Implementation of the wireless ATM access terminal

Multimedia applications with audio and video connections have created totally new bandwidth and Quality of Service (QoS) requirements for the computer data networks. In order to meet the new customer requirements also the wireless access networks have to be enhanced to support the increased demand for broadband services. Wireless ATM (WATM) technology has emerged as one of the most promising alternatives for implementing multimedia capable mobile networks. The Magic WAND (Wireless ATM Network Demonstrator) is an international research project designing a WATM network that provides indoor radio coverage and user mobility. The system is mainly targeted for customer premises networks and hot spots with a large number of people within a restricted area, such as airports. This paper describes the architecture of the wireless ATM terminal developed for the Magic WAND demonstrator. The focus is on the terminal software which supports the user mobility and the native ATM access on the Windows NT operating system environment. The first part of the paper presents the generic reference model for the broadband radio networks and describes the Magic WAND system architecture. The latter part of the document focuses on the terminal implementation presenting the structural breakdown of the terminal, the Windows NT operating system and the actual implementation. Finally, the paper depicts briefly the development process and applied design methods.     

Connection Rerouting for Wireless ATM Networks

Wireless ATM (Asynchronous Transfer Mode) is an emerging technology designed to provide multimedia and other Quality of Service-oriented applications to mobile users by extending ATM connections to involve wireless links. The use of wireless ATM has also been motivated by an increasing deployment of ATM technology in backbone networks and also due to the need to support emerging services in the next generation (broadband) wireless networks, both terrestrial and satellite based. Since ATM was originally designed for high bandwidth and low error rate environment to support stationary users, the use of ATM in wireless environment raises many interesting issues. These include managing end-to-end ATM connection (using connection re-routing), maintaining location information about users as they move, supporting transmission of ATM cells over wireless links, and supporting quality of service )QoS( requirements in limited bandwidth environment. As users move, the end-to-end ATM connections need to be rerouted to support continued communications. The design of such rerouting schemes has recently received some consideration in literature, however many important issues including support for multicast and overhead requirements have not been fully addressed. In this paper, we present a detailed treatment of connection rerouting issues, design and performance evaluation of two rerouting schemes, and the support for multicast rerouting.     

无线ATM网络体系结构及MAC层协议研究

无线ATM网络作为宽带多媒体通信的一种解决方案,近年来得到了广泛的研究。基于高速率、高可靠性的光纤信道的ATM网络扩展到无线环境面临着许多问题。本文介绍了无线ATM网络体系结构、协议栈、应用特点和关键技术,并重点讨论了无线ATM网络的MAC层协议。     

Performance evaluation for on-demand routing protocols based on OPNET modules in wireless mesh networks

In wireless networks, users expect to get access to the network securely and seamlessly to share the data flow of access points anytime and anywhere. However, either point-to-point or point-to-multipoint methods in traditional wireless networks make the network bandwidth decrease rapidly, which cannot meet the requirements of users. Recently, a new wireless broadband access network, wireless mesh networks (WMNs), has emerged. As one of the key technologies in WMNs, wireless routing protocols plays an important role in performance optimization of WMNs. Therefore, in this paper, we address the on-demand routing protocols by focusing on dynamic source routing (DSR) protocol and ad hoc on-demand distance vector (AODV) routing protocol in WMNs. Then, we use the OPNET modules to establish the simulation models of DSR and AODV protocols in WMNs. Simulation and results show that, DSR protocol that is based on the dynamic source routing is not suitable for wireless transmission, while AODV routing protocol that is based on the purpose-driven routing is suitable for wireless transmission with rapid change of network topology.     

Mobility information for resource management in wireless ATM networks

User mobility poses a significant technical challenge to network resource management in wireless ATM (Asynchronous Transfer Mode) networks. In order to guarantee quality of service (QoS) to mobile users and to achieve a high efficiency in network resource management, the information of mobile users' handoff at a future moment is essential for statistical multiplexing. This paper develops a novel fuzzy logic inference system to estimate the user mobility information for a wireless ATM network which uses a direct sequence code division multiple access (DS/CDMA) protocol. The estimation is based on measured pilot signal strengths from a number of the nearest base stations by the mobile user. Numerical results are presented to demonstrate the performance of the proposed technique under various path losses and channel shadowing conditions. The proposed technique can achieve simplicity, accuracy and low cost.     

