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ABSTRACT: This paper proposed a new normalized transform domain conjugate gradient algorithm (NT-CGA), which applies the data independent
normalized orthogonal transform technique to approximately whiten the input signal and utilises the modified conjugate gradient
method to perform sample-by-sample updating of the filter weights more efficiently. Simulation results illustrated that the
proposed algorithm has the ability to provide a fast convergence speed and lower steady-error compared to that of traditional
least mean square algorithm (LMSA), normalized transform domain least mean square algorithm (NT- LMSA), Quasi-Newton least
mean square algorithm (Q-LMSA) and time domain conjugate gradient algorithm (TD-CGA) when the input signal is heavily coloured.
Journal of Electronics (China) 04/2012; 17(1):69-76.
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ABSTRACT: In this paper, a semi-blind time-domain equalization technique is proposed for general multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. The received OFDM symbols are shifted by more than or equal to the cyclic prefix (CP) length, and a blind equalizer is designed to completely suppress both intercarrier interference (ICI) and intersymbol interference (ISI) using second-order statistics of the shifted received OFDM symbols. Only a one-tap equalizer is needed to detect the time-domain signals from the blind equalizer output, and one pilot OFDM symbol is utilized to estimate the required channel state information for the design of the one-tap equalizer. The technique is applicable irrespective of whether the CP length is longer than, equal to, or shorter than the channel length. Computer simulations show that the proposed technique outperforms the existing techniques, and it is robust against the number of shifts in excess of the CP length.
IEEE Transactions on Vehicular Technology 08/2008; · 1.92 Impact Factor
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ABSTRACT: Novel adder and multiplier circuits for bit-stream signal processing customised for quad-level sigma-delta modulated signals are proposed. Compared with existing sorter-based quad-level sigma-delta adders and multipliers, the proposed implementation is more resource-efficient (>76% hardware savings) and faster (>93% higher clock frequency) when realised on state-of-the-art FPGA architecture featuring six- input look-up tables.
Electronics Letters 02/2008; · 0.96 Impact Factor
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ABSTRACT: A four-input adder structure for the FPGA implementation of a sigma-delta bit-stream multiplier is proposed. Conventional bit-stream multiplier implementations involve two-input adder circuits. It is shown that the four-input adder structure is more resource-efficient (over 40% hardware savings) and faster (over 20% higher clock frequency) when implemented using state-of-the-art FPGA architecture featuring six-input look-up tables
Electronics Letters 02/2007; · 0.96 Impact Factor
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ABSTRACT: This paper presents a noise analysis model, which allows basic phase noise calculations of a ΣΔ PLL fractional-N synthesizer. Calculation results on various ΣΔ orders of multiple architectures, feedback and feedforward, and on transient process, which provides quick visualization of the design methods used to minimize the required settling-time, will be presented.
Radio Frequency Integrated Circuits (RFIC) Symposium, 2003 IEEE; 07/2003
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ABSTRACT: The use of multiple-input multiple-output (MIMO) antennas for achieving diversity and/or support of multi-stream signaling has recently been demonstrated to gain lots of benefits including reduction in average power error probability and capacity enhancement. However, studies are limited to a point-to-point communication. In this paper, we address the optimization problem of enhancing the performance of a downlink multi-user system (i.e., point-to-multipoint communication) through joint use of multiple antennas at the base station (BS) and mobile stations (MS). The optimization is performed by finding the antenna weights at the BS and MS, jointly, to orthogonalize the multi-user multi-stream signals as well as maximizing the resultant channel gains of the diagonalized system for optimal performance.
Communications, 2003. ICC '03. IEEE International Conference on; 06/2003
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ABSTRACT: An M-estimate adaptive filter for robust adaptive filtering in
impulse noise is proposed. Instead of using the conventional
least-square cost function, a new cost function based on an M-estimator
is used to suppress the effect of impulse noise on the filter weights.
