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ABSTRACT: This paper proposes and studies a combined modulation scheme for time hopping ultra wideband (TH-UWB) radio system based on
orthogonal pulse position modulation (OPPM) and biorthogonal pulse shape modulation (BPSM). The proposed scheme offers a high
data rate with satisfactory system performance by using high-level multi-dimensional modulation schemes. It allows one to
increase the number of orthogonal pulses in each pulse position and, consequently, be able to adopt shorter pulse repetition
intervals than those used in conventional M-ary OPPM or M-ary biorthogonal PPM (BPPM) modulation schemes. The performance is analyzed by using characteristic function and Gaussian
approximation in additive white Gaussian and multipath scenarios, respectively. The proposed scheme reduces multiple access
interference considerably in multi-user environments. Finally, simulation results are provided to validate the theoretical
results.
Keywords
M-ary modulation schemes–Multiple access interference (MAI)–Inter symbol interference (ISI)–Performance of OPPM-BPSM Scheme
Wireless Personal Communications 04/2012; 56(3):583-597. · 0.46 Impact Factor
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ABSTRACT: A new narrowband signal detection method called subspace detection (SD) was proposed recently for achieving improved detection performance in shallow ocean. The SD method requires the knowledge of mode functions and modal wavenumbers of the ocean channel. In this paper we present three new methods of narrowband signal detection in a partially known ocean using an array of acoustic vector sensors (AVS). These methods require less prior information about the ocean channel; and yet they provide a better performance than SD especially at higher signal frequencies or shorter array lengths. Two of the new methods require only knowledge of sound speed at the sensor locations. The performance of the proposed methods is frequency-independent. These methods can be used with arrays in either horizontal or vertical configurations, and with either linear or circular geometries.
OCEANS, 2011 IEEE - Spain; 07/2011
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ABSTRACT: Estimating DOA of an underwater acoustic source is a challenging problem due to low signal-to-noise ratio (SNR) in an ocean environment. This problem is even more challenging when the source is dynamic since the received signal can only be assumed to be stationary for a small number of snapshots. In this paper, a Bayesian framework and its particle filtering (PF) implementation are introduced to cope with this problem. At each time step, the particles are sampled according to a constant velocity model, and then corrected with the corresponding likelihood. Since the likelihood function is usually spread and distorted in the heavy noisy environment, it is exponentially weighted to enhance the weight of particles in high likelihood area. The particles can then be weighted more appropriately and resampled efficiently. Experiments show that the proposed PF tracking algorithm significantly outperforms the traditional localization approaches as well as the existing PF algorithm in challenging environments.
OCEANS, 2011 IEEE - Spain; 07/2011
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ABSTRACT: A novel number theoretic transform called Inverse Gray Robust Symmetrical Number System (IGRSNS) is proposed for error control coding in this paper. IGRSNS is obtained by modifying Robust Symmetrical Number System (RSNS) that was proposed earlier, using Inverse Gray code property. Due to ambiguities present in each residue, RSNS has a short dynamic range (DR) compared to that in other number systems. The short DR of RSNS enables it to be effectively used for error detection without the addition of any redundant modulus as in Redundant Residue Number System. Although RSNS has a large redundant range, its detection ability is not optimal due to the Gray code property associated with it. In an attempt to overcome this limitation, we have proposed Inverse Gray coding to be combined with RSNS in increasing its effectiveness in error detection. The resulting IGRSNS thus inherits properties of both RSNS and Gray code. Analysis and simulations show that IGRSNS has a near-optimal error detection ability. The potential of IGRSNS for error correction is also investigated. Further, a novel error correction algorithm using one redundant modulus is proposed. Simulations show that the proposed algorithm performs well under all cases of single bit errors.
