Dinko Begusic

Optimized network management for energy savings of wireless access networks

The energy consumption of wireless access networks is rapidly increasing and in some countries it amounts for more than 55% of the whole communication sector and for a non negligible part of the operational costs of mobile operators. The new wireless technologies with a growth of data rates by a factor of roughly 10 every 5years and the increase in the number of users result in a doubling of the power consumption of cellular networks infrastructure every 4-5 years - to 60TWh in 2007.In this paper we consider possible energy savings through optimized management of on/off state and transmitted power of access stations according to traffic estimates in different hours of the day or days of the week. We propose an optimization approach based on some ILP models that minimizes energy consumption while ensuring area coverage and enough capacity for guaranteeing quality of service. Proposed models capture system characteristics considering different management constraints that can be considered based on traffic requirements and application scenarios. Energy minimization problems are solved to the optimum or with a gap to the optimum of less than 2.7% on a set of synthetic instances that are randomly generated. Obtained results show that remarkable energy savings, up to more than 50%, can be obtained with the proposed management strategies.

Impact of service rates and base station switching granularity on energy consumption of cellular networks

Over the last two decades we have witnessed significant growth of the cellular network energy consumption caused by a rapid increase in the number of mobile users and data volumes. This is contributed to by a tenfold increase of data rates every 5 years, and such a trend in up growth of energy consumption will continue with the introduction of a new throughput demanding services. Hence, development of new energy-saving techniques and estimation of the influence on energy savings when ensuring different service rates are the focus of this article. For the purpose of reducing cellular network energy consumption, this article proposes a new approach to energy-efficient management of network resources. The energy-efficient management is based on adaptive changes of on/off states of a complete base station (BS) site in accordance with the traffic pattern variations. Besides adaptations to the temporal traffic variations, the BS can adapt capacity to the spatial traffic variations through dynamic scaling of transmitted power according to capacity demand. We formulate the problem of energy-efficient management as a binary integer programming problem dedicated to energy consumption minimization of a complete network. Proposed methodology is simulated on a set of real size Universal Mobile Telecommunications System network instances consisting of different radio propagation environments. In addition, this article analyzes the influence on the energy savings potential of BSs switching granularity. Obtained results show that the proposed optimization approach offers significant reductions in the network energy consumption while preserving the most important QoS constraints like full area coverage and guaranteed service rates.

Location Determination in Indoor Environment based on RSS Fingerprinting and Artificial Neural Network

Wireless microsensor networks have been identified as one of the most important technologies for the 21st century. Cheap, smart devices with multiple onboard sensors, networked through wireless links and the Internet and deployed in large numbers, provide unprecedented opportunities for instrumenting and controlling homes, cities, and the environment. One of the crucial issues in wireless sensor networks is position determination. In this work a positioning system based on received signal strength (RSS) and WLAN is presented. In indoor environments, received signal strength is a complex function of distance. In this work artificial neural network is used to establish a relationship between RSS and location. The location determination accuracy of the proposed system has been investigated and promising results have been achieved. Although based on WLAN technology, the same positioning technique can be applied to any wireless mobile device or sensor in a wireless sensor networks.

Physical layer analysis of emerging IEEE 802.11n WLAN standard

In January 2004 IEEE announced that it had formed a new 802.11 Task Group N (TGn) to develop a new amendment to the 802.11 standard for wireless local-area networks that is known as the IEEE 802.11n standard. The real data throughput is at least 100 Mbps, with the possibility of even higher raw data rate at the physical layer (PHY), and should be up to 5 times faster than 802.11a or 802.11g, and perhaps 25 times faster than 802.11b in mandatory modes of operation. It is projected that 802.11n also offer better operating distance and full compatibility with current WLANs. There are two competing proposals of the 802.11n standard, expected to be ratified: WWiSE and TGnSync. This paper on PHY compares new technical solutions of these two proposals believing that the best of these proposals is incorporated in 802.11n standard. We also emphasize features and technical solutions on PHY that is inevitably built in the emerging 802.11n standard

Adaptive Noise Cancellation Based on Neural Network

There are many noise cancellation applications which require utilization of adaptive filters. An adaptive noise canceller adaptively filters a noise reference input to maximally match and subtract out noise or interference from the primary (signal plus noise) input. In this work we use a simple neural network called Adaline as adaptive filter. Our experiments are based on engine noise cancellation in cars

