ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Thu, 17 Oct 2019 23:56:14 GMT2019-10-17T23:56:14Z502481- Estimating the frequency and phase of a noisy sinusoid by Kalman filterhttps://scholarbank.nus.edu.sg/handle/10635/51158Title: Estimating the frequency and phase of a noisy sinusoid by Kalman filter
Authors: Kam, P.Y.; Fu, H.
Abstract: A linear, two-dimensional state-space model involving the instantaneous signal frequency and carrier phase is formulated. This enables Kalman filtering to be used for estimating the frequency and phase. Two Kalman filters are presented here, one based on the old observation model of Tretter [3], and the other based on our newly proposed model in [1]. The Kalman filter for the old observation model requires knowledge of the signal amplitude and the noise variance, while for the new observation model, only knowledge of the noise variance is required. Their mean square estimation error performances are compared using simulations, and it is shown that the filter based on the new observation model performs better, especially at low signal-to-noise ratio. Kalman filtering also allows the incorporation of prior knowledge of the interval of distribution of the frequency to improve the estimation performance. ©2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/511582007-01-01T00:00:00Z
- Simple tight exponential bounds on the first-order Marcum Q-function via the geometric approachhttps://scholarbank.nus.edu.sg/handle/10635/84184Title: Simple tight exponential bounds on the first-order Marcum Q-function via the geometric approach
Authors: Kam, P.Y.; Li, R.
Abstract: The geometric interpretation of the first-order Marcum Q-function, Q(a, b), has been shown as the probability that a complex, Gaussian random variable Z̃ with real, nonzero mean a takes on values outside of a circular region CO,b of radius b centered at the origin O. Based on this interpretation, many new, simple, tight, upper/lower exponential bounds on Q(a, b) are easily obtained by computing the probability of Z lying outside of some simple geometrical shapes, such as circular regions, semicircular regions, sectors, and angular sectors of annuli, whose boundaries tightly enclose, or are tightly enclosed by the boundary of CO,b. The new bounds presented here only involve two exponential functions, and the best of them are in most cases much tighter than the best existing exponential bounds. In addition to these bounds, more new bounds can be obtained by using similar methods. Even some bounds in the literature can also be obtained via this geometric approach. ©2006 IEEE.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/841842006-01-01T00:00:00Z
- A robust GLRT receiver with implicit channel estimation and automatic threshold adjustment for the free space optical channel with IM/DDhttps://scholarbank.nus.edu.sg/handle/10635/81905Title: A robust GLRT receiver with implicit channel estimation and automatic threshold adjustment for the free space optical channel with IM/DD
Authors: Song, T.; Kam, P.-Y.
Abstract: Atmospheric turbulence and pointing errors cause intensity fluctuation of free space optical communication signals and impair link performance. Several receiver structures which could mitigate the signal fluctuations were proposed in the past, but these existing receivers depend highly on the channel model and the model parameters. The performance deteriorates if the channel model or the model parameters are inaccurate. In this paper, we develop a Viterbi-type trellis-search sequence receiver based on the generalized likelihood ratio test principle that jointly detects the data sequence and estimates the unknown channel gain. This receiver requires very few pilot symbols, and therefore, does not significantly reduce the bandwidth efficiency. It is robust in that it continuously performs maximum likelihood (ML) estimation of the unknown channel gain without the knowledge of the channel model, and adapts the decision metric accordingly. It works well in a slowly time-varying environment and its error performance approaches that of ML detection with perfect knowledge of the channel gain, as the memory length used for forming the sequence detection metric increases. A new, decision-feedback, symbol-by-symbol receiver with lower implementation complexity and higher memory efficiency is obtained as an approximation to the sequence receiver. The performance improvement and implementation simplicity of our receivers compared to existing receivers are pointed out. © 2013 IEEE.
Sat, 01 Feb 2014 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/819052014-02-01T00:00:00Z
- On the mutual information distribution of MIMO Rician fading channelshttps://scholarbank.nus.edu.sg/handle/10635/56898Title: On the mutual information distribution of MIMO Rician fading channels
Authors: Zhu, Y.; Kam, P.-Y.; Xin, Y.
Abstract: In a fading environment, the statistical distribution of the mutual information of a multiple-input multiple-output (MIMO) system depends on the joint distribution of the eigenvalues of a Wishart matrix, and is quite complex in general. We obtain here simple expressions for the distributions of the determinant and the trace of a Wishart matrix. Based on the obtained distributions, we derive some simple and tight bounds on the complementary cumulative distribution function (CCDF) of the mutual information of a MIMO system in Rician fading environments. The bounds obtained on the CCDF of mutual information provide further insights into the channel mutual information, and show the effects of the system parameters on the mutual information distribution explicitly. In addition, results for the Rayleigh channels are obtained as a special case. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/568982009-01-01T00:00:00Z
- Bit-error probability of QPSK with noisy phase referencehttps://scholarbank.nus.edu.sg/handle/10635/61899Title: Bit-error probability of QPSK with noisy phase reference
Authors: Some, Y.K.; Kam, P.Y.
Abstract: An approximate result is obtained for the bit-error probability of quadriphase shift keying in the presence of additive white Gaussian noise and a Tikhonov distributed-phase-reference error. The accuracy of the approximation is verified via actual numerical integration of the bit-error-probability formula. The approximation is easy to compute, and shows correctly the behaviour of the bit-error probability as a function of the signal-to-noise ratio. In particular, it shows that, for high signal-to-noise ratios, the bit-error probability behaves as the reciprocal of the square root of the former.
Sun, 01 Oct 1995 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/618991995-10-01T00:00:00Z
- ARQ with channel gain monitoringhttps://scholarbank.nus.edu.sg/handle/10635/55144Title: ARQ with channel gain monitoring
Authors: Wu, M.-W.; Kam, P.-Y.
Abstract: Automatic repeat request (ARQ) schemes with cyclic redundancy check (CRC) codes are designed specifically for additive white Gaussian noise channels based on average performance measures. Average performance measures are known to be inadequate for high data rate wireless communication where the channel gain varies randomly in time, because they do not reflect the poor QoS in deep fades. The instantaneous accepted packet error outage (IAPEO) probability is a more meaningful performance measure. Therefore, we examine the IAPEO of conventional ARQ and observe that, to achieve a certain IAPEO performance, the system must operate above a minimum signal-to-noise ratio (SNR), which may be too high to achieve. This motivates us to propose ARQ with channel gain monitoring (CGM), in which a packet is only demodulated and checked for errors when the channel gain exceeds a threshold; otherwise retransmission is requested. We show that it does not have a minimum SNR requirement. The average performance measures of ARQ-CGM with selective-repeat, go-back-n and stop-and-wait retransmission protocols, i.e. the average accepted packet error probability, throughput and goodput, are also obtained as functions of the pilot length and the CRC code length. The allocation of bandwidth and energy between channel estimation and CRC coding is studied. © 2012 IEEE.
