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ABSTRACT: We have analyzed the performance of a predetection equal gain combining (EGC) receiver over correlated Nakagami-m fading channels with arbitrary and non-identical m and unequal branch SNRs. Closed-form expression for average bit error rate (ABER) for coherent binary modulation schemes is derived by finding the characteristic function (CHF) of the sum of two correlated Nakagami-m envelopes with different fading parameters and then using Parseval's theorem. The derived expression can be viewed as a generalization of four different special cases reported in the literature. It was observed that depending on the values of m<sub>1</sub> and m<sub>2</sub> the ABER curves for two different pairs of (m<sub>1</sub>,m<sub>2</sub>) may intersect. Thus, if the performance corresponding to a pair is inferior to another pair at any SNR, this may not hold true over the entire SNR range.
IEEE Communications Letters 08/2008; · 0.98 Impact Factor
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ABSTRACT: Recently Golay complementary sets were shown to exist in the subsets of second-order cosets of a q-ary generalization of the first-order Reed-Muller (RM) code. We show that mutually orthogonal Golay complementary sets can also be directly constructed from second-order cosets of a q-ary generalization of the first-order RM code. This identification can be used to construct zero correlation zone (ZCZ) sequences directly and it also enables the construction of ZCZ sequences with special subsets.
IEEE Transactions on Information Theory 04/2008; · 3.01 Impact Factor
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ABSTRACT: A new expression for the probability density function of the signal-to-noise ratio (SNR) at the output of a predetection dual-equal-gain-combining (dual-EGC) receiver over independent but non-identical Rayleigh fading paths with different noise levels is derived. A closed-form expression for the average bit error rate (ABER) for coherent binary modulation schemes is also derived. The effect of the degree of noise imbalance on ABER is studied. From the results we determine the ranges of noise imbalance for a given average SNR per path over which the performance of predetection dual-EGC is better or worse than SC and single path receivers.
Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE; 12/2007
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ABSTRACT: Using the approximate Fourier series technique we obtain expressions for the probability of error for bandlimited BPSK signalling in the presence of timing errors and fading. The derived results can be used to compute the error probabilities to any desired accuracy for Nakagami-m and Weibull fading channels. The effect of timing error on the performance of the raised cosine pulse has been evaluated for several fading parameters. We also compare the performance of some useful Nyquist pulses known
IEEE Transactions on Wireless Communications 03/2007; · 2.59 Impact Factor
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ABSTRACT: In this correspondence, new characterizations for the construction of zero correlation zone (ZCZ) sequences from mutually orthogonal Golay complementary sets (MOGCS) is presented. It is shown that the recursive construction of MOGCS is inherent in these characterizations. Previously known constructions of ZCZ sequences and MOGCS are shown to be special cases of this characterization. The notion of mutually orthogonal ZCZ sequence sets is also introduced
IEEE Transactions on Information Theory 09/2006; · 3.01 Impact Factor
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ABSTRACT: Average symbol error rate (ASER) of an equal gain combining (EGC) receiver with an arbitrary number of branches in exponentially correlated, Nakagami-m fading channels has been derived for binary, differential phase-shift keying (DPSK) and noncoherent frequency-shift keying (NCFSK) modulations. A Parseval's theorem based approach has been used. Numerical and simulation results have been found to be in close agreement. Results show that for a given ASER, as expected, exponentially correlated fading requires a higher SNR with respect to independent fading. For a given number of branches L, increase in SNR required (SNR penalty) with respect to independent fading is less for higher values of fading parameter m while for a given m, SNR penalty is more for higher L
IEEE Transactions on Wireless Communications 08/2006; · 2.59 Impact Factor
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ABSTRACT: In UWB systems, FCC mask puts a constraint on the Maximum Allowable Transmit Power (MATP) of a pulse. The transmit power of a pulse is an important parameter that determines the BER performance and range. In this paper a subspace based approach has been found to make the MATP optimization easier which otherwise seems intractable due to mask constraints. The design procedure begins with some pulse width and then we optimize for MATP. The obtained pulses turn out to have higher MATP than the known pulses of the same width. We show that using the proposed pulses, a lower BER than that of the existing pulses can be achieved. The proposed approach is applicable to the FCC mask or any other piecewise constant mask that may be proposed in future.
Communications, 2006. ICC '06. IEEE International Conference on; 07/2006
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ABSTRACT: In this letter, we present a new construction of interleavers for turbo codes from 3-regular Hamiltonian graphs. The interleavers can be generated using a few parameters, which can be selected in such a way that the girth of the interleaver graph (IG) becomes large, inducing a high summary distance. The size of the search space for these parameters is derived. The proposed interleavers themselves work as their de-interleavers.
IEEE Communications Letters 05/2006; · 0.98 Impact Factor
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ABSTRACT: The maximum-likelihood multiuser detection problem in code-division multiple-access is known to be an optimization problem with an objective function that is required to be optimized over a combinatorial decision region. Conventional suboptimal detectors relax the combinatorial decision region by a convex region, without altering the objective function to be optimized. We take an approach wherein the objective function is reduced to a form appropriate for the application of a polynomial complexity algorithm in computational geometry, while keeping the decision region combinatorial. The resulting detector allows a tradeoff between performance and computational complexity. The bit-error rate performance of the detector has been found to be better than the decorrelator and the linear minimum mean-square error detectors, for the same level of complexity.
