下使用的可靠性和抗毁性,减小位置管理的开销,节省无线信道的带宽。