Paul Pangalos

End-to-end SIP based real time application adaptation during unplanned vertical handovers

This paper describes practical tests and evaluation of different ways in which the session initiation protocol (SIP) could be used to assist application adaptation for IP applications during a vertical handover (VH), that is one between base stations that are using different wireless link technologies. Such an approach has been implemented on a software testbed based at the Centre for Telecommunication Research (CTR), Kings College London as part of a joint project with BTexact Technologies.

Seamless handover between WLAN and UMTS

One of the most important aims of next generation mobile communications systems (systems beyond 3G) is to achieve the inter-operation of heterogeneous networks such as WLAN, 3G and digital video broadcasting (DVB). Interworking among these networks would allow network operators to cooperate to provide new value added services which they could not individually provide in a satisfactory manner. These services should be provided in a cost effective, reliable and secure manner. The paper addresses handover between WLAN and UMTS. We propose a network architecture, and address seamless handover issues from the users point of view. Moreover, the paper explains how two popular mobility protocols (SIP and Mobile IP) may each be deployed in this scenario. Performance of SIP and Mobile IP in similar situations are compared, in consideration of network characteristics such as available bandwidth (throughput), overhead, end-to-end delay, latency and packet lost rate. Finally, alternative solutions such as SIP-based approach, hybrid solution, integrated solution and multilayer solution are examined and compared.

Energy savings for cellular access network through Wi-Fi offloading

This paper investigates the energy savings a cellular operator can achieve in the access network by dynamically offloading users or traffic loads to Wi-Fi networks. The method used to analyze energy savings is presented, followed by detailed simulations using different traffic types. Results show that significant savings of up to 65-70% can be achieved by opportunistically powering down cellular radio network equipment as facilitated by the offloading of users to Wi-Fi.

Dynamic QoS Aware Route Optimization for Networks with Mobility Agents

To minimize the large handover delays associated with Mobile IPv6 numerous micro-mobility protocols were proposed. In this paper, we consider the Mobility Agent (MA) based family of micro-mobility protocols such as Hierarchical Mobile IPv6 and Proxy Mobile IPv6 and focus on the issue of the bottlenecks that MAs can lead up to under high network load. We propose a Dynamic QoS aware Route Optimization with the aim of reducing the bottlenecks around MAs. We exploit the fact that not all classes of IP traffic require low handover latency support; for example, P2P traffic, web browsing, etc. do not require high QoS and are delay tolerant. Hence, such traffic classes can be forced to establish a direct connection with the CN and the routing policies at edge routers can ensure these traffic classes bypass the MA. The number of traffic classes that are to bypass the MA increases dynamically according to the congestion of the network. Results show that by implementing the dynamic route optimization the network utilization increases and the average packet delay in the network are reduced.

The Impact of Mobility Agent Based Micro Mobility on the Capacity of Wireless Access Networks

The rise in the number of mobile wireless devices accessing IP based communication networks has fuelled the need for efficient mobility support for seamless communication. As a consequence a profusion of mobility protocols were proposed. The mobility agent based family of protocols have risen in popularity due to the simplicity in implementing them compared to per host based protocols. The mobility agents located within wireless access networks hide the movement of the mobile nodes by acting as an anchor point through which all the packets traverses to and from the mobile node. The presence of these mobility agents will result in bottlenecks of high congestion within the access network. This paper provides a formal definition to study this effect of mobility agents on wireless access networks. Using maximum concurrent flow problem we model the access network as a multicommodity flow problem and study the throughput of the network with and without the presence of the mobility agents. From the results it can be confidently concluded that by implementing local mobility solutions based on agents, the wireless access network capacity is reduced and the number and location of the agents within the access network have direct impact on the loss.

