21 research outputs found
Algebraic Hybrid Satellite-Terrestrial Space-Time Codes for Digital Broadcasting in SFN
Lately, different methods for broadcasting future digital TV in a single
frequency network (SFN) have been under an intensive study. To improve the
transmission to also cover suburban and rural areas, a hybrid scheme may be
used. In hybrid transmission, the signal is transmitted both from a satellite
and from a terrestrial site. In 2008, Y. Nasser et al. proposed to use a double
layer 3D space-time (ST) code in the hybrid 4 x 2 MIMO transmission of digital
TV. In this paper, alternative codes with simpler structure are proposed for
the 4 x 2 hybrid system, and new codes are constructed for the 3 x 2 system.
The performance of the proposed codes is analyzed through computer simulations,
showing a significant improvement over simple repetition schemes. The proposed
codes prove in addition to be very robust in the presence of power imbalance
between the two sites.Comment: 14 pages, 2 figures, submitted to ISIT 201
Codes over Matrix Rings for Space-Time Coded Modulations
It is known that, for transmission over quasi-static MIMO fading channels
with n transmit antennas, diversity can be obtained by using an inner fully
diverse space-time block code while coding gain, derived from the determinant
criterion, comes from an appropriate outer code. When the inner code has a
cyclic algebra structure over a number field, as for perfect space-time codes,
an outer code can be designed via coset coding. More precisely, we take the
quotient of the algebra by a two-sided ideal which leads to a finite alphabet
for the outer code, with a cyclic algebra structure over a finite field or a
finite ring. We show that the determinant criterion induces various metrics on
the outer code, such as the Hamming and Bachoc distances. When n=2,
partitioning the 2x2 Golden code by using an ideal above the prime 2 leads to
consider codes over either M2(F_2) or M2(F_2[i]), both being non-commutative
alphabets. Matrix rings of higher dimension, suitable for 3x3 and 4x4 perfect
codes, give rise to more complex examples
Division algebra codes achieve MIMO block fading channel capacity within a constant gap
This work addresses the question of achieving capacity with lattice codes in
multi-antenna block fading channels when the number of fading blocks tends to
infinity. In contrast to the standard approach in the literature which employs
random lattice ensembles, the existence results in this paper are derived from
number theory. It is shown that a multiblock construction based on division
algebras achieves rates within a constant gap from block fading capacity both
under maximum likelihood decoding and naive lattice decoding. First the gap to
capacity is shown to depend on the discriminant of the chosen division algebra;
then class field theory is applied to build families of algebras with small
discriminants. The key element in the construction is the choice of a sequence
of division algebras whose centers are number fields with small root
discriminants.Comment: Submitted to ISIT 201
Arithmetic fuchsian groups and space time block codes
In the context of space time block codes (STBCs) the theory of arithmetic Fuchsian groups is presented. Additionally, in this work we present a new class of STBCs based on arithmetic Fuchsian groups. This new class of codes satisfies the property full-diversity, linear dispersion and full-rate. Mathematical subject classification: 18B35, 94A15, 20H10.48549