A. Wittneben

Eawag: Das Wasserforschungs-Institut des ETH-Bereichs, Duebendorf, Zurich, Switzerland

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Publications (150)46.09 Total impact

  • Raphael T.L. Rolny, Marc Kuhn, Armin Wittneben
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    ABSTRACT: We consider the up- as well as downlink of a cellular network with multi-user multiple-input multiple-output (MIMO) communication and propose to turn the entire network into a two-hop network where a large amount of relays assist the bidirectional communication. To this end, many two-way relays are spread over the entire area of the network. In addition to introducing the concept of ubiquitous relaying, different two-way relaying protocols are developed, for amplify-and-forward (AF) as well as decode-and-forward (DF) relays. The goal is to efficiently apply two-way relaying to interference limited cellular networks. To achieve this, relaying is combined with a simple form of base station (BS) cooperation that allows canceling some interference terms. The relays are used to reduce the complexity at the terminal nodes and to improve the overall performance by distributed interference management. Our results show that the proposed concept can offer significant gains compared to a conventional multi-user MIMO strategy without relays.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2013 IEEE 24th International Symposium on; 01/2013
  • Yahia Hassan, Raphael T.L. Rolny, Armin Wittneben
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    ABSTRACT: It is well known that compact arrays introduce spatial channel correlation, antenna coupling, superdirectivity and noise correlation. While these effects have been thoroughly investigated for point to point MIMO, only isolated results are available on the effect of such phenomena on performance of relaying systems. This paper tries to fill part of this void. Specifically we study the impact of lossless and lossy compact antenna arrays on multiuser amplify and forward (AF) relaying in the presence of different noise sources. We optimize the gain allocation for sum rate maximization under a dissipated power constraint. For compact arrays this constraint is more relevant than the commonly used radiated power constraint. We provide an extensive insight-oriented discussion of our results, some of which may appear counterintuitive at first glance. We show that for compact MIMO relaying the standard model, considering only channel correlation but ignoring antenna coupling and noise correlation, is insufficient and may lead to a wrong system characterization.
    Personal Indoor and Mobile Radio Communications (PIMRC), 2013 IEEE 24th International Symposium on; 01/2013
  • Jörg Wagner, Armin Wittneben
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    ABSTRACT: The sum-capacity $C$ of a static uplink channel with $n$ single-antenna sources and an $n$-antenna destination is known to scale linearly in $n$, if the random channel matrix fulfills the conditions for the Marcenko-Pastur law: if each source transmits at power $P/n$, there exists a positive $c_{0}$, such that $\lim_{n \ura{} \infty}C/n=c_{0}$ almost surely. This paper addresses the question to which extent this result carries over to multi-hop networks. Specifically, an $L+1$-hop network with $n$ non-cooperative source antennas, $n$ fully cooperative destination antennas, and $L$ relay stages of $n_{\cal R}$ (cooperative or non-cooperative) relay antennas each is considered. Four relaying strategies are assessed based on the interrelationship between two sequences. For each considered strategy ${\rm XF}$, there exists a sequence $(c_{L}^{\rm XF})_{L=0}^{\infty}$ , such that $c_{L}^{\rm XF}=\lim_{n \ura{} \infty}R^{\rm XF}_{L}/n$ almost surely, where $R^{\rm XF}_{L}$ denotes the supremum of the set of sum-rates that are achievable by the strategy over $L\!+\!1$ hops. This sequence depends on the sequence $(P_{L})_{L=0}^{\infty}$ , where $P_{L}$ corresponds to the power of the source stage and each of the relay stages in an $L\!+\!1$-hop network. Results are summarized as follows: Decode & forward (DF): For $n_{\cal R}=n$, $c^{\rm DF}_{L}$ is constant with respect to $L$, if also $P_{L}$ is constant with respect to $L$.
