Bangnan Xu

Improving the Performance of the Distributed Scheduler in IEEE 802.16 Mesh Networks

Wireless mesh networks are a viable solution to provide broadband wireless access (BWA) in a cost efficient and flexible manner. The IEEE 802.16 standard is currently one of the most interesting BWA standards. Besides the popular point-to-multipoint mode it defines an optional mesh mode. This paper evaluates the performance of the coordinated distributed scheduler (C-DSCH), defined by the IEEE 802.16 standard for mesh mode. Analytical as well as simulation results show, that this mechanism has a scalability problem that leads to poor performance in dense networks and aggravates QoS provisioning. To solve this, a dynamic adaptation mechanism is proposed, that is able to reduce the contention and to enhance the performance (throughput) in dense networks.

IPTV Systems, Standards and Architectures: Part II - IPTV Services over IMS: Architecture and Standardization

This article presents an architecture to support IPTV services in an IMS-based NGN. The architecture extends the current IMS specification with the required functionality to meet additional requirements of IPTV services. The proposed architecture can be deployed by an IPTV provider over heterogeneous access networks (mobile, wireless, and fixed) as a part of standardized NGN solutions. After presenting an overview of the IPTV standardization activities in DVB, ITU-T, ETSI, ATIS, 3GPP, and OMA, this article focuses on the ETSI TISPAN IPTV standardization. IMS-based IPTV architectural functions and possible IPTV evolutionary steps are discussed, and then the article presents an implementation example.

IMS based IPTV services: architecture and implementation

This paper presents a novel architecture for providing converged IP-based TV (IPTV) services specified by ETSI TISPAN standardisation for IPTV in ongoing NGN release 2 specifications. The described IPTV architecture is based on utilisation of the IP Multimedia Subsystem concept used by NGN architectural framework and its adaptation to provide the IPTV specific functionalities and services. Using the foundation provided by the IMS based architecture, we propose a new functional architecture to enhance the functionalities and features needed for scalable converged networks, flexible media delivery and advanced IPTV service scenarios. The proposed architecture, leveraging on the FMC architecture that operators may deploy to provide IPTV service across different access networks in future deployments (mobile, wireless, fixed) has prototypically been implemented in the ScaleNet* demonstrator testbed. This paper analyses in detail the main principles for such a converged reference architecture. The paper also presents the IPTV service scenario prototype called Click-to-Multimedia which shows some basic features and advantages implemented on top of the presented architecture by prototyping demo applications as proof of concept reference.

Application-aware scheduling for VoIP in Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are seen as a means to provide last mile connections in Next Generation Networks (NGNs). Because of their auto-configuration capabilities and the low deployment cost WMNs are considered to be an efficient solution for the support of multiple voice, video and data services in NGNs. This paper looks at the optimal provision of resources in WMNs for Voice over IP (VoIP) traffic, which has strict performance requirements in terms of delay, jitter and packet loss. In WMNs, because of the challenges introduced by wireless multi-hop transmissions and limited resources, providing performance quality for VoIP comparable to the voice quality in the traditional circuit-switched networks is a major challenge. This paper analyses different scheduling mechanisms for TDMA-based access control in mesh networks as specified in the IEEE 802.16-2004 WiMAX standard. The performance of the VoIP applications when different scheduling mechanisms are deployed is analysed on a variety of topologies using ns-2 simulation and mathematical analysis. The paper concludes that on-demand scheduling of VoIP traffic - typically deployed in 802.11-based WMNs - is not able to provide the required VoIP quality in realistic mesh WiMAX network scenarios and is therefore not optimal from a network operators point of view. Instead, it is shown, that continuous scheduling is much better suited to serve VoIP traffic. The paper then proposes a new VoIP-aware resource coordination scheme and shows, through simulation, that the new scheme is scalable and provides good quality for VoIP service in a wide range of network scenarios. The results shown in the paper prove that the new scheme is resilient to increasing hop count, increasing number of simultaneous VoIP sessions and the background traffic load in the network. Compared to other resource coordination schemes the VoIP-aware scheduler significantly increases the number of supported calls.