Sun, 01 Jan 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/551442012-01-01T00:00:00Z
- Kalman estimation of single-tone parameters and performance comparison with MAP estimatorhttps://scholarbank.nus.edu.sg/handle/10635/56441Title: Kalman estimation of single-tone parameters and performance comparison with MAP estimator
Authors: Fu, H.; Kam, P.Y.
Abstract: By incorporating a priori knowledge via the a priori probability density function of the frequency and phase, the Kalman estimator for linear, minimum mean-square error estimation of these single-tone parameters in additive, white, Gaussian noise is presented. First, a linear, two-dimensional state-space model for the frequency and phase of a sinusoid is formulated. Then, two Kalman filters are proposed, one based on Tretter's phase noise model [S. A. Tretter, ldquoEstimating the Frequency of a Noisy Sinusoid by Linear Regression,rdquo IEEE Transactions on Information Theory, vol. IT-31, no. 6, pp. 832-835, Nov. 1985], and the other based on our newly proposed model in [H. Fu and P. Y. Kam, ldquoMAP/ML Estimation of the Frequency and Phase of a Single Sinusoid in Noise,rdquo IEEE Transactions on Signal Processing, vol. 55, no. 3, Mar. 2007]. Finally, their mean-square error performances are compared with each other and with that of the maximum a posteriori probability (MAP) estimator, using computer simulations. The results show that the MAP estimator performs best and the Kalman filter based on the improved phase noise model has better performance than that based on Tretter's model, especially at low signal-to-noise ratio. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/564412008-01-01T00:00:00Z
- Approximate results for the bit error probability of binary phase shift keying with noisy phase referencehttps://scholarbank.nus.edu.sg/handle/10635/61860Title: Approximate results for the bit error probability of binary phase shift keying with noisy phase reference
Authors: Kam, Pooi Yuen; Teo, Seow Khye; Some, Yew Kong; Tjhung, Tjeng Thiang
Abstract: Approximate results for the bit error probability (BEP) of binary phase shift keying in the presence of a noisy carrier phase reference are presented. The results show correctly the behavior of the BEP as a function of SNR. The accuracy of the approximations is verified by simulations and numerical integration of the BEP formulas. Comparisons of results with existing bounds are also given.
Thu, 01 Jul 1993 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/618601993-07-01T00:00:00Z
- Power control for MIMO diversity systems with nonidentical Rayleigh fadinghttps://scholarbank.nus.edu.sg/handle/10635/57097Title: Power control for MIMO diversity systems with nonidentical Rayleigh fading
Authors: Cao, L.; Tao, M.; Kam, P.Y.
Abstract: We investigate the performance limits and associated power-allocation problems in a multiple-antenna diversity system with statistical channel information available at the transmitter. The channels are assumed to be independent and nonidentically distributed Rayleigh fading. By studying both ergodic mutual information and information outage, we derive two simple and near-optimal power-allocation schemes. Specifically, for ergodic information rate maximization in a system with multiple transmit antennas and a single receive antenna, the proposed power control only depends on the ratios between channel gains and is independent of the total transmit signal-to-noise ratio (SNR). Meanwhile, for information outage minimization in a system with an arbitrary number of transmit and receive antennas, the proposed power allocation follows the water-filling principle and pours more power into the transmit antenna with a larger geometric mean of channel gains. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/570972009-01-01T00:00:00Z
- Analysis of differential orthogonal space-time block codes over semi-identical MIMO fading channelshttps://scholarbank.nus.edu.sg/handle/10635/55073Title: Analysis of differential orthogonal space-time block codes over semi-identical MIMO fading channels
Authors: Tao, M.; Kam, P.Y.
Abstract: We study the performance of differential orthogonal space-time block codes (OSTBC) over independent and semi-identically distributed block Rayleigh fading channels. In this semi-identical fading model, the channel gains from different transmit antennas to a common receive antenna are identically distributed, but the gains associated with different receive antennas are nonidentically distributed. Arbitrary fluctuation rates of the fading processes from one transmission block to another are considered. We first derive the optimal symbol-by-symbol differential detector, and show that the conventional differential detector is suboptimal. We then derive expressions of exact bit-error probabilities (BEPs) for both the optimal and suboptimal detectors. The results are applicable for any number of receive antennas, and any number of transmit antennas for which OSTBCs exist. For two transmit antennas, explicit and closed-form BEP expressions are obtained. For an arbitrary number of transmit antennas, a Chernoff bound on the BEP for the optimal detector is also derived. Our results show that the semi-identical channel statistics degrade the error performance of differential OSTBC, compared with the identical case. Also, the proposed optimal detector substantially outperforms the conventional detector when the channel fluctuates rapidly. But in near-static fading channels, the two detectors have similar performances. © 2007 IEEE.
Thu, 01 Feb 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/550732007-02-01T00:00:00Z
- Dual-stage cascaded frequency offset estimation for digital coherent receivershttps://scholarbank.nus.edu.sg/handle/10635/55709Title: Dual-stage cascaded frequency offset estimation for digital coherent receivers
Authors: Zhang, S.; Xu, L.; Yu, J.; Huang, M.-F.; Kam, P.Y.; Yu, C.; Wang, T.
Abstract: Frequency offset estimation is a key function in carrier phase recovery to enable digital coherent reception. We propose a novel, feed-forward, dual-stage frequency offset estimator, and demonstrate its performance through both simulation and experiment. Our simulation results show that the estimation range can be as large as ±9 GHz for a 10.7-GBaud polarization-multiplexed (PolMux) quadrature phase-shift keying (QPSK) system. In addition, the widest range of ±0.5 times the system symbol rate is achieved for the first time in an experimental 42.8-Gb/s coherent PolMux QPSK receiver. © 2006 IEEE.
Mon, 15 Mar 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/557092010-03-15T00:00:00Z
- A symbol-by-symbol channel estimation receiver for space-time block coded systems and its performance analysis on the nonselective Rayleigh fading channelhttps://scholarbank.nus.edu.sg/handle/10635/54829Title: A symbol-by-symbol channel estimation receiver for space-time block coded systems and its performance analysis on the nonselective Rayleigh fading channel
Authors: Shan, C.; Kam, P.Y.; Nallanathan, A.
Abstract: We present a symbol-by-symbol channel estimation receiver for an orthogonal space-time block coded system, and derive its analytical performance on a slow, nonselective, Rayleigh fading channel. Exact, closed-form expressions for its bit error probability (BEP) performance for M-ary phase shift-keying modulations are obtained, which enable us to theoretically predict the actual performance achievable under practical conditions with channel estimation error. Our BEP expressions show explicitly the dependence of BEP on the mean square error of the channel estimates, which in turn depend on the channel fading model and the channel estimator used. Tight upper bounds are presented that show more clearly the dependence of the BEP on various system parameters. Simulation results using various fading models are obtained to demonstrate the validity of the analysis. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/548292008-01-01T00:00:00Z
- Differential detection of DPSK with frequency offset compensationhttps://scholarbank.nus.edu.sg/handle/10635/62038Title: Differential detection of DPSK with frequency offset compensation
Authors: Kam, P.Y.; Teong, L.C.; See, C.C.