Fingerprinting based localization in heterogeneous wireless networks

Due to advances in mobile technology, context-aware applications are continuously growing in importance; therefore, the ability of developing accurate and reliable localization system has become a necessity. Since methods based on received signal strength (RSS) fingerprints are today widely adopted and most of mobile devices comprise different wireless access technologies, it is feasible to use fingerprints from heterogeneous wireless networks (HWN) for localization purposes. In this paper we propose a novel approach for localization based on searching the area which best matches the test RSS fingerprint. We evaluated the proposed method in realistic environment in WLAN, GSM and UMTS networks, and compared it with other commonly used approaches. The results showed that our method compares favorably to others, and practically always achieves the lowest localization error. We also extended the proposed system using a model of cooperative positioning by combining the estimates obtained in the heterogeneous wireless network. The obtained results showed that with combined location estimate, significant improvement over any single system was achieved.

Secure Initialization of Multiple Constrained Wireless Devices for an Unaided User

A number of protocols and mechanisms have been proposed to address the problem of initial secure key deployment in wireless networks. Most existing approaches work either with a small number of wireless devices (i.e., two) or otherwise rely on the presence of an auxiliary device (such as a programmable camera, computer, or Faraday cage). In this paper, we design a solution that allows a user unaided initialization (free from auxiliary devices) of a relatively large number of wireless devices. The proposed solution is based on a novel multichannel Group message Authentication Protocol (GAP), in which information is transmitted over both a radio and a visible light channel (VLC). A notable feature of GAP is that the information to be authenticated is independent of the short authentication string\o be verified by the user (an indirect binding protocol [28]). This, as we show, results in a lower communication cost compared to existing direct binding protocols. The advantage in terms of the communication cost of our GAP protocol is especially important for power-constrained devices, such as wireless sensor motes. Another appealing feature of GAP is that it is secure in the attacker model where the VLC is semiauthentic, whereas existing protocols consider VLC to be authentic. This is made possible by using joint Manchester-Berger unidirectional error-detection codes that are secure and easy to interpret by a nonspecialist and unaided end user. Our overall key deployment mechanism has minimal hardware requirements: one LED, one button and, of course, a radio transceiver, and is thus suitable for initializing devices with constrained interfaces, such as (multiple) wireless sensor motes. We demonstrate the feasibility of the proposed method via a preliminary usability study. The study indicates that the method has reasonably low execution time, minimal error rate, and is user friendly.

Speech recognition over Bluetooth ACL and SCO links: a comparison

Bluetooth is an emerging technology for short-range wireless communication. It is designed to transfer data over asynchronous connectionless (ACL) links and voice over synchronous connection-oriented (SCO) links. SCO packets are sent at regular intervals and are never retransmitted, while ACL packets are retransmitted in case of error. In this paper we have investigated speech recognition performance for voice transferred over ACL and SCO links at various channel qualities. Our experiments have shown that channel quality has severe impact on speech recognition performance for voice earned over SCO. This justifies the use of ACL links for voice transmissions in speech recognition applications.