Reliability Analysis of IEEE 802.16 Mesh Networks

The problem of terminal-pair reliability has been extensively studied for wired computer networks, however comparatively less research has been done on the reliability of wireless networks. With mesh networks becoming a more attractive option than the traditional point- to-multipoint network design due to extended coverage and increased overall link quality, a method is needed to evaluate the added reliability obtained through the available path diversity in fixed wireless mesh networks. Methods are available to evaluate the reliability of wired networks, however they do not take into account the outage conditions found in a wireless environment such as multipath fading and interference. This paper combines the currently available reliability algorithms for wired networks along with methods to calculate the link and node outage in a fixed station IEEE 802.16 environment in order the simulate the reliability of a mesh subscriber stations connection to the base station. An example calculation is also provided.

QoS provisioning in WLAN mesh networks using dynamic bandwidth control

WLAN, based on the IEEE 802.11 standard has been extensively studied since its release. In addition to infrastructure access to WLAN, mesh networks currently attract a lot of attention. This comes from the envisioned advantages of wireless mesh networks, such as cheap installation costs, extended coverage, robustness, easy maintenance, and self-configuration possibilities. In this paper we focus on Quality of Service support for multimedia applications in WLAN-based mesh networks. Therefore, a dynamic bandwidth control mechanism is implemented on the network layer and the results show that high prioritized traffic can be protected from disturbing best effort traffic.

ScaleNet – Converged Networks of the Future (ScaleNet – Konvergente Netze der Zukunft)

This article provides an overview of ongoing research within the framework ScaleNet. Considering IP as the basis transport scheme, the wireless and the wireline world have just started to move towards each other. ScaleNet is pushing this development by evolving a new system concept and by developing technologies for Fixed & Mobile Convergence. Der folgende Beitrag präsentiert die aktuellen Arbeiten des Forschungsprojektes ScaleNet. Der Einsatz von IP als gemeinsame Transportplattform sowohl für schnurlose als auch für drahtgebundene Kommunikation führt zu einer immer stärkeren Annäherung beider Welten. ScaleNet treibt diese Entwicklung voran und liefert ein neues Systemkonzept für die Konvergenz von Festnetz und Mobilfunk.

Time Behaviour and Network Encumbrance Due to Authentication in Wireless Mesh Access Networks

In this paper we investigate the authentication behaviour of mobile nodes within wireless mesh access networks. This work evaluates the authentication time and the authentication network resource consumption within wireless mesh networks, considering mobility of mobile nodes. Three authentication architectures, such as centralised, hierarchical and distributed, are presented. This paper work proposes a fundamental authentication architecture for mesh networks that provides mobility support. Furthermore, general aspects and requirements to achieve carrier grade mesh networks are discussed.

On the Performance of Enhanced Hierarchical Mobile IPv6

This paper defines a multi-hierarchical architecture of mobile anchor points (MAP) in a micro mobility network to enhance the performance of hierarchical mobile IPv protocol. By deploying this multi-hierarchical architecture of MAPs the latency of IP handoffs is reduced significantly so that the traffic performance during handoffs can be improved. For this purpose a new multi-binding update signalling packet is developed to accelerate the handoff process using a new registration mechanism, with which the MAP can forward the multi-binding update message to the next hierarchical MAP level. The acknowledgement message for the multi-binding update message will be sent by the last MAP or the home agent. Moreover, a modified function for processing the data packets destined to mobile nodes is introduced in MAPs so that the packet overhead can still keep small by avoiding multi-tunnelling that can be resulted from the multi-hierarchy of MAPs without this modification. The investigated proposal is implemented in NS2 and the improvements of the traffic performance are verified by the simulation results

Bandwidth Sensitive Adaptation of Applications during MRM Controlled Multi-Radio Handover

In heterogeneous radio access networks mobile terminals can dynamically change their radio access not only between access points but also between different radio access technologies (RATs). We present a network based Multi-Radio Management (MRM) for seamless control of inter-RAT mobility. Access Selection can be triggered by a change of radio channel quality, by the start of an application or by system load and handover is executed by enhanced MobileIPv6. Dynamic adaptation of the IMS services, e.g. adaptation of IPTV to the available bandwidth, is realized by triggering additional mid-call SIP signaling between communicating parties so that Quality of Experience (QoE) can be significantly improved. The described MRM and dynamic adaptation of IMS services are validated by a prototypical implementation in an integrated demonstrator.