International Zurich Seminar on Communications, 2004

2004

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Displaying Results 1 - 25 of 65
  • Stability region of arrival rates and optimal scheduling for MIMO-MAC-a cross-layer approach

    Publication Year: 2004, Page(s):18 - 21
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (391 KB) | HTML iconHTML

    With the imminent proliferation of new services in wireless standards beyond 3G, which require low-delay and/or high-rate uplinks, is associated a need for flexible and fair uplink scheduling. In this work we give an overview of our recent results regarding optimal scheduling schemes and stability properties of a system of bit-queues in the multiple input multiple output multiple access channel (M... View full abstract»

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  • Design methodologies and power setting strategies for WCDMA serial interference cancellation receivers

    Publication Year: 2004, Page(s):28 - 31
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (386 KB) | HTML iconHTML

    The uplink capacity and coverage of CDMA cellular systems with the conventional single user detection receiver are interference limited. In this work, we show that serial interference cancellation (SIC) is a competent and flexible receiver structure to enhance the uplink of power-controlled WCDMA cellular systems with a remarkable tradeoff between performance and complexity. We show that there are... View full abstract»

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  • Multipath: curse or blessing? A system performance analysis of MIMO wireless systems

    Publication Year: 2004, Page(s):14 - 17
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (347 KB) | HTML iconHTML

    In this paper, we look at the performance of noise-limited MIMO wireless systems and compare analytically line-of-sight (LOS) and nonLOS dominated environments on coverage and cell capacity. Through a few key examples, we show that neither a LOS scenario or a NLOS scenario always provides the best performance as it appears the most favorable propagation scenario heavily depends on the chosen metri... View full abstract»

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  • M-ary optical data storage for CD, DVD and beyond

    Publication Year: 2004, Page(s):52 - 55
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (312 KB) | HTML iconHTML

    In this paper, we introduce the theoretical and practical concepts behind M-ary signaling on optical recording systems such as compact disc (CD), digital versatile disc (DVD) and evolving next generation formats based on blue lasers. We show that there is sufficient signal-to-noise ratio on all recording formats (ROM, R and R/W) and give examples of how density and data transfer rate can be improv... View full abstract»

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  • LDPC coded MIMO multiple access communications

    Publication Year: 2004, Page(s):106 - 110
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (464 KB) | HTML iconHTML

    An efficient scheme for the multiple-access MIMO channel is proposed, which operates well also in the single user as well as in a DS-CDMA regime. The design features scalability and is of limited complexity. The system employs optimized LDPC codes and an efficient iterative (belief propagation) detection which combines linear minimum mean square error (LMMSE) and iterative interference cancellatio... View full abstract»

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  • A posteriori probability detection of pulse position modulated signals under imperfect channel estimation

    Publication Year: 2004, Page(s):72 - 75
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (346 KB) | HTML iconHTML

    In this paper, we consider two sets of pulse position modulated (M-PPM) signals related by M estimation error signals. The first signal set is transmitted on a Gaussian channel and is unknown to the receiver. The second signal set is used in the receiver filter bank in order to generate likelihoods for coherent a posteriori probability (APP) detection. The error model is defined by a Toplitz matri... View full abstract»

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  • MIMO channel for modal multiplexing in highly overmoded optical waveguides

    Publication Year: 2004, Page(s):196 - 199
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (385 KB) | HTML iconHTML

    In order to meet the increasing demand for data rate in modern multiprocessor systems optical transmission has become an important technology. Due to cost reasons only highly multimodal waveguides come into question for mass-producible board level interconnects. We present the idea of an optical multiple-input multiple-output (MIMO) channel by having more than one data source at the channel input ... View full abstract»

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  • Symbol-rate timing error detectors for DSL transceivers

    Publication Year: 2004, Page(s):144 - 147
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (387 KB) | HTML iconHTML

    Symbol-rate timing error detectors are derived which allow to optimize the synchronization of single carrier DSL transceivers. The synchronizer input signal in DSL receivers does not have the ideal characteristics which are assumed by many synchronizer algorithms in the literature. Impairments and distortion of the DSL channel require a decision feedback equalizer in the receiver. A timing error d... View full abstract»

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  • Achievable rates for UWB peer-to-peer networks