Abstract: A baseband differential-detection receiver for DPSK, incorporating a planar extended Kalman filter for Doppler frequency offset estimation and compensation, is presented. Simulations show that its performance is close to the ideal case of no frequency offset. It is ideal for digital implementation and finds applications in mobile radio communications.
Thu, 06 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/620381994-01-06T00:00:00Z
- Coherent detection of MPSK via efficient block estimationhttps://scholarbank.nus.edu.sg/handle/10635/61943Title: Coherent detection of MPSK via efficient block estimation
Authors: Kam, P.Y.; Tay, S.Y.
Abstract: A tree approach is proposed for efficient block estimation of MPSK sequences with unknown carrier phase. Its computational load increases with block length at a much lower rate than in previous algorithms. This enables coherent detection performance to be achieved through the use of large block lengths.
Thu, 03 Feb 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/619431994-02-03T00:00:00Z
- Decision-aided carrier phase estimation for coherent optical communicationshttps://scholarbank.nus.edu.sg/handle/10635/82114Title: Decision-aided carrier phase estimation for coherent optical communications
Authors: Zhang, S.; Kam, P.-Y.; Yu, C.; Chen, J.
Abstract: We analytically studied the block length effect (BLE) of decision-aided maximum likelihood (DA ML) carrier phase estimation in coherent optical phase-modulated systems. The results agree well with the trends found using extensive Monte Carlo simulations. In order to eliminate the BLE and accurately recover the carrier phase, an adaptive decision-aided (DA) receiver is proposed that does not require knowledge of the statistical characteristics of the carrier phase, or any parameter to be preset. The simulation results show that using the adaptive DA receiver, the maximum tolerance ratio of the linewidth per laser to symbol rate (ΔνT) at a bit error rate (BER) = 10-4 has been increased to 2.5×10-4, 4.1×10-5, and 9.5×10-6, respectively, for quadrature-, 8- and 16-phase-shift keying formats. The ratio (Δ ν T) of the adaptive DA receiver in 16 quadrature amplitude modulation (QAM) is decreased to2 × 10-5 due to the constellation penalty from 2.5 × 10-5 by using DA ML with optimum memory length, though it consistently performs well without optimizing any parameters as in DA ML. The phase error variance of the adaptive DA receiver is also analytically investigated. In addition, an analog-to-digital converter with bit resolution higher than 4 bits is shown to be sufficient to implement our adaptive DA receiver. © 2010 IEEE.
Fri, 01 Jan 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/821142010-01-01T00:00:00Z
- An adaptive coherent receiver for MPSK/MDPSK over the nonselective rayleigh fading channel with unknown characteristicshttps://scholarbank.nus.edu.sg/handle/10635/54979Title: An adaptive coherent receiver for MPSK/MDPSK over the nonselective rayleigh fading channel with unknown characteristics
Authors: Tan, H.; Ho, P.; Kam, P.Y.; Shan, C.
Abstract: A coherent symbol-by-symbol (SBS) diversity receiver for m-ary phase-shift keying (MPSK) and differentially encoded MPSK (MDPSK) signals transmitted over a nonselective Rayleigh fading channel is presented. It incorporates a new adaptive filter for channel estimation that does not require any prior knowledge of the fading process model. It estimates the fading gains through decision-feedback and recursive least squares adaptation of the filter coefficients. A novel forgetting-factor adaptation algorithm that enables the filter to react quickly to randomly changing fading statistics caused by shadowing and acceleration/deceleration is introduced. Simulations show that the receiver performs better than that of Adachi's ( IEEE Trans. Veh. Technol. vol. 47 p. 909, 1998), either without shadowing or under slow lognormal shadowing. © 2005 IEEE.
Tue, 01 Nov 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/549792005-11-01T00:00:00Z
- Performance of differentially detected DPSK over nonselective Rayleigh fading channels with maximal ratio combining and multiple cochannel interferershttps://scholarbank.nus.edu.sg/handle/10635/57032Title: Performance of differentially detected DPSK over nonselective Rayleigh fading channels with maximal ratio combining and multiple cochannel interferers
Authors: Zhang, S.; Kam, P.Y.; Ho, P.
Abstract: In this paper, we investigate the performance of differentially detected differential phase-shift keying (DPSK) modulation with postdetection maximal ratio combining, in nonselective Rayleigh fading channels with multiple asynchronous cochannel interferers. The approach is based on an analytical technique we have presented earlier in the literature. Exact bit-error probability (BEP) results for binary DPSK and quaternary DPSK are derived. More specifically, we look into the effects of symbol-timing offsets between the interfering signals and the desired signal on the error performance. Our results show that when all the interfering signals are synchronous with the desired signal, the impairment caused by the cochannel interference to the desired user is maximum. On the other hand, when all the interfering signals are half-symbol-duration-delayed with respect to the desired user, they introduce the minimum impairment. Based on these findings, upper and lower bounds on the BEP are derived in simple closed form. Our explicit BEP results also show that the error probabilities of different transmitted symbols of the desired user are affected differently by the interfering signal. © 2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/570322007-01-01T00:00:00Z
- Performance analysis and computational complexity comparison of sequence detection receivers with no explicit channel estimationhttps://scholarbank.nus.edu.sg/handle/10635/57007Title: Performance analysis and computational complexity comparison of sequence detection receivers with no explicit channel estimation
Authors: Wu, M.; Kam, P.Y.
Abstract: We consider a single-inputmultiple-output (SIMO) fading channel that can be assumed static over a duration of L symbols. We show that the generalized likelihood ratio test (GLRT) receiver for detecting a block of L uncoded symbols does not require channel-state information (CSI). By deriving an exact closed-form pairwise error probability expression for the detector over slowly time-varying Rayleigh fading, we show that its performance approaches that of coherent detection with perfect CSI when L becomes large. To detect a very long sequence of S symbols over a channel that can be assumed to remain static only over L symbols, where S≫L, while keeping computational complexity low, we consider three pilot-based algorithms, namely, the trellis search algorithm, pilot-symbol-assisted block detection, and decision-aided block detection. We compare them with the two existing block-by-block detection algorithms, namely, lattice decoding and sphere decoding, and show the former's advantages in complexity and performance. © 2010 IEEE.
Tue, 01 Jun 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/570072010-06-01T00:00:00Z
- Feedback power control with bit error outage probability QoS measure on the rayleigh fading channelhttps://scholarbank.nus.edu.sg/handle/10635/56037Title: Feedback power control with bit error outage probability QoS measure on the rayleigh fading channel
Authors: Wang, P.; Kam, P.-Y.