The resulting optimal weight vector is governed by an M-estimate normal
equation. A recursive least M-estimate (RLM) adaptive algorithm and a
robust threshold estimation method are derived for solving this
equation. The mean convergence performance of the proposed algorithm is
also analysed using the modified Huber (1981) function (a simple but
good approximation to the Hampel's three-parts-redescending M-estimate
function) and the contaminated Gaussian noise model. Simulation results
show that the proposed RLM algorithm has better performance than other
recursive least squares (RLS) like algorithms under either a
contaminated Gaussian or alpha-stable noise environment. The initial
convergence, steady-state error, robustness to system change and
computational complexity are also found to be comparable to the
conventional RLS algorithm under Gaussian noise alone
IEE Proceedings - Vision Image and Signal Processing 09/2001;
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ABSTRACT: This paper proposes a recursive least M-estimate (RLM) algorithm for robust adaptive filtering in impulse noise. It employs an M-estimate cost function, which is able to suppress the effect of impulses on the filter weights. Simulation results showed that the RLM algorithm performs better than the conventional RLS, NRLS, and the OSFKF algorithms when the desired and input signals are corrupted by impulses. Its initial convergence, steady-state error, computational complexity, and robustness to sudden system change are comparable to the conventional RLS algorithm in the presence of Gaussian noise alone.
IEEE Signal Processing Letters 12/2000; · 1.39 Impact Factor
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ABSTRACT: We proposed a novel interleaving technique, namely adaptive
interleaving, which can break the bursty channel errors more effectively
than traditional block interleaving. This new scheme resequences the
transmitted symbols adaptively according to the instantaneous subcarrier
channel state information. In this way, the bursty errors introduced by
the channel can be broken more effectively, thus a better BER
performance can be achieved. This technique is well-suited to OFDM
systems because the CSI values of the whole frame could be estimated at
once when transmitted symbols are framed in the frequency dimension.
Computer simulation shows that significant SNR gains can be achieved,
compared with traditional block interleaving
Communications, 2000. ICC 2000. 2000 IEEE International Conference on; 02/2000
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ABSTRACT: We analyze the performance of a novel multiresolution joint source
and channel coding (MR-JSCC) scheme for mobile radio channels with
feedback. The transmitter and receiver can match the resolution of each
other synchronously, according to the channel state information (CSI).
Bandwidth requirements can be met by carefully adjusting the resolution
thresholds. The threshold determination algorithm is outlined.
Simulation results show that MR-JSCC scheme has much better performance
than baseline-I (no UEP and no feedback) and baseline-II (UEP without
feedback) at the same bandwidth and power
Personal Wireless Communications, 2000 IEEE International Conference on; 02/2000
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ABSTRACT: We proposed a novel interleaving technique, namely adaptive
interleaving, which can break the bursty channel errors more effectively
than traditional block interleaving. This new scheme resequences the
transmitted symbols adaptively according to the instantaneous subcarrier
channel state information sequence. In this way, the bursty errors
introduced by the channel can be broken more effectively, thus a better
BER performance can be achieved. This technique is well-suited to OFDM
systems because the CSI values of the whole frame could be estimated at
once when transmitted symbols are framed in the frequency dimension. In
this paper, we consider applying the technique to high
bandwidth-efficiency systems. It is shown that the proposed scheme
achieves significant SNR gains compared with the regular block
interleaving scheme. In addition, the SNR gains is larger than the gains
in BPSK OFDM systems
MILCOM 2000. 21st Century Military Communications Conference Proceedings; 02/2000
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ABSTRACT: A new cost function, which is a modification of the cost function
of Castedo and Figugiras-Vidal (1995) for the adaptive blind beamforming
of cyclostationary signals, is proposed. The proposed cost function
enables the well-known recursive least-squares technique to be applied.
Simulations demonstrate that the resulting algorithm has a faster
convergence speed than the stochastic gradient-based algorithm of
Castedo and Figugiras-Vidal
Electronics Letters 08/1999; · 0.96 Impact Factor
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ABSTRACT: Closed-form solutions for the average bit error rate (BER)
performance of a direct-sequence code division multiple-access system
with imperfect power control are derived for both coherent and
noncoherent reception operating over a multipath Rayleigh fading
channel. The RAKE structure receivers under consideration employ
despreading sequences weighted by adjustable exponential chip waveforms
optimized for multiple-access interference rejection. The chip-weighting
waveforms employed are determined only by one parameter γ which
leads to easy tuning of the waveforms in practice to achieve the best
performance. The results indicate that the number of active users
supported at a given BER for the case of γ tuned to maximize the
average signal to interference plus noise ratio Hˆ is much larger
than the case of γ=0 (fixed or rectangular despreading sequence).