    IEEE Transactions on Information Theory 01/2012; 58(4):2107-2133. · 2.62 Impact Factor
  • H. Luecken, C. Steiner, A. Wittneben
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    ABSTRACT: Future wireless networks based on Ultra-Wideband (UWB) will offer localization capabilities with centimeter accuracy. We propose to use this inherently obtainable location knowledge to adapt the transceiver to the multipath channel conditions. This saves overhead for channel estimation and dissemination and enables low cost, low complexity and low power data transmission. In particular, we study the location-aware adaptation of generalized energy detection receivers for UWB impulse radio communication with binary pulse position modulation. Conventionally, these receivers are very vulnerable to narrowband interference. Therefore, we derive transmitter and receiver optimization schemes based on the Signal-to-Interference-plus-Noise-Ratio (SINR): First, we present the SINR optimization based on full channel knowledge. The location knowledge is then incorporated by means of a statistical channel model, which depends on the position of the nodes. Performance evaluation based on a simple channel model is used to give insight about the fundamental behavior of the derived optimization schemes. Moreover, an extensive measurement campaign in a rich scattering environment proves that location information can improve the data transmission and helps to successfully suppress narrowband interference. Performance gains of 2 to 5 dB compared to conventional energy detection can be obtained.
    IEEE Transactions on Wireless Communications 01/2012; 11(9):3068-3078. · 2.42 Impact Factor
  • E. Slottke, R. Rolny, A. Wittneben
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    ABSTRACT: We propose a method for enabling complex computations in a network of low-complexity wireless devices. By utilizing multihop relaying, such devices can form the wireless equivalent of an artificial neural network (ANN). We provide a method for programming the network functionality in a decentralized fashion and demonstrate the robustness of wireless ANNs against node failures and imperfections. Applications of this scheme exist in low-complexity sensor networks, where elaborate calculations can be carried out in a distributed fashion, or for creating powerful ANNs with very high degrees of interconnectivity realized by the wireless medium.
    Signals, Systems and Computers (ASILOMAR), 2012 Conference Record of the Forty Sixth Asilomar Conference on; 01/2012
  • Source
    C. Steiner, A. Wittneben
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    ABSTRACT: Location fingerprinting utilizing ultrawideband (UWB) radio frequency (RF) signals is an attractive alternative to conventional positioning concepts based on range, angle, or received signal strength estimates. Such a location fingerprinting method proves particularly beneficial in indoor environments with dense multipath propagation and nonline-of-sight situations where conventional approaches would fail. The ultrawide bandwidth allows for location fingerprints with many degrees of freedom and thus gives the important advantage that a single anchor suffices for good localization performance. The downside is that a large amount of training data is usually required, which makes the training phase time-consuming and tedious. In this paper, we propose and study a novel and efficient training method which is based on the idea of spatial signal prediction. We develop a regional channel model which supports spatial signal prediction in the vicinity of a reference point. We show that the parameters of this regional channel model can be estimated from very few measured received signals with known transmitter and receiver positions. The prediction accuracy and the location fingerprinting performance are evaluated with measured channel impulse responses obtained in an anechoic chamber and in a typical office environment.
    IEEE Transactions on Signal Processing 01/2012; · 2.81 Impact Factor
  • R. Rolny, M. Kuhn, A. Wittneben, T. Zasowski
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    ABSTRACT: We develop a unified framework to investigate the performance of future cellular networks with relays and/or co-ordinated multipoint (CoMP) transmission. Based on this framework, we study the benefits of CoMP and relaying in a realistic setup. We consider imperfect channel knowledge, different power levels, and simple (thus practically relevant) cooperation schemes with different complexity: non-cooperative reference, decode-and-forward relaying with relay selection, base station cooperation with block zero-forcing (coherent joint transmission), and a combination of relaying and CoMP. Based on computer simulations, we compare the different schemes with respect to performance, robustness, complexity, and required transmit power.
    Signals, Systems and Computers (ASILOMAR), 2012 Conference Record of the Forty Sixth Asilomar Conference on; 01/2012
  • Source
    H. Luecken, A. Wittneben
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    ABSTRACT: Conventional Time-of-Arrival (ToA) based Ultra-Wideband (UWB) positioning suffers strongly from multipath. Harsh propagation environments or non-line-of-sight (NLOS) situations lead to biased position estimates with high estimation errors. To overcome this problem, we propose a radar imaging based method to predict delays of dominant propagation paths. This is done in a three-step approach: First, a radar image of the environment is created using measured training data. We generate a scattering coefficient map with the large synthetic aperture of distributed and moving antennas. The training data can easily be obtained from channel estimates of a UWB communication system with mobile nodes. Second, the radar image is used to reconstruct path gains and path delays. Thus, the channel response is predicted for arbitrary transmitter and receiver positions. Finally, dominant multipath delays are extracted using WRELAX. The proposed algorithm is validated by anechoic chamber measurements with controlled reflectors. Moreover, an extensive measurement campaign in a laboratory/office environment shows that strong paths can be predicted with nanosecond accuracy in a real world scenario.
