J. Puttonen, “Mobility Management in Wireless Networks“, Phd. thesis, University of Jyväskylä, Finland, 2006.
This dissertation discusses mobility management in IP based wireless environments. Mobility management can include both handovers within one technology and selection of access technology in a heterogeneous overlapping environment.
IETF has standardized Mobile IP and its IPv6 version for handling mobility management in the IP networks. Even though Mobile IPv6 handles mobility in an application transparent way, several unresolved problems remain.
This dissertation focuses on minimizing the Mobile IPv6 handover delays and interface selection in heterogeneous wireless environments. An enhancement called Flow-based Fast Handover for Mobile IPv6 is presented for speeding up the Mobile IPv6 address registration phase.
The address registration phase, and thus also packet loss, can be notably decreased. More importantly, the delay is not dependent on the distance of the Corresponding Nodes as is the case with Mobile IPv6.
In addition, mechanisms to control Mobile IPv6 handovers to offer the users and applications a best access were researched. Real time information about the link status and quality as well as user preferences are taken into account in the interface selection. The objective is to offer an Always Best Connected access to the user, and seamless handovers.
K. Aho, “Performance enhancements on Multimedia Broadcast Multicast Services“, Master’s Thesis, University of Jyväskylä, November, 2006.
The aim of this paper is to evaluate the effect of receive diversity on multimedia broadcast multicast service (MBMS) performance in wideband code division multiple access (WCDMA) networks.
In addition to time diversity provided by long interleaving and receive diversity provided by multiple receive antennas, 3GPP release 6 specifications for MBMS introduce two macro diversity schemes: soft and selective combining.
Diversity techniques are introduced in order to improve the MBMS performance. Improvements help especially the cell edge MBMS users who suffer most from the fading channel conditions. As receive diversity is one of the most efficient diversity techniques this paper examines the system level performance of MBMS point-to-multipoint (p-t-m) mode with receive diversity together with and without macro diversity schemes.
These concepts are studied with dynamic system level tool in which e.g. mobility of users and interactions of the radio resource management functionalities are explicitly taken into account.
Our studies indicate that the receive diversity brings significant gains to the MBMS performance. Receive diversity together with macro diversity schemes improves the performance even more.
T. Nihtilä, J. Puttonen, E. Wallenius, T. Hämäläinen and J. Joutsensalo, “Simulation Study on 3G and WLAN Interworking“, IEICE Transactions on Communications, Vol. E89-B, No. 2, pp. 446-459, 2006.
Seamless interconnection with wireless LAN and 3G technologies is essential for the future wireless environment.
The Wireless Local Area Network (WLAN) integrated mobile device is designed to extend the reach of enterprise applications and to create new collaboration environments. Also rapid new service development has started to change traffic mixes in the cellular networks towards IP dominating carriers like GPRS (General Packet Radio Service) and WLAN.
These drastic changes require new research in the network as well as system inter-working areas for both the cellular and WLAN technology areas. This is the main challenge our research is trying to solve giving answers to rising inter-working and interoperability questions.
J. Puttonen, G. Fekete, P. Rybczyk, and J. Narikka, “Practical Experimentation of Mobile IPv6 in Heterogeneous Environment“, Acta Electrotechnica et Informatica, volume 6, number 1, pp. 31-36, 2006.
In this paper we present a Mobile IPv6 analysis related to its performance in heterogeneous multi-access environment.
The used access technologies include IEEE 802.3 Ethernet, IEEE 802.11b Wireless LAN and Bluetooth. We also discuss the capability of Mobile IPv6 to provide Always-Best-Connected access in multi-access environment to the user and applications.
The analysis is made according to real-life tests in Mobile IPv6 for Linux (MIPL) test network. The Mobile IPv6 protocol by itself cannot handle all the tested scenarios in the best possible way even though it provides a good ground for the All-IP mobility management.
We claim that a cross-layer approach would enable intelligent and proactive handovers, and thus improve the end-user experience.
J. Puttonen, A. Viinikainen, M. Sulander, T. Hämäläinen, T. Ylönen, and H. Suutarinen, “Flow-based Fast Handover Method for Mobile IPv6 Environment – Implementation and Analysis“, Computer Communications, More than a Protocol for Next Generation Internet, volume 29, issue 16, pp. 3051-3065, October 2006.
Mobility Support in IPv6 (MIPv6) has been approved by the Internet Engineering Task Force as the standardized solution for mobility management in the upcoming IPv6 network. However, the MIPv6 handover procedures result in a time, when the Mobile Node (MN) cannot receive or send data.
In this paper we present the Flow-based Fast Handover for Mobile IPv6 (FFHMIPv6) for fast redirection of the MN’s downstream flows during the Care-of-Address registration (binding update) process and another method speeding up the upstream handover by using a special Hand-of-Address (HofA) during registration process.