Group Handover among Heterogeneous Wireless Networks

In the past few years, significant work has been done towards inter-operation of heterogeneous networks such as WLAN, UMTS and DVB. Most work so far has aimed to provide an integration of these networks rather than their co-operation. In the mobile VCE III program, heterogeneous networks remain autonomous, independently-managed entities. In other words, networks are inter-worked and cooperate with each other to provide enriched services to users. The networks are owned by and under the control of their respective operators. The access cores of these networks are inter-connected via a logical interface enabling inter-working at the network and service layers. As part of the mobile VCE Core III program, we focus on mobility management, which is the key issue to support seamless roaming of the mobile users among these heterogeneous networks in an efficient way. In this paper, we consider a group handover scenario from a WLAN to DVB/UMTS network within the network mobility (NEMO) framework

Proactive autonomic load uniformisation with mobility management for wireless Internet Protocol (IP) access networks

The agent micro-mobility protocols, such as Hierarchical Mobile IPv6 and Proxy Mobile IPv6, have become leading contenders for providing micro-mobility support to mobile nodes (MNs). The presence of mobility agents (MAs) in these networks can lead to constrained routing and create areas of bottleneck around the MAs. When an MA is integrated in the access network all traffic is forced to flow through that MA potentially over-utilising paths along the MA, whereas other paths of the network remain under-utilised. For the efficient deployment of such networks, optimal and robust MA selection and load balancing mechanisms are required. This study introduces proactive autonomic load uniformisation, a self-managed load balancing scheme in which the congestion caused by MAs is reduced leading to better utilisation of the network resources. Assuming that the network supports multiple MAs, the proposed solution selects the optimal MAs by distributing optimally the incoming load within the network while at the same time maintaining the quality of service requirements for the MNs. The results show that the congestion is lowered by 25% within the network and the load is distributed uniformly across the MAs.

Opportunistic load and spectrum management for mobile communications energy efficiency

Dynamic load and spectrum usage management techniques can significantly improve the energy efficiency of mobile communications systems. This paper considers: (i) the opportunistic reallocation of traffic loads between bands to allow radio network equipment in the bands that the traffic is originated from to be powered down, and (ii) the opportunistic selection of more appropriate spectrum based on propagation characteristics to minimize necessary transmission power through improving propagation and/or reducing power leaking into co-channel cells in frequency reuse cases. This paper addresses the simulation of video, FTP and HTTP (web browsing) traffic sources for configurations representing LTE and HSDPA telecommunications networks, and shows that the opportunistic reallocation of users between bands to power down radio equipment achieves a significant saving of 50% or more in from-the-socket power. Furthermore, it shows that the opportunistic reallocation of users/links to minimize transmission power through using more appropriate propagation spectrum leads to a further modest reduction in from-the-socket power consumption.

An integrated QoS, security and mobility framework for delivering ubiquitous services across all IP-based networks

With the advent of various access technologies and increasing number of applications, a set of challenges concerning efficient delivery of ubiquitous services to heterogeneous users and devices have been posed. One of the important challenges is to integrate quality of service (QoS), security and mobility support in heterogeneous networks. To facilitate the interworking of these mechanisms we propose the concept of enhanced node (EN) in this paper. The EN is an intelligent entity with a network sub-layer, which integrates QoS, security and mobility management (MM). ENs are located in the access network and they communicate with each other via signalling. In this paper, the functionalities of the ENs are described and the framework with ENs to integrate QoS, security and MM in IP-based networks is presented. The mechanisms to provide the authenticated and authorized access control and to enhance the secured QoS combined fast handovers are also proposed.

Fuzzy non-dominance multipath link-state routing framework for network routing management with inaccurate information

An open problem for quality of service routing management is the use of inaccurate metric information. Due to the periodic link-state updates, the router always contains out-of-date information. This paper proposes a novel framework for routing management with inaccurate information. We introduce fuzzy metric representation and the concept of non-dominance or Pareto-optimal fuzzy shortest path routing into our framework. The term fuzzy shortest path routing used here is distinct from the classic sense of fuzzy rule controlled routing. We map the crisp link-state information to a new plane by fuzzification factor, and use fuzzy non-dominated multipath routing algorithm for path selection in order to achieve a better network usage. Under our framework, a network administrator can easily switch between fuzzy or non-fuzzy routing. We will discuss and investigate how this framework could be merged with the current network infrastructure to support better QoS for emerging services and applications. A case study is shown in the paper, and simulation results are also included to validate the network preference enhancement under our framework.