Above packet level admission control and bandwidth allocation for IEEE 802.16 wireless MAN

IEEE 802.16 wireless Metropolitan Area Network (MAN) is expected to revolutionize the broadband wireless access technology. Efficient resource management is essential in providing scalability in such large IEEE 802.16-based wireless network and Quality of Service (QoS) for multimedia applications (VoIP, MPEG, FTP, WWW) is usually achieved by appropriate classification of scheduling services and grant/request mechanism. In this paper, we firstly discuss the QoS issue in IEEE 802.16 wireless MANs and propose a dynamic admission control scheme for scheduling services defined in the 802.16 specification. The proposed scheme provides the highest priority for Unsolicited Grant Service (UGS) connections and maximizes the bandwidth utilization by employing bandwidth borrowing and degradation. We develop an approximate analytical model to evaluate the system performance by assuming that the traffic processes of all scheduling services are Poisson processes. In fact, the self-similarity of non-voice traffic makes its traffic process far from Poisson process and should be modeled by Poisson Pareto Burst Process (PPBP). Therefore, in the later part of the paper, we analyze upper bound blocking probabilities of all scheduling services above the packet level using PPBP model for fractal traffic and Gaussian model for aggregated traffic in large wireless network as well as using the Chernoff bound method. Based on the analytical results, we give another admission control and bandwidth allocation mechanism above the packet level so as to minimize the blocking probability of each type of service in IEEE 802.16 wireless MAN. Analytical and simulation results are obtained and compared to demonstrate the effectiveness of proposed schemes and validate our analytical models.     

IEEE802．16中的无线Mesh网络研究

1980年3月13日,IEEE批准了一个新的的工程802。IEEE802由LAN／MAN Standard Committee（LMSC）负责。就无线通信而言,802WG定义了802．11WLAN,802．15WPAN和802．16WMAN。与以前的无线技术一样,随着通信实体的距离的增大,数据的传输速率随之降低。对新的应用层业务而言,无论距离多远,都必须要保障高的数据率。要克服链路速率的限制,必须密集地布置无线网路设备。WMN有助于克服当前的无线通信系统对有线主干网络的依赖,因为它们价格便宜并能保证新的无线应用。概括了WMN的发展历程和最新的发展动态,并指出了进一步的发展方向。     

应用于OFDM系统中的高速FFT处理器设计

针对无线城域网中工作在2GHz~11GHz频带的IEEE802.16a标准,在实现其OFDM系统时提出一种高速而且经济的FFT处理器设计方案。设计中采用了Radix-4的频率抽取算法和并行的蝶型计算单元结构,而且将旋转因子预先存储在ROM中以提高处理器运行的速度。设计方案采用了单个蝶型运算单元以达到控制FFT处理器规模的目的。数据的输入与输出都共用一个存储器,这进一步节约了硬件资源损耗。     

Integration of a speech activated control system and a wireless interworking unit for a CAN-based distributed application

Ever increasing number of mobile devices in automation systems have revealed the requirement of utilizing wireless communication systems enabling interoperability between existing wired and wireless systems. Therefore, a wireless interworking unit (WIU) is usually employed to provide required interworking functionality. This work briefly exploits a controller area network (CAN)/IEEE 802.11b WIU and a speech activated control application to be used in a CAN-based industrial networking environment and presents its prototype. The WIU employed provides communication skills with the speech activated control system including a speech recognition process and CAN-based distributed control application over the wireless medium.     

On the performances of IEEE 802.16(d) mesh CDS-mode networks using Single-Switched-Beam Antennas

The IEEE 802.16(d) mesh coordinated distributed scheduling (CDS) mode is a novel technology for future fixed wireless backbone networks and designed for the use of omnidirectional antennas. The use of Single-Switched-Beam Antennas (SSBAs) may have great potential to increase network capacity due to the antenna directivity. However, a network designed for omnidirectional antennas usually cannot operate well or achieve good performance with the presence of antenna directivity.In this paper, we review the designs of the IEEE 802.16 mesh CDS-mode network, study the issues of this network with the use of Single-Switched-Beam Antennas (SSBAs), and propose a complete solution to solve these issues. The performances of our proposed scheme is evaluated using simulations. The simulation results show that our proposed scheme can effectively solve the issues of using SSBAs in the IEEE 802.16 mesh CDS-mode network and greatly increase its network capacity.     

