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Search Results: 1 - 10 of 326029 matches for " Reiner S. Thom? "
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Using Quaternion-Valued Linear Algebra
Dominik Schulz,Reiner S. Thom
Mathematics , 2013,
Abstract: Linear algebra is usually defined over a field such as the reals or complex numbers. It is possible to extend this to skew fields such as the quaternions. However, to the authors' knowledge there is no commonly accepted notation of linear algebra over skew fields. To this end, we discuss ways of notation that account for the non-commutativity of the quaternion multiplication.
Cognitive Scout Node for Communication in Disaster Scenarios
Rajesh K. Sharma,Anastasia Lavrenko,Dirk Kolb,Reiner S. Thom
Journal of Computer Networks and Communications , 2012, DOI: 10.1155/2012/160327
Abstract: The cognitive radio (CR) concept has appeared as a promising technology to cope with the spectrum scarcity caused by increased spectrum demand due to the emergence of new applications. CR can be an appropriate mean to establish self-organization and situation awareness at the radio interface, which is highly desired to manage unexpected situations that may happen in a disaster scenario. The scout node proposed in this paper is an extended concept based on a powerful CR node in a heterogeneous nodes environment which takes a leading role for highly flexible, fast, and robust establishment of cooperative wireless links in a disaster situation. This node should have two components: one is a passive sensor unit that collects and stores the technical knowledge about the electromagnetic environment in a data processing unit so-called “radio environment map” in the form of a dynamically updated database, and other is an active transceiver unit which can automatically be configured either as a secondary node for opportunistic communication or as a cooperative base station or access point for primary network in emergency communications. Scout solution can be viable by taking advantage of the technologies used by existing radio surveillance systems in the context of CR. 1. Introduction Communication has been an indispensable part of everyday life in the present days. Apart from making the general life better, modern communications should also be applicable for relief and support to the victims of exceptional adverse situations which include disaster scenarios like earthquakes, floods, cyclones, forest fires and terrorist attacks. Such scenarios impose new requirements on the communication systems. Some of the tasks of a cognitive radio network for emergency situations may be (1) to support specific service requests (higher traffic, coverage, localization, emergency messages, etc.), (2) to re-establish communications in a short time, and (3) to assist rescue forces communications and provide interoperability among them and also among rescue forces and public network. One of the first tasks in disaster is to organize rescue operations in a quick and efficient manner which as well requires rescue forces to be provided with reliable and stable communication facilities. One of the common problems here is providing interoperability among rescue responders originally using different communication standards [1, 2]. In terms of public communication systems, obvious problems in such scenarios are capacity overload with the resulting service denial and absence of coverage
Quantification of Scenario Distance within Generic WINNER Channel Model
Milan Narand?i?,Christian Schneider,Wim Kotterman,Reiner S. Thom
International Journal of Antennas and Propagation , 2013, DOI: 10.1155/2013/176704
Range-Based Localization for UWB Sensor Networks in Realistic Environments
Guowei Shen,Rudolf Zetik,Ole Hirsch,Reiner S. Thomä
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/476598
Abstract: The Non-Line of Sight (NLOS) problem is the major drawback for accurate localization within Ultra-Wideband (UWB) sensor networks. In this article, a comprehensive overview of the existing methods for localization in distributed UWB sensor networks under NLOS conditions is given and a new method is proposed. This method handles the NLOS problem by an NLOS node identification and mitigation approach through hypothesis test. It determines the NLOS nodes by comparing the mean square error of the range estimates with the variance of the estimated LOS ranges and handles the situation where less than three Line of Sight (LOS) nodes are available by using the statistics of an arrangement of circular traces. The performance of the proposed method has been compared with some other methods by means of computer simulation in a 2D area.
