Abstract
Future public transportation systems will provide broadband access to passengers, carrying legacy terminals with 802.11 connectivity. Passengers will be able to communicate with the Internet and with each other, while connected to 802.11 Access Points deployed in vehicles and bus stops/metro stations, and without requiring special mobility or routing protocols to run in their terminals. Existing solutions, such as 802.11s and OLSR, are not efficient and do not scale to large networks, thereby requiring the network to be segmented in many small areas, causing the terminals to change IP address when moving between areas. This paper presents WiMetroNet, a large mesh network of mobile routers (Rbridges) operating at layer 2.5 over heterogeneous wireless technologies. This architecture contains an efficient user plane that optimizes the transport of DHCP and ARP traffic, and provides a transparent terminal mobility solution using techniques that minimize the routing overhead for large networks. We offer two techniques to reduce routing overhead associated with terminal mobility. One approach is based on TTL-limited flooding of a routing message and on the concept of forwarding packets only to the vicinity of the last known location of the terminal, and then forward the packets to a new location of the terminal. The other technique lets the network remain unaware for a very long time that the terminal has moved; only when packets arrive at the old PoA does the PoA send back a "binding update" message to the correspondent node, to correct the route for future packets for the same terminal. Simulation and analytical results are presented, and the routing protocol is shown to scale to large networks with good user plane results, namely packet delivery rate, delay, and handover interruption time.

Abstract
Interconnection of different access network technologies is an important research topic in mobile telecommunications systems. In this paper, we propose an ns-3 architecture for simulating the interconnection of wireless local area network (WLAN) and Universal Mobile Telecommunications System (UMTS). This architecture is based on the architecture proposed by the Third Generation Partnership Project, being the use of virtual interfaces as its main innovation. In order to demonstrate the value of the proposed simulation framework, we implemented the UMTS and WLAN interconnection considering three joint radio resource management strategies for distributing arriving calls. From the simulations results, we can conclude that the proposed simulation architecture is suitable to test and evaluate performance aspects related to the interconnection and joint management of UMTS and WLAN technologies. Copyright (c) 2012 John Wiley & Sons, Ltd.

Abstract
Foreseeing a future where IPv6 and mobile terminals play an important role in public access communication networks, this article introduces a monitoring system capable of identifying relevant traffic flows and tracking them while terminal equipment moves between network attachment points. The mobile flows are characterized and represented so that individual users and flows can perceive the quality of service they receive, and operators can have global traffic views of their heterogeneous access networks.

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