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A main drawback of near-field measurement techniques is the long measurement time which is a strong limiting factor in many measurements. The reason for this is the large number of required measurement points and a reduction without loss of accuracy is hence desirable. In many spherical near-field measurements the relevant information is mostly concentrated in a few spherical wave coefficients. Methods...
Several attractive features of ultra wideband (UWB) communications make it a good candidate for physical-layer of wireless sensor networks (WSN). These features include low power consumption, low complexity and low cost of implementation. In this paper, we present an opportunistic power assignment strategy for distributed detection in parallel fusion WSNs, considering a Nakagami-m fading model for...
Many communication channels with discrete input have non-uniform capacity achieving probability mass functions (PMF). By parsing a stream of independent and equiprobable bits according to a full prefix-free code, a modulator can generate dyadic PMFs at the channel input. In this work, we show that for discrete memoryless channels and for memoryless discrete noiseless channels, searching for good dyadic...
For planning, analysis, and optimization of modern, self organizing radio networks field strength prediction plays an essential role. A huge number of predictions is needed for planning purposes while high quality and level of detail are important as well. In this paper, we present a promising ray optical approach for radio wave propagation to meet those demands. As the performance improvement of...
In this paper, we present a general analytical framework for the exact mutual information (MI) cumulants of multiple-input multiple-output (MIMO) systems with perfect receiver channel state information (CSI) and no transmitter CSI. Our derivation is based on a recent parameterization of the joint ordered eigenvalue probability density function (PDF), that encompasses both uncorrelated/semi-correlated...
This work is inspired by the general question of how to choose signaling points from a bounded set such that capacity of the corresponding channel is maximized. Since subject to peak power constraints capacity achieving distributions become discrete, this question is most relevant for practical application. However, a solution seems to be difficult in general. In this paper we confine ourselves to...
Reliable detection of primary user activity by spectrum sensing is a crucial issue of cognitive radio systems. The objective of cooperative spectrum sensing is to combine the detection results of multiple cognitive radios in order to maximize the probability of detecting unused spectrum while meeting a required reliability of detecting primary user activity. In this paper, a Kullback-Leibler distance-based...
In this paper, the rate region of the two user MIMO broadcast channel (BC) with linear filtering at high signal-to-noise ratio (SNR) is studied when time sharing is not available and the transmitter has fewer antennas than the sum of the receiving antennas. To reach the boundary of the rate region, the sum rate is maximized subject to a rate ratio constraint. Furthermore, the sum rate is approximated...
This paper presents a framework for studying amplify-and-forward Gaussian relay networks and optimizing the strategy of source/sink pairs. A typical communication scenario is that many pairs of users try to exchange information over the same network. Changing the strategy of the relays, in such a network, for each communication might be an overwhelming task. We consider the case where the behavior...
Allpass transformed filter banks provide a nonuniform frequency resolution and can be used in mobile speech processing systems, e.g., cellular phones or digital hearing aids. The nominal design of such an allpass transformed analysis-synthesis filter bank (AS FB) with near perfect reconstruction (NPR) is achieved by numerical optimization of finite-impulse response (FIR) equalizers in each subchannel...
Imposing so called peak power constraints on the input of a channel in many cases leads to a discrete capacity-achieving distribution with finite support. Given a finite number of signaling points ab initio, in this paper we determine reduced subsets in order to simplify the receiver design. The objective is to still keep the channel quality high. Two criteria are maximized, channel capacity and cutoff...
In [1], Benenson, Gedicke and Raivio propose a user authentication scheme for sensor networks. The scheme considers how to organize access control to a wireless sensor network for authorized users and rejection of unauthorized adversaries. In the first part of this paper we analyze and optimize the proposed authentication scheme. The second part deals with distribution of public keys to sensor nodes...
Generally, planning and configuring cellular radio networks lead to multi-objective optimization problems with conflicting objectives, e.g., coverage and cost. In this paper, we present an approach to combine those opponents in a closed-form objective for maximization of operator profit by means of joint base station and relay station placement in 4G multi-hop relay networks. The corresponding optimization...
Based on the factor graph, a joint channel estimation and detection method is proposed for orthogonal frequency division multiplexing (OFDM) systems employing multiple transmit and receive antennas (MIMO). Using belief propagation, statistics of the fast varying MIMO multipath channel are utilized in estimating channel coefficients. By proper message scheduling and passing, the proposed receiver is...
In wireless local area networks, spatially varying channel conditions result in a severe performance discrepancy between different nodes in the uplink, depending on their position. Both throughput and energy expense are affected. Cooperative protocols were proposed to mitigate these discrepancies. However, additional network state information (NSI) from other nodes is needed to enable cooperation...
In this paper we propose a new Direction-specific Land use based Path loss model (DiLaP) that benefits from both approaches by utilizing the particular radio wave propagation characteristics of all land use segments that lay on the direct path between receiver and transmitter. It is intended for application to suburban/rural areas.
In adaptive orthogonal frequency division multiplexing (OFDM)systems, different powers and rates can be allocated to subcarriers optimally by water-filling. This strategy has been proved to improve the system performance significantly. However, a large signalling overhead is induced by water-filling to contain the group of presently employed mapping schemes. The faster the channel varies in time,...
Optimal utilization of radio resources (bandwidth, transmit power) in multi-carrier based systems becomes very challenging due to coexistence of various wireless standards within the same frequency band. One possible solution is dynamic spectrum access (DSA) approach that allows several standards or users to opportunistically share the available spectrum resources without introducing mutual interference...
In the first chapter of Shannon's A Mathematical Theory of Communication, it is shown that the maximum entropy rate of an input process of a constrained system is limited by the combinatorial capacity of the system. Shannon considers systems where the constraints define regular languages and uses results from matrix theory in his derivations. In this work, the regularity constraint is dropped. Using...
A low-cost deployment of wireless sensor networks heavily depends on the availability of low-complexity sensor nodes. In this paper, a sensor network with simple transmit-only IR-UWB sensor nodes is analyzed, that is deployed for distributed detection of signals in a region of interest. The nodes transmit their local decisions with a fixed transmission power over non-orthogonal channels to a fusion...
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