Background and Mission

The Wireless Communication Systems Group (WICS) consists of the Telecommunication Laboratory and the Centre for Wireless Communications (CWC) at the University of Oulu. The core competence of WICS is in the overall wireless systems design for commercially important applications. WICS, with a staff of 120, has an annual budget of approximately 6 million euros, consisting to a large extent of external funding received for research projects. The broad variety of its customers include Nokia Siemens Networks, Nokia, the Finnish Funding Agency for Technology and Innovation, the European Commission, the European Defence Agency, the European Space Agency, the Finnish Defence Forces, Nethawk, Xilinx and Elektrobit.

WICS has a two-fold mission. On the one hand, WICS wants to excel in academic performance by producing world class graduates, as well as publications. On the other hand, the group was established to bridge the grand canyon of academic results and industry needs. Thus WICS seeks to help its customers by creating new technology and by giving support to industry in their aspirations. WICS’s track record in designing both commercial and military communication systems that are operational today is unique and exceptional at both the national and global levels.

Wireless technologies are envisioned to be mature enough within the next 10–15 years to be among the key enablers in solving some of the essential global challenges, including: climate change, population growth and emerging economies, ageing and well-being, dependence on ICT, ubiquitous internet and scarcity of energy.

New technical solutions are needed to answer to the aforementioned challenges. Amongst the major challenges for communication technologies to be employed in future systems are the following: support for higher data throughputs, improved spectral and energy efficiency, transparent interoperability on heterogeneous networks, mobile wireless driven internet, robust and trustworthy communications.

The close relation between the global challenges and wireless technology challenges is more than evident. The major challenge is to investigate how modern wireless technologies can be applied and developed further to address some of the serious global problems. To solve some of today’s challenges the approach in WICS is cross-layer design and optimization for future inter-connected networks driven by mobile wireless technologies. Because the future internet will be a network of networks efficiently taking into account all the above requirements and even more, we will concentrate on a unified framework to optimize, tailor, and harmonize the joint operation of various networks with different requirements and deployment. This research is targeted at developing cross-layer optimized fundamental technologies for future wireless networks and then applying them in various application areas. This fundamental technology and competence are developed based on the constraints posed by the challenges and opportunities. The proposed cross-layer approach for future networks requires the mastering of several fields of wireless communications: the physical layer, radio channel characterization, the data link and network layers, all the way to the application layer of the open system interconnect (OSI) model and moreover, the overall wireless systems design across all layers.

Another, possibly even greater challenge is to develop application and system level knowledge to solve optimization problems for inter-connected systems, such as communication & control networks for smart energy grids. This area requires an understanding of electricity generation and distribution, energy markets, control engineering, measurements technologies, communication technologies, data fusion etc. The potential scenarios to be studied include buildings (residential houses, office environment, factories), group of households forming a so-called microgrid and electric vehicle based approach leading to mobile electricity. Each of the scenarios pose a multitude of interesting research problems suitable for a person with a background in wireless communications. For example, the future cellular networks will be based on distributed network management principles which can be readily applied to power grids management. Many of the underlying theoretical tools such as game theory and other optimization methods can be applied to power grid usage optimization. As power grids are even more vital for modern society than communication networks, the requirements for the control and communication networks for power grids are more demanding than mobile communication systems, for example. Novel robust solutions need to be developed. The overall approach to be taken in this project is to investigate inter-systems networking, i.e., how the future internet, telecommunications and energy sectors can be co-designed to result in robust solutions for the needs of customers, businesses and societies in the future.

Future networks will employ new topologies, such as multi-hop wireless networks, mobile ad hoc networks, and the integration of wireline and wireless networks. It further calls for advanced routing, scheduling, radio resource management, and radio link control solutions capable of using the spectrum efficiently and adapting to diverse traffic behaviour. A fundamental problem in designing such complex systems is to derive network control mechanisms comprising of flow control, routing, scheduling, and physical resource management. The control mechanisms must ensure network stability under a large set of service demands and, simultaneously, provide a certain degree of fairness between concurrent sessions. This necessitates holistic network optimization across the OSI model layers. Network protocols for layered architectures have historically been obtained mainly based on an engineering intuition, and many of the recent cross-layer designs are conducted in the same heuristic manner. Despite the recent progress, there is little understanding of how to divide the network protocol into layers in a systematic way. A new approach, based on a rigorous mathematical theory, is required for optimizing the future network architectures and technologies. The research will also address the technologies needed in realization of the network nodes, devices, and the computational paradigms in an energy-saving and cost efficient manner.