IEEE Transactions on Communications 03/2006; · 1.68 Impact Factor
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ABSTRACT: In this letter we present a new construction of interleavers for turbo codes from 3-regular Hamiltonian graphs. The interleavers can be generated using a few parameters, which can be selected in such a way that the girth of the interleaver graph (IG) becomes large, inducing a high summary distance. The size of the search space for these parameters is derived. The proposed interleavers themselves work as their de-interleavers.
01/2006;
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ABSTRACT: For a given blocklength we determine the number of interleavers which have spread equal to two. Using this, we find out the probability that a randomly chosen interleaver has spread two. We show that as blocklength increases, this probability increases but very quickly converges to the value $1-e^{-2} \approx 0.8647$. Subsequently, we determine a lower bound on the probability of an interleaver having spread at least $s$. We show that this lower bound converges to the value $e^{-2(s-2)^{2}}$, as the blocklength increases.
11/2005;
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ABSTRACT: The bit error rate (BER) performance improvement of a correlated dual-diversity predetection EGC receiver in a Nakagami-m fading channel when an additional antenna which is receiving signals independent of the correlated pair is available is analysed. Two percentage improvement criteria have been considered. Numerical results show that the percentage improvement is more for higher SNRs. One of them has been found to be almost independent of the correlation between the correlated pair of antennas.
IEE Proceedings - Communications 11/2005; · 0.32 Impact Factor
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ABSTRACT: For a given blocklength we determine the number of interleavers which have spread equal to two. Using this, we find out the probability that a randomly chosen interleaver has spread two. We show that as blocklength increases, this probability increases but very quickly converges to the value 1 - e<sup>-2</sup> ap 0.8647. Subsequently, we determine a lower bound on the probability of an interleaver having spread at least s. We show that this lower bound converges to the value e<sup>-2(s-2)2</sup>, as the blocklength increases
Information Theory, 2005. ISIT 2005. Proceedings. International Symposium on; 10/2005
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ABSTRACT: Using a Gil-Palaez lemma-based approach, we derive a general expression for the bit-error rate of a predetection equal gain combining receiver for coherent binary phase-shift keying modulation in exponentially correlated, Nakagami- $m$ fading channel for an arbitrary number of branches. The obtained expressions are different for even and odd numbers of branches. Numerical results have been corroborated with simulations.
IEEE Transactions on Communications 09/2005; · 1.68 Impact Factor
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ABSTRACT: A family of ISI free polynomial pulses that can have an asymptotic decay rate of t<sup>-k</sup> for any integer value of k has been proposed. The proposed family provides flexibility in designing bandlimited pulses in accordance with the desired application, even after the roll-off factor α has been chosen. Pulses obtained from this family have been found to be better than the currently known good pulses.
IEEE Communications Letters 07/2005; · 0.98 Impact Factor
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ABSTRACT: We consider the linear combination of two ISI free pulses, the raised cosine (RC) and the recently proposed better than raised cosine (BTRC). We determine their optimum combination using the distribution of timing error. The obtained pulses perform better than RC and BTRC for fixed as well as randomly distributed timing errors.
IEEE Communications Letters 05/2005; · 0.98 Impact Factor
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ABSTRACT: There exist two SNR thresholds in finite frame length turbo codes. These thresholds depend on the component encoder as well as the frame length. A simple technique to find the upper threshold using the EXIT chart method is proposed.
Personal Wireless Communications, 2005. ICPWC 2005. 2005 IEEE International Conference on; 02/2005
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ABSTRACT: The predetection equal gain combining (EGC) receiver is generally known to have a performance that is close to the maximal ratio combining (MRC) receiver while having relatively less implementation complexity. The bit error rate (BER) of an EGC receiver for binary, coherent and noncoherent modulations has been analysed for an independent Weibull fading channel. Numerical results have been compared with the available results for selection combining (SC) and MRC diversity receivers.
Electronics Letters 02/2005; · 0.96 Impact Factor
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ABSTRACT: A new algorithm for multipath delay estimation based upon autocorrelation estimator (AE) has been proposed. The existing generalized autocorrelation estimator (GAE) has been modified by passing it through a sliding window of suitable shape and size resulting in improvement in performance. The performance improvement obtained because of the window has been determined for the case when the input is a filtered version of a white Gaussian signal. Accuracy percentage (AP) has been plotted against SNR. Simulation results show that the proposed scheme performs better delay estimation even at relatively low SNR
TENCON 2004. 2004 IEEE Region 10 Conference; 12/2004
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ABSTRACT: Recently, there has been work in use of LDPC codes over channels with memory, in particular, over Gilbert-Elliott (GE) channels. In this paper, we derive expressions for upper bounds on the rate of LDPC codes for reliable communication over a large class (non-oscillatory and non-inverting) of GE channels using the methods for memoryless channels.
Information Theory Workshop, 2004. IEEE; 11/2004
