TKK | Tietoverkkolaboratorio | Julkaisut

3. Research Projects

3.1 Models for Integrated Telecommunication network Traffic and Architecture (MITTA)

Other researchers: Luoma, Marko; Kankare, Janne; Peuhkuri, Markus

In this project we are concentrating on issues of traffic measurement. And management. Our starting point has been high speed networks (ATM) and problems which they have brought to management of traffic streams. Our assumption has been that `old fashion' analytical modelling of traffic and sources has reached it's limits and new more novel approaches should be used. Our aim is to find out which are the key factors in the effective traffic management and how they should be adjusted in order to minimise the load of the traffic management. We try to solve problems by using real time measurements and predict what is the traffic distribution by using an estimation from the measured traffic stream. This research is done through the simulations using a commercial and a self made tools. Instrumented version of Linux-kernel which we produced as a tool for analysing effects of OS-processes to network traffic is distributed from web-pages http://keskus.hut.fi/tutkimus/mitta/abstract.shtml

Figure 2 Instrumented kernel measurement system

3.2 Signal processing in digital receivers

Other researchers: Xie, Dazhao

In this project pulse shaping digital filter design especially for digital subscriber line applications was investigated. Based on the minimum mean-squared-error criterion, a general iterative technique for simultaneous optimisation of transmit and receive filters was developed, assuming a general linear channel, coloured noise and co-channel (cross-talk) interference with a known power spectrum. The new technique can provide several decibels of better noise and interference attenuation than the standard root-raised-cosine filters.

3.3 Smart antennas in new radio systems

Other researchers: Baghaie, Ramin; Karttunen, Petri; Werner, Stefan

Figure 3 Mobile communication system

In this project, digital signal processing for smart antennas is investigated. The main focus is on CDMA systems provided with multiple antennas. The work has been divided into 3 subprojects. Petri Karttunen has investigated the simultaneous tracking of multiple users with an adaptive beamformer with an adaptive step size algorithm which finds a good compromise between tracking speed and misadjustment noise. Stefan Werner has studied blind adaptive interference cancellation at the mobile CDMA receiver and showed that the use of multiple antennas can speed up the convergence of the adaptation. Ramin Baghaie has investigated efficient implementation of adaptive algorithms using pipelining and transformation techniques. The visiting researcher Jose Apolinario from Federal University of Rio de Janeiro took part in the development of the adaptive algorithms for mobile reception.

3.4 COST 257

Other researchers: Aalto, Samuli; Lassila, Pasi; Hyytiä, Esa; Kyläkoski, Kaisa

COST 257 is a joint project between the Laboratory of Telecommunications Technology at HUT and VTT Information Technology. It represents the Finnish contribution to the European COST 257 Action, in which laboratories and research institutes from 18 countries participate. At HUT, the project was started in January 1997. The research is mainly funded by TEKES with the support by Nokia Telecommunications and Telecom Finland. The research focuses on developing models and methods for the performance analysis of telecommunication systems. Five problem areas have been addressed:

1) Effective simulation of multiservice loss systems (such as an ATM network considered at the call level). A new method based on the use of Gibbs sampling with an enhanced data collection techniques has been developed. A significant variance reduction was obtained in the test cases.

Figure 4 The simulation problem

2) Optimal routing and wavelength assignment in all optical WDM backbone networks. Optimal wavelength assignment is equivalent to the so called graph colouring problem. The basic theory of this problem has been reviewed and several heuristic techniques for finding "good" solutions for the problem have been implemented. Benchmark tests have been made in order to evaluate their effectiveness and computational complexity.

3) Proxy cache algorithms. Caching is an important means for reducing latency times and network costs of www requests. Different modelling approaches for analysing the behaviour of a cache have been studied with the aim of developing algorithms that would improve the cache performance.

4) Resource allocation. Computational methods have been developed for the transient blocking problem whose solution is needed in the optimal VP capacity allocation in ATM networks.

5) Multicast traffic. A generalised Engset model has been applied for calculating the end-to-end blocking probabilities of calls dynamically joining or leaving multicast trees. This work has been done jointly with the Laboratory of Telecommunication Software and Multimedia.

3.5 Studies in queuing theory

This study aims at Ph.D. Thesis in Queueing Theory. It consists of two separate parts. In Part I optimal control problems of various batch service queueing systems are considered, focusing on the case of finite service capacity. The models of this kind have natural applications in the area of transportation systems. In Part II the aim is to characterize the output process of some fluid flow storage models used in the teletraffic theory as burst scale models of multiplexers.

3.6 IP/Voice

Other researcher: Yletyinen, Tomi; Betlehem, Ulf; Nurmi, Jukka

Voice over IP studies the transmission, switching and routing of voice in IP networks and service interoperability of such networks with PSTN/ISDN. The project was initiated in April 1997 and is planned to continue for 3 years. The project is mainly funded by a TEKES grant, it has also four industrial partners (Nokia Research Center, Nokia Telecommunications, Telecom Finland and Omnitele/Helsinki Telephone Research).

Results for the first year include Tomi's M.Sc thesis on Quality of Voice over IP, contributions to ETSI/TIPHON -project on number portability and network scenarios and a presentation on Telecoms Voice & Data Switching conference in London. In addition internal reports and student papers were produced.

3.7 IP / Switch

Other researchers: Ilvesmäki, Mika; Peräläinen, Ilkka; Brax, Veikko

The project was initiated in April 1997 and is planned to continue for 3 years. The project is mainly funded by a TEKES grant, it has also five industrial partners ( Nokia Research Center, Nokia Telecommunications, Telecom Finland, Omnitele/Helsinki Telephone Research and Tellabs).

Although viewed as the prototype of the future Information Superhighway, the current Internet technology has a number of drawbacks including: limited transmission and routing capacity and limited speed, long and variable transmission delays and no support for quality of service. The project is aimed at helping to solve some of these problems by focusing on issues of deployment of ATM to increase the performance of the Internet and to improve the quality of service available to the user.

Figure 5 The integrating dimensions of the future Internet

For overcoming the switching capacity shortfall, it has been suggested that the Internet should be boosted by building its backbone using ATM technology and by using cut-through switching in addition to packet forwarding to increase the performance economically. The project studies the different approaches to multi-layer routing, the performance of these schemes and aims at suggesting improvements in the concepts. The project will also develop methodology in Internet traffic measurements and network planning.

Results of the first year include set-up of a IP-switching laboratory, building basic competence in this new research area. Three conference papers and several student reports were published. Several theses are under preparation.

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