Abstract: We propose to use the probability of instantaneous bit error outage (IBEO) as a new performance measure in the design of an actual feedback power control system. It is defined as the probability that the instantaneous bit error probability (IBEP) exceeds an IBEP threshold. We propose the IBEO-based power control law where the transmitted power is adjusted according to the variations of the channel such that the IBEO probability is kept within some quality of service (QoS)-specified threshold. It ensures that in the long term, no more than a certain fraction of received bits would have IBEP exceeding some IBEP threshold. Therefore, the instantaneous QoS is guaranteed. Based on a practical system model with channel estimation and prediction, we develop the traditional average bit error probability (ABEP)-based power control law and the new IBEO-based power control law. For both laws, we derive explicit ABEP and IBEO probability results. The IBEO-based law shows a remarkable gain over the ABEP-based law in terms of IBEO probability, and sacrifices only a little in the ABEP performance. © 1972-2012 IEEE.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/560372013-01-01T00:00:00Z
- Performance analysis of coherent optical 8-star QAM systems using decision-aided maximum likelihood phase estimationhttps://scholarbank.nus.edu.sg/handle/10635/57013Title: Performance analysis of coherent optical 8-star QAM systems using decision-aided maximum likelihood phase estimation
Authors: Zhang, H.; Kam, P.-Y.; Yu, C.
Abstract: An approximate bit-error rate (BER) expression of 8-star quadrature amplitude modulation (QAM) in the presence of a phase estimation error is derived. The accuracy of the approximate BER is verified via numerical integration of the conditional BER and the Monte-Carlo (MC) simulations. This approximation allows quick estimation of the BER performance and prediction of laser linewidth tolerance, and also facilitates optimization of the ring ratio. © 2012 Optical Society of America.
Mon, 09 Apr 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/570132012-04-09T00:00:00Z
- A New Class of Signal Constellations for Differential Unitary Space-Time Modulation (DUSTM)https://scholarbank.nus.edu.sg/handle/10635/54499Title: A New Class of Signal Constellations for Differential Unitary Space-Time Modulation (DUSTM)
Authors: Shan, C.; Nallanathan, A.; Kam, P.Y.
Abstract: In this letter, a new class of signal constellations is proposed for differential unitary space-time modulation with multiple transmit antennas. In the proposed method, a rotation matrix is introduced to design signal constellations with large diversity product which is a primary property for signal constellations to have good performance in high signal to noise ratio (SNR).
Thu, 01 Jan 2004 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/544992004-01-01T00:00:00Z
- Differential diversity reception of MDPSK over independent Rayleigh channels with nonidentical branch statistics and asymmetric fading spectrumhttps://scholarbank.nus.edu.sg/handle/10635/51148Title: Differential diversity reception of MDPSK over independent Rayleigh channels with nonidentical branch statistics and asymmetric fading spectrum
Authors: Fu, H.; Kam, P.Y.
Abstract: This paper is concerned with optimum diversity receiver structure and its performance analysis of differential phase shift keying (DPSK) with differential detection over nonselective, independent, nonidentically distributed, Rayleigh fading channels. The fading process in each branch is assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth, but to have distinct, asymmetric fading power spectral density characteristic. Using 8-DPSK as an example, the average bit error probability (BEP) of the optimum diversity receiver is obtained by calculating the BEP for each of the three individual bits. The BEP results derived are given in exact, explicit, closed-form expressions which show clearly the behavior of the performance as a function of various system parameters. ©2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/511482007-01-01T00:00:00Z
- Tanlock carrier phase recovery without a divider and VCOhttps://scholarbank.nus.edu.sg/handle/10635/62845Title: Tanlock carrier phase recovery without a divider and VCO
Authors: Kam, P.Y.
Abstract: A novel approach for implementing the tanlock carrier phase estimator for binary phase-shift keyed signals is presented. The approach does not require the use of a divider which has been the main drawback in previous implementations. The estimator is open-loop and, thus, does not require a VCO.
Sat, 01 Jan 1994 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/628451994-01-01T00:00:00Z
- New tight bounds on the pairwise error probability for unitary space-time modulationshttps://scholarbank.nus.edu.sg/handle/10635/56805Title: New tight bounds on the pairwise error probability for unitary space-time modulations
Authors: Li, R.; Yuen Kam, P.
Abstract: We present two upper bounds and one lower bound on the pairwise error probability (PEP) of unitary space-time modulation (USTM) over the Rayleigh fading channel. The two new upper bounds are the tightest so far, and the new lower bound is the tightest at low signal-to-noise ratio. Some implications for USTM constellation design are also pointed out. © 2005 IEEE.
Fri, 01 Apr 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/568052005-04-01T00:00:00Z
- Decision-aided maximum likelihood detection in coherent optical phase-shift-keying systemhttps://scholarbank.nus.edu.sg/handle/10635/55504Title: Decision-aided maximum likelihood detection in coherent optical phase-shift-keying system
Authors: Zhang, S.; Kam, P.Y.; Chen, J.; Yu, C.
Abstract: A novel decision-aided maximum likelihood (DA ML) technique is proposed to estimate the carrier phase in coherent optical phase-shiftkeying system. The DA ML scheme is a totally linear computational algorithm which is feasible for on-line processing in the real systems. The simulation results show that the DA ML receiver can outperform the conventional Mth power scheme, especially when the nonlinear phase noise is dominant. © 2008 Optical Society of America.
Mon, 19 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/555042009-01-19T00:00:00Z
- Averages of the product of two Gaussian Q-functions over fading statistics and applicationshttps://scholarbank.nus.edu.sg/handle/10635/55178Title: Averages of the product of two Gaussian Q-functions over fading statistics and applications
Authors: Li, R.; Kam, P.Y.
Abstract: The averages of the product of two Gaussian Q-functions over the Nakagami-m and the Rician fading distributions are evaluated. The results obtained are applied to deriving closed-form bounds on the average bit error probability for a variety of single channel, partially coherent, differential and quadratic detections. © 2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/551782007-01-01T00:00:00Z
- Computing and bounding the generalized Marcum Q-function via a geometric approachhttps://scholarbank.nus.edu.sg/handle/10635/83573Title: Computing and bounding the generalized Marcum Q-function via a geometric approach
Authors: Li, R.; Kam, P.Y.
Abstract: The generalized Marcum Q-function, Qm(a,b), is here explained geometrically as the probability of a 2m-dimensional, real, Gaussian random vector, whose mean vector has a Frobenius norm of a, lying outside of a hypersphere of 2m dimensions, with radius b, and centered at the origin. Based on this new geometric interpretation, a new closed-form representation for Qm (a, b) is derived for the case where m is an odd multiple of 0.5. This representation involves only the exponential and the erfc functions, and thus is easy to handle, both numerically and analytically. For the case where m is an even multiple of 0.5, Qm+0.5(a,b) and Qm-0.5(a,b), which can be evaluated using our new representation mentioned above, are shown to be tight upper and lower bounds on Qm(a,b), respectively. They are shown in most cases to be much tighter than the existing bounds in the literature, and are valid for the entire ranges of a and b concerned. Their average is also a good approximation to Qm(a,b). ©2006 IEEE.
Sun, 01 Jan 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/835732006-01-01T00:00:00Z
- Weighted phase averager for frequency estimation of a noisy single sinusoid: Application of the observation phase noise modelhttps://scholarbank.nus.edu.sg/handle/10635/72190Title: Weighted phase averager for frequency estimation of a noisy single sinusoid: Application of the observation phase noise model
Authors: Fu, H.; Kam, P.Y.
