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Tuning In to Sound: Frequency-Selective Attentional Filter in Human Primary Auditory Cortex

Da Costa, Sandra; van der Zwaag, Wietske; Miller, Lee M.; Clarke, Stephanie; Saenz, Melissa
Fonte: Society for Neuroscience Publicador: Society for Neuroscience
Tipo: Artigo de Revista Científica
Publicado em 30/01/2013 Português
Relevância na Pesquisa
15.91%
Cocktail parties, busy streets, and other noisy environments pose a difficult challenge to the auditory system: how to focus attention on selected sounds while ignoring others? Neurons of primary auditory cortex, many of which are sharply tuned to sound frequency, could help solve this problem by filtering selected sound information based on frequency-content. To investigate whether this occurs, we used high-resolution fMRI at 7 tesla to map the fine-scale frequency-tuning (1.5 mm isotropic resolution) of primary auditory areas A1 and R in six human participants. Then, in a selective attention experiment, participants heard low (250 Hz)- and high (4000 Hz)-frequency streams of tones presented at the same time (dual-stream) and were instructed to focus attention onto one stream versus the other, switching back and forth every 30 s. Attention to low-frequency tones enhanced neural responses within low-frequency-tuned voxels relative to high, and when attention switched the pattern quickly reversed. Thus, like a radio, human primary auditory cortex is able to tune into attended frequency channels and can switch channels on demand.

A non-coherent ultra-wideband receiver : algorithms and digital implementation; Non-coherent UWB receiver : algorithms and digital implementation

Vitavasiri, Sinit
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 121 leaves
Português
Relevância na Pesquisa
15.91%
Ultra-wideband (UWB) communication is an emerging technique for wireless transmission in the 3.1-10.6 GHz unlicensed band with signal bandwidths of 500 MHz or greater. A non-coherent receiver based on energy collection reduces complexity, cost, and power consumption at the cost of channel spectral efficiency. The receiver collects the signal energy in two time windows and determines the transmitted bits based on which window has greater energy. This thesis explains the implementation of low-complexity detection, synchronization, and decoding algorithms for a non-coherent ultra-wideband receiver. The receiver is modeled in MATLAB to measure performance. The UWB receiver performs effectively in noisy channels. At the signal-to-noise ratio (SNR) of 0 dB, the receiver achieves a detection miss rate of 2.1% and a false alarm rate of 1.2%. The synchronization error (within ±2 chip periods) rate is 0.5%. The bit error rate is 8.6%, but it drops sharply to 0.1% at an SNR of 5 dB. Moreover, the detection and the synchronization processes take 19.72 p.s and 22.53 pts, respectively. The digital system is implemented in Verilog, which is mapped to hardware (FPGA). In the final system, a radio frequency and an analog front-end interface with the FPGA...

A double-sideband radio-frequency speech processor for increasing the intelligibility of speech signals over noisy single-sideband channels.

Belanger, Raymond Louis.
Fonte: Monterey, California ; Naval Postgraduate School Publicador: Monterey, California ; Naval Postgraduate School
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
15.82%

Increasing uplink capacity via user cooperation diversity

Sendonaris, Andrew; Erkip, Elza; Aazhang, Behnaam; Sendonaris, Andrew; Erkip, Elza; Aazhang, Behnaam
Fonte: IEEE Publicador: IEEE
Tipo: Conference paper; Text; Text
Português
Relevância na Pesquisa
26.08%
Conference Paper; Mobile users' capacity is limited by the fact that within the duration of any given call, they experience severe variations in signal attenuation, thereby necessitating the use of some type of diversity. We are proposing a new form of diversity, whereby diversity gains are achieved via the cooperation of in-cell users. Results show that, even though the inter-user channel is noisy, cooperation leads not only to an increase in capacity but also to a more robust system, where users' achievable rates are less susceptible to channel variations.; Nokia

