Current Research Projects
Existing wireless networks are constructed for coexistence rather than for cooperation. For instance, in current cellular networks different transmitters are orthogonal to each other, e.g. using TDMA , CDMA or FDMA methods.
However, current research results show that cooperative techniques are able to solve many of the basic problems that future wireless networks will face: multinode cooperation and relay based concepts are expected to be the key enablers for higher data rates, larger coverage, low latency and robust communication.
The aim of this project is to develop cooperative techniques to be used in 3G and 4G cellular mobile networks (focus on LTE and its upcoming 4G successor LTE-Advanced) and in wireless home networking.
The aim of this project “Cellular MIMO Multihop Communication” is to develop transmission strategies for cellular
infrastructure multihop networks. The intermediate nodes (relays) shall increase the maximum distance to the base
station and also increase the capacity of the network. These intermediate relays can operate in an
Amplify-and-Forward (AF) or Decode-and-Forward (DF) fashion. Which strategy is optimum in an infrastructure
multihop network is one of the issues to be investigated. A major focus lies on the MIMO relay case.
Most wireless nodes comprise typical analog and digital signal processing blocks such as frequency synthesis, down-conversion, filters, etc. In the long term we anticipate a major paradigm shift, as the systems become more dense and node separation is no longer much larger than the wavelength: the functionality of a classical wireless node may be dispersed into spatially separate subnodes, which communicate with each other through the wireless medium (including near field coupling effects).
In this project, we explore the potential of joint wireless communication, localization and imaging in dense networks with low complexity Ultra-Wideband (UWB) nodes. The aim is to develop a unified theoretical framework for communication, localization and imaging and to exploit synergies. Moreover, algorithm implementation and complexity is considered as well as future applications in the field of biomedical, industrial and environmental technology.
The main goal of this project is to investigate an Ultra-Wideband (UWB) radio based human motion tracking system. We consider a system setup where both the agents and the anchors are attached on the body. The agents are low-cost transmit-only nodes which might be unsynchronized. On the other hand, anchors are relatively complex transceiver nodes which are synchronized to each other.
An extremely adaptive mobile simulation laboratory with 10 cooperative nodes will be used to analyze the behavior of multihop/multinode multiple-input multiple-output (MIMO) systems. In a frequency band from 5.1 GHz to 5.9 GHz channel measurements with simple amplify and forward relays can be performed as well as the emulation of current and future wireless communication standards.
In the frame of the Nonlinear MIMO Systems project, we implement a MIMO envelope detection testbed. The multiple antenna envelope detector is custom made inside our institute. RACooN nodes are employed as transmitters.
A way to reduce both complexity and power consumption of MIMO systems is using nonlinear detection methods, i.e. amplitude and phase detection. However, conventional MIMO systems studied so far strictly employ linear receivers, meaning that an I/Q demodulator yields a complex baseband received signal. Our work considers the combination of nonlinear receivers and MIMO systems. Nonlinear MIMO systems offer a new unexplored field for research.
In this project we investigate capacity related scaling behaviours of various multiuser multihop networks. Networks are classified according to the level of cooperation within relay stages and destination stage and according to the availability of channel state information at transmitting nodes. Performance measures of interest are the diversity-multiplexing tradeoff and the sum-capacity scaling in the number of nodes/antennas per stage.
The Key to Efficient and Robust Localization. Ultra-Wideband (UWB) Geo-Regioning is novel localization and clustering technique developed at the Communication Technology Laboratory based on channel impulse response fingerprinting. The UWB technology enables a high spatio-temporal resolution of the wireless channel. Consequently, a channel impulse response between transmitter and receiver can be interpreted as signature (fingerprint) for their relative positions.
Systems for locating and tracking users or goods within closed or open environments are of great interest for the human society as well as for world economy. Typical applications are e.g. emergency services and avalanche victim search or in mobile computing applications, tracking of goods and any location-aware services.
Completed Research Projects
Current WLAN protocols, e.g. IEEE 802.11n, specify MIMO techniques to enhance
data rates in WLANs. However,
using carrier sense multiple access with collision avoidance (CSMA/CA), 802.11n can
support only point-to-point links. On the other hand, it is known that
Multiuser MIMO (MU-MIMO) techniques significantly increase the spectral efficiency of
a network. There are already some enhanced MIMO signal processing techniques
available which enable concurrent multiuser transmissions by utilising
multiuser interference cancellation techniques. To enhance future WLAN systems
such that multiple users can transmit simultaneously, we propose novel
cooperative protocols in this project.
A rigorous low duty cycle operation of UWB impulse radio (UWB-IR) transceivers
seems a potential key to ultra low power communication.
Low pulse rate (LPR) systems realize the low duty cycle by a large pulse
repetition period. High pulse rate (HPR) systems achieve the low duty cycle
by burst-wise transmission at high peak data rate. Analysis and optimization
of these two approaches is the main contribution of this project.
