13.2.2009

D302

14.15

6.2.2009

D302

14:15

(Joint work with Hung X. Nguyen, Univ. of Adelaide)

Jorma Virtamo

D302

12:00

Seong-Lyun Kim

School of Electrical & Electronic Engineering
Yonsei University, Seoul, Korea

Hierarchically Modulated Network Coding for Two-way Relay Channel

Network Coded ALOHA for Wireless Multihop Networks

25.11.2008

G317

13:00

Prof. Dr. Holger Karl

Universität Paderborn

Mobile opportunities: From wireless cooperation to distributed search

This talk will present two different aspects. The first part is about exploiting spatial diversity in a wireless system by cooperation among terminals. This technique can realize substantial gains in reliability of a wireless link; it can also, done properly, increase capacity of wireless links. The talk will go over baisc idea, design decisions, and evaluation by analysis, simulation, and prototypes.

In a seond, shorter part, issues of doing search in a P2P system consisting of mobile devices will be considered. Functions like the support of range queries in such systems will be discussed.

21.11.2008

G317

Spanning tree approach for dependability

KuuselaSpanningTree.pdf

G317

7.11.2008

G317

Dr. Riikka Susitaival

Ericsson

Introduction to LTE and its battery optimization with DRX

G317

UPnP based applications available in existing devices with WLAN and future plans in that area.

G317

G317

Mobile computer users often have a false sense of anonymity when they connect to the Internet at cafes, hotels, airports or other public places. We have analyzed information leaked by mobile computers to the local access link when they are outside their home domain. We found that all layers of the protocol stack leak various plaintext identifiers of the user, the computer and their affiliations to the local link, which a casual attacker can observe. We propose two independent mitigation mechanisms for these leaks: network location awareness can be used to prevent unnecessary service discovery attempts and protocol stack virtualization provides isolation for the traffic sent to the network, for example, every application uses a distinct identifier space on all layers of the protocol stack.

D302

By definition, the Global Information Infrastructure (GII) will be an infrastructure which facilitates the development, implementation and interoperability of existing and future information services and applications within and across the telecommunications, information technology, consumer electronics and content provision industries.

A Next Generation Network (NGN), as a packet-based network, is able to make use of multiple broadband, QoS-enabled transport technologies to provide Telecommunication Services to users: the service-related functions are independent of the underlying transport-related technologies and supports generalised mobility which will allow consistent and ubiquitous provision of services to users.

TKK-GII-NGN.pdf

30.5.2008

E208

23.5.2008

E208

Perfect codes, such as the Hamming codes, are an interesting class of error-correcting codes. By using a combinatorial approach and utilizing the classification of Steiner quadruple systems, a complete classification of the perfect binary codes of length 15 is achieved.

16.5.2008

E208

Optimality of the best known solution for a difficult set covering problem A₁₃₅ that arises from a Steiner triple system of the order of 135 has been an open problem last decade. The question can be settled with reasonable computational time by utilizing the orbits of subsets in the pruning of the search space.

9.5.2008

E208

10:30

S1
12:00

Doctoral dissertation

25.4.2008

E208

S4
12:00

Doctoral dissertation

28.3.2008

E208
14:00

Open Source software is easily seen as a way to lower R&D costs, and so is an attractive choice in modern communications industry. Still, the "free" software does not come without a price. In this presentation some of these hidden costs and long term effects are briefly presented. Finally some software research areas in Nokia Siemens Networks are highlighted on the topic level.

7.3.2008

E208

Abstract: We consider bandwidth-sharing networks, and show how the SRPT (Shortest Remaining Processing Time) discipline can be used in order to improve the delay performance of the system. Our main idea is not to use SRPT globally between the traffic classes, which has been shown to induce instability, but rather deploy SRPT only locally within each traffic class. We show that with this approach, the performance of any stable bandwidth allocation policy can be improved. Importantly, our result is valid for any network topology and any flow size distribution. A numerical study is included to illustrate the results.

BSnetworks.ppt

8.2.2008

E208

We analyze the impact of size-based scheduling on the flow level performance of elastic traffic in wireless downlink data channels. In the case, where the scheduler only has information about the averate rate of the users' channels, the gains from employing flow-level size information can be significant. However, when instantanous rate variations (e.g., due to fast fading) are taken into account, the scheduler must simultanously utilize instantaneous rate information and the flow-size information. We experiment with several different approaches for utilizing rate and size information. Some numerical results are shown, where the tradeoffs between the two types of information are explored.

1.2.1008

E208

14:00

25.1.2008

E208

It is known that coding over wired networks increases spectral efficiency, reducing the required number of transmissions. However, the properties of wireless networks, such as omni-directional transmissions and interference, make the gain of network coding different from that in wired networks. In wireless networks, network coding strongly reflects interactions with underlying MAC protocols, and recently many researchers jointly study on network coding with MAC of scheduling. Starting from the same motivation as above, however, we take a different viewpoint in this study. We investigate the gain of network coding using spectral radius analysis, based on carrier-sensing MAC protocol such as CSMA/CA. For the purpose, we firstly analyze if there exists an optimal forwarding factor, which means the ratio between the number of packets transmitted and the number of packets received, per node.

18.1.2008

E208

In an ad hoc network, important performance measures include connectivity, capacity, and energy consumption. Compared to the uniform power allocation where each node has same transmission power, the optimized power configuration may result in large savings in energy usage without losing the connectivity or capacity of the network. In this talk, we introduce and analyse a distributed algorithm which converges to the optimal power configuration for a given initial connectivity graph defined e.g. by the maximal powers at each node.

11.1.2008

E208

Traditionally Extensible Messaging and Presence Protocol (XMPP) has been thought to be the "Linux of instant messaging". However, Internet service providers, such as Google, Twitter and Jaiku, have proved that XMPP is suitable for a wide variety of near real-time services. While XMPP is easily extensible, it is also extremely efficient compared to Session Initiation Protocol (SIP). That combined with the complexity of SIP have made XMPP a respectable solution also for mobile and fixed operators.

20080111.ppt