Source-Channel Coding Techniques in the Presence of Interference and Noise

ABOU SALEH, AHMAD
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
25.82%
As wireless systems proliferate worldwide, interference is becoming one of the main problems for system designers. Interference, which occurs when multiple transmissions take place over a common communication medium, limits system performance. Wireless devices can coordinate the use of scarce radio resources in order to manage the interference and establish successful communication. To effectively deal with the interference problem, some wireless devices must have a certain level of knowledge about the interference. In practice, this knowledge comes at the expense of using more resources (such as employing a proper channel training mechanism). With the remaining available resources, the question is how to achieve reliable communication? This thesis investigates an information theoretic approach and employs several coding techniques to improve system performance by either cancelling the interference or extracting knowledge from it about the information signal. The first part of this thesis considers the transmission of information signals over a fading channel that is disturbed with additional interference. The system's information theoretic limit in terms of mean square error distortion is assessed. Moreover, hybrid coding schemes are proposed and analyzed to obtain an achievable performance. As an extension to this problem...

Characterisation of noisy speech channels in 2G and 3G mobile networks

Leite, Bruno Daniel Moreira
Fonte: Instituto Politécnico do Porto Publicador: Instituto Politécnico do Porto
Tipo: Dissertação de Mestrado
Publicado em //2013 Português
Relevância na Pesquisa
56.13%
As the wireless cellular market reaches competitive levels never seen before, network operators need to focus on maintaining Quality of Service (QoS) a main priority if they wish to attract new subscribers while keeping existing customers satisfied. Speech Quality as perceived by the end user is one major example of a characteristic in constant need of maintenance and improvement. It is in this topic that this Master Thesis project fits in. Making use of an intrusive method of speech quality evaluation, as a means to further study and characterize the performance of speech codecs in second-generation (2G) and third-generation (3G) technologies. Trying to find further correlation between codecs with similar bit rates, along with the exploration of certain transmission parameters which may aid in the assessment of speech quality. Due to some limitations concerning the audio analyzer equipment that was to be employed, a different system for recording the test samples was sought out. Although the new designed system is not standard, after extensive testing and optimization of the system's parameters, final results were found reliable and satisfactory. Tests include a set of high and low bit rate codecs for both 2G and 3G, where values were compared and analysed...

Spectrum Sharing in Cognitive Radio with Quantized Channel Information

He, Yuan Yuan; Dey, Subhrakanti
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/06/2010 Português
Relevância na Pesquisa
26%
We consider a wideband spectrum sharing system where a secondary user can share a number of orthogonal frequency bands where each band is licensed to an individual primary user. We address the problem of optimum secondary transmit power allocation for its ergodic capacity maximization subject to an average sum (across the bands) transmit power constraint and individual average interference constraints on the primary users. The major contribution of our work lies in considering quantized channel state information (CSI)(for the vector channel space consisting of all secondary-to-secondary and secondary-to-primary channels) at the secondary transmitter. It is assumed that a band manager or a cognitive radio service provider has access to the full CSI information from the secondary and primary receivers and designs (offline) an optimal power codebook based on the statistical information (channel distributions) of the channels and feeds back the index of the codebook to the secondary transmitter for every channel realization in real-time, via a delay-free noiseless limited feedback channel. A modified Generalized Lloyds-type algorithm (GLA) is designed for deriving the optimal power codebook. An approximate quantized power allocation (AQPA) algorithm is also presented...

A Wideband Spectrum Sensing Method for Cognitive Radio using Sub-Nyquist Sampling

Rashidi, Moslem; Haghighi, Kasra; Owrang, Arash; Viberg, Mats
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/10/2010 Português
Relevância na Pesquisa
25.91%
Spectrum sensing is a fundamental component in cognitive radio. A major challenge in this area is the requirement of a high sampling rate in the sensing of a wideband signal. In this paper a wideband spectrum sensing model is presented that utilizes a sub-Nyquist sampling scheme to bring substantial savings in terms of the sampling rate. The correlation matrix of a finite number of noisy samples is computed and used by a subspace estimator to detect the occupied and vacant channels of the spectrum. In contrast with common methods, the proposedmethod does not need the knowledge of signal properties that mitigates the uncertainty problem. We evaluate the performance of this method by computing the probability of detecting signal occupancy in terms of the number of samples and the SNR of randomly generated signals. The results show a reliable detection even in low SNR and small number of samples.