    Ultra-Wideband (ICUWB), 2011 IEEE International Conference on; 10/2011
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    Christoph Steiner, Armin Wittneben
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    ABSTRACT: Location fingerprinting utilizing ultra-wideband radio frequency signals is an attractive alterna-tive to conventional positioning concepts based on range, angle, or received signal strength estimates. Such a location fingerprinting method proves particularly beneficial in indoor environments with dense multipath propagation and non-line-of-sight situations where conventional approaches would fail. The ultra-wide bandwidth allows for location fingerprints with many degrees of freedom and thus gives the important advantage that a single anchor suffices for good localization performance. The downside is that a large amount of training data is usually required, which makes the training phase time-consuming and tedious. In this paper, we propose and study a novel and efficient training method which is based on the idea of spatial signal prediction. We develop a regional channel model which supports spatial signal prediction in the vicinity of a reference point. We show that the parameters of this regional channel model can be estimated from very few measured received signals with known transmitter and receiver positions. The prediction accuracy and the location fingerprinting performance are evaluated with measured channel impulse responses obtained in an anechoic chamber and in a typical office environment. for any other purposes must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org. Christoph Steiner was with the Communication Technology Laboratory, ETH Zurich, and is now with Infineon Technolo-gies Austria AG, Babenbergerstr. 10, 8010 Graz, Austria (email: christoph.steiner@infineon.com). Armin Wittneben is with the Communication Technology Laboratory, ETH Zurich, 8092 Zurich, Switzerland (email: wittneben@nari.ee.ethz.ch). The authors would like to thank Dr. Juergen Kunisch from IMST GmbH, Kamp-Lintfort, Germany for providing ultra-wideband channel impulse response measurements.
    09/2011;
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    Z.W. Mekonnen, A. Wittneben
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    ABSTRACT: In this paper, we propose and investigate a low-complexity human motion tracking system which is based on ultra-wideband (UWB) radio nodes. The maximum likelihood (ML) solution of the localization problem that arises in such a system has been presented in. However, the ML solution has a computational complexity that prohibits cost-effective real-time human motion tracking. In this paper, an iterative solution of the localization problem, which is based on the first order Taylor series (TS) approximation of the ranges between the anchors and the agents, is presented. The localization algorithm can handle range measurements with unknown offsets which arise due to the asynchronism between the clock of the agents and the anchors. By means of computer simulations, it is shown that the TS based approximate solution performs close to the ML solution within a few number of iterations if it is started with a “good” initial guess of the agents position. With the a priori knowledge of the agents trajectory and position estimates in the previous time-steps, the position in the next time-step can be predicted. It has been shown that using these predicted positions as an initial guess for the TS based approximation scheme greatly improves performance.
    Positioning Navigation and Communication (WPNC), 2011 8th Workshop on; 05/2011
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    ABSTRACT: We investigate the potential of restricted PHY co- operation for the downlink of 4G networks. The cooperation is restricted to a cluster of eNodeBs. We distinguish between low and high mobility users, and propose two appropriate cooperation methods. The goal is to guarantee high user rates even on cell edges. We present a simulation study to analyze the spectral efficiency achieved by cooperation methods for urban micro cells. To investigate their influence on coordinated multipoint (CoMP), we consider different frequency allocation strategies and different sector orientations in a cell. In addition, we compare CoMP transmission to Multiuser MIMO and investigate how cooperation can improve power allocation. Based on the results, we provide important insights into future cell planing aspects.
