Joint data detection and channel estimation for OFDM systems

We develop new blind and semi-blind data detectors and channel estimators for orthogonal frequency-division multiplexing (OFDM) systems. Our data detectors require minimizing a complex, integer quadratic form in the data vector. The semi-blind detector uses both channel correlation and noise variance. The quadratic for the blind detector suffers from rank deficiency; for this, we give a low-complexity solution. Avoiding a computationally prohibitive exhaustive search, we solve our data detectors using sphere decoding (SD) and V-BLAST and provide simple adaptations of the SD algorithm. We consider how the blind detector performs under mismatch, generalize the basic data detectors to nonunitary constellations, and extend them to systems with pilots and virtual carriers. Simulations show that our data detectors perform well

Bound-intersection detection for multiple-symbol differential unitary space-time modulation

This paper considers multiple-symbol differential detection (MSD) of differential unitary space-time modulation (DUSTM) over multiple-antenna systems. We derive a novel exact maximum-likelihood (ML) detector, called the bound-intersection detector (BID), using the extended Euclidean algorithm for single-symbol detection of diagonal constellations. While the ML search complexity is exponential in the number of transmit antennas and the data rate, our algorithm, particularly in high signal-to-noise ratio, achieves significant computational savings over the naive ML algorithm and the previous detector based on lattice reduction. We also develop four BID variants for MSD. The first two are ML and use branch-and-bound, the third one is suboptimal, which first uses BID to generate a candidate subset and then exhaustively searches over the reduced space, and the last one generalizes decision-feedback differential detection. Simulation results show that the BID and its MSD variants perform nearly ML, but do so with significantly reduced complexity

Heuristic Tree Search for Detection and Decoding of Uncoded and Linear Block Coded Communication Systems

A heuristic tree search algorithm is developed for the maximum likelihood detection and decoding problem in a general communication system. We propose several "cheap" heuristic functions using constrained linear detectors and the minimum mean square errors (MMSE) detector. Even though the MMSE heuristic function does not guarantee the optimal solution, it has a negligible performance loss and provides a good complexity-performance tradeoff. For linear block coded systems, heuristic tree search is modified for soft decision decoding. High rate codes are decoded via the minimum state trellis, and low rate codes via the minimum complexity tree. Preprocessing is also discussed to further speed up the algorithms

Maximum likelihood detection for differential unitary space-time modulation with carrier frequency offset

Can conventional differential unitary space time modulation (DUSTM) be applied when there is an unknown carrier frequency offset (CFO)? This paper answers this question affirmatively and derives the necessary maximum likelihood (ML) detection rule. The asymptotic performance of the proposed ML rule is analyzed, leading to a code design criterion for DUSTM by using the modified diversity product. The resulting proposed decision rule is a new differential modulation scheme in both the temporal and spatial domains. Two sub-optimal multiple-symbol decision rules with improved performance are also proposed. For the efficient implementation of these, we derive a modified bound intersection detector (BID), a generalization of the previously derived optimal BID for the conventional DUSTM. The simulation results show that the proposed differential modulation scheme is more robust against CFO drifting than the existing double temporal differential modulation

Polynomial Moment Relaxation for MIMO Detection

We develop a polynomial-time detector for maximum likelihood (ML) detection over multiple-input multiple-output (MIMO) channels. Our proposed polynomial moment relaxation (PMR) detection gives a unified framework for MIMO detection with relaxation including semi-definite relaxation as a special case. We give three approaches to replace a finite alphabet constraint with a polynomial constraint. Since both the objective function and the constraints are polynomials, we use a moment relaxation approach by applying the dual theories of moments and positive polynomials solvable by semi-definite programming. With different relaxation orders, our PMR achieve a flexible trade-off between complexity and performance

Generation of Bivariate Rayleigh and Nakagami-m Fading Envelopes

The letter presents an algorithm for generating bivariate Nakagami-m distributed fading envelopes with any desired power cross correlation. For this algorithm, the fading index m should be a positive integer ( m = 1 for Rayleigh fading). Its applications include dual-branch selection combining diversity, dualbranch switch diversity systems, and wireless channel modeling

On the Trivariate Rician Distribution

An exact expression for the Joint density of three correlated Rician variables is not available in the open literature. In this letter, we derive new infinite series representations for the trivariate Rician probability density function (pdf) and the Joint cumulative distribution function (cdf). Our results are limited to the case where the inverse covariance matrix is tridiagonal. This case seems the most general one that is tractable with Miller's approach and cannot be extended to more than three Rician variables. The outage probability of triple branch selective combining (SC) receiver over correlated Rician channels is presented as an application of the density function

Analysis of Self-Interference Cancellation under Phase Noise, CFO and IQ Imbalance in GFDM Full-Duplex Transceivers

This paper investigates a full-duplex base station using a generalized frequency division multiplexing (GFDM) transceiver with the radio frequency (RF) impairments phase noise, carrier frequency offset (CFO) and in-phase (I) and quadrature (Q) imbalance. To fully focus on the RF impairment issue, we study the simple configuration of single uplink user and single downlink user. They both are half duplex wireless. In the uplink, we study analog and digital self-interference (SI) cancellation and propose a complementary SI suppression method. Desired signal and residual SI powers and signal-to-interference ratio (SIR) are derived in closed form. Similarly, in the downlink, we derive desired signal power, co-channel interference signal power caused by the uplink user and SIR. The RF impairments degrade the efficiency of SI cancellation and affect GFDM more negatively than full-duplex orthogonal frequency division multiplexing (OFDM). Hence, we propose full-duplex GFDM receiver filters for maximizing the SIR for both uplink and downlink transmissions. Finally, the uplink and downlink rates and the uplink-downlink rate region are derived. Significantly, the optimal-filter based GFDM outperforms full-duplex OFDM by 25 dB higher SIR and an uplink rate increase of 500%.acceptedVersionPeer reviewe

Envelope and Phase Distribution of Two Correlated Gaussian Variables

Probability density functions (pdf's) are derived for the phase and amplitude (envelope) of the complex gain X + jY (j = root-1), where X and Y are two correlated non zero-mean Gaussian random variables. The pdf of the amplitude is derived as an infinite series, but reduces to a closed-form expression when the means are zero. The classical Rayleigh and Rician pdf's turn out to be special cases of the derived pdf. This pdf is used to analyze the error performance of non-coherent binary frequency shift keying (BFSK) with in-phase/quadrature(I/Q) imbalance over an additive white Gaussian noise (AWGN) channel. The resulting bit error rate (BER) expression is derived as an infinite series. The analytical expressions are validated by simulation, and the I/Q imbalance related performance degradation is quantified. Convergence of the PDF series and the BER series is established