摘要 :
Orthogonal pulse-shape modulation using Hermite pulses for ultra-wideband communications is reviewed. Closed-form expressions of cross-correlations among Hermite pulses and their corresponding transmit and receive waveforms are pr...
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Orthogonal pulse-shape modulation using Hermite pulses for ultra-wideband communications is reviewed. Closed-form expressions of cross-correlations among Hermite pulses and their corresponding transmit and receive waveforms are provided. These show that the pulses lose orthogonality at the receiver in the presence of differentiating antennas. Using these expressions, an algebraic model is established based on the projections of distorted receive waveforms onto the orthonormal basis given by the set of normalized orthogonal Hermite pulses. Using this new matrix model, a number of pulse-shape modulation schemes are analyzed and a novel orthogonal design is proposed. In the proposed orthogonal design, transmit waveforms are constructed as combinations of elementary Hermites with weighting coefficients derived by employing the Gram-Schmidt (QR) factorization of the differentiating distortion model's matrix. The design ensures orthogonality of the vectors at the output of the receiver bank of correlators, without requiring compensation for the distortion introduced by the antennas. In addition, a new set of elementary Hermite Pulses is proposed which further enhances the performance of the new design while enabling a simplified hardware implementation.
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Ultra wideband (UWB) is the most preferred candidate for body area networks (BAN). The higher data rate and lower multipath fading makes it highly suitable for the design of BAN. However, narrowband interference (NBI) may signific...
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Ultra wideband (UWB) is the most preferred candidate for body area networks (BAN). The higher data rate and lower multipath fading makes it highly suitable for the design of BAN. However, narrowband interference (NBI) may significantly degrade the performance of UWB. The paper presents an effective method of NBI mitigation for UWB BAN. The method uses modified Hermite pulse (MHP) in lieu of Gaussian and other pulse shapes. The spectral characteristics of the MHP make them immune to interference. The performance has been tested in various body postures in the CM4 channel model of the BAN, and further validated by transmitting medical signals like electrocardiography and MRI. The results show that MHP pulse is highly immune to NBI.
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Biorthogonal Pulse Shape Modulation based on Modulated Modified Hermite Pulses has been introduced to combat the Inter Symbol Interference and Inter User Interference. However, signal detection is mostly done in time domain, which...
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Biorthogonal Pulse Shape Modulation based on Modulated Modified Hermite Pulses has been introduced to combat the Inter Symbol Interference and Inter User Interference. However, signal detection is mostly done in time domain, which requires RAKE receiver to combine the energy in the multipath rich environment. Recently, frequency domain detection scheme was also introduced in the signal detection for Impulse Radio UWB. This paper investigates on the performance of the modulation scheme in Frequency Domain Detection with Channel Estimation and Equalization, which reduces the complexity of the operation while improve the BER. System simulation is carried out in this study to compare the performance to that of the Time Domain.
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In a Letter in 2003, L.E. Miller derived autocorrelation functions for ultra-wideband pulses based on Hermite polynomials. It is pointed out here that equation (1) of that Letter and hence the subsequent results are incorrect. A c...
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In a Letter in 2003, L.E. Miller derived autocorrelation functions for ultra-wideband pulses based on Hermite polynomials. It is pointed out here that equation (1) of that Letter and hence the subsequent results are incorrect. A correct and elementary expression is derived for the autocorrelation function of Hermite-Gauss pulses
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Filter bank multicarrier (FBMC) has been developed as an alternative to overcome the drawbacks of orthogonal frequency-division multiplexing (OFDM) in certain areas, especially for improved spectral efficiency and errorless commun...
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Filter bank multicarrier (FBMC) has been developed as an alternative to overcome the drawbacks of orthogonal frequency-division multiplexing (OFDM) in certain areas, especially for improved spectral efficiency and errorless communication under doubly dispersive channel conditions. The prototype filters in FBMC systems must satisfy dual orthogonality conditions and be well localized in both time and frequency domains; hence have to be analysed in both dimensions. Ambiguity function is a two-dimensional function of time and frequency, which is the correlation between the filter coefficients and its frequency-modulated versions. In the present study, a matrix formulation of discrete ambiguity function generation is derived based on which the prototype filters for FBMC and OFDM are analysed and compared in terms of time frequency localization, dual orthogonality criterion, side-lobe levels in time and frequency, signal-to-interference ratio, constellation diagram concentration, and bit error rate plots. FBMC systems prove to be better than OFDM in all these criteria.
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In short-range networks such as wireless personal area networks (WPAN), multiple user wireless connectivity for surveillance would require a wireless technology that supports multiple streams of high-speed data and consumes very l...
