3 research outputs found
HybridConcatenated Coding Scheme for MIMO Systems
Abstract: Inthis paper, two hybrid concatenated super-orthogonal space-time trellis codes(SOSTTC) applying iterative decoding are proposed for flat fading channels. Theencoding operation is based on the concatenation of convolutional codes,interleaving and super-orthogonal space-time trellis codes. The firstconcatenated scheme consists of a serial concatenation of a parallelconcatenated convolutional code with a SOSTTC while the second consists ofparallel concatenation of two serially concatenated convolutional and SOSTTCcodes. The decoding of these two schemes is described, their pairwise errorprobabilities are derived and the frame error rate (FER) performances areevaluated by computer simulation in Rayleigh fading channels. The proposedtopologies are shown to perform better than existing concatenated schemes with aconstituent code of convolutional andspace-time codes in literature
Concatenated codes for the multiple-input multiple-output quasi-static fading channel
The use of multiple antennas at the transmitter and/or the receiver promises
greatly increased capacity. This can be useful to meet the ever growing demand
of wireless connectivity, provided we can find techniques to efficiently exploit the
advantages of the Multiple-Input Multiple-Output (MIMO) system.
This work explores the MIMO system in a flat quasi-static fading scenario. Such
a channel occurs, for example, in packet data systems, where the channel fade is constant
for the duration of a codeword and changes independently from one transmission
to another. We first show why it is hard to compute the true constrained modulation
outage capacity. As an alternative, we present achievable lower bounds to this capacity
based on existing space-time codes. The bounds we compute are the fundamental
limits to the performance of these space-time codes under maximum-likelihood decoding,
optimal outer codes and asymptotically long lengths. These bounds also indicate
that MIMO systems have different behavior under Gaussian signaling (unconstrained
input) and under the finite alphabet setting. Our results naturally suggest the use of
concatenated codes to approach near-capacity performance. However, we show that a
system utilizing an iterative decoder has a fundamental limit it cannot be universal
and therefore it cannot perform arbitrarily close to its outage limit.
Next, we propose two different transceiver structures that have good performance.
The first structure is based on a novel BCJR-decision feedback decoder which
results in performance within a dB of the outage limit. The second structure is based
on recursive realizations of space-time trellis codes and uses iterative decoding at the
receiver. This recursive structure has impressive performance even when the channel
has time diversity. Thus, it forms the basis of a very flexible and robust MIMO
transceiver structure
Super-orthogonal space-time turbo coded OFDM systems.
Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2012.The ever increasing demand for fast and efficient broadband wireless communication
services requires future broadband communication systems to provide a high data rate,
robust performance and low complexity within the limited available electromagnetic
spectrum. One of the identified, most-promising techniques to support high
performance and high data rate communication for future wireless broadband services
is the deployment of multi-input multi-output (MIMO) antenna systems with
orthogonal frequency division multiplexing (OFDM). The combination of MIMO and
OFDM techniques guarantees a much more reliable and robust transmission over a
hostile wireless channel through coding over the space, time and frequency domains.
In this thesis, two full-rate space-time coded OFDM systems are proposed. The first
one, designed for two transmit antennas, is called extended super-orthogonal space-time
trellis coded OFDM (ESOSTTC-OFDM), and is based on constellation rotation. The
second one, called super-quasi-orthogonal space-time trellis coded OFDM (SQOSTTCOFDM),
combines a quasi-orthogonal space-time block code with a trellis code to
provide a full-rate code for four transmit antennas. The designed space-time coded
MIMO-OFDM systems achieve a high diversity order with high coding gain by
exploiting the diversity advantage of frequency-selective fading channels.
Concatenated codes have been shown to be an effective technique of achieving reliable
communication close to the Shannon limit, provided that there is sufficient available
diversity. In a bid to improve the performance of the super orthogonal space-time
trellis code (SOSTTC) in frequency selective fading channels, five distinct
concatenated codes are proposed for MIMO-OFDM over frequency-selective fading
channels in the second part of this thesis. Four of the coding schemes are based on the
concatenation of convolutional coding, interleaving, and space-time coding, along
multiple-transmitter diversity systems, while the fifth coding scheme is based on the
concatenation of two space-time codes and interleaving. The proposed concatenated
Super-Orthogonal Space-Time Turbo-Coded OFDM System I. B. Oluwafemi 2012 vii
coding schemes in MIMO-OFDM systems achieve high diversity gain by exploiting
available diversity resources of frequency-selective fading channels and achieve a high
coding gain through concatenations by employing the turbo principle. Using computer
software simulations, the performance of the concatenated SOSTTC-OFDM schemes is
compared with those of concatenated space-time trellis codes and those of conventional
SOSTTC-OFDM schemes in frequency-selective fading channels. Simulation results
show that the concatenated SOSTTC-OFDM system outperformed the concatenated
space-time trellis codes and the conventional SOSTTC-OFDM system under the
various channel scenarios in terms of both diversity order and coding gain