One of the major challenges for mobile wireless internet operation is that all content related to the operating environment becomes highly dynamic. Under such a setting, server based information acquisition will become very inefficient and user co-operation and information exchange will become more attractive, leading to, for example, “publish and subscribe” -style internet architectures. Furthermore, due to the time-varying environment, the network must be selected and optimized dynamically. Environment-aware intelligent radio networks are often called cognitive radio networks. In order to be able to develop a functioning cognitive radio network, one must master radio channel phenomena, physical layer techniques, MAC and link layer techniques, and overall wireless network optimization, as well as the intelligence necessary to self-optimize and manage the whole system. This type of cross-layer optimization is one of the key elements in the development of future cognitive radio networks.

As outcomes, the Wireless Communication Systems Group aims at providing:

• theoretical breakthroughs for understanding the capacity of future wireless networks;
• alternatives for mobile wireless driven internet architectures;
• cross-layer optimized protocols and transmission methods for inter-systems networks;
• methods for intelligent and context aware network management for various applications;

and finally, understanding on the co-design of future merging inter-connected systems e.g. internet, wireless networks and energy grids.

Research Groups

WICS’ mission statement and research strategy have resulted in an organisation where research is divided into basic research oriented groups and application oriented groups. Currently we have the following groups (and group level teams):

Communication Signal Processing (CSP)

The requirements of wireless systems change steadily. Future systems must offer higher system capacity, higher data rates and smaller latency than current systems to enable the increasing diversity of services offered by different service providers. New network topologies and smart ubiquitous environments are needed to satisfy the requirements of future services. The implementation of these systems requires cross layer designs and optimizations close to realization. Devices operating in future wireless networks must be reconfigurable and more flexible than current designs. To fulfil these requirements joint system level and device level, and joint signal processing algorithm and architecture research are needed.

Goal: The Communication Signal Processing Group (CSP) implements the strategy of CWC in the area of signal processing and radio engineering research for wireless systems. The group’s research goals are to allow more efficient use of network devices, decrease the power/energy consumption of wireless devices and allow the development of smaller and lighter wireless devices, as well as improve understanding on the fundamental limits of wireless systems. Application areas of CSP group’s research results are mainly cellular systems, sensor networks and smart wireless devices. Interest groups for the application areas include device manufacturers, operators and semiconductor vendors.

Focus areas: the group’s focus areas are information theoretic foundations and their impact on wireless system design, signal processing system and device level algorithms, implementation architectures and efficient implementations, as well as radio engineering and channel modelling. Currently, future technologies under investigation include multiuser multi-antenna technologies for relay based and mesh networks, sensor network and wide area network integration, efficient computation platforms, and implementation design processes.

Teams: the CSP group is led by Prof. Markku Juntti, and currently consists of five teams, each concentrating on their specific expertise areas:

• Algorithms and Architectures for Wireless Systems
• Iterative Information Processing
• Positioning and Mesh Networks
• Radio Engineering
• Robust Signal Processing

Radio Access Technologies (RAT)

The telecommunications industry is growing fast. The increase both in the number of users and data rates poses serious challenges to the energy efficiency and overall architecture of wireless networks. At the same time, an ever increasing share of internet access has become wireless, which sets new requirements on the structures and management policies for the future internet. Cellular network topologies are being diversified. A full coverage backbone network can be supplemented with various short range local connectivity options (e.g., device-to-device links, sensor networks, relays, femtocells) to improve spectral plus energy efficiency and coverage, and to reduce costs. Intelligent context aware network control is needed to manage these dynamic and heterogeneous environments. A thorough understanding of radio access networks and their impact on other layers and segments of the network is imperative, and therefore a mission of this research group.