IEEE Transactions on Communications 05/2011; · 1.68 Impact Factor
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ABSTRACT: Mitigating inter-symbol interference (ISI) in impulse radio is one of the challenges in achieving the high data rate potential of Ultra Wideband (UWB). Available techniques such as the use of Multiband OFDM and equalizer provide a good solution but they require complex implementation. This letter investigates and expands a newly proposed ISI reduction technique proposed in named "shift window" approach. The shift window approach was not designed to combat ISI under a severe indoor wireless channel. An enhancement based on the generalization of the shift window approach is introduced for ISI reduction for wireless personal area network (WPAN). The newly proposed approach is shown to perform better under severe ISI.
IEEE Communications Letters 08/2010; · 0.98 Impact Factor
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ABSTRACT: The main application of Cognitive Radio (CR) is for the broadband wireless access in the rural areas which demand adequate data rate and multi user support. IEEE 802.22, the first standard evolved for CR suggests Orthogonal Frequency Division Multiple Access (OFDMA) as the physical layer technique. In this paper wavelet packet based multi carrier multiple access scheme is proposed which can be an equally promising candidate for high data rate multi user CR applications. The performance of the proposed system is evaluated using standard wavelet bases and is compared with OFDMA.
Vehicular Technology Conference (VTC 2010-Spring), 2010 IEEE 71st; 06/2010
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ABSTRACT: In this paper, a preprocessing architecture for folding Analog-to-Digital converter (ADC) based on a new number system called Robust Folding Number System (RFNS) is presented. The RFNS is developed from robust symmetrical number system (RSNS) that was proposed by Pace et al. The enhanced Dynamic Range (DR) of RFNS due to the introduction of the folding bit results in higher ADC resolution. The Symmetrical Residues (SRs) that are obtained in the intermediate step during processing of analog signals are converted to equivalent residues by simple mapping. This results in a conversion architecture that is less complex compared to that proposed in.
Acoustics Speech and Signal Processing (ICASSP), 2010 IEEE International Conference on; 04/2010 · 4.63 Impact Factor
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ABSTRACT: Layered space-time block spread CDMA (LST BSCDMA) has been previously proposed as an alternative to conventional CDMA systems for high-rate mobile communications. This paper proposes two approaches to obtain channel state information (CSI) for LST BS-CDMA system. The basic approach suffers from high computational complexity and poor performance in systems with high order of transmitter diversity due to inter-layer interference (ILI). The second approach reduces computation complexity and eliminates ILI, making it suitable for systems with higher order of transmitter diversity. The detailed simulation studies show that the highly accurate CSI obtained using the improved technique leads to considerable superior performance.
IEEE Transactions on Wireless Communications 04/2010; · 2.59 Impact Factor
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ABSTRACT: Digital signal processing (DSP) algorithms are computationally intensive and require recursive multiplication and addition. Residue number systems (RNS) offer significant advantages over conventional number systems when used in the design of special purpose DSP architectures. However, conversion of analogue signals into their residue equivalents requires first converting the signal to binary equivalents and subsequently using modular circuits to convert the resultant binary to residues. A new number system called the folding number system (FNS) is proposed and used as the basis for residue conversion. Since FNS has one-to-one correspondence with RNS, the proposed method converts the analogue signal to its RNS equivalents using concealed symmetrical residues in FNS domain. The conversion is simple and uses analogue folding circuits, comparators and combinatorial logic circuits. High-frequency analogue signals can be efficiently converted thus enabling RNS to be implemented in high-speed signal processing architectures.
IET Circuits Devices & Systems 02/2010; · 0.55 Impact Factor
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ABSTRACT: In this paper, a new architecture to compute 1-D Discrete Wavelet Transform (DWT) based on Folding Number System (FNS) is introduced. Numbers for FNS are extracted directly from analog input without any forward converter like in the Residue Number System (RNS) based DWT. The large Dynamic Range makes the FNS DWT more efficient than those implemented using RNS systems. The proposed 1D DWT architecture makes use of the relation between the coefficients of the low-pass and high-pass decomposition filters for orthogonal wavelets families to compute the transform with minimum numbers of modular multipliers. These multipliers are based on pipelined Look-Up Tables (LUT). A 6-tap Daubechies analysis filter bank is synthesized at a structural level using VHDL. FLEX10K devices of Altera are used in the simulation of DWT using binary arithmetic, RNS and FNS to evaluate its performance. Simulations show a significant throughput improvement is achieved in the proposed FNS DWT architecture when {2<sup>k</sup> - 1.2<sup>k</sup>,2<sup>k</sup> + 1} moduli set is used.
Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010
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ABSTRACT: Localization of acoustic sources in the ocean is a problem of tremendous interest in underwater acoustics. One of the many factors that limit the performance of processors used for underwater acoustic source localization is the low signal - to -noise ratio (SNR) in the ocean. Preprocessors based on wavelet denoising and suprathreshold stochastic resonance (SSR) have been proposed in the literature for enhancing SNR and thereby improving the performance of processors used for bearing estimation. Denoising techniques based on SSR exploit the fact that the environmental noise in shallow ocean has a heavy -tailed non- Gaussian distribution. In this paper, a method for designing an SSR based preprocessor is presented. It is shown that the use of this preprocessor leads to a significant improvement in the bearing - estimation performance of Bartlett, Multiple Signal Classification (MUSIC) and Subspace Intersection Method (SIM) processors at low SNR. The improved performance appears in the form of a sharper peak in the ambiguity function, lower bias and lower RMS error in bearing estimation, and better resolution of closely spaced sources.
OCEANS 2009, MTS/IEEE Biloxi - Marine Technology for Our Future: Global and Local Challenges; 11/2009
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ABSTRACT: In an ideal Software Radio, digitization of the received signal occurs immediately after receive antenna to enable channelization to be performed in the discrete time domain. However, this vision is still far from reality due to limitations of current analog to digital converter performance. In this paper, a novel number system called the Folding Number System (FNS) is proposed for use in Software Radio. We implement sample rate conversion immediately after the receive antenna using this number system thus providing an efficient solution to the above problem. By decomposing the input analog signal into separate channels in parallel, symmetrical residues are obtained with reduced number of comparators. These residues together with the folding information are processed in parallel in the FNS domain. The FNS has the same computational complexity as that in Residue Number System but the need for the intermediate steps such conversion of the analog data into binary and subsequently into residues is absent.
Communications, 2009. ICC '09. IEEE International Conference on; 07/2009
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ABSTRACT: This paper presents a novel robust number theoretic transform called inverse gray robust symmetrical number system (IGRSNS) and proposes its application for CDMA systems. The transceiver structure for three moduli IGRSNS-CDMA with one redundant modulus is proposed. The proposed system is simulated for different values of moduli sets under various channel conditions. Simulation results show that the BER performance of IGRSNS-CDMA outperforms that of RNS-CDMA under all circumstances.
IEEE Transactions on Wireless Communications 07/2009; · 2.59 Impact Factor
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ABSTRACT: The paper describes information theoretic capacity of orthogonal pulse based modulation schemes for time hopping ultra wideband (TH-UWB) systems over a multiple access and multipath fading channel. Orthogonal pulse based modulation schemes such as pulse shape modulation (PSM), biorthogonal PSM (BPSM) and a combination of orthogonal pulse position modulation (OPPM) and BPSM have been proposed for reducing inter symbol interference (ISI) and multiple access interference (MAI) as well as for improving system performance. System capacity of TH-UWB systems can be increased by employing these modulations for higher level modulation schemes. The capacity of OPPM-BPSM outperforms PSM and BPSM schemes over a multipath fading channel. The complete mathematical analysis and theoretical simulation results are provided in detail.
Vehicular Technology Conference, 2008. VTC 2008-Fall. IEEE 68th; 10/2008
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ABSTRACT: This paper studies two MIMO architectures for single-carrier CDMA system employing block spreading, namely Layered Space-Time Block Spread CDMA (LST BS-CDMA) and Space-Time Coded Block Spread CDMA (STC BS-CDMA). It is shown that under low mobility conditions, the proposed systems are virtually free from Multiple User Interference (MUI) and the block processing technique used leads to considerable reduction in the overall processing complexity. Extensive simulation was performed to study the impact of the spreading factor and Doppler frequency on the proposed systems. A new parameter called channel coherence ratio (CCR) is introduced as a key parameter in determining the performance of MIMO BS-CDMA.