Abstract: The exact statistical models for the observation phase noise (OPN) and their approximations in time-domain, phase-based estimation of the frequency and phase of a noisy single sinusoid are summarized, and the underlying physical interconnections are highlighted. The application of the various OPN models to the design of the weighted phase averager (WPA) estimator is developed. Simulation results show that using the time-varying OPN variance information which can intelligently indentify those phase samples with large errors, the performance of the WPA estimators can be improved, especially for low SNR. ©2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/721902009-01-01T00:00:00Z
- Phase-based, time-domain estimation of the frequency and phase of a single sinusoid in AWGN-the role and applications of the additive observation phase noise modelhttps://scholarbank.nus.edu.sg/handle/10635/57049Title: Phase-based, time-domain estimation of the frequency and phase of a single sinusoid in AWGN-the role and applications of the additive observation phase noise model
Authors: Fu, H.; Kam, P.-Y.
Abstract: This paper presents the theoretical foundation for time-domain, phase-based estimation of the frequency and phase of a single sinusoid in additive white Gaussian noise (AWGN), analogous to the theoretical foundation provided by Rife and Boorstyn for frequency-domain, Fourier-transform-based estimation. It is shown from the maximum a posteriori probability (MAP) and the maximum likelihood (ML) estimation principles that with the additive observation phase noise (AOPN), due to the AWGN, being described by its a posteriori distribution conditioned on the received signal magnitude, the received signal phase is a sufficient statistic for estimating the single-sinusoid angle parameters. Using a geometric approach, the exact statistical model for the AOPN is derived, where the a posteriori probability density function (pdf) and the corresponding a priori pdf are given by explicit, closed-form expressions that are valid for arbitrary signal-to-noise ratios (SNRs). The a posteriori pdf is Tikhonov, and is of particular interest as it establishes the AOPN model for phase-based frequency/phase MAP/ML estimation in the time domain. It is further illustrated that the results derived can yield various AOPN models as special cases, and the underlying physical insights and interconnections that exist among these models are revealed. It is shown that the model derived by Tretter is an ultimate specialization in the high SNR limit of the AOPN models developed here. For high SNR, the a posteriori Tikhonov pdf can be accurately approximated by a Gaussian distribution, which leads to the best linearized AOPN model. The applications of these AOPN models to the design of linear estimators, including the linear minimum mean square error (LMMSE) estimator, the linear minimum variance estimator, and the LMMSE implementation of the weighted phase averager are presented, and their estimation performances are compared through computer simulations, with the Cramer-Rao lower bound (CRLB) and the Bayesian CRLB as the benchmark. To facilitate estimator design, the a priori statistical models of the frequency and phase are proposed from the information-theoretic perspective, and an improved phase unwrapping algorithm over that given by Fu and Kam is presented. It is shown that by incorporating all the information available in the AOPN, the estimation accuracy can be much improved. © 1963-2012 IEEE.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/570492013-01-01T00:00:00Z
- Orthogonal space-time block codes over semi-identical channels with channel estimationhttps://scholarbank.nus.edu.sg/handle/10635/71341Title: Orthogonal space-time block codes over semi-identical channels with channel estimation
Authors: He, J.; Kam, P.Y.
Abstract: Assuming the channel gains associated with different receive antennas are not identically distributed, we study the orthogonal space-time block codes over non-identical channels with channel estimation. It is shown that the non-identical statistics lead to non-identical channel estimation errors, which make the conventional optimum decoder sub-optimum in this case. A new optimum decoder is derived. We show that it can be simplified to a symbol-by-symbol decoder under certain conditions. Analytical and simulation results show that our new decoder substantially outperforms the conventional decoder. © 2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/713412008-01-01T00:00:00Z
- Performance comparison of selection combining schemes for binary DPSK on nonselective Rayleigh-fading channels with interferencehttps://scholarbank.nus.edu.sg/handle/10635/57024Title: Performance comparison of selection combining schemes for binary DPSK on nonselective Rayleigh-fading channels with interference
Authors: Fu, H.; Kam, P.Y.
Abstract: This paper is concerned with the error performance analysis of binary differential phase shift keying (DPSK) with differential detection over the nonselective Rayleigh-fading channel with selection diversity reception and with an additive, correlated, Gaussian interference process in each diversity channel. The fading process is assumed to have an arbitrary Doppler spectrum with arbitrary Doppler bandwidth. The selection schemes investigated are: 1) the selection combining (SC) scheme based on signal-to-noise power ratio (SNR); 2) the SC scheme based on signal-plus-noise (S + N) ; and 3) the SC scheme based on maximum output (MO). New, exact, closed-form bit-error probability (BEP) expressions are derived, and a performance comparison among the three SC schemes and combining diversity reception is given. The results obtained reduce to previously known results when the correlated interference process is absent, and when the fading process does not fluctuate over the duration of several symbol intervals. The results indicate that the performance of each scheme depends on the tradeoff between the number of diversity branches, the SNR, the interference level, and the correlation of the interference process. However, the SC-(S + N) scheme generally performs worse than the SC-SNR scheme, the SC-MO scheme and combining diversity reception scheme. The findings presented here are not only of fundamental theoretical value, but are also of practical interest to the designers of future mobile communication systems. © 2005 IEEE.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/570242005-01-01T00:00:00Z
- Decision-aided, pilot-aided, decision-feedback phase estimation for coherent optical OFDM systemshttps://scholarbank.nus.edu.sg/handle/10635/55505Title: Decision-aided, pilot-aided, decision-feedback phase estimation for coherent optical OFDM systems
Authors: Cao, S.; Kam, P.Y.; Yu, C.
Abstract: We propose two phase estimation methods for coherent optical orthogonal frequency-division multiplexing (OFDM) systems, the decision-aided (DA) plus pilot-aided (PA) scheme and DA plus decision feedback (DF) scheme. We further investigate the combinations of DA, PA, and DF in a simulated 40-Gb/s single polarization system. DA+PA helps to increase the phase noise tolerance of DA and reduce the overhead of PA, while DA+DF reduces the overhead to zero and achieves the best performance with one more step of estimation, compensation, and demodulation. © 1989-2012 IEEE.
Sun, 01 Jan 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/555052012-01-01T00:00:00Z
- Improved signal constellations for differential unitary space-time modulations with more than two transmit antennashttps://scholarbank.nus.edu.sg/handle/10635/56281Title: Improved signal constellations for differential unitary space-time modulations with more than two transmit antennas
Authors: Soh, T.P.; Ng, C.S.; Kam, P.Y.
Abstract: In this paper, we propose new and improved unitary signal constellations for differential unitary space-time modulations utilizing more than two transmit antennas. The proposed unitary designs are constructed from fundamental building blocks which comprise the generator matrices of diagonal cyclic codes, and the 2×2 and 3×3 rotational matrices. The performances of the proposed codes are superior to those of previously proposed codes. © 2005 IEEE.