In this project, we focus on wireless multiuser networks and aim at designing novel cooperative communication protocols, developing corresponding transmission and signal processing techniques, and optimizing the network performance.
Conventional wireless communication architecture does not seem to be feasible
to offer the high data rate transmission required for future generation
wireless communication systems in reasonably large areas, e.g., for the
fourth generation (4G) cellular wireless networks. Relay communication was
proposed as a means to extending the coverage range in wireless networks
with reduced infrastructure deployment costs. However, conventional relaying
protocols require two channel uses to transmit the data from the source to the
destination via the relay, which leads to a loss in the spectral efficiency.
This project deals with the analysis and design of communication techniques in
MIMO relaying systems, especially in MIMO two-way relaying systems.
Due to the miniaturization of sensors and actors, more and more applications arise where such devices are placed close to the body. Therefore, wireless body area networks will be of increasing interest in future.
The principle research goal of our project is the design, optimization and demonstration of a noninvasive wireless
body area network (BAN) with unprecedented energy efficiency, unobtrusiveness, scalability and cost structure. We refer a BAN as noninvasive if the electromagnetical exposure to the body is kept extremly low.
The requirements on future wireless ad-hoc communications systems in terms of da
ta rates and quality of service are several orders of
magnitude higher than what is offered by current standards. The use of MIMO tech
nology has been recognized as a promising means to
meet these requirements and provide broadband wireless access with significantly enhanced spectral efficiency and quality of service.Ad-hoc networks with MIMO capability have received less attention so far. Topic
of this research project is MIMO ad-hoc networkswith special emphasis on physical layer and link layer aspects. This project is
part of the COST 273 Action: Towards Mobile Broadband Multimedia Networks.
Space-time codes enable the use of multiple antennas at the transmitter and/ or at the receiver. Future wireless networks will be heterogeneous regarding the co
mmunicating nodes; therefore flexible and adaptive codes are needed.
In this project a class of linear space-time block codes which meet the requirem
ents of future wireless communication systems are developed. These space-time codes are highly flexible and adaptive, we refer to them as linear scalable disper
sion (LSD) codes.
They allow a joint usage of transmit diversity and spatial multiplexing.
Next generation WLANs will operate beyond 5 GHz (e.g. 17/24GHz) and will require a peak link level throughput beyond 1Gbps.
Spatial multiplexing (MIMO) will be indispensible to achieve the required scalability and spectral efficiency.
Beyond 5GHz we face a rich array/poor scattering situation as opposed to the rich scattering/poor array situation at 5GHz.
In this project we study distributed antenna approaches and cooperative relaying for the rich array/poor scattering regime.
Next generation Wireless LANs will accommodate heterogeneous nodes with data rate requirements ranging from 1kbps (sensors) to 1Gbps (PCs).
The main goal of the project ChaseLow (Channel adaptive signalling and scheduling in MIMO enhanced heterogeneous wireless networks with low mobility and low channel rank) is to open up the benefits of cooperative diversity, channel adaptive scheduling and spatial multiplexing (MIMO) in a low mobility environment with poor scattering and with heterogeneous nodes.
This project is part of the COST 289 Action: Spectrum and Power Efficient Broadband Communications.
To provide wireless multimedia applications future generation wireless local are
a networks (WLAN) have to support much higher data rates (>200 MBit/s up to 1 GB
it/s) at a high link reliability.
The focus of this project is to enhance the IEEE 802.11.a technology especially by the use of multiple antenna array in combination with a transparent MIMO subl
ayer and to develop new concepts for future high-speed wireless LANs.
QoS measurements are essential for quality assurance and benchmarking; but usual
ly they lead to high effort and costs. In this project we develop techniques to
optimize QoS measurements and benchmarking based on knowledge of the considered
system, propagation conditions and air interface.
PULSERS, Pervasive Ultra-wideband Low Spectral Energy Radio Systems, is an indus
try led Integrated Project which is funded by the European Commission. The consortium comprises 30 key industrial and academic organisations. PULSERS will develop advanced systems and usage concepts and deliver innovative enabling physical layer and medium access technologies.Our group is leader of the Multiple Antenna Systems workpackage exploring co-loc
ated and distributed antenna techniques to establish reliability and location tr
acking in industrial scenarios.
The project iTrain aims at a technically innovative and commercially attractive integrated solution for train on board information, entertainment and communicat
ion services, which are considered as an essential part of a future Intelligent Transport System (ITS) for trains. The main focus of iTrain is on the train-to-ground access, connecting the train with the ground infrastructure.
In the project ''Wireless Local Area Network with Integration of Professional-Qu
ality DECT Telephony'', short WINDECT, wireless LAN and DECT cordless telephony networks are merged by integrating professional quality telephony into WLANs.
WINDECT is a STREP of the Sixth Framework Programme
"Information Society Technologies" of the European Commission.