Qiubin Gao

Exact BEP Analysis for Coherent M-ary PAM and QAM over AWGN and Rayleigh Fading Channels

A novel and unified framework is presented to evaluate the exact bit error probability (BEP) of M-ary pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) over additive white Gaussian noise (AWGN) channel for any bit-mapping techniques. Tight approximations are also provided for both of them. Using these results, we obtain the exact and tight approximate BEP expressions for maximal-ratio combining (MRC) and selection combining (SC) in Rayleigh fading.

BEP Analysis of MRT/MRC Diversity in Rayleigh Fading Channels

This letter analyzes the bit error probability (BEP) performance of multiple-input/multiple-output (MIMO) systems employing maximal ratio transmission/maximal ratio combining (MRT/MRC) diversity in Rayleigh fading channels, where the channels are known at the both transmitter and receiver. An exact closed-from expression for the BEP performances of square and rectangular quadrature amplitude modulation (QAM) is derived for systems with arbitrary number of transmit antennas and two receive antennas. Moreover, by approximating the probability density function of output signal-to-noise ratio (SNR) and using the close approximation of BEP performance with QAM in additive white Gaussian noise (AWGN), we obtain a simple expression for arbitrary number of transmitter antennas and receive antennas. Simulations show that our approximation is very close to the exact one.

Linear precoding and finite rate feedback design for V-BLAST architecture

Linear precoding is a simple method to improve the performance of V-BLAST architecture. However, it requires perfect channel state information at the transmitter, which necessitates a great amount of feedback. In this paper, we propose a linear precoding scheme for the V-BLAST architecture with an MMSE-SIC receiver. The whole scheme includes the design of an unquantized precoder and its finite rate feedback. The unquantized precoder, consisting of a beamforming matrix and a power allocation matrix, is designed by maximizing the minimum post-detection SINR of the MMSE-SIC receiver. In addition to the optimal precoder, we give a suboptimal solution which is shown to be asymptotically optimal at low SNR. The advantage of this suboptimal solution is that its extension to finite rate feedback is straightforward. Specifically, beamforming vectors are selected sequentially from a predetermined codebook and the indices are fed back. Besides, elements of the power allocation matrix are scalar quantized and fed back. Theoretical analysis reveals that the unquantized beamforming vectors are uniformly distributed on the unit sphere, leading to a very natural codebook design criterion - the Grassmannian criterion. Moreover, the proposed scheme is flexible enough to allow for a change in the number of data streams without redesigning the codebook. Simulation results are presented to demonstrate the effectiveness of the proposed scheme.

Particle-based iterative blind receiver for orthogonal frequency-division multiplexing with frequency offset

Abstract Orthogonal frequency-division multiplexing (OFDM) systems are sensitive to carrier frequency offset (CFO) which introduces intercarrier interference and significantly degrades system performance. This paper describes an iterative blind receiver consisting of a sequential Monte Carlo detector, a CFO estimator, and a compensator to reduce intercarrier interference. The framework is of low complexity due to the separation of tasks in a joint detection problem. In addition, the CFO estimator utilizes soft output of the sequential Monte Carlo detector, which reduces the information loss caused by hard decisions and can obtain the CFO estimate in only one OFDM symbol. Simulation results demonstrate the effectiveness of the algorithm.

Successive Interference Cancellation for DS-CDMA Downlink/Uplink

In this paper, we introduce two novel successive interference cancellation (SIC) algorithms for multiuser detection (MUD) in direct-sequence code-division multiple-access (DS-CDMA) systems. One is proposed for receivers in the downlink and the other for receivers in the uplink. The downlink SIC algorithm is a blind MUD which consists of two parts: estimating the signature sequences and amplitudes of interference users first, and then implementing the SIC detection. The uplink SIC algorithm is implemented by accurately estimating the amplitudes of each active user first and then performing the QR-decomposition based SIC. Simulation results show that the proposed algorithms are near-far resistant and outperform the conventional well-known SIC algorithms significantly.

Bandwidth-Efficient Distributed Estimation in Inhomogeneous Wireless Sensor Networks

This paper presents a distributed estimation scheme (DES) along with the bit allocation algorithm, which minimizes the total required bandwidth while ensuing a given average estimation mean-squared error (MSE). The DES comprises of a probabilistic Lloyd-Max quantization rule, and a best linear unbiased estimation (BLUE). Since the optimum bit allocation problem does not have a closed form, we present a suboptimal solution utilizing the alternating minimization (AM) algorithm. Finally, simulation results are provided to show the effectiveness of the proposed DES along with the bit allocation algorithm.

Performance Analysis of Universal Distributed Estimation in Bandwidth-Constrained Sensor Networks

This letter analyzes the performance of several typical one-bit universal distributed estimation schemes (DESs) in bandwidth-constrained sensor networks. We theoretically obtain the mean and mean-square error (MSE) of the DES based on binary form (BF) of the observation along with the MSE upper bound. It is proved that in some cases, the BF-based DES has larger MSE than the DES based on the complementary cumulative distribution function (CCDF) of the observation. Moreover, performance analysis is presented for the CCDF-based and BF-based DESs employing probabilistic quantization, respectively.

Universal distributed estimation scheme for a bandwidth constrained ad hoc sensor network

This paper describes a distributed estimation scheme (DES) for a bandwidth constrained ad hoc sensor network. The DES is universal in the sense that operations on all sensors are identical and independent of noise distribution. The scheme requires each sensor to transmit just a 1-bit message per observation. Simulation results show that the scheme achieves much better mean-squares error (MSE) performance than the simplified isotropic universal DES and even outperforms the isotropic universal DES which requires more than twice the bandwidth of this scheme.

Quantized Feedback for Spatial Multiplexing System

In this paper we present a quantized preceding scheme for the spatial multiplexing system equipped with MMSE-SIC receiver. The preceding matrix, consisting of a beamforming matrix and a power allocation matrix, is selected to maximize the minimum post-detection SINR of the MMSE-SIC receiver. Rather than the whole beamforming matrix, the beamforming vector for each data stream is selected sequentially from a predetermined codebook. The advantage of the sequential selection is that the computational burden and storage requirements are significantly reduced while the performance degradation is marginal. This is especially appealing for mobile terminals due to their physical limitation. The codebook is constructed by the Grassmannian beamforming criterion. Moreover, the proposed scheme is flexible enough to allow for a change in the number of data streams without redesigning the codebook. Simulation results are presented to demonstrate the effectiveness of the proposed scheme.

Limited feedback design for V-BLAST

We present a quantized precoding scheme for the V-BLAST system. The precoding matrix is decomposed into the multiplication of a beamforming matrix and a power allocation matrix. They are obtained by solving an optimization problem that maximizes the minimum post-detection SINR of the MMSE-SIC receiver under a total power constraint. The beamforming matrix is constrained to be in a predetermined codebook. We show that the precoder of UCD- VBLAST happens to be the optimal solution of the problem. Therefore, the proposed scheme can be regarded as a natural but nontrivial limited feedback version of UCD-VBLAST Simulation results are presented to demonstrate the effectiveness of the proposed scheme.