Goal: The Radio Access Technologies Group (RAT) implements the strategy of CWC in the broad area of future access network development. The group’s research goal is to gain a fundamental knowledge on how to optimize wireless networks for different settings:

• macrocellular, femtocells and relay based topologies
• opportunistic spectrum use concepts
• self-organizing networks
• future internet driven access networks
• energy and cost effective networks

and to continue to offer support to local industry in International Mobile Telecommunications - Advanced (IMT-A) (and beyond) and its further development within the group’s expertise areas. The application areas of RAT group’s research results are mainly broadband cellular systems, heterogeneous wireless networks and smart wireless devices. Interest groups for the application areas include network and device manufacturers, operators and semiconductor vendors

Focus areas: The group’s focus areas are cognitive radio networks, energy efficient networking technologies, femtocell concepts for capacity boosting, local connectivity in mobile cellular systems, fundamental networking research (e.g., cross layer optimization and network coding), mobile wireless driven future internet architecture, the evolution of mobile cellular networks, position assisted network(s) management and experimental networking research using WARP platforms.

Teams: theRAT group is led by Prof. Matti Latva-aho and currently consists of 4 teams each concentrating on their specific expertise areas:

• Mobile Cellular Systems
• Radio Access Networks
• Cognitive Radio Systems
• Broadband Short-range Access

Internetworking

The growing interest in new services with higher quality and increasing usage in the internet is one of the major challenges in the near future. Different networks are becoming more and more interdependent and joint optimization of such networks should provide more efficient solutions, resulting in better performance and lower cost of operation. Recent advances in development of low-cost wireless internet coupled sensor platforms also open up opportunities for novel wireless sensor network applications, with increasing security threats that deserve ever increasing attention. Finding solutions to these problems requires an approach that jointly optimizes several networking core functionalities and interconnects both theoretical modelling of the system and limitations set by the functional devices in the network.

Goal: The Internetworking Group fulfils the mission of CWC in the area of wireless communication network research by developing new methodologies and concepts around the evolving new wireless internet. The research goals of the group involve finding new solutions for optimizing network utility through layered network architecture. The results will be used to define new common air interfaces for 4G cellular together with ad hoc and sensor networks. Application areas of Internetworking Group’s research results are mainly cellular networks and wireless data networks with varying geographical coverage. The interest groups for the application areas include network operators and network system and security designers.

Focus areas: The group’s focus areas are those key issue in networking necessary to complement the existing solutions on the physical layer for building up the new generation of wireless communications. The research will include: network optimization, opportunistic network coding as an alternative to the conventional routing concept, intercell interference aware resource management, game theory based solutions, introduction of active network elements (mobile agent traffic optimization), topology control and security issues in wireless networks.

Teams: The Internetworking Group is led by Prof. Savo Glisic and currently consists of 2 teams each concentrating on their specific expertise areas

• Networking
• Secure and Trustworthy Wireless Internet

Wireless Systems (WS)

The world is changing and ICT is expected to penetrate new areas as an enabler of new services and applications. It is therefore a necessity to start looking at cross-diciplinary approaches to research. This calls for the identification of opportunities, interpretation of weak signals and thus new openings for ICT.

Goal: Wireless Systems (WS) implements the strategy of CWC by identifying new opportunities and performing research in these new areas, and especially identifying new system development opportunities as well as continuing work on pre-identified areas. CWC has extremely broad expertise in wireless systems research as our results in security and defence related systems development shows. The goal is to carry out research in such a fashion that it supports the needs of our customers in their product development or system specification work.

Focus areas: Security and defence related communication, navigation and radar systems have been on our research agenda since the inception of CWC. Medical ICT and Short Range Communication (SRC) have a history spanning more than 10 years. In the SRC area especially sensor networking has attracted a great deal of research effort in recent years. New emerging areas include smart energy grids and solutions for emerging markets. In smart energy grids, our research efforts are concentrated on identifying novel architectures for smart distributed control and data distribution, including modifications to existing communication systems such as LTE or LTE-A.

Teams: WS group is led by Ari Pouttu and currently consists of 3 teams each concentrating on their specific expertise areas:

• Security and Defence Systems
• SRC and Medical ICT
• Transfer for Emerging Technologies

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Scientific Progress

2010 was a successful year in CWC for its implementation and demonstration activities. On January 11th, the world’s first telephone call over a cognitive radio network was made between the University of Oulu’s Rector, Lauri Lajunen and the CWC Board Chairman Juha Hulkko using CWC’s cognitive radio network demonstration system, as shown in Figure 1. In September, the same demo system won the best demo award of the ACM MOBICOM 2010 conference. There were almost 30 demos from various universities and companies, such as Rice University, University of Illinois at Chicago, Stanford University, University of California (Santa Barbara), ETH Zurich, Nokia Research Centre, INRIA, Thales etc.