First, we have studied the FFHMIPv6 method combined with the use of HofA theoretically, followed by the Network Simulator 2 (ns-2) simulations. Finally the effectiveness of FFHMIPv6 method is verified in real Mobile IPv6 for Linux environment.
The FFHMIPv6 method with the use of HofA has been found to be a simple and promising candidate for faster handovers in MIPv6 networks with only a few minor changes to the MIPv6 specification.
J. Kurjenniemi, T. Nihtilä, E. Virtej and T. Ristaniemi, “On the Effect of Reduced Interference Predictability to the HSDPA Network Performance with Closed Loop Transmit Diversity“, Proc. of the IEEE Wireless Personal Multimedia Communications, San Diego, USA, September 17 – 20, 2006.
In this paper the performance of Closed Loop (CL) Mode 1 transmit diversity in an HSDPA network is studied and the effect of other sector interference is carefully addressed. Though CL Mode 1 has proved to be beneficial for dedicated channels, its benefit with HSDPA is not obvious due to availability of new link features which may not be fully compliant with Tx diversity.
A recent study explored the interaction between CL transmit diversity and fast channel dependent scheduling, and raised a question whether the reduced interference predictability degrade the system performance in terms of cell throughput.
In this paper we address this issue in detail and study how the changes of the tx-weights in the neighboring sectors affect the performance of CL Mode 1 with HSDPA.
The results presented in this paper are obtained by the means of a fully dynamic system-level WCDMA/HSDPA simulator, which showed no indication of reduced system performance in the presence of CL Mode 1. Gains of CL Mode 1 over 1-Tx with Round Robin scheduler are 39 % and 46 % in Pedestrian A and Vehicular A, while gains are reduced to 10 % and 23 % with Proportional Fair (PF) scheduler, respectively.
Downlink transmit diversity schemes, such as Closed Loop (CL) Mode 1 and STTD, are supported for dedicated channels already in 3GPP Release 99 and also for HSDPA (High Speed Downlink Packet Access) in Release 5.
In CL Mode 1 a base station weights the transmitted signal according to the feedback commands by UE, in order to maximize the received power at the UE. In ideal conditions CL Mode 1 provides significant gains over the single antenna case but its performance is affected by rapid channel variations.
On the other hand, STTD is an open loop technique, i.e. it does not require any knowledge of the channel state at the receiver. Therefore, it is very robust against channel variations in link level.
Though CL Mode 1 and STTD have been shown to be beneficial for dedicated channels, more research is needed with HSDPA due to the fact that the new features introduced along with HSDPA might affect to the observed gains of Tx diversity. On the other hand, Rx diversity is also a very efficient method in battling against signal fading and advanced UE receivers such as LMMSE equalizer can also be used in order to further enhance the signal quality.
In this paper we consider the system level performance of transmit diversity schemes in combination with receive antenna diversity and advanced UE receivers such as LMMSE equalizer in WCDMA network when HSDPA is used.
Flow-based fast handover for mobile IPv6 (FFHMIPv6) is a new handover method designed for mobile IP networks. The FFHMIPv6 uses the flow-state information and packet encapsulation to enable reception of packets simultaneously with the address registration process of mobile IPv6.
Analysis and performance evaluation of FFHMIPv6 shows it handles the handover delay more efficiently than the basic mobile IPv6, hierarchical MIPv6, as well as fast handovers for MIPv6 handover mechanisms. However, if FFHMIPv6 is to be the primary mechanism for handover in mobile IP networks it has to be secure, efficient as well as reliable alternative to the existing handover mechanisms.
In this paper, we present the security analysis and assessment of FFHMIPv6. We also recommend solutions to the identified security vulnerabilities and defense mechanisms to FFHMIPv6. The major security threat of FFHMIPv6 is related to the process of Flow-based fast handover binding update (FFHBU).
J. Puttonen and G. Fekete, “Interface Selection for Multihomed Mobile Hosts“, Proc. of the IEEE International Symposium on Personal Indoor and Mobile Radio Communications, Helsinki, Finland, September 2006.
In this paper we discuss the problem related to interface selection in a multihomed mobile host.
Traditional signal strength or priority based handover algorithms may not be sufficient for providing an always-best-connected access for the user in a heterogeneous multi-access environment.
We present the policy based handover logic of VERHO mobility management system, where handover decisions are made in a more intelligent way with several affecting cross-layer parameters, policies and interface selection algorithms.
Mainly, in this paper, we concentrate on comparing and analyzing different interface selection algorithms in Matlab simulations to find out the best alternative for the VERHO system
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