Sat, 01 Jan 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/562812005-01-01T00:00:00Z
- Pilot-assisted decision-aided maximum-likelihood phase estimation in coherent optical phase-modulated systems with nonlinear phase noisehttps://scholarbank.nus.edu.sg/handle/10635/82913Title: Pilot-assisted decision-aided maximum-likelihood phase estimation in coherent optical phase-modulated systems with nonlinear phase noise
Authors: Zhang, S.; Li, X.; Kam, P.Y.; Yu, C.; Chen, J.
Abstract: We proposed pilot-assisted (PA) decision-aided maximum-likelihood (DA ML) phase estimation for coherent optical M-ary phase-shift-keying systems. In a nonlinear-phase-noise channel with laser phase noise, the required launched power at bit-error-rate (BER) =10 -4 using the proposed PA DA ML algorithm without differential encoding (DE) can be reduced by about 0.7 dB in quadrature phase-shift keying and eight-phase-shift keying systems, and about 0.4 dB in 16-quadrature amplitude modulation format, compared to their DE counterparts using DA ML. © 2006 IEEE.
Mon, 15 Mar 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/829132010-03-15T00:00:00Z
- Bit-error probability for orthogonal space-time block codes with differential detectionhttps://scholarbank.nus.edu.sg/handle/10635/82015Title: Bit-error probability for orthogonal space-time block codes with differential detection
Authors: Soh, T.P.; Kam, P.Y.; Ng, C.S.
Abstract: Explicit closed-form expressions of the bit-error probabilities are obtained for space-time block codes based on generalized orthogonal designs with differential encoding and differential detection using 2b-ary phase-shift keying mapping. The frequency-nonselective, block-wise constant Rayleigh fading channel is considered here. The results are applicable to any number of transmit and receive antennas, where the number of transmit antennas is dictated by the available coding schemes. © 2005 IEEE.
Tue, 01 Nov 2005 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/820152005-11-01T00:00:00Z
- Orthogonal space-Time block codes in vehicular environments: Optimum receiver design and performance analysishttps://scholarbank.nus.edu.sg/handle/10635/56971Title: Orthogonal space-Time block codes in vehicular environments: Optimum receiver design and performance analysis
Authors: He, J.; Kam, P.Y.
Abstract: We consider orthogonal space-time block codes (OSTBC) in vehicular environments, where the channels are nonidentically distributed. It is shown that the nonidentical channel statistics lead to nonidentical channel estimation errors, which consequently affect the performance and even the existing receiver structure of OSTBC. We show that the conventional symbol-by-symbol (SBS) decoder of OSTBC is suboptimum in vehicular environments. A new optimum decoder is derived, which can be simplified to a new SBS decoder under certain conditions. To the best of our knowledge, our work here is the first to consider the optimum decoder for OSTBC in vehicular environments. Performance analysis and simulations are provided, which show that our new decoder substantially outperforms the conventional decoder. © 2009 J. He and P. Y. Kam.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/569712009-01-01T00:00:00Z
- Decision-aided joint compensation of transmitter IQ mismatch and phase noise for coherent optical OFDMhttps://scholarbank.nus.edu.sg/handle/10635/55503Title: Decision-aided joint compensation of transmitter IQ mismatch and phase noise for coherent optical OFDM
Authors: Cao, S.; Yu, C.; Kam, P.Y.
Abstract: We study the joint effects of transmitter in-phase/quadrature-phase (IQ) mismatch, channel distortion, and laser phase noise in a coherent optical orthogonal frequency-division-multiplexed system. We propose a decision-aided joint compensation scheme, which separates the transmitter IQ mismatch as well as channel distortion and phase noise compensation into two consecutive steps. Simulation results show this novel technique to be effective in mitigating the three effects simultaneously. © 2012 IEEE.
Sun, 01 Jan 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/555032012-01-01T00:00:00Z
- MAP/ML estimation of the frequency and phase of a single sinusoid in noisehttps://scholarbank.nus.edu.sg/handle/10635/56582Title: MAP/ML estimation of the frequency and phase of a single sinusoid in noise
Authors: Fu, H.; Kam, P.Y.
Abstract: The problem of estimating the frequency and carrier phase of a single sinusoid observed in additive, white, Gaussian noise is addressed. Much of the work in the literature considers maximum likelihood (ML) estimation. However, the ML estimator given by the location of the peak of a periodogram in the frequency domain shown in D.C. Rife and R. R. Boorstyn, "Single-tone parameter estimation from discrete-time observations," IEEE Transactions on Information Theory, vol. IT-20, pp. 591-598, Sep. 1974, has a very high computational complexity. This paper derives the explicit structure of the ML estimator for data processing in the time domain, assuming only reasonably high signal-to-noise ratio (SNR). The result of this approximate ML estimator shows that both the phase and the magnitude of the noisy signal samples are utilized in the estimator, and the phase data alone as assumed in S. A. Tretter, "Estimating the frequency of a noisy sinusoid by linear regression," IEEE Transactions on Information Theory, vol. IT-31, pp. 832-835, Nov. 1985 and S. Kay, "A fast and accurate single frequency estimator," IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 39, pp. 1203-1205, May 1991, is not a sufficient statistic. The sample-by-sample iterative processing nature of the estimator enables us to propose a novel, recursive phase-unwrapping algorithm that allows the estimator to be implemented efficiently. To facilitate the performance analysis, a new, linearized observation model for the instantaneous signal phase that is more accurate than that of S. A. Tretter, "Estimating the frequency of a noisy sinusoid by linear regression," IEEE Transactions on Information Theory, vol. IT-31, pp. 832-835, Nov. 1985 and of S. Kay, "A fast and accurate single frequency estimator," vol. 39, pp. 1203-1205, May 1991, is proposed. This new model explains physically why the phase data are weighted by the magnitude information in the ML estimator. Moreover, by incorporating a priori knowledge via the a priori probability density function of the unknown frequency and the carrier phase, the explicit structure of the approximate maximum a posteriori probability (MAP) estimator is derived, and the Bayesian CramerRao lower bound (BCRLB) on the mean-square error (mse) is obtained. Our analysis shows that the mse performance of the MAP estimator can approach the BCRLB very closely. © 2007 IEEE.
Thu, 01 Mar 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/565822007-03-01T00:00:00Z
- New representations and bounds for the generalized marcum Q-function via a geometric approach, and an applicationhttps://scholarbank.nus.edu.sg/handle/10635/82754Title: New representations and bounds for the generalized marcum Q-function via a geometric approach, and an application
Authors: Li, R.; Kam, P.Y.; Fu, H.