 

Figure 1. World’s first phone call over a cognitive radio network.

 

The cognitive radio networking demo is built on WARP platforms from Rice University (see Figure 2). The platforms are very flexible software defined radio platforms where every layer of the protocol stack is programmable. Most of the development work has been carried out on the MAC layer as it is the single most important part of cognitive radio networking in its traditional meaning, which is the efficient usage of the spectrum. The developed novel MAC protocol is designed for mobile ad hoc networks and is capable of using different frequencies for each link in the network. As there is no centralized frequency management, the system has a built-in interference avoidance capability. The physical layer of the demo system is traditional OFDM with spectrum sensing capability. The network layer uses OLSRv2 routing protocol. The layers are interconnected by a special control interface, which enables transmitting measured performance information between the layers. The control interface also enables fine-tuning of the operating parameters of the different layers on the fly with a cognitive engine.

 

Figure 2. The WARP Wireless Open-Access Research Platform.

 

 

The on-going effort with a demonstrator is a spectrum usage database and how it can be utilized in spectrum management. In this scheme each node of the network sends its measured spectrum information to a spectrum manager, from which spectrum usage strategies can be made.

Demonstration of a VOIP Call through a Cognitive Radio Network

The demonstration is about making a voice over internet protocol (VOIP) call over a combination of a cognitive radio network, LAN and Wi-Fi network. A laptop that is connected to a secondary user (SU) node which is in the cognitive radio network (CRN) forms one end of the call connection, and the other end of the call connection is formed by mobile equipment connected to a VOIP network. The CRN operates in the presence of primary users (PUs) which is using a different MAC protocol compared with the secondary users (SUs). The frequency channels used by the SU might be used by a PU randomly at any time, and this might cause disruption to the PU data communication. To avoid this disturbance the SU uses a simple spectrum sensing technique to detect the existence of a PU and avoid the corresponding frequency channel used by the PU. The SUs use the opportunistic MAC for a mobile ad hoc network (OMAN) MAC protocol as shown in Figure 3, where in the MAC frame is divided into a TDMA part using a common control channel (CCH) and a random access part. The TDMA slots are used for broadcast transmissions whereas the random access slot is used to exchange a RTS CTS message to determine an opportunistic channel (OTCH), and eventually send the data over the selected OTCH. The PUs however use distributed time division multiple access (DTDMA). The demonstration will consist of 6 nodes, 4 of which will be SUs, and 2 will be PUs. The SUs exchange control packets over a common control channel (CCH) which is free from interference by the PU. The data transmission happens over an opportunistic traffic channel (OTCH) which is in general one of the licensed channels used by PUs and this is selected as a result of spectrum sensing by the communicating SU pairs. All the SUs use optimized link state routing protocol (OLSR) on the network layer, and hence communication between SUs, which are several hops away, can be realized.

 

Figure 3. Flow diagram of the OMAN.

 

Each demonstrator node is built on a Linux enriched wireless open access research platform (LE-WARP); this is an improvised form of the WARP platform from Rice University, and the following modifications were made to WARP:

• Porting of the Linux kernel to the WARP hardware
• Using the one remaining processor as the network layer handler
• Adding hardware and software drivers to facilitate inter processor communication

In the process of modifying, we had change the system assembly of the FPGA design. The changes that facilitate the above modifications are reflected in Figure 4. LE-WARP added a fully functional network layer with IPv4 stack and transport, application layer to WARP. The open source Linux enables utilization of the OLSR routing protocol or any other routing protocol designed for Linux to be used on WARP.

 

Figure 4. The system assembly of LE-WARP.

