71 research outputs found
High-Rate Space Coding for Reconfigurable 2x2 Millimeter-Wave MIMO Systems
Millimeter-wave links are of a line-of-sight nature. Hence, multiple-input
multiple-output (MIMO) systems operating in the millimeter-wave band may not
achieve full spatial diversity or multiplexing. In this paper, we utilize
reconfigurable antennas and the high antenna directivity in the millimeter-wave
band to propose a rate-two space coding design for 2x2 MIMO systems. The
proposed scheme can be decoded with a low complexity maximum-likelihood
detector at the receiver and yet it can enhance the bit-error-rate performance
of millimeter-wave systems compared to traditional spatial multiplexing
schemes, such as the Vertical Bell Laboratories Layered Space-Time Architecture
(VBLAST). Using numerical simulations, we demonstrate the efficiency of the
proposed code and show its superiority compared to existing rate-two space-time
block codes
Comparison of code rate and transmit diversity in MIMO systems
A thesis submitted in ful lment of the requirements
for the degree of Master of Science in the Centre of Excellence in Telecommunications and Software School of Electrical and Information Engineering, March 2016In order to compare low rate error correcting codes to MIMO schemes with transmit
diversity, two systems with the same throughput are compared. A VBLAST MIMO
system with (15; 5) Reed-Solomon coding is compared to an Alamouti MIMO system
with (15; 10) Reed-Solomon coding. The latter is found to perform signi cantly better,
indicating that transmit diversity is a more e ective technique for minimising errors than
reducing the code rate. The Guruswami-Sudan/Koetter-Vardy soft decision decoding
algorithm was implemented to allow decoding beyond the conventional error correcting
bound of RS codes and VBLAST was adapted to provide reliability information.
Analysis is also performed to nd the optimal code rate when using various MIMO
systems.MT201
Improved Spatial Modulation for High Spectral Efficiency
Spatial Modulation (SM) is a technique that can enhance the capacity of MIMO
schemes by exploiting the index of transmit antenna to convey information bits.
In this paper, we describe this technique, and present a new MIMO transmission
scheme that combines SM and spatial multiplexing. In the basic form of SM, only
one out of MT available antennas is selected for transmission in any given
symbol interval. We propose to use more than one antenna to transmit several
symbols simultaneously. This would increase the spectral efficiency. At the
receiver, an optimal detector is employed to jointly estimate the transmitted
symbols as well as the index of the active transmit antennas. In this paper we
evaluate the performance of this scheme in an uncorrelated Rayleigh fading
channel. The simulations results show that the proposed scheme outperforms the
optimal SM and V-BLAST (Vertical Bell Laboratories Layered space-time at high
signal-to-noise ratio (SNR). For example, if we seek a spectral efficiency of 8
bits/s/Hz at bit error rate (BER) of 10^-5, the proposed scheme provides 5dB
and 7dB improvements over SM and V-BLAST, respectively.Comment: 7 pages, 4 figures, 1 table, International Journal of Distributed and
Parallel Systems (IJDPS) Vol.3, No.2, March 201
A Family of Hybrid Space-Time Codes for MIMO Wireless Communications
Hybrid MIMO space-time codes combine the benefits of spatial multiplexing with diversity gain to achieve both high spectral efficiency and link reliability. In this paper, we present a family of hybrid codes, known as LD STBC-VBLAST codes, along with a receiver architecture suitable for low-complexity hardware implementation. We show that, under Rayleigh fading, the performance of LD STBC-VBLAST codes is superior to other recently proposed hybrid codes. We also present a technique to derive, from a given propagation scenario, spatially correlated MIMO channel models adequate for space-time coding performance analysis. Using this technique, we evaluate the performance of LD STBC-VBLAST codes under several correlated channels.ITESO, A.C.ITSONCINVESTAV-IPNPROME
High-Rate and Low-Complexity Space-Time Block Codes for 2x2 MIMO Systems
The main design criteria for space-time block codes (STBCs) are the code rate, diversity order, coding gain, and low decoder complexity. In this letter, we propose a full-rate full-diversity STBC for 2 Ă— 2 multiple-input multiple-output (MIMO) systems with a substantially lower maximum likelihood (ML) detection complexity than that of existing schemes. This makes the implementation of high-performance full-rate codes feasible for practical systems. Our numerical evaluation shows that the proposed code achieves significantly lower decoding complexity while maintaining a similar performance compared to that of existing rate-2 STBCs
Performance Enhancement in SU and MU MIMO-OFDM Technique for Wireless Communication: A Review
The consistent demand for higher data rates and need to send giant volumes of data while not compromising the quality of communication has led the development of a new generations of wireless systems. But range and data rate limitations are there in wireless devices. In an attempt to beat these limitations, Multi Input Multi Output (MIMO) systems will be used which also increase diversity and improve the bit error rate (BER) performance of wireless systems. They additionally increase the channel capacity, increase the transmitted data rate through spatial multiplexing, and/or reduce interference from other users. MIMO systems therefore create a promising communication system because of their high transmission rates without additional bandwidth or transmit power and robustness against multipath fading. This paper provides the overview of Multiuser MIMO system. A detailed review on how to increase performance of system and reduce the bit error rate (BER) in different fading environment e.g. Rayleigh fading, Rician fading, Nakagami fading, composite fading
Robust concatenated codes for the slow Rayleigh fading channel
In this thesis, we design a robust concatenated code for the Multiple-Input
Multiple-Output (MIMO) system in the presence of slow Rayleigh fading with no
channel side information at the transmitter (no CSIT) and perfect channel side
information at the receiver (perfect CSIR). Since we are interested in the slow fading
channel, outage capacity is used as the measure of performance. Good space-time codes
can be designed so as to maximize the so-called rank and the determinant criteria.
However, a practical system will concatenate a space-time code with an outer code at the
transmitter and perform iterative decoding at the receiver. It is necessary to design the
space-time code together with the outer code in practice. We will call this kind of code a
concatenated space-time code.
At the transmitter, we will consider the bit-to-symbol mapping and space-time
code together as a space-time modulator and thus, Bit Interleaved Coded Modulation
(BICM) and Multilevel coding (ML) can be applied to design outer codes for the nonbinary
constellation. However, the concatenated space-time codes designed by these two
methods can only be decoded with arbitrarily small error probability for a fixed channel
realization and such designs are not robust over the ensemble of fading channels.
Our approach of designing concatenated space-time code is to design an outer
code for a space-time modulator such that the concatenated space-time code can be
decoded with arbitrarily small error probability in a set of fixed channels which have the
same capacity. Through this approach, we discovered a new design criterion for spacetime
codes: a good space-time code should stabilize its Extrinsic Information Transfer
(EXIT) charts. In other words, the robustness of a space-time code in the slow fading
channel and its performance in iterative decoding can be visualized by the EXIT charts. The rank and the determinant criterion do not evaluate the performance of a space-time
code in iterative decoding, but the new criterion does. Therefore, the new criterion is
applicable to design concatenated space-time codes.
Applying our approach and new criterion, a rate 7.2 bits/s/Hz concatenated
space-time code is designed. The performance is close to the outage capacity, and the
rate lost is 0.2 bits/s/Hz
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