Vectorial Radio Interferometry with LOPES 3D

Huber, D.; Apel, W. D.; Arteaga, J. C.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Chiavassa, A.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Fuchs, B.; Fuhrmann, D.; Gem
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/08/2013 Português
Relevância na Pesquisa
25.96%
One successful detection technique for high-energy cosmic rays is based on the radio signal emitted by the charged particles in an air shower. The LOPES experiment at Karlsruhe Institute of Technology, Germany, has made major contributions to the evolution of this technique. LOPES was reconfigured several times to improve and further develop the radio detection technique. In the latest setup LOPES consisted of 10 tripole antennas. With this, LOPES 3D was the first cosmic ray experiment measuring all three vectorial field components at once and thereby gaining the full information about the electric field vector. We present an analysis based on the data taken with special focus on the benefits of a direct measurement of the vertical polarization component. We demonstrate that by measuring all polarization components the detection and reconstruction efficiency is increased and noisy single channel data can be reconstructed by utilising the information from the other two channels of one antenna station.; Comment: Proceedings of 33rd International Cosmic Ray Conference, RIO 2013

Analyzing the performance of probabilistic algorithm in noisy manets

Al-Bahadili, Hussein; Kaabneh, Khalid
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/09/2010 Português
Relevância na Pesquisa
26.05%
Probabilistic broadcast has been widely used as a flooding optimization mechanism to alleviate the effect of broadcast storm problem (BSP) in mobile ad hoc networks (MANETs). Many research studies have been carried-out to develop and evaluate the performance of this mechanism in an error-free (noiseless) environment. In reality, wireless communication channels in MANETs are an error-prone and suffer from high packet-loss due to presence of noise, i.e., noisy environment. In this paper, we propose a simulation model that can be used to evaluate the performance of probabilistic broadcast for flooding in noisy environment. In the proposed model, the noise-level is represented by a generic name, probability of reception (pc) (0<=pc<=1), where pc=1 for noiseless and <1 for noisy environment. The effect of noise is determined randomly by generating a random number \zeta (0<=\zeta<1); if \zeta<=pc means the packet is successfully delivered to the receiving node, otherwise, unsuccessful delivery occurs. The proposed model is implemented on a MANET simulator, namely, MANSim. The effect of noise on the performance of probabilistic algorithm was investigated in four scenarios. The main conclusions of these scenarios are: the performance of probabilistic algorithm suffers in presence of noise. However...

A NLLS Based Sub-Nyquist Rate Spectrum Sensing for Wideband Cognitive Radio

Avendi, M. R.; Haghighi, K.; Panahi, A.; Viberg, M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/08/2014 Português
Relevância na Pesquisa
26%
For systems and devices, such as cognitive radio and networks, that need to be aware of available frequency bands, spectrum sensing has an important role. A major challenge in this area is the requirement of a high sampling rate in the sensing of a wideband signal. In this paper a wideband spectrum sensing method is presented that utilizes a sub-Nyquist sampling scheme to bring substantial savings in terms of the sampling rate. The correlation matrix of a finite number of noisy samples is computed and used by a non-linear least square (NLLS) estimator to detect the occupied and vacant channels of the spectrum. We provide an expression for the detection threshold as a function of sampling parameters and noise power. Also, a sequential forward selection algorithm is presented to find the occupied channels with low complexity. The method can be applied to both correlated and uncorrelated wideband multichannel signals. A comparison with conventional energy detection using Nyquist-rate sampling shows that the proposed scheme can yield similar performance for SNR above 4 dB with a factor of 3 smaller sampling rate.; Comment: IEEE Dyspan 2011. arXiv admin note: substantial text overlap with arXiv:1010.2157