WiMAX在宽带无线城市中的应用

WiMAX是基于IEEE802．16标准的无线宽带接入技术,可为固定、移动、便携形式的通信终端提供更为便捷的宽带无线接入。与wi—Fi等无线通信技术相比,WiMAX具有更强的抗干扰性,更高的带宽利用率,因此,在无线城市建设中WiMAX、3G和WiFi三者的技术结合会创造出一个完美的宽带无线网络,实现数字化生活。     

WiMAX网络不同模式下的位置管理策略分析

在固定无线城域网基础上支持其移动性的IEEE802.16e[1]是一种有效的移动宽带无线接入解决方案,将HMIPv6[2]与IEEE802.16e有机结合,可以使切换的时延和丢包率都明显减小。IEEE802.16同时支持Mesh模式,可以获得更大的网络覆盖范围以及降低设备成本。本文从理论上分析了在无线Mesh网络中采用传统位置管理策略的网络开销,并与典型的采用HMIPv6的WiMAX网络进行了对比。分析结果表明,WiMAX Mesh网络需要结合拓扑特性考虑更加有效的位置管理策略,以更好地支持移动性及多种业务的应用。     

Scheduling solution for the IEEE 802.16 base station

The IEEE 802.16 standard defines a wireless broadband access network technology called WiMAX. It introduces several advantages, one of which is the support for QoS at the MAC level. To ensure meeting the QoS requirements, the 802.16 base station must run some algorithm to allocate slots between connections. This algorithm is not defined in the 802.16 specification but rather is open for alternative implementations. We propose a simple, yet efficient, solution that is capable of allocating slots based on the QoS requirements, bandwidth request sizes, and the 802.16 network parameters. To test the proposed solution, we have implemented the 802.16 MAC and PHY layers in the NS-2 simulator. Several simulation scenarios are presented that demonstrate how the scheduling solution allocates resources in various cases. According to the simulation results, the proposed scheduling solution ensures the QoS requirements of all 802.16 service classes. The solution shares free resources fairly and demonstrates work-conserving behaviour.     

Overview of IEEE 802.16 security

When creating the new wireless communication standard IEEE 802.16, designers attempted to reuse a security scheme designed for wired media. The authors review the standard, enumerate its flaws, and outline changes that could defend it against threats.     

IEEE 802.16标准安全机制研究

作为无线城域网的标准,陋EE 802.16已经取得了巨大进展,但是无线信道自身的弱点使得802.16的安全问题依然受到关注.本文在对802.16标准安全机制进行分析的基础上,指出了803.16d存在的安全问题以及802.16e所作的改进,并对未来要解决的问题提出建设性的意见.     

IPv6 based relay gateway protocol in hybrid networks

During the past few years, WMAN (Wireless Metropolitan Area Network) and WLAN (Wireless Local Area Network) provided fast, convenient and reliable solution for all kinds of users. With the development of the communication technology, the future wireless networks will allow mobile users access Internet anywhere, anytime. Therefore, it is a natural trend to combine different wireless networks to provide a seamless roaming for users. It is feasible for mobile terminal which have multiple modes to handoff between different networks. A relay gateway protocol for the WLAN-mode nodes (mono-mode WLAN nodes and dual-mode nodes) in the hybrid network of IEEE 802.16 WMANs and IEEE 802.11 WLANs is proposed to provide wider mobility. Dual-mode mobile nodes with good service can provide WLAN links to nearby WLAN-mode nodes with bad service or out of the WLAN coverage. Simulation results show that the relay gateway scheme can improve network performance of the hybrid networks. Moreover, the relay gateway method can bring additional service coverage and increase the capacity of WMANs and WLANs.     

Is WiMax's Future Up in the Air?

When the IEEE 802.16 WiMax technology standard emerged from its working group in 2004, it was greeted with great anticipation as a key building block in future network Infrastructure. Service providers who had tried to deploy fixed wireless broadband access with proprietary technologies welcomed WiMax's promise of off-the-shelf long-range wireless networking gear; public-policy experts were equally enthusiastic about 802.16's prospects as a competitor to landline networks in developed regions and as an economically viable solution in regions in which landline broadband was difficult or Impossible to construct. However, a funny thing happened on the way to wireless nirvana. WiMax's entry into the broadband market has been marked with confusion and conflict. Across the networking industry, a period of reappraisal has replaced the post-release euphoria.     

A survey on emerging broadband wireless access technologies

Wireless broadband technologies provide ubiquitous broadband access to wireless users, enabling services that were available only to wireline users. In this paper, we summarize emerging wireless broadband access technologies, ranging from WLANs to satellite communications. We explain the latest standards in the IEEE 802.11 and IEEE 802.16 families in detail. The MAC layer mechanisms of IEEE 802.11e, 802.11n, and 802.11s standards are explained as well as the point-to-multipoint and Mesh modes of IEEE 802.16. The recent mobility amendment to the WiMAX family, IEEE 802.16e, is also described. Though the earliest versions of some of these technologies date back to 1996 (such as IEEE 802.11) and some are obsolete (such as HiperLAN), they have been included in this survey for the sake of completeness.Wireless technologies can be categorized based on their coverage areas. IEEE 802.11 and ETSI HiperLAN standards are considered for wireless access in local areas. IEEE 802.16 and 802.22, ETSI HiperACCESS and HiperMAN, WiBro, and HAP technologies can be used to provide service in metropolitan areas. Lastly, IEEE 802.20 and satellite systems provide service as wide area networks. Since the aim of this survey is to summarize wireless broadband technologies for data services, technologies such as Wireless USB are excluded. 3G and 4G systems have also been excluded since they are covered in detail in [C. Smith, D. Collins, 3G Wireless Networks, second ed., McGraw-Hill Osborne Media, 2006; S.G. Glisic, Advanced Wireless Networks: 4G Technologies, Wiley Publishing, 2005].     