Academic networking in alps-adria countries

he featured topic of the 8th IEEE Conference 011 Software, Telecommunications and Computcr Networks (SoftCOM 2000), which was held aboard the ship Marko Polo cruising along the Adriatic coast on the route Split (Croatia) Rijeka (Croatia) Trieste (Italy) Venice (Italy) from October 10-13,2000, was Academic Networking in AlpsAdria Countries. The conference was sponsored by the University of Split, Croatian Telecom, Telecom Center Split, and IEEE Communications Society. Besides the conference itself a number of accompanying events took place aboard the ship, including the Business Forum and Exhibition, which was organized on the car deck. The special session was divided into two parts and held on October 13 aboard the ship Marko Polo, which was anchored in Venice, Italy. The first part of the session was chaired by professor Algirdas Pakstas from the University of North London, United Kingdom and the second part by Professor Ignac Lovrek from the Faculty of Electrical Engineering and Computing of the University of Zagreb, Croatia. The featured topic attracted authors and participants from government institutions dealing with academic networking as service/infrastructure providers, and teachers from universities and researchers from institutes as users. A total of 12 papers were presented by authors from Italy, Hungary, Germany, Slovenia, Switzerland, and Croatia: *Advanced Solutions for Distance Learning via Satellite, by M. de Blasi, University of Lecce, Italy; C. des Dorides, Alenia Spazio, Italy. *Trends in Networked Collaborative Virtual Environments, by S. Pandzic, C. Joslin, N. Magnenat Thalmann, University of Geneva, Switzerland. *Homer 11: Man-Machine Interface to Internet for Blind and Visually Impaired People, by N. Pavesic, J. Gros, S. Dobrisek, F. Mihelic, University of Ljubljana, Slovenia. *Academic and Research Network of Slovenia, by A. Jauk, M. Bonac, ARNES, Slovenia; I. Ozimek, G. Kandus, Jozef Stefan Institute, Slovenia. .The LAN of TUB and its Links with other Universities in Budapest, by G. Nemeth, G. Remzso, L. Szandi, G. Varga, University of Budapest, Hungary Collaboration between Academia and Industry: Telecommunications and Informatics at the University of Zagreb, by I. Lovrek, M. Kos, B. Mikac, University of Zagreb, Croatia. *The Role and Strategy of an ARNet in a Developing Country, by Z. Bekic, J. Gojsic, P. Pale, CARNet, Croatia *The Implementation of Broadband Network Technologies in CARNet, by N. Bartolincic, I. Pezelj, I .Velimirovic, A. Zigman, CARNet, Croatia. *CARNet: Educated Users for Effective Utilization of IT, by M. Milinovic, J . Tingle, V. Vrga, CARNet, Croatia. *The Italian Academic Network GARR: Evolution in the Gigabit Era, by Claudio Allocchio, Claudia Battista, Massimo Carboni, Luca dell’Agnello, GARR Italian Academic and Research Network, Italy. *DFN Gigabit Network The Backbone for Teleteachingmelelearning in Higher Education: Status Report, by Ralf Paffrath, DFN, Germany. The presented papers cover main topics of academic networking including national strategies and network architectures, the role of academic networks in education and collaboration with industry, technological aspects, particularly applications of broadband and satellite systems, and user aspects including services for impaired persons. The Italian academic network Gruppo Armonizzazione Reti di Ricerca (GARR) was presented including various aspects, particularly its evolution, described through GARR-B and GARR-G phases. The GARR-B phase deals with increasing access bandwidth, introduction of new services like a computational GRID, a large dedicated mesh of VPNs for a user group, and increasing connectivity in southern and Mediterranean regions. GARR-G phase represent a GARR gigabit pilot project with SDH and WDM transmission systems in a multicarrier and multi-operator reality. The idea of expanding GEANT service to Italy and possibly beyond Italy toward the Mediterranean area is explored through the GARR-G phase. The Academic and Research Network of Slovenia (ARNES) is described as part of the TEN-155 EU project for high-speed pan-European interconnection between national research networks. ARNES participates in a number of international projects dealing with advanced networking. It is a full national member of the Trans-European Research and Educational Networking Association (TERENA). ARNES joined TF-Cashe activities and was one of the proposers of the socalled 1.5-level cache hierarchy concept. Croatian Academic and Research Network (CARNet) was presented in a wider way than only as an Internet provider for the academic community. As it has stated, an Academic and Research Network (ARNet) should not only provide communication and information infrastructure for the academic community, but also be a research testbed and even a pilot for other nationwide networks, thus taking the role of organizer and motivator for the community. To accomplish this, ARNet’s strategy should be to ensure connectivity and provide content through reference information, referral information, common databases, centralized databases, and information services. The development of CARNet was slight(Continued on page 4)

A new method for low-rank transform domain adaptive filtering

This paper introduces a least squares, matrix-based framework for adaptive filtering that includes normalized least mean squares (NLMS), affine projection (AP) and recursive least squares (RLS) as special cases. We then introduce a method for extracting a low-rank underdetermined solution from an overdetermined or a high-rank underdetermined least squares problem using a part of a unitary transformation. We show how to create optimal, low-rank transformations within this framework. For obtaining computationally competitive versions of our approach, we use the discrete Fourier transform (DFT). We convert the complex-valued DFT-based solution into a real solution. The most significant bottleneck in the optimal version of the algorithm lies in having to calculate the full-length transform domain error vector. We overcome this difficulty by using a statistical approach involving the transform of the signal rather than that of the error to estimate the best low-rank transform at each iteration. We also employ an innovative mixed domain approach, in which we jointly solve time and frequency domain equations. This allows us to achieve very good performance using a transform order that is lower than the length of the filter. Thus, we are able to achieve very fast convergence at low complexity. Using the acoustic echo cancellation problem, we show that our algorithm performs better than NLMS and AP and competes well with FTF-RLS for low SNR conditions. The algorithm lies in between affine projection and FTF-RLS, both in terms of its complexity and its performance.