IEEE Transactions on Wireless Communications 07/2008; · 2.59 Impact Factor
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ABSTRACT: A radio that is capable of adapting to its environment by continuous learning and observation is called cognitive radio (CR). The developments in DSP and IC technologies catalyze the evolution of this 4G wireless system which makes reliable communication and efficient usage of radio spectrum. To make cognitive radio a reality changes in physical, MAC and network layers of the conventional system is essentially required. The major physical layer issues include wideband front end, intelligent spectrum sensing and adaptive transmission scheme. In our work, we address the adaptive transmission issue and propose a new method. The method is for generating a time domain pulse in radio frequency (RF) range with the required frequency response. The proposed method is compared with existing potential candidates for cognitive radio transmission.
Cognitive Radio Oriented Wireless Networks and Communications, 2008. CrownCom 2008. 3rd International Conference on; 06/2008
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ABSTRACT: One of the major issues in cognitive radio is obtaining an adaptive transmitting waveform based on environmental measurements. An efficient Radio frequency (RF) carrier waveform generation based on approximate prolate spheroidal wave function and bandpass filters is proposed in this paper. Bandpass filters are designed using interpolation and masking technique which gives a sharp cut off at lower order. The bit error performance of the waveform is evaluated. The proposed system will be useful in accessing TV spectrum and has good spectral utilization efficiency.
Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE; 06/2008
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ABSTRACT: The transmitted reference (TR) receiver provides a good alternative to the good-yet-expensive RAKE receiver for ultra wideband impulse radio (UWB-IR). TR receiver is however inefficient due to the necessity in transmitting a reference prior to the data symbol. In this paper, the performance of TR receiver is investigated under high data rate transmission and compared to that of RAKE receiver. It is shown that the performance of basic TR is worse than a fractionally spaced selective RAKE receiver. A simple selective TR transceiver is then proposed to improve the performance of TR under ISI. It is shown that the proposed approach achieves almost similar performance to that of selective RAKE receiver while still maintains the simplicity of TR.
Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE; 06/2008
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ABSTRACT: This paper proposes a novel method for constructing ultra wide band (UWB) pulses based on a linear combination of Gaussian pulses. These pulses while meeting FCC power spectral density (PSD) mask requirements insure negligible interference with narrow band (NB) systems using flexible interference avoidance property they possess. Improved performance is achieved when errors due to imperfect synchronization exist between the transmitter and receiver (timing jitter). The coefficients of pulses designed can be generated using simple delay elements and amplifiers. The performance of these pulses in multipath channel such as channel model 1 (CM1) with timing jitter is evaluated by simulation and is found to be better than that of other designs.
IEEE Transactions on Wireless Communications 06/2008; · 2.59 Impact Factor
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ABSTRACT: This paper describes a combined modulation scheme for time-hopping ultra-wideband (TH-UWB) radio systems by using on-off keying (OOK) and pulse-shape modulation (PSM). A set of orthogonal pulses is used to represent bits in a symbol. These orthogonal pulses are transmitted simultaneously in the same pulse repetition interval resulting in a composite pulse. This scheme transmits the same number of bits by using fewer orthogonal pulses and receiver correlators than those used in PSM and biorthogonal PSM (BPSM). The proposed scheme reduces multiple-access interference and multipulse interference considerably by using crosscorrelation properties of orthogonal pulses. Since each bit is individually received by OOK, the proposed scheme requires less power. Hence, it is applicable for energy constrained and low-cost TH-UWB systems. The bit-error-rate (BER) performance is analyzed both mathematically and through computer simulations under the different channel environments. The performance of this scheme is compared with that of existing PSM and its combined modulation schemes by using two sets of orthogonal pulses.
EURASIP Journal on Wireless Communications and Networking. 01/2008;