基于免疫计算的IEEE 802.16j网络基站及中继站选址优化

IEEE802.16j标准引入了中继站,从而能获得覆盖能力和容量的提升.与传统的单跳无线接入网络相比,IEEE802.16j网络具有以较低代价获得较高容量的优势.中继站和基站的联合优化是移动网络运营商进行网络规划的重要内容之一.由于中继站建站代价远小于基站建站代价,在给定候选站址和覆盖需求的前提下,通过对中继站和基站的站址进行联合优化可以减少基站的建设数目,从而降低网络的建设总代价.为了解决802.16j网络基站及中继站选址优化问题,给出了一个基于免疫计算的选址优化方案.设计了802.16j网络选址优化问题的数学模型,给出了求解选址优化问题的免疫优化算法,并进行了仿真实验.实验结果表明：所给出的方案能以较小的网络建设代价获得较大的网络容量增益,具有较好的应用价值.     

IEEE802.16e标准安全机制的改进

指出了IEEE802.16e安全机制中所存在的严重漏洞。针对无线移动设备存在存储容量有限、处理速度慢、带宽低等问题,利用无线公钥设施中的证书标识符URL和椭圆曲线加密算法对IEEE802.16e中的密钥管理协议（PKM）进行了改进。仿真结果表明改进后的安全机制更适合于无线网络环境。     

一种基于IEEE 802.16的ARQ反馈类型选择算法

IEEE 802.16中规定的ARQ机制能够很好地解决无线链路上的数据传输问题,但是对于规定的几种ARQ反馈方式,协议并没有定义一个合适的选择算法。算法的关键是根据无线链路的实时情况选择一种最合适的ARQ反馈类型来发送反馈消息,从而提高资源利用率。针对IEEE 802.16的特点,提出一种新的反馈类型选择算法,以满足实时选择反馈类型的需求。仿真结果表明,该算法能够显著提高资源利用率。     

基于模数的WiMAX网络高负载自适应冲突解决算法

根据现有的部分研究结果发现,IEEE 802.16标准中使用的截断二进制指数后退算法在解决网络冲突时效率很低;并且当网络的负载增多时,该算法的运行性能更差.在此基础上,提出了一种基于模数的自适应冲突解决算法来优化WiMAX网络的冲突解决过程.该算法将所有用户站按照当前时间帧内的传输机会数量分为多个小组,并且要求用户站只能通过特定的传输机会发送请求.与此同时,为了保证整个网络的高性能,本算法要求基站和用户站根据上一轮请求过程中的平均冲突概率和传输机会使用率来调整当前时间帧内的传输机会数量,以及挑选部分用户站参与带宽请求,保证了WiMAX网络在高负载情况下的运行性能.模拟结果表明,本算法在WiMAX网络运行过程中能够较好地解决请求过程中的冲突,对网络性能提高较大.     

一种用于无人机的分布式飞行控制系统设计①

分布式结构已广泛应用于高可靠航空电子设备的设计中。设计了一种基于控制局域网（CAN）的分布式飞行控制计算机,用于在执行飞行任务过程中无人机的飞行控制律解算和系统管理。根据无人机控制的实时性和可靠性需求,提出了一种CAN通信、双端口随机访问存储器（DPRAM）通信和控制任务相互配合的内部通信机制。实验表明根据该通信机制设计的通信方案完全满足无人机控制的实时性和可靠性要求,同时解决了分布式结构引入的数据延时问题。     

Dynamic end-to-end capacity in IEEE 802.16 wireless mesh networks

The IEEE 802.16 standard defines mesh mode as one of its two operational modes in medium access control (MAC). In the mesh mode, peer-to-peer communication between subscriber stations (SSs) is allowed, and transmissions can be routed via other SSs across multiple hops. In such an IEEE 802.16 mesh network, accurate and reliable determination of dynamic link capacity and end-to-end capacity of a given multi-hop route is crucial for robust network control and management. The dynamic capacities are difficult to determine in a distributed system due to decentralized packet scheduling and interference between communicating nodes caused by the broadcast nature of radio propagation. In this paper, we first propose a method for computing the dynamic link capacity between two mesh nodes, and extend that to determine the dynamic end-to-end capacity bounds of a multi-hop route based on the concept of Bottleneck Zone. The physical deployments of networks are also considered in the capacity estimation. We demonstrate the effectiveness and accuracy of our methods for computing dynamic link capacity and end-to-end capacity bounds through extensive simulations.     

多服务WiMAX系统的调度与资源分配策略

基于IEEE802.16标准的WiMAX技术已成为宽带无线接入的主要技术,IEEE802.16标准没有规定调度和资源分配策略,网络运营商可以自行选择。根据用户需求并考虑信道条件的影响,提出基于NS2的扩展WiMAX系统级仿真平台,给出一种公平有效的调度与资源分配策略。仿真结果证明该策略可以满足多种服务流的QoS需求并最大化系统吞吐量。