It is shown that imperfect power control affects the irreducible BER for
the case of γ=0. On the other hand, the effect of imperfect power
control on the BER performance for the case of γ tuned to maximize
Hˆ is equivalent to a reduction in the average signal-to-noise
ratio, and, hence, system performance can be compensated by increasing
the transmitter power. It is further shown that the effect due to
imperfect power control on BER performance is significant while that on
the maximum value of Hˆ obtained by tuning γ is rather
insignificant
IEEE Transactions on Vehicular Technology 08/1999; · 1.92 Impact Factor
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ABSTRACT: A new class of orthogonal code-division multiple access (CDMA)
system is developed. The key characteristic of the system is that the
data symbols are spreaded by a spread-sequence that is longer than the
period of the symbol and hence overlapped with the neighboring symbols.
Using this approach, temporal diversity is incorporated with other
diversities. Due to the temporal diversity, the proposed CDMA system
performs well in a fading environment. In this paper, a method for
designing such a spread-sequence using filter bank theory is presented.
The length of the spread-sequence could be varied according to the
requirement. Simulation results show that the proposed spread-sequence
based system yields lower BER than the conventional Gold codes based
DS/CDMA system
Vehicular Technology Conference, 1999 IEEE 49th; 08/1999
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ABSTRACT: In this paper, a robust M-estimate adaptive filter for impulse noise suppression is proposed. The objective function used is based on a robust M-estimate. It has the ability to ignore or down weight large signal error when certain thresholds are exceeded. A systematic method for estimating such thresholds is also proposed. An advantage of the proposed method is that its solution is governed by a system of linear equations. Therefore, fast adaptation algorithms for traditional linear adaptive filters can be applied. In particular, a M-estimate recursive least square (M-RLS) adaptive algorithm is studied in detail. Simulation results show that it is more robust against individual and consecutive impulse noise than the MN-LMS and the N-RLS algorithms. It also has fast convergence speed and a low steady state error similar to its RLS counterpart
Acoustics, Speech, and Signal Processing, 1999. ICASSP '99. Proceedings., 1999 IEEE International Conference on; 04/1999
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ABSTRACT: A new method for carrier recovery in an MPSK DS/CDMA receiver is
presented. The proposed scheme employs two balanced X-correlators to
form a frequency discriminator which has a tracking range of double the
symbol rate, and the tracking range is independent of the keying phase
number and the spreading code length
Electronics Letters 03/1999; · 0.96 Impact Factor
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ABSTRACT: This correspondence presents a new factorization for linear-phase
biorthogonal perfect reconstruction (PR) FIR filter hanks. Using this
factorization, we propose a new family of lapped transform called the
generalized lapped transform (GLT). Since the analysis and synthesis
filters of the GLT are not restricted to be time reverses of each other,
they can offer more freedom to avoid blocking artifacts and improve
coding gain in subband coding applications. The GLT is found to have
higher coding gain and smoother synthesis basis functions than the
lapped orthogonal transform (LOT). Simulation results also demonstrated
that the GLT has significantly less blocking artifacts, higher peak
signal-to-noise ratio (PSNR), and better visual quality than the LOT in
image coding. Simplified GLT with different complexity/performance
tradeoff is also studied
IEEE Transactions on Signal Processing 03/1999; · 2.63 Impact Factor
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ABSTRACT: Castedo et al. (1995) have present a blind beamforming criterion
based on the property of cyclostationary signals. A stochastic
gradient-based algorithm, which needs to choose the step size suitably,
was derived to compute the optimum weight vector. In this paper a fast
adaptive algorithm is proposed. We show that the recursive least square
techniques can be applied to solve this problem successfully by making
an appropriate approximation. Simulation results demonstrate the effect
of the theoretic analysis
TENCON 99. Proceedings of the IEEE Region 10 Conference; 02/1999
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ABSTRACT: In this paper, a new 8-channel integer-valued lapped transform,
called the Integer Lapped Orthogonal Transform (ILOT), is proposed. The
new transform can be implemented using simple integer arithmetic and has
very low implementation complexity. Using 5-bits to represent its
transform kernel, it was found that good coding gain and stop band
attenuation similar to the LOT, could be achieved. The multiplier-less
fast ILOT requires only 106 additions and 42 shifts and can be
implemented in 32-bit integer arithmetic [13]
Circuits and Systems, 2000. 42nd Midwest Symposium on; 02/1999
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ABSTRACT: The performance of an asynchronous orthogonal multi-carrier code
division multiple access (MC-CDMA) system for the reverse link of the
mobile communication system with equal gain combining is obtained. The
performance of MC-CDMA is compared with that of conventional CDMA and
MC-DS-CDMA in numerical results in a multipath Rayleigh fading channel
Communication Technology Proceedings, 1998. ICCT '98. 1998 International Conference on; 11/1998
