2 research outputs found
Error Performance of Multidimensional Lattice Constellations-Part I: A Parallelotope Geometry Based Approach for the AWGN Channel
Multidimensional lattice constellations which present signal space diversity
(SSD) have been extensively studied for single-antenna transmission over fading
channels, with focus on their optimal design for achieving high diversity gain.
In this two-part series of papers we present a novel combinatorial geometrical
approach based on parallelotope geometry, for the performance evaluation of
multidimensional finite lattice constellations with arbitrary structure,
dimension and rank. In Part I, we present an analytical expression for the
exact symbol error probability (SEP) of multidimensional signal sets, and two
novel closed-form bounds, named Multiple Sphere Lower Bound (MLSB) and Multiple
Sphere Upper Bound (MSUB). Part II extends the analysis to the transmission
over fading channels, where multidimensional signal sets are commonly used to
combat fading degradation. Numerical and simulation results show that the
proposed geometrical approach leads to accurate and tight expressions, which
can be efficiently used for the performance evaluation and the design of
multidimensional lattice constellations, both in Additive White Gaussian Noise
(AWGN) and fading channels
Accurate Approximation of QAM Error Probability on Quasi-static MIMO Channels and its Application to Adaptive Modulation
An accurate approximation for the conditional error probability on quasi-static multiple antenna (MIMO) channels is proposed. For a fixed channel matrix, it is possible to accurately predict the performance of quadrature-amplitude modulations (QAM) transmitted over the MIMO channel in presence of additive white Gaussian noise. The tight approximation is based on a simple Union bound for the point error probability in the n-dimensional real space. Instead of making an exhaustive evaluation of all pairwise error probabilities (intractable in many cases), a Pohst or a Schnorr-Euchner lattice enumeration is used to limit the local theta series inside a finite radius sphere. The local theta series is derived from the original lattice theta series and the point position within the finite multi-dimensional QAM constellation. In particular, we take into account the number of constellation facets (hyperplanes) that are crossing the sphere center. As a direct application to the accurate approximation for the conditional error probability, we describe a new adaptive QAM modulation for quasi-static multiple antenna channels. Index Terms Multiple antenna channels, sphere decoding, adaptive modulation, lattice constellations