    Proceedings of the 74th IEEE Vehicular Technology Conference, VTC Fall 2011, 5-8 September 2011, San Francisco, CA, USA; 01/2011
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    ABSTRACT: It is known that multiuser multiple-input multiple-output (MIMO) communication can enhance the performance of wireless networks. It can substantially increase the spectral efficiency of wireless networks by utilising multiuser interference rather than avoiding it. This paradigm shift has most impact on the medium access control (MAC) protocol because most existing MAC protocols are designed to reduce the interference. In this article, we propose a novel cluster-based carrier sense multiple access with collision avoidance (CB-CSMA/CA) scheme. The proposed scheme enables multiuser MIMO transmissions in wireless local area networks (WLANs) by utilising the multiuser interference cancellation capability of the physical layer. In this article we focus on the performance analysis of CB-CSMA/CA. We investigate saturation throughput applying optimum backoff parameters and in the presence of synchronisation errors. Furthermore, we study the impact of different clustering methods on non-saturation throughput. We show that CB-CSMA/CA improves throughput significantly compared to the CSMA/CA scheme used in the IEEE 802.11 system. It is a promising approach for a variety of network configurations including typical infrastructure WLANs as well as many other wireless cooperative networks.
    EURASIP Journal on Wireless Communications and Networking 01/2011; 2011(1):1-14. · 0.54 Impact Factor
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    Heinrich Luecken, Armin Wittneben
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    ABSTRACT: We consider the downlink of an Ultra-Wideband (UWB) sensor network, i.e. communication from a central unit to many sensor nodes. The key to achieve low-complexity, low-power and low-cost sensor nodes are non-coherent receivers. Conventionally, their detection performance strongly suffers from inter-symbol interference due to multipath, which substantially limits the data rate or requires expensive receiver post-processing. To overcome this problem, we propose a novel precoding scheme to transmit to several nodes simultaneously. This way the sum data rate can be increased, while low complexity of sensor nodes is maintained. Specifically, we consider nodes with generalized energy detection receivers and transmission of pulse position modulated data. First, precoding optimization is derived from a Signal-to-Interference-plus-Noise Ratio (SINR) expression for this setup based on full channel state information. To achieve the best sensor network coverage, the minimum SINR of all nodes is maximized. In a second step, optimization is extended to statistical channel knowledge, which depends on the position of the nodes. Performance evaluation based on an extensive measurement campaign shows that multiple nodes can efficiently be served simultaneously. Only marginal increase in transmit power is necessary compared to time-multiplexing.
    8th International Symposium on Wireless Communication Systems, ISWCS 2011, Aachen, Germany, November 6-9, 2011; 01/2011
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    ABSTRACT: We present the first implementation of a MIMO envelope detection system. Such systems have so far been theoretically studied in the framework of nonlinear MIMO. The design considered employs an envelope detector on each receive antenna. The simplicity of the receiver enables extreme low-cost low-power implementations, making such systems attractive for wireless sensor networks and alike applications. The test bed presented here is a first implementation of such a system and demonstrates detection of spatially-multiplexed data streams using envelope detectors.
    Proceedings of the 74th IEEE Vehicular Technology Conference, VTC Fall 2011, 5-8 September 2011, San Francisco, CA, USA; 01/2011
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    R. Rolny, J. Wagner, A. Wittneben
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    ABSTRACT: In this work, we study distributed gain allocation to maximize the achievable sum-rate in non-regenerative multihop networks with multiple users and multi-antenna nodes. The source and relay nodes are constrained to forward linear transformations of their input and calculate their transformation matrices based on locally available channel state information and limited feedback from the destination. We relax the optimization problem by imposing a norm constraint instead of a power constraint on each node, and devise a gain allocation scheme that is based on an approximation of the gradient of the sum-rate. By means of computer simulations, we show that the proposed algorithm achieves close to optimal solutions, if a good initialization is provided. This makes the scheme particularly useful for channel tracking in slow fading environments.
    Signals, Systems and Computers (ASILOMAR), 2010 Conference Record of the Forty Fourth Asilomar Conference on; 12/2010
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    ABSTRACT: In this paper, the problem of human motion tracking with ultra-wideband radio nodes is addressed. We provide a general maximum likelihood formulation of the positioning problem based on range measurements which can handle synchronous and asynchronous agents. Geometrical constraints on the node topology, which are imposed by the human body, are also taken into account. For a Gaussian ranging error model and the specific problem of arm motion tracking, we derive the maximum likelihood estimation rule and calculate an analytical expression for the unconstrained and constrained Cramér-Rao Lower Bound. With these results, we study analytically and via computer simulations under what circumstances the geometrical constraints lead to performance gains. It is found that the largest benefits are obtained in case of asynchronous agents and for certain arm positions. Intuitive reasons for this phenomenon are given. Finally, we verify these findings and evaluate the position location performance experimentally with range estimates obtained from measured ultra-wideband channel impulse responses including the impact of the human body.