通过基于ATM方式的ADSL宽带接入技术构建虚拟专用网络

VPN的出现使企业通过Internet既安全又经济地传输私有的机密信息成为可能。而构架在公用网络之上的专用网的性能直接取决于宽带数据接入技术。对基于ATM方式的ADSL宽带接入技术进行了探讨，分析了该种方式开展业务的特点，给出了一种基于ATM方式的ADSL宽带接入技术来构建虚拟专网的实现方案。     

An adaptive congestion control mechanism for intelligent broadband networks

The provision of novel multimedia services in broadband networks through intelligent network (IN) technology is a promising solution that guarantees fast deployment of new services and minimum changes to already operating networks. In this architecture, the broadband service control point (B-SCP) is the main actor in the processing of complex IN service requests. This centralized approach which is reflected in the multiplicity of tasks undertaken by the B-SCP in a broadband IN architecture, can easily lead to network performance degradation. Therefore, the presence of a congestion control mechanism operating at the level of calls is considered essential in order to protect the network nodes from overload conditions and to attain high levels of network performance. In this paper, we propose an adaptive congestion control mechanism (ACCM) which is able to guarantee the desirable quality of service under overload conditions. The proposed mechanism gradually reduces the message transmission rate from the source node to the destination node when overflow conditions have been detected, taking as feedback the buffer capacity state of the destination. Results, obtained by simulation show that the proposed ACCM improves the network performance by maximising the number of established calls and reducing the number of rejected calls.     

用基于ATM方式的ADSL宽带接入技术构建VPN

在公用网络上提供专用网服务的技术,已成为当前网络技术研究的热点之一。而构架在公用网络之上的专用网的性能直接取决于宽带数据接入技术。文章对基于ATM方式的ADSL宽带接入技术进行了探讨,分析了该方式开展业务的特点,给出了一种基于ATM方式的ADSL宽带接入技术来构建虚拟专网的实现方案。     

An Efficient Resource Allocation Mechanism for LTE–GEPON Converged Networks

Optical–wireless convergence is becoming popular as one of the most efficient access network designs that provides quality of service (QoS) guaranteed, uninterrupted, and ubiquitous access to end users. The integration of passive optical networks (PONs) with next-generation wireless access networks is not only a promising integration option but also a cost-effective way of backhauling the next generation wireless access networks. The QoS performance of the PON–wireless converged network can be improved by taking the advantages of the features in both network segments for bandwidth resources management. In this paper, we propose a novel resource allocation mechanism for long term evolution–Gigabit Ethernet PON (LTE–GEPON) converged networks that improves the QoS performance of the converged network. The proposed resource allocation mechanism takes the advantage of the ability to forecast near future packet arrivals in the converged networks. Moreover, it also strategically leverages the inherited features and the frame structures of both the LTE network and GEPON, to manage the available bandwidth resources more efficiently. Using extensive simulations, we show that our proposed resource allocation mechanism improves the delay and jitter performance in the converged network while guarantying the QoS for various next generation broadband services provisioned for both wireless and wired end users. Moreover, we also analyze the dependency between different parameters and the performance of our proposed resource allocations scheme.     

Enhancing multi-hop communication over multi-radio multi-channel wireless mesh networks: A cross-layer approach

The multi-channel multi-radio technology represents a straightforward approach to expand the capacity of wireless mesh networks (WMNs) in broadband wireless access scenarios. However, the effective leveraging of this technology in WMNs requires (i) enhanced MAC protocols, to coordinate the access to multiple channels with a limited number of radio interfaces, and (ii) efficient channel allocation schemes, to mitigate the impact of co-channel interference. The design of channel assignment schemes and MAC protocols is strictly interrelated, so that joint design should be considered to optimize the mesh network performance. In this paper, a channel assignment and fast MAC architecture (CAFMA) is proposed, which exploits the benefits provided by the multi-channel multi-radio technology to (i) enhance the performance of multi-hop communications, (ii) maximize the resource utilization, and (iii) support differentiation of traffic classes with different quality of service (QoS) requirements. CAFMA is designed with a cross-layer approach and includes (1) a novel MAC scheme, which provides multi-channel coordination and fast data relaying over multi-hop topologies, and (2) a distributed channel allocation scheme, which works in cooperation with the routing protocol. Simulation results confirm the effectiveness of CAFMA when compared with other single-layer and cross-layer solutions for multi-radio multi-channel WMNs.     

