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Spatial data stream multiplexing scheme for high-throughput WLANs
A novel scheme using spatial data stream multiplexing (SDSM) in the upcoming multiple-input multipleoutput (MIMO)-based IEEE 802.11n physical layer is proposed. It is shown that with SDSM, the same data rate can be achieved by using less number of transmit and receive antennas and therefore this scheme can reduce the number of antennas which results in reducing mutual coupling effects, hardware costs and implementation complexities. The maximum data rates that can be achieved using a 2 * 2 MIMO system is 270 Mbps and for a 4 * 4 MIMO system is 540 Mbps. The same data rates can be achieved using the SDSM technique which reduces the 2 * 2 MIMO system to 1 * 1 SISO system and the 4 * 4 MIMO system to a 2 * 2 MIMO system
A Novel Construction of Multi-group Decodable Space-Time Block Codes
Complex Orthogonal Design (COD) codes are known to have the lowest detection
complexity among Space-Time Block Codes (STBCs). However, the rate of square
COD codes decreases exponentially with the number of transmit antennas. The
Quasi-Orthogonal Design (QOD) codes emerged to provide a compromise between
rate and complexity as they offer higher rates compared to COD codes at the
expense of an increase of decoding complexity through partially relaxing the
orthogonality conditions. The QOD codes were then generalized with the so
called g-symbol and g-group decodable STBCs where the number of orthogonal
groups of symbols is no longer restricted to two as in the QOD case. However,
the adopted approach for the construction of such codes is based on sufficient
but not necessary conditions which may limit the achievable rates for any
number of orthogonal groups. In this paper, we limit ourselves to the case of
Unitary Weight (UW)-g-group decodable STBCs for 2^a transmit antennas where the
weight matrices are required to be single thread matrices with non-zero entries
in {1,-1,j,-j} and address the problem of finding the highest achievable rate
for any number of orthogonal groups. This special type of weight matrices
guarantees full symbol-wise diversity and subsumes a wide range of existing
codes in the literature. We show that in this case an exhaustive search can be
applied to find the maximum achievable rates for UW-g-group decodable STBCs
with g>1. For this purpose, we extend our previously proposed approach for
constructing UW-2-group decodable STBCs based on necessary and sufficient
conditions to the case of UW-g-group decodable STBCs in a recursive manner.Comment: 12 pages, and 5 tables, accepted for publication in IEEE transactions
on communication
Modulation Diversity for Spatial Modulation Using Complex Interleaved Orthogonal Design
In this paper, we propose modulation diversity techniques for Spatial
Modulation (SM) system using Complex Interleaved Orthogonal Design (CIOD) meant
for two transmit antennas. Specifically, we show that by using the CIOD for two
transmit antenna system, the standard SM scheme, where only one transmit
antenna is activated in any symbol duration, can achieve a transmit diversity
order of two. We show with our simulation results that the proposed schemes
offer transmit diversity order of two, and hence, give a better Symbol Error
Rate performance than the SM scheme with transmit diversity order of one.Comment: 7 page
On the MIMO Channel Capacity of Multi-Dimensional Signal Sets
In this contribution we evaluate the capacity of Multi-Input Multi-Output (MIMO) systems using multi-dimensional PSK/QAM signal sets. It was shown that transmit diversity is capable of narrowing the gap between the capacity of the Rayleigh-fading channel and the AWGN channel. However, since this gap becomes narrower when the receiver diversity order is increased, for higher-order receiver diversity the performance advantage of transmit diversity diminishes. A MIMO system having full multiplexing gain has a higher achievable throughput than the corresponding MIMO system designed for full diversity gain, although this is attained at the cost of a higher complexity and a higher SNR. The tradeoffs between diversity gain, multiplexing gain, complexity and bandwidth are studied
A Low-Complexity, Full-Rate, Full-Diversity 2 X 2 STBC with Golden Code's Coding Gain
This paper presents a low-ML-decoding-complexity, full-rate, full-diversity
space-time block code (STBC) for a 2 transmit antenna, 2 receive antenna
multiple-input multiple-output (MIMO) system, with coding gain equal to that of
the best and well known Golden code for any QAM constellation. Recently, two
codes have been proposed (by Paredes, Gershman and Alkhansari and by Sezginer
and Sari), which enjoy a lower decoding complexity relative to the Golden code,
but have lesser coding gain. The STBC presented in this paper has
lesser decoding complexity for non-square QAM constellations, compared with
that of the Golden code, while having the same decoding complexity for square
QAM constellations. Compared with the Paredes-Gershman-Alkhansari and
Sezginer-Sari codes, the proposed code has the same decoding complexity for
non-rectangular QAM constellations. Simulation results, which compare the
codeword error rate (CER) performance, are presented.Comment: Submitted to IEEE Globecom - 2008. 6 pages, 3 figures, 1 tabl
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