Estimation of Radio Channel Parameters in Case of an Unknown Transmitter
Stephan H?fner,Reiner Thom
Mathematics , 2015,
Abstract: This paper investigates the estimation of radio channel parameters from receiver data, whereby the transmitter is fully unknown. We use a multipath model to describe the radio channel between transmitter and receiver. According to this model, we discuss the accessibility of parameters for estimation. Based on the Maximum-Likelihood principle, we derive a cost function. A second cost function is derived from the cross relation between the receiver channels. To estimate the parameters, we seek for the minimum of these cost functions. The performance of the presented cost functions are compared in simulations.
Measurement-Based Performance Evaluation of Advanced MIMO Transceiver Designs
Uwe Trautwein,Christian Schneider,Reiner Thom
EURASIP Journal on Advances in Signal Processing , 2005, DOI: 10.1155/asp.2005.1712
Abstract: This paper describes the methodology and the results of performance investigations on a multiple-input multiple-output (MIMO) transceiver scheme for frequency-selective radio channels. The method relies on offline simulations and employs real-time MIMO channel sounder measurement data to ensure a realistic channel modeling. Thus it can be classified in between the performance evaluation using some predefined channel models and the evaluation of a prototype hardware in field experiments. New aspects for the simulation setup are discussed, which are frequently ignored when using simpler model-based evaluations. Example simulations are provided for an iterative ( ¢ € turbo ¢ € ) MIMO equalizer concept. The dependency of the achievable bit error rate performance on the propagation characteristics and on the variation in some system design parameters is shown, whereas the antenna constellation is of particular concern for MIMO systems. Although in many of the considered constellations turbo MIMO equalization appears feasible in real field scenarios, there exist cases with poor performance as well, indicating that in practical applications link adaptation of the transmitter and receiver processing to the environment is necessary.
S. Thom
Akroterion , 2012, DOI: 10.7445/51-0-64
Abstract: Can a lyric poet have anything valid to say about historic realities?2 In this paper I argue that by looking carefully at Horace’s use of myth3 as a larger frame of reference against which Odes 3.1 – 64 should be read, a case can be made for a lyric poet’s subtly critical assessment of the contemporary reality.5 In short I want to suggest that the poet uses myth as a means to comment (implicitly) on the contemporary historic reality concerned. Furthermore, if a reference to myth can operate as implied comment on the present, this reference can also include didactic purpose, or more specifically advice on how to act in the present reality.
S. Thom
Akroterion , 2012, DOI: 10.7445/49-0-88
Abstract: Quot homines tot sententiae seems a good summary of the variety of critical readings of lyric poetry in general and of Horace’s position on Augustus in particular. This raises the interesting question of the position of factual information in poetry: does lyric as genre imply a choice for fiction as opposed to fact or can some references to contemporary personalities or incidents be taken as realistic? In this case specifically: can what Horace says about Augustus be taken as a realistic assessment of the emperor? To complicate matters, Augustus was a powerful personage who wanted and often managed to put his own stamp on things1 — in himself an embodiment of the opposition between fact and fiction. Given this undoubtedly heady mix, the paper will try to make some
Classics in post-colonial worlds
S. Thom
Akroterion , 2012, DOI: 10.7445/53-0-127
Abstract: The volume grew out of a conference on Classics in Post-Colonial Worlds held at theOpen University in the West Midlands Centre in Harborne, Birmingham in May2004.
S. Thom
Akroterion , 2012, DOI: 10.7445/48-0-99
Abstract: A cluster of six poems, Odes 3. 7–12, enhanced by their position in the collection of Odes (following as they do the Roman Odes, Odes 3. 1–6) seems to stake Horace’s claim as a poet of personal relationships to the same extent that the Parade Odes (Odes 1. 1–9) staked his claim as a master craftsman.1 Nowhere else in the collection do we have such a large group of poems dedicated exclusively to expressing aspects of personal relationships.2 In addition, it is striking that the group as a whole also seems to focus on ironic points of view on the situations concerned. The most obvious explanation for this special focus could lie in the fact that the poems are meant to be read as a group, which in turn requires that the perspective reflected by the group as a whole should be taken into careful consideration.
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