 

The CRN demonstrator comprises of the following modules:

• Spectrum Sensing at PHY layer (SS)
• Cognitive Engine module (CE)
• Time synchronization module (TS)
• Opportunistic MAC with Network layer information (OMAN)
• Linux OS as the Network layer handler with OLSR and full IPv4 TCP/IP protocol stack running on it
• PUs using DTDMA protocol
• Logging unit used to set up a GUI for interactive usage

The graphical user interface can show the network topology and its changes, and the whole data transmission process from a projector display. By clicking on nodes, we can show information like

• Whether a node is a PU or SU
• Current state of the node and the packet types received and transmitted
• Neighbouring radio environment information as seen by the node considered
• Routing table information
• Throughput
• Information on critical PHY and MAC parameters of the node considered
• Slot structure by the PU
• MAC frame intervals of PU and SU
• Current channel used by the PU and SU

LE-WARP design, with its improved performance and added features, has enabled us to achieve our goal of realizing a self configurable and self aware wireless ad hoc network demonstrator system. The observations and results achieved can be used as inference in the ongoing projects in the research community across academic institutes and industries striving to achieve a similar objective. The award winning performances at different international conferences say a lot about the potential of using the LE-WARP design. It can be further used to set up a wireless ad hoc network test bed to verify theoretical algorithms at different layers, and thus establish the practical limitations of theoretical results.

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Personnel

professors & doctors	27
doctoral students	57
others	34
total	118
person years	94

 

External Funding

Source	EUR
Academy of Finland	767 000
Ministry of Education and Culture	151 000
Tekes	2 042 000
other domestic public	285 000
domestic private	856 000
international	2 098 000
total	6 199 000

 

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Doctoral Theses

Vartiainen J (2010) Concentrated signal extraction using consecutive mean excision algorithms. Acta Universitatis Ouluensis C 368.

Haapola J (2010) Evaluating medium access control protocols for wireless sensor networks. Acta Universitatis Ouluensis C 350.

Ylioinas J (2010) Iterative detection, decoding, and channel estimation in MIMO-OFDM. Acta Universitatis Ouluensis C 358.

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Selected Publications

Khan Z, Lehtomäki J, Codreanu M & Latva-aho M (2010) Throughput-efficient dynamic coalition formation in cognitive radio networks. EURASIP Journal on Wireless Communications and Networking 2010, doi:10.1155/2010/653913, 13 p.

Khan Z, Glisic S, Da Silva L & Lehtomäki Janne (2011) Modeling the dynamics of coalition formation games for cooperative spectrum sharing in an interference channel. IEEE Transactions on Computational Intelligence and AI in Games 3(1): 17-30.

Viittala H, Nahar BN, Hämäläinen M & Iinatti J (2010) Medical applications adapting ultra wideband - a system study. International Journal of Ultra Wideband Communications and Systems - Special Issue on Applications of Ultra Wideband Systems in Biomedicine 1(4): 237-247.

Taparugssanagorn A, Pomalaza-Raez C, Isola A, Tesi R, Hämäläinen M & Iinatti J (2010) UWB channel modelling for wireless body area networks in a hospital. International Journal of Ultra Wideband Communications and Systems 1(2010).

Weeraddana C, Codreanu M, Latva-aho M & Ephremides A (2010) On the effect of self-interference cancelation in multiHop wireless networks. EURASIP Journal on Wireless Communications and Networking, doi:10.1155/2010/513952, 10 p.

Myllymäki S, Huttunen A, Palukuru V & Jantunen H, Berg M, Salonen E (2010) Capacitive recognition of the user’ s hand grip position in mobile handsets. Progress In Electromagnetics Research B (22): 203-220.

Ketonen J, Juntti M & Cavallaro JR (2010) Performance-complexity comparison of receivers for a LTE MIMO-OFDM system. IEEE Transactions on Signal Processing 58(6): 3360-3372.

Pantelidou A & Ephremides A (2010) A cross-layer view of optimal scheduling. IEEE Transactions of Information Theory 56(11).

Vehkaperä M & Juntti M (2010) On the performance of space-time coded and spatially multiplexed MIMO systems with linear receivers. IEEE Transactions on Communications 58(2): 642-651.

Niemelä V, Rabbachin A, Attaphongse T, Hämäläinen M, Iinatti J (2010) Simulations of some UWB WBAN receivers in a hospital environment. Sports And Wellbeing - Multidisciplinary research symposium: Technological and nutritional aspects.