    Publication Year: 2004, Page(s):82 - 85
    Cited by:  Papers (8)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (353 KB) | HTML iconHTML

    Some achievable information rates for one-dimensional peer-to-peer networks using ultra-wideband signaling are presented. For a simple propagation model and coherent detection, achievable rates with and without interference mitigating techniques are provided showing the influence of node density and communication distance on achievable rates of peer-to-peer links. The model is made more precise by... View full abstract»

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  • TCP with end-to-end FEC

    Publication Year: 2004, Page(s):152 - 155
    Cited by:  Papers (10)  |  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (376 KB) | HTML iconHTML

    In this paper we investigate the effects of combining end-to-end forward error correction (FEC) with TCP. FEC reduces the number of retransmissions and results in different congestion control behaviour, effectively running the network at a higher load. The interaction between TCP and FEC is discussed and the conclusion is that the FEC has to be adaptive to work efficiently. Unless the block length... View full abstract»

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  • Design of near-orthogonal LD space-time codes

    Publication Year: 2004, Page(s):10 - 13
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (387 KB) | HTML iconHTML

    This work considers a wireless multiinput-multioutput (MIMO) communication system in a frequency-nonselective scenario with spatially uncorrelated Rayleigh fading channel coefficients and investigates the design of linear dispersion (LD) space-time block codes. By optimizing the constituent weight matrices so that an upper bound on the union bound of the codeword error probability is minimized, go... View full abstract»

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  • Traffic engineering and routing in survivable multiservice networks

    Publication Year: 2004, Page(s):48 - 51
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (407 KB) | HTML iconHTML

    This paper presents a new framework for traffic engineering (TE) of primary and backup paths and routing of quality of service (QoS) and best-effort (BE) flows in multiservice backbone networks capable of surviving against single or multiple node and/or link failure(s). The aforementioned framework involves an off-line and an on-line phase. In the off-line phase either a method based on an integer... View full abstract»

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  • Multistage detectors in asynchronous CDMA systems

    Publication Year: 2004, Page(s):102 - 105
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (363 KB) | HTML iconHTML

    The demand of detectors able to efficiently mitigate crosstalk for large CDMA systems has led to the analysis of reduced rank detectors, especially multistage detectors. The increasing interest for this class of detectors is due to at least two reasons. Firstly, a low number of stages is sufficient for near-LMMSE performance, even as the system size grows large. Secondly, implementations with the ... View full abstract»

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  • Sensor networks: towards a theory of computation and communication of functions of measurements to a fusion center

    Publication Year: 2004, Page(s):176 - 178
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (305 KB) | HTML iconHTML

    Sensor networks consist of nodes with sensing as well as limited wireless and computation capabilities. In many applications, some statistic, or more generally function of the various sensor measurements, is required to be communicated to a fusion center. Computing and communicating such a function efficiently is an important, and perhaps a primary, task to be performed by a sensor network. We are... View full abstract»

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  • Is the number of neighbors in ad hoc wireless networks a good indicator of connectivity?

    Publication Year: 2004, Page(s):40 - 43
    Cited by:  Papers (14)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (401 KB) | HTML iconHTML

    Finding the minimum necessary number of neighbors required to provide full connectivity in wireless networks is an important problem which has been addressed by several researchers. In this paper, we show that the number of neighbors is a meaningful parameter to describe the connectivity only if the ad hoc wireless network has a perfectly uniform node distribution, i.e., the nodes lie approximatel... View full abstract»

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  • Multiuser precoders for fixed receivers

    Publication Year: 2004, Page(s):94 - 97
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (361 KB) | HTML iconHTML

    We consider the problem of designing precoders for multiuser systems using fixed receivers. We first derive a precoder that minimizes the transmitted power subject to signal to interference plus noise ratio (SINR) constraints, and then derive a precoder that maximizes the worst case SINR subject to a power constraint. We show that both problems can be solved using standard optimization packages. I... View full abstract»

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  • Bounds on information combining for parity-check equations

    Publication Year: 2004, Page(s):68 - 71
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (346 KB) | HTML iconHTML

    When several independent channels are coupled by a parity check constraint on their inputs, the mutual information between the input of one channel and the outputs of all other channels can be expressed as a combination of the mutual information between the input and the output of each individual channel. This concept is denoted as information combining. For binary-input symmetric discrete memoryl... View full abstract»