Management Architecture for ATM Over ADSL-Based Access Networks

ADSL (Asymmetric Digital Subscriber Line) is a new key technology for offering broadband services to home users and small businesses. ADSL technology is ready to take off. Management discussions aim at achieving an ADSL broadband service architecture are still taking place, however. In order to support multiple services over widely spread networks incorporating various transmission techniques, a cost-effective network operation requires an end-to-end network management architecture. We describe here how to integrate ADSL equipment into the existing telecommunications management network. Alternative protocols and information models are also discussed. The overall network management architecture gives the motivation for the management concept applied to our Digital Subscriber Line Access Multiplexer (DSLAM). The design of such a network element covers all management functionality that is required to multiplex ATM connections being transferred over the ADSL system and to integrate the network element into any telecommunications network. We have chosen a flexible approach to adapt the DSLAM management to different usage environments.     

SRPM: Secure Routing Protocol for IEEE 802.11 Infrastructure Based Wireless Mesh Networks

Infrastructure based IEEE 802.11 wireless mesh networks (WMNs) are new paradigm of low cost broadband technology. The large scale city-wide community-based coverage and multi-hop architecture are such characteristics which are vulnerable to network layer threats, and the adversary can exploit them for large scale degradation of the broadband services. So far many secure routing protocols have been proposed for ad-hoc networks, however, due to the different nature and characteristics; they cannot perform well in a WMN environment. In this paper, we discuss the limitations and challenges as well as propose an exclusive secure routing protocol for an infrastructure based wireless mesh (SRPM) network. SRPM is robust against a variety of multi-hop threats and performs well over a range of scenarios we tested.     

基于ATM技术的无线PCS网

文中介绍了无线ATM的网络结构、协议参考模型和PCS支持的固定ATM网的信令协议,它是对目前的ATM和PCS规范的最小修改。     

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.     

Access control protocols with two-layer architecture for wireless networks

In this paper we study two access control protocols which have similar two-layer access control architectures for wireless networks in public places. The first protocol, called the Lancaster protocol, employs user password for authentication and enforces access control at the IP layer; while the second protocol, referred to as the Stanford protocol, uses public key cryptosystems (PKC) for authentication and performs access control at the link layer. Although both protocols are intended to restrict access to wireless networks only to authorized users, our analysis shows that both protocols have serious security flaws which make them vulnerable to attacks. Then we propose a password-based protocol and a PKC-based protocol for the Lancaster architecture and the Stanford architecture, respectively. Both of our protocols provide mutual authentication, perfect forward secrecy and access control for wireless networks. Moreover, they also provide DoS resistance and identity confidentiality for the client. We present detailed security and performance analysis for our protocols, and show that both of our protocols are secure and efficient for access control in wireless networks.     

A trusted access method in software-defined network

In software-defined networks (SDN), most controllers do not have an established control function for endpoint users and access terminals to access network, which may lead to many attacks. In order to address the problem of security check on access terminals, a secure trusted access method in SDN is designed and implemented in this paper. The method includes an access architecture design and a security access authentication protocol. The access architecture combines the characteristics of the trusted access technology and SDN architecture, and enhances the access security of SDN. The security access authentication protocol specifies the specific structure and implementation of data exchange in the access process. The architecture and protocol implemented in this paper can complete the credibility judgment of the access device and user's identification. Furthermore, it provides different trusted users with different network access permissions. Experiments show that the proposed access method is more secure than the access method that is based on IP address, MAC address and user identity authentication only, thus can effectively guarantee the access security of SDN.     