Abstract: The generalized Marcum Q-function of order m, Qm(a, b), is interpreted geometrically as the probability of a 2m-dimensional, real, Gaussian random vector z2m, whose mean vector has a Frobenius norm of a, lying outside of a hyperball B2m o,b of 2m dimensions, with radius b, and centered at the origin O. Based on this new geometric view, some new representations and closed-form bounds are derived for Qm(a, b). For the case that m is an odd multiple of 0.5, a new closed-form representation is derived, which involves only simple exponential and erfc functions. For the case that m is an integer, a pair of new, finite-integral representations for Q m(a, b) is derived. Some generic exponential bounds and erfc bounds are also derived by computing the probability of z2m lying outside of various bounding geometrical shapes whose surfaces tightly enclose, or are tightly enclosed by the surface of B2m o,b. These bounding shapes consist of an arbitrarily large number of parts. As their closeness of fit with B2m o,b improves, our generic bounds approach the exact value of Qm(a, b). The function Qm(a, b) is proved to be an increasing function of its order when 2m is a positive integer. Thus, Qm+0.5(a, b) and Qm-0.5(a, b) can be used as tight upper and lower bounds, respectively, on Qm(a, b). Their average is a good approximation to Qm(a, b). An application of our new representations and bounds is also given. © 2010 IEEE.
Fri, 01 Jan 2010 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/827542010-01-01T00:00:00Z
- 6-GHz radio-over-fiber upstream transmission using a directly modulated RSOAhttps://scholarbank.nus.edu.sg/handle/10635/53876Title: 6-GHz radio-over-fiber upstream transmission using a directly modulated RSOA
Authors: Meiyappan, A.; Kam, P.Y.; Kim, H.
Abstract: We propose and demonstrate 40-km upstream transmission of a 2-Gb/s 6-GHz binary phase-shift keyed radio signal using a directly modulated reflective semiconductor optical amplifier (RSOA). A delay interferometer, acting as an optical equalizer, compensates for limited RSOA modulation bandwidth and simultaneously performs single sideband filtering to relieve dispersion-induced radio-frequency (RF) fading effect. Furthermore, extended transmission distance of up to 40 km is shown to be made possible by reduced Rayleigh backscattering-induced crosstalk. © 2011 IEEE.
Sat, 01 Jan 2011 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/538762011-01-01T00:00:00Z
- Cutoff rate of MIMO systems in Rayleigh fading channels with imperfect CSIR and finite frame error probabilityhttps://scholarbank.nus.edu.sg/handle/10635/82112Title: Cutoff rate of MIMO systems in Rayleigh fading channels with imperfect CSIR and finite frame error probability
Authors: Ho, P.K.M.; Yar, K.-P.; Kam, P.Y.
Abstract: Using the random coding argument, in this paper, we derive the effective cutoff rate RE of multiple-input-multiple-output (MIMO) space-time (ST) codes in Rayleigh fast-fading channels with imperfect channel state information at the receiver (CSIR). In contrast to conventional cutoff rate analysis, where the codeword length N is infinity and the frame error probability Pf is implicitly zero, we loosen the definition to include the more realistic case of finite N and finite Pf. Using the tight upper and lower bounds on the pairwise error probability (PEP) in the work of Li and Kam, we are able to derive in turn tight lower and upper bounds on the cutoff rate of MIMO ST coding systems. The results are very general and can be applied to any linear modulation scheme, like M-ary phase-shift keying (MPSK) and M-ary quadrature-amplitude modulation (MQAM). Numerically, we found that for the two-transmit and two-receive antenna configuration, the nonasymptotic segments of our cutoff rate upper bounds for four, 16, and 64 MQAM actually coincide with the ergodic capacity curve. Furthermore, we found that the performance of the Smart-Greedy codes proposed in the seminal work of Tarokh et al. falls within the range predicted by our cutoff rate bounds. Finally, we show in this paper that for MIMO systems employing pilot-symbol-assisted channel estimation, the asymptotic cutoff rate no longer linearly increases with the number of transmit antennas. Instead, for a normalized fade rate of fD and a signal constellation of size M, the maximum effective cutoff rate is (8fD)-1 log2M, which is achieved when the number of transmit antennas is the integer closest to 1/(4fD). The result suggests that with a large antenna array and high user mobility, a more bandwidth-efficient channel-estimation strategy is desired. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/821122009-01-01T00:00:00Z
- Experiment on coherent optical RZ 8-Star QAM systems using decision-aided maximum likelihood phase estimationhttps://scholarbank.nus.edu.sg/handle/10635/55953Title: Experiment on coherent optical RZ 8-Star QAM systems using decision-aided maximum likelihood phase estimation
Authors: Zhang, H.; Zhang, B.; Yu, C.; Kam, P.-Y.
Abstract: In this letter, a return-to-zero 8-star quadrature amplitude modulation (QAM) signal is generated for the first time by using a parallel I/Q modulator followed by an amplitude modulator with binary drive signals. Our experimental results verify the theoretically derived approximate bit-error rate and ring ratio optimization algorithm of the 8-star QAM. Decision-aided maximum likelihood phase estimation (PE) shows comparable performance with V&V Mth-power PE, but with much less computational complexity. © 1989-2012 IEEE.
Sun, 01 Jan 2012 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/559532012-01-01T00:00:00Z
- Laser linewidth tolerance of decision-aided maximum likelihood phase estimation in coherent optical M-ary PSK and QAM systemshttps://scholarbank.nus.edu.sg/handle/10635/56461Title: Laser linewidth tolerance of decision-aided maximum likelihood phase estimation in coherent optical M-ary PSK and QAM systems
Authors: Zhang, S.; Kam, P.Y.; Yu, C.; Chen, J.
Abstract: This letter extends the decision-aided (DA) maximum likelihood (ML) phase estimation in an Mary phase-shift keying (PSK) system to quadrature amplitude modulation (QAM) signals. The block length effect is simulated for both M-ary PSK and QAM systems, and also investigated in M-ary PSK systems through analysis. Our results show that the tolerance of DA ML to laser linewidth for square 16-QAM can be increased by >10 times compared to the block Mth power scheme. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/564612009-01-01T00:00:00Z
- Computing and bounding the first-order Marcum Q-function: A geometric approachhttps://scholarbank.nus.edu.sg/handle/10635/55388Title: Computing and bounding the first-order Marcum Q-function: A geometric approach
Authors: Kam, P.Y.; Li, R.
Abstract: A geometric interpretation of the first-order Marcum Q-function, Q(a, b), is introduced as the probability that complex, Gaussian random variable with real mean a, takes on values outside of a disk CO,b of radius b centered at the origin O. This interpretation engenders a fruitful approach for deriving new representations and tight, upper and lower bounds on Q(a, b). The new representations obtained involve finite-range integrals with pure exponential integrands. They are shown to be simpler and more robust than their counterparts in the literature. The new bounds obtained include the generic exponential bounds which involve an arbitrarily large number of exponential functions, and the simple erfc bounds which involve just a few erfc functions, together with exponential functions in some cases. The new generic exponential bounds approach the exact value of Q(a, b) as the number of exponential terms involved increases. These generic exponential bounds evaluated with only two terms and the new simple erfc bounds are much tighter than the existing exponential bounds in most cases, especially when the arguments a and b are large. Thus, in many applications requiring further analytical manipulations of Q(a, b), these new bounds can lead to some closed-form results which are better than the results available so far. © 2008 IEEE.