    Indoor Positioning and Indoor Navigation (IPIN), 2010 International Conference on; 10/2010
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    Jian Zhao, M. Kuhn, A. Wittneben, G. Bauch
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    ABSTRACT: We propose a novel transmission scheme for the broadcast phase of two-way relaying systems. The proposed scheme employs network coding at the relay and is able to transmit with asymmetric data rates to the receivers according to their individual link qualities. The idea is that the weaker link receiver exploits a priori bit information in each transmit symbol, so that it only needs to decode on a subset of the transmit symbol constellation. Subject to the same bit error rate constraint, the weaker link receiver can decode at lower signal-to-noise ratio compared to the stronger link. The signal labeling used for mapping bits to symbols at the relay is shown to be crucial for the performance at the receivers, and we provide the criterion and method for finding the optimized labeling schemes. Simulations show that the proposed transmission scheme can be applied to practical scenarios with asymmetric channel qualities, and the optimized labeling greatly outperforms conventional ones at both receivers.
    Communications (ICC), 2010 IEEE International Conference on; 06/2010
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    H. Luecken, A. Wittneben
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    ABSTRACT: In this paper, we consider localization based on the Time-of-Arrival (ToA) of Ultra-Wideband (UWB) impulse radio pulses. We present a receiver structure for ToA estimation, which can be implemented with very low complexity and low power consumption. Standard approaches for ToA estimation of UWB pulses require very high speed A/D conversion, which makes them impractical for implementation. Although ToA estimation based on phase estimation of narrowband signals circumvents that problem, the estimation performance suffers strongly from multipath propagation. We propose to combine the advantages of both techniques by performing spectral estimation at the output of a UWB energy detection receiver. This system benefits from resolvability of multipath components due to a large signaling bandwidth, but requires only low sampling rates. The impact of bandwidth on the ToA estimation accuracy is derived analytically and a closed form approximation of the estimation variance for a multipath channel is given. Moreover, we present a performance evaluation based on measured channels and show that accuracy up to 20 cm can be reached in strong multipath environments.
    Communications (ICC), 2010 IEEE International Conference on; 06/2010
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    G.K. Psaltopoulos, A. Wittneben
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    ABSTRACT: We consider a MIMO system for very low-power applications, e.g, sensor networks, where the receiver employs an envelope detector at each receive antenna. Properties of such systems have been studied, where the channel was considered to be perfectly known at the receiver, or a linear channel estimation model was used. In this paper we propose a very simple channel estimation scheme, which allows the non-coherent MIMO envelope detector to estimate all required channel knowledge necessary for maximum likelihood detection. In contrast to linear MIMO system, complete knowledge of the channel coefficients is not required.
    Communications (ICC), 2010 IEEE International Conference on; 06/2010
  • Stefan Berger, Armin Wittneben
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    ABSTRACT: In this work we investigate the impact of imperfect local oscillators (LOs) at the relays in nonregenerative two-hop networks. Due to the specific traffic pattern of multihop networks, hardware imperfections at the relays have a different impact on the system than hardware imperfections at the sources and destinations. Based on the assumption that one LO generates all oscillations in each node, we consider baseband sampling time as well as sampling frequency offsets, RF frequency and phase offsets, timing errors, and phase noise. In the presence of these imperfections, time division duplex (TDD) and frequency division duplex (FDD) relays introduce errors to their forwarded signals. We identify these errors for both types of relays and use Monte-Carlo simulations to compare the performance of a multiuser network employing either TDD or FDD relays with imperfect LOs.
    Vehicular Technology Conference (VTC 2010-Spring), 2010 IEEE 71st; 06/2010

Publication Stats

3k Citations
46.09 Total Impact Points

Institutions

  • 2010
    • Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
      Duebendorf, Zurich, Switzerland
  • 2005–2009
    • ETH Zurich
      • Communication Technology Laboratory
      Zürich, Zurich, Switzerland
  • 2008
    • German Aerospace Center (DLR)
      Köln, North Rhine-Westphalia, Germany
  • 2002
    • Universität des Saarlandes
      Saarbrücken, Saarland, Germany