A Unified Framework for the Ergodic Capacity of Spectrum Sharing Cognitive Radio Systems

Sboui, Lokman; Rezki, Zouheir; Alouini, Mohamed-Slim
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 28/11/2012 Português
Relevância na Pesquisa
25.91%
We consider a spectrum sharing communication scenario in which a primary and a secondary users are communicating, simultaneously, with their respective destinations using the same frequency carrier. Both optimal power profile and ergodic capacity are derived for fading channels, under an average transmit power and an instantaneous interference outage constraints. Unlike previous studies, we assume that the secondary user has a noisy version of the cross link and the secondary link Channel State Information (CSI). After deriving the capacity in this case, we provide an ergodic capacity generalization, through a unified expression, that encompasses several previously studied spectrum sharing settings. In addition, we provide an asymptotic capacity analysis at high and low signal-to-noise ratio (SNR). Numerical results, applied for independent Rayleigh fading channels, show that at low SNR regime, only the secondary channel estimation matters with no effect of the cross link on the capacity; whereas at high SNR regime, the capacity is rather driven by the cross link CSI. Furthermore, a practical on-off power allocation scheme is proposed and is shown, through numerical results, to achieve the full capacity at high and low SNR; Comment: 12 pages...

Hybrid Centralized-Distributed Resource Allocation for Device-to-Device Communication Underlaying Cellular Networks

Maghsudi, Setareh; Stanczak, Slawomir
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 16/02/2015 Português
Relevância na Pesquisa
15.91%
The basic idea of device-to-device (D2D) communication is that pairs of suitably selected wireless devices reuse the cellular spectrum to establish direct communication links, provided that the adverse effects of D2D communication on cellular users is minimized and cellular users are given a higher priority in using limited wireless resources. Despite its great potential in terms of coverage and capacity performance, implementing this new concept poses some challenges, in particular with respect to radio resource management. The main challenges arise from a strong need for distributed D2D solutions that operate in the absence of precise channel and network knowledge. In order to address this challenge, this paper studies a resource allocation problem in a single-cell wireless network with multiple D2D users sharing the available radio frequency channels with cellular users. We consider a realistic scenario where the base station (BS) is provided with strictly limited channel knowledge while D2D and cellular users have no information. We prove a lower-bound for the cellular aggregate utility in the downlink with fixed BS power, which allows for decoupling the channel allocation and D2D power control problems. An efficient graph-theoretical approach is proposed to perform the channel allocation...

Fundamental Limits of Communications in Interference Networks-Part I: Basic Structures

Farsani, Reza K.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
15.91%
In these series of multi-part papers, a systematic study of fundamental limits of communications in interference networks is established. Here, interference network is referred to as a general single-hop communication scenario with arbitrary number of transmitters and receivers, and also arbitrary distribution of messages among transmitters and receivers. It is shown that the information flow in such networks follows similar derivations from many aspects. This systematic study is launched by considering the basic building blocks in Part I. The Multiple Access Channel (MAC), the Broadcast Channel (BC), the Classical Interference Channel (CIC) and the Cognitive Radio Channel (CRC) are proposed as the main building blocks for all interference networks. First, a brief review of existing results regarding these basic structures is presented. New observations are also presented in this regard. Specifically, it is shown that the well-known strong interference conditions for the two-user CIC do not change if the inputs are dependent. Next, new capacity outer bounds are established for the basic structures with two receivers. These outer bounds are all derived based on a unified framework. By using the derived outer bounds, some new capacity results are proved for the CIC and the CRC; a mixed interference regime is identified for the two-user discrete CIC where the sum-rate capacity is established. Also...