Tue, 01 Jul 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/553882008-07-01T00:00:00Z
- An all-optical modulation format conversion for 8QAM based on FWM in HNLFhttps://scholarbank.nus.edu.sg/handle/10635/81948Title: An all-optical modulation format conversion for 8QAM based on FWM in HNLF
Authors: Zhang, B.; Zhang, H.; Yu, C.; Cheng, X.; Yeo, Y.K.; Kam, P.-K.; Yang, J.; Zhang, H.; Wen, Y.-H.; Feng, K.-M.
Abstract: In this letter, we propose and experimentally demonstrate an all-optical modulation format conversion scheme from amplitude shift keying (ASK) and quadrature phase shift keying (QPSK) to 8-ary quadrature amplitude modulation (8QAM), using four-wave mixing (FWM) effect in highly nonlinear fiber. In the FWM process, a 20-Gbits/s return-to-zero QPSK (RZ-QPSK) signal and a 10-Gbit/s ASK signal are utilized as probe light and pump light, respectively. A 30-Gbits/s RZ-8QAM signal, which is the idler light, is successfully obtained with optical signal-to-noise ratio larger than 30 dB and bit-error rate lower than 10-5. © 1989-2012 IEEE.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/819482013-01-01T00:00:00Z
- A performance investigation of correlation-based and pilot-tone-assisted frequency offset compensation method for CO-OFDMhttps://scholarbank.nus.edu.sg/handle/10635/54702Title: A performance investigation of correlation-based and pilot-tone-assisted frequency offset compensation method for CO-OFDM
Authors: Cao, S.; Yu, C.; Kam, P.-Y.
Abstract: We carry out a comprehensive analysis to examine the performance of our recently proposed correlation-based and pilot-toneassisted frequency offset compensation method in coherent optical OFDM system. The frequency offset is divided into two parts: fraction part and integer part relative to the channel spacing. Our frequency offset scheme includes the correlation-based Schmidl algorithm for fraction part estimation as well as pilot-tone-assisted method for integer part estimation. In this paper, we analytically derive the error variance of fraction part estimation methods in the presence of laser phase noise using different correlation-based algorithms: Schmidl, Cox and Cyclic Prefix based. This analytical expression is given for the first time in the literature. Furthermore, we give a full derivation for the pilot-tone-assisted integer part estimation method using the OFDM model. © 2013 Optical Society of America.
Mon, 23 Sep 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/547022013-09-23T00:00:00Z
- Spectrum sensing for digital primary signals in cognitive radio: A bayesian approach for maximizing spectrum utilizationhttps://scholarbank.nus.edu.sg/handle/10635/57467Title: Spectrum sensing for digital primary signals in cognitive radio: A bayesian approach for maximizing spectrum utilization
Authors: Zheng, S.; Kam, P.-Y.; Liang, Y.-C.; Zeng, Y.
Abstract: With the prior knowledge that the primary user is highly likely idle and the primary signals are digitally modulated, we propose an optimal Bayesian detector for spectrum sensing to achieve higher spectrum utilization in cognitive radio networks. We derive the optimal detector structure for MPSK modulated primary signals with known order over AWGN channels and give its corresponding suboptimal detectors in both low and high SNR (Signal-to-Noise Ratio) regimes. Through approximations, it is found that, in low SNR regime, for MPSK (M>2) signals, the suboptimal detector is the energy detector, while for BPSK signals the suboptimal detector is the energy detection on the real part. In high SNR regime, it is shown that, for BPSK signals, the test statistic is the sum of signal magnitudes, but uses the real part of the phase-shifted signals as the input. We provide the performance analysis of the suboptimal detectors in terms of probabilities of detection and false alarm, and selection of detection threshold and number of samples. The simulations have shown that Bayesian detector has a performance similar to the energy detector in low SNR regime, but has better performance in high SNR regime in terms of spectrum utilization and secondary users' throughput. © 2002-2012 IEEE.
Tue, 01 Jan 2013 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/574672013-01-01T00:00:00Z
- Capacity analysis and power allocation over non-identical MISO Rayleigh fading channelshttps://scholarbank.nus.edu.sg/handle/10635/69549Title: Capacity analysis and power allocation over non-identical MISO Rayleigh fading channels
Authors: Cao, L.; Tao, M.; Kam, P.Y.
Abstract: We analyze the capacity of a multiple-input single-output system over Rayleigh fading channels. The channels are assumed to be independent and non-identically distributed. Simple, explicit and closed-form expressions of ergodic mutual information and outage probability are obtained. Moreover, two suboptimal but efficient analytical power allocation schemes for mutual information maximization and outage minimization are derived, respectively. In specific, for mutual information maximization, more power is assigned to those channels with higher channel variances, while for outage minimization the power allocation scheme follows the water-filling principle. ©2008 IEEE.
Tue, 01 Jan 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/695492008-01-01T00:00:00Z
- Space-time trellis codes over rapid Rayleigh fading channels with channel estimation - Part II: Performance analysis and code design for non-identical channelshttps://scholarbank.nus.edu.sg/handle/10635/57453Title: Space-time trellis codes over rapid Rayleigh fading channels with channel estimation - Part II: Performance analysis and code design for non-identical channels
Authors: Li, Y.; Kam, P.Y.
Abstract: We consider the maximum likelihood (ML) receiver design, performance analysis and code design for space-time trellis codes (STTC) over non-identical, rapid fading channels with imperfect channel state information (CSI). The exact pairwise error probability (PEP) and PEP bounds for the ML receiver are obtained. A new code design criterion exploiting the statistical information of the channel estimates is proposed, which can minimize the performance loss caused by channel estimation error. New codes are obtained via an iterative search algorithm with reduced complexity. Under actual channel estimation conditions, our codes perform better than the existing codes in the literature which are designed on the assumption of identical channels, and perfect CSI at the receiver. More performance gain can be achieved by our codes when the degree of imbalance among the links is higher. © 2009 IEEE.
Thu, 01 Jan 2009 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/574532009-01-01T00:00:00Z
- Bit error performance of orthogonal space-time block codes over time-selective channelhttps://scholarbank.nus.edu.sg/handle/10635/69512Title: Bit error performance of orthogonal space-time block codes over time-selective channel
Authors: He, J.; Kam, P.Y.
Abstract: Most of the existing works on space-time block codes (STBC) assume the channels are quasi-static, i.e., they remain invariant within one block. This assumption is not always true. In a more general case of time-selective channel, the channel matrix is no longer orthogonal. If conventional linear decoder is applied as it is in the quasi-static channel, it will introduce an irreducible error floor. In order to improve the performance, we can use zero-forcing decoder, which completely removes the interference. In this paper, we analyze the average bit error performance for BOTH conventional linear and zeroforcing decoders in the time-selective channels. The closed-form average bit error probabilities are obtained for both decoders, together with the irreducible error floor for the conventional linear decoder. Asymptotic analysis and numerical examples are also provided. © 2007 IEEE.
Mon, 01 Jan 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/695122007-01-01T00:00:00Z