HN
Homayoun Nikookar
139 records found
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Authored
Cooperative diversity networks have been receiving a lot of attention recently as an attractive way to combat frequency-selectivity of wireless channel, as it consumes neither time nor frequency resources. In the conventional cooperative strategies, relays employ either a decode-
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Wireless personal area networks applications may benefit from the use of ultra-wideband (UWB) technology. In these applications transmit and receive antennas are very close to each other and the far-field condition assumed in most of the link budget models may not be satisfied. U
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This paper presents the performance comparison of cognitive radio TDCS and OFDM based for MIMO system using VBLAST receiver architecture to reconstruct the transmitted data. The interference avoidance performance in terms of BER and bitrate are improved by adding multiple antenna
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In this paper, ranging based on UWB signals is investigated for indoor dense multipath environments. To this end, a large set of time domain measurements covering the 3.1-10.6 GHz frequency band is carried out. Different approaches to detect the time of arrival of the first path
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This paper presents the results of Ultra Wide Band (UWB) channel measurements carried out at the campus of Delft University of Technology. The measurements were conducted in an indoor office and industrial environment using a time domain setup which allows measurements from 3.1 t
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This paper presents the combination of adaptive bit loading and spectrum pooling to be applied in a Cognitive Radio system. Adaptive bit loading is a method to adapt the constellation size of the transmitted signal according to the channel variations by exclusion of heavily faded
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Technology of wireless communication has advanced rapidly over the last few years. Much technology developed for this domain of application can be applied to data throughput if the radar signal is coded like a telecommunication message. The message content can for instance consis
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Ultra Wide Band (UWB) technnology is prome to be used in wireless personal area networks (WPAN) applications. In these applications transmit and receive antennas are very close to each other and the far field condition assumed in most of the link budget modesl may not be satisfie
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This paper proposes a new concept of Radar coding using OFDM signals. The Doppler tolerance of such a Radar is expressed as a function of Doppler frequency and time delay. In order to set a limit to the compression loss due to Doppler, it is shown that the target speed that can b
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Performance degradation of the UWB communication system due to interference form other services is a major issue. To reduce the effect of interference, the usage of modified template in UWB transceiver and its multi-carrier representation has recently been reported [1]-[2]. In th
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In this paper, the results of Ultra Wide Band (UWB) measurements carried out in indoor environments are presented and a statistical propagation model for the UWB channel covering the frequency band from 3.1. to 10.6 GHz is proposed. The measurements have been performed in the tim
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Wavelets have been favorably applied in almost all aspects of digital wireless communications systems including data compression, source and channel coding, signal denoising, channel modeling and design of tranceivers. The main property of wavelets in these applications is in the
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This paper presents the results of Ultra Wide Band (UWB) channel measurements for Wireless Personal Area Networks (WPAN). A time domain measurement setup has been developed covering the frequency band from 2.1 GHz. Relevant scenarios for WPAN applications have been proposed and m
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Using the impulse response method, the statistical modeling of wideband multi-input-multi-output (mimo) wireless channels is adressed. Rayleigh and Ricean distributions are used to model the mimo channel amplitude fading. Both poisson and modified poisson processes are employed t
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In this paper, the impact of the noise due to undersampling of noncoherent narrowband interference in time domain UWB channel measurements is investigated. Different measurements were carried out within the building for LOS and NLOS situations. The obtained results show that ener
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In this paper, a new method for UWB channel characterization is introduced. This method is based on the knowledge of the frequency response of several (but not all) randomly selected portions (chunks) of the UWB band. Employing this method, estimation of the root mean square (rms
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In this paper a newly applied approach to model the effects high-rise blocking buildings near a base station (BS) in cellular communications networks is presented. Although recently accurate determenistic propagation prediction methods jave become popular to account for these pro
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In Dynamic Spectrum Access Networks, detection of spectral opportunity can be viewed as a frequency scanning process leading to detection of legitimate users of radio channel. Continuous scanning results in complete detection but it becomes inefficient in terms of power consumpti
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Cognitieve Radio is a revolutionaary tehcnolgoy which provides efficient use of spectrum. OFDM is a proper technique for the cognitieve radio. In this paper, we present an overview of adaptive OFDM techniques in the context of cognitive radio. Major adaptive OFDM schemes for cogn
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Spatial diversity techniques are advantageous if the received signals of the diversity branches are sufficiently uncorrelated. Theoretical study using the power unbalance between the two branches employing Laplacian direction of arrival (DOA) distribution is carried out. It is sh
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