基于压缩感知的水下传感器网络预约多址接入协议

相比于陆地无线传感器网络, 水下传感器网络拥有更大的传播时延, 导致许多已经比较成熟的MAC协议不能直接应用于水下。提出了基于压缩感知的水下传感器网络预约多址接入协议, 充分利用水下环境中的长传播时延, 使网络中各节点能够在时间和空间上对信道资源进行共用, 实现多个用户同时进行信道预约, 提高了信道的利用率。在考虑多用户分集基础上, 该协议使成功预约到信道的用户可以利用有限的全部带宽资源进行高速传输, 以此来提高整个网络的吞吐性能。仿真结果表明, 与传统的RTS/CTS方案相比, 该协议具有更高效的信道预约能力, 更高的数据传输效率, 以及更好的吞吐性能。     

A novel network mobility handoff scheme using SIP and SCTP for multimedia applications

In a heterogeneous wireless environment, seamless mobility is the basis of network support with which mobile users who roam between or among various wireless access networks are able to fully enjoy uninterrupted wireless services. When users are in a mass transportation vehicle, e.g., a bus or a train that provides network service, the vehicle can be regarded as a network which is serving users as it moves from one location to another. The movement of a network is called network mobility (NEMO). The network mobility protocol based on Mobile IPv6 as proposed by the Internet Engineering Task Force (IETF) in 2005 has some fundamental drawbacks, such as header overhead and the pinball problem. In this paper, we propose a novel hybrid method for network mobility called Hybrid-NEMO, which provides a soft handoff scheme at the transport layer basically utilizing SIP and SCTP protocols to ensure a lossless packet-transmission environment and less handoff-delay variation, which are critical in providing QoS voice and multimedia applications. Experimental validation and performance evaluation were also conducted in this study.     

Modeling and evaluating IPTV applications in WiMAX networks

Internet Protocol-based Television (IPTV) is a digital television service which delivers television content via an IP network. The rapid growth of wireless network technology in recent years has changed, the way people access the Internet. Adding mobility to IPTV can create a truly compelling ubiquitous service which spans different network domains and varied IP-enabled terminals and devices, such as set-top boxes, PCs and cell phones. However, extending IPTV service to wireless networks requires overcoming bandwidth bottlenecks and high packet loss rates. Following the IEEE 802.16 standard, worldwide interoperability for microwave access (WiMAX) features high data rates and large service coverage, offering a wireless broadband solution for IPTV services. While previous research has focused on creating a broadband IPTV service few studies have practically evaluated IPTV applications in a wireless broadband network environment. In this paper, we model and evaluate a common constant bit rate (CBR)¹ based IPTV application and an IPTV live streaming (PPStreaming)² application while retrieving IPTV content via a WiMAX network. We also use the NS2 simulation tool to evaluate the performance of these two IPTV applications. The evaluation metrics include latency, packet loss, data rate and throughput statistics when the two IPTV applications are run in the WiMAX network. ¹The simplest IPTV solution is to convey video content by CBR. IPTV operators and content delivery networks relay CBR streaming content to control the demand for network capacity. Broadcasters prefer CBR video as it conserves bandwidth resources, but CBR delivery can degrade video quality result in higher overall demand on network capacity. ²PPStreaming (also referred to as P2P streaming Internet TV) is a network for live media streaming. In principle it’s similar to BitTorrent (BT) in that it provides stable and smooth broadcast of TV programs to broadband users. Unlike traditional streaming media, PPStreaming adopts P2P-streaming technology and supports full-scale visits with tens of thousands of simultaneous users. Its client software can be used in the browser or as a standalone executable.     

电力通信异构多网共存网络发现与识别算法

电力无线通信网支撑用户量大面广、业务高并发、运行环境复杂,表现为异构多网混合共存。为了支持智能电力终端动态选择网络接入,必须首先执行网络发现与识别。针对TD-LTE无线通信专网、WiMAX无线通信专网、智能电网邻域网和230 MHz电力无线专网异构多网共存场景,提出一种融合物理层信号时频特征和MAC层协议特征的网络识别算法。该算法结合改进的窗口滑动能量检测和多周期特性加权循环平稳特征检测执行网络发现与识别。仿真结果表明,该算法能有效识别异构的多种电力无线通信网络。