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In short-range networks such as wireless personal area networks (WPAN), multiple user wireless connectivity for surveillance would require a wireless technology that supports multiple streams of high-speed data and consumes very little power. Ultra wideband (UWB) technology enables wireless connectivity across multiple devices (users) addressing the need for high-speed WPAN. Apart from having a distinct advantage of higher data rate over Bluetooth v4.0 (24 Mbps), the UWB technology is also found to be tolerant to frequency-selective multipath fading. In this paper authors discuss a time-hopping pulse shape modulation UWB signalling scheme for ad-hoc high bit rate wireless connectivity for defence applications. Authors analyse multiple access interference for both Gaussian channel and frequency selective multipath fading channel to compare the effects of timing jitter on two types of pulse shapes, namely modified Hermite pulse (MHP) and prolate spheroidal wave functions (PSWF). Authors make a comparative analysis of the system performance with respect to PSWF and MHP to ascertain robustness to timing jitter. In the process, authors introduced a new metric of decision factor in timing jitter analysis.
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In this paper we present a novel method for improving RAKE receiver reception in UWB systems. Due to the fact that practical pulses that can he produced for UWB-IR (Ultra Wideband-Impulse Radio) may occupy a longer time than the t...
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In this paper we present a novel method for improving RAKE receiver reception in UWB systems. Due to the fact that practical pulses that can he produced for UWB-IR (Ultra Wideband-Impulse Radio) may occupy a longer time than the typical multipath resolution of the actual UWB channel, multiple channel components may arrive within this typical pulse width. Performance degradation may occur due to the resulting intrapulse (overlapping received pulses) interference. We here propose an adaptive, pilot aided RAKE receiver for UWB communications in the multipath environment. The proposed system estimates the actual received signal with intrapulse interference in each RAKE finger using projections onto a Hadamard-Hermite subspace. By exploiting the orthogonality of this subspace it is possible to decompose the received signal so as to better match the template waveform and reduce the effects of intrapulse interference. By using the projections onto this subspace, the dimension of the received signal is effectively increased allowing for adaptive correlator template outputs. RAKE receivers based on this proposal are designed which show significant performance improvement and require less fingers to achieve required performance than their conventional counterparts.
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An analytical expression of the carrier-envelope (CE) phase of ultrashort pulsed Hermite-Gaussian beams on propagation has been deduced in detail. Numerical calculations have been carried out to illustrate the evolution of the CE ...
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An analytical expression of the carrier-envelope (CE) phase of ultrashort pulsed Hermite-Gaussian beams on propagation has been deduced in detail. Numerical calculations have been carried out to illustrate the evolution of the CE phase of ultrashort pulsed Hermite-Gaussian beams on propagation with different parameters. The results show that the order of the Hermite function greatly affects the evolution of the CE phase. The higher the order of the Hermite function, the larger the CE phase is. The beam waist affects the CE phase in the near field, especially in a few Rayleigh distances. In addition, the variation in the CE phase on the axis is larger than that on the beam periphery on propagation.
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In this paper, we propose a method for designing a set of pulses whose spectrum is efficiently contained in amplitude and bandwidth. Because these pulses are derived from and have shapes that are either equal or similar to the Her...
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In this paper, we propose a method for designing a set of pulses whose spectrum is efficiently contained in amplitude and bandwidth. Because these pulses are derived from and have shapes that are either equal or similar to the Hermite pulses, we name our proposed transmit pulses as spectrally efficient Hermite pulses. Given that the proposed set of pulses does not constitute an orthonormal one, we also propose a set of receive templates which permit orthonormal detection of the incoming signals at the receiver. The importance of our proposal is in the potential implementation of M-ary pulse shape modulation systems, for ultra wideband communications, with sets of pulses that are efficiently contained within a specific bandwidth and limited to a certain amplitude.
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This paper presents the design of a class of pulses that are based on Hermite functions for ultra-wideband communication systems. The presented class of pulses can not only meet the power spectral emission constraints of federal c...
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This paper presents the design of a class of pulses that are based on Hermite functions for ultra-wideband communication systems. The presented class of pulses can not only meet the power spectral emission constraints of federal communications commission, but also have a short duration for multiple accesses. This paper gives closed form expressions of auto-and cross-correlation functions of the proposed pulses, which can be used to evaluate the performance of the correlator receiver. Furthermore, the paper investigates, under various channel conditions, the spectrum characteristic and the bit error rate of the pulses' waveforms. The investigation conditions include additive white Gaussian noise channels, multiple-access interference channels, and fading multipath channels. Our results indicate that our systematic algorithm is flexible for designing ultra-wideband pulses that conform to spectral emission constraints and offer good bit error rate performance.
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