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  • Information-theoretic multihopping for relay networks

    Publication Year: 2004, Page(s):192 - 195
    Cited by:  Papers (31)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (357 KB) | HTML iconHTML

    Recent advances in multihopping are extended to relay networks having multiple antennas and multiple sources. As for the single-antenna and single-source case, one can achieve the ergodic capacity of wireless relay networks with phase fading if the relays are in a region near the source terminal, and if information is available only locally. The capacity results further generalize to Rayleigh fadi... View full abstract»

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  • Toeplitz method for blind equalization in MIMO OFDM systems

    Publication Year: 2004, Page(s):212 - 215
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (370 KB) | HTML iconHTML

    In this paper we address the problem of blind recovery of multiple OFDM streams in a multiple-input multiple-output (MIMO) system. We propose an equalization algorithm which is based on a combined criterion that cancels both inter-symbol interference (ISI), and co-channel interference (CCI). ISI is minimized by using a modified vector constant modulus (VCM) criterion, while CCI is minimized by a d... View full abstract»

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  • PALATIN: a platform for interactive algorithms

    Publication Year: 2004, Page(s):168 - 171
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (399 KB) | HTML iconHTML

    In this paper, we outline the design of a platform, called PALATIN, that allows easy development and reliable and efficient execution of concurrent algorithms in a distributed, potentially unreliable environment. The platform consists of three parts: a philosophy of how to write code for concurrent data structures and algorithms, a C++ library called Spheres support this philosophy, and the design... View full abstract»

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  • Protecting the robustness of ADSL and VDSL DMT modems when applying DSM

    Publication Year: 2004, Page(s):140 - 143
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (337 KB) | HTML iconHTML

    Recent techniques for ADSL and VDSL like power backoff (PBO) and dynamic spectrum management (DSM) focus on the crosstalk and try to operate with lower noise margin to increase the performance of the network. However, if the noise increases, the DSM modem may lose showtime, unless the modem can adapt its PSD to compensate for the increase of noise. The intent of the paper is to know what the impac... View full abstract»

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  • Cluster analysis of wireless channel impulse responses

    Publication Year: 2004, Page(s):124 - 127
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (363 KB) | HTML iconHTML

    This paper introduces a novel wireless channel clustering technique based on the Saleh-Valenzuela channel model. The impulse response is regarded as a single realization of the statistical channel model based on which the prior density functions of cluster arrival times are derived. Cluster analysis is done by means of extending the original Saleh-Valenzuela model by allowing different cluster arr... View full abstract»

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  • On time-variant distortions in multicarrier systems: general analysis and application to OFDM

    Publication Year: 2004, Page(s):232 - 235
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (322 KB) | HTML iconHTML

    Phase noise and frequency offsets are due to their time-variant behavior one of the most limiting disturbances in practical OFDM designs and therefore intensively studied by many authors. In this paper we present a generalized framework for the prediction of uncoded system performance including the transmitter and receiver pulseshapes as well as the time-invariant known channel. Moreover, unlike e... View full abstract»

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  • Cellular capacity gains of cooperative MIMO transmission in the downlink

    Publication Year: 2004, Page(s):22 - 26
    Cited by:  Papers (18)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (445 KB) | HTML iconHTML

    In this paper cooperation among users at the physical layer level is studied for the downlink. Distributed space time linear dispersion codes are proposed for the cooperative strategies amplify and forward (AF) and decode forward (DF), assuming no channel state knowledge at the transmitter. Both AF and DF strategies are evaluated in a cellular multiuser realistic scenario based on TDMA access, con... View full abstract»

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  • A multiMAC approach to overcome the throughput limits of 802.11 WLANs

    Publication Year: 2004, Page(s):32 - 35
    Cited by:  Papers (1)  |  Patents (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (437 KB) | HTML iconHTML

    In this paper, we explore MAC approaches that could provide increased throughput to 802.11 WLANs. First we analyze the throughput performance of 802.11 WLANs by deriving expressions for the maximum achievable throughput. Based on these results, we identify the main throughput-limiting factors and discuss approaches that may reduce their impact. We also propose a novel approach, called multiMAC, wh... View full abstract»

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