4 research outputs found
Low-complexity blind maximum-likelihood detection for SIMO systems with general constellations
The demand for high data rate reliable communications poses great challenges to the next generation wireless systems in highly dynamic mobile environments. In this paper, we investigate the joint maximum-likelihood (ML) channel estimation and signal detection problem for single-input multiple-output (SIMO) wireless systems with general modulation constellations and propose an efficient sequential decoder for finding the exact joint ML solution. Unlike other known methods, the new decoder can even efficiently find the joint ML solution under high spectral efficiency non-constant- modulus modulation constellations. In particular, the new algorithm does not need such preprocessing steps as Cholesky or QR decomposition in the traditional sphere decoders for joint ML channel estimation and data detection. The elimination of such preprocessing not only reduces the number of floating point computations, but also will potentially lead to smaller size and power consumption in VLSI implementations while providing better numerical stability
Momentum-inspired Low-Rank Coordinate Descent for Diagonally Constrained SDPs
We present a novel, practical, and provable approach for solving diagonally
constrained semi-definite programming (SDP) problems at scale using accelerated
non-convex programming. Our algorithm non-trivially combines acceleration
motions from convex optimization with coordinate power iteration and matrix
factorization techniques. The algorithm is extremely simple to implement, and
adds only a single extra hyperparameter -- momentum. We prove that our method
admits local linear convergence in the neighborhood of the optimum and always
converges to a first-order critical point. Experimentally, we showcase the
merits of our method on three major application domains: MaxCut, MaxSAT, and
MIMO signal detection. In all cases, our methodology provides significant
speedups over non-convex and convex SDP solvers -- 5X faster than
state-of-the-art non-convex solvers, and 9 to 10^3 X faster than convex SDP
solvers -- with comparable or improved solution quality.Comment: 10 pages, 8 figures, preprint under revie
Optimal Joint Detection/Estimation in Fading Channels with Polynomial Complexity
The problem of sequence detection in frequency-non-selective/time-selective fading channels, when channel state information (CSI) is not available at the transmitter and receiver, is considered in this paper. The traditional belief is that exact maximum likelihood sequence detection (MLSD) of an uncoded sequence over this channel has exponential complexity in the channel coherence time