370 research outputs found
On OSTBC Codes for LTE-A Systems-Design and Performance Evaluation
Long Term Evolution-Advanced (LTE-A) is a Fourth Generation (4G) standard of wireless communications that introduces high data rate, high performance, and low delay. These features of LTE-A resulted from the new techniques developed for wireless communications such as Multiple-Input Multiple-Output (MIMO) technique. At the heart of this technique is the Space Time Codes, which were developed by the researchers in recent decades to achieve the mentioned features. The designs of OSTBC codes for MIMO systems having any number of transmit antennas and any number of receive antennas have attracted the attention of many researchers. Based on the theory of real and complex orthogonal designs, this paper deals with the design of real and complex OSTBC codes to be used with real signal set constellation such PAM and complex signal constellation such as PSK and QAM. Real and complex OSTBC codes for MIMO systems with two, three, four, five, six, seven and eight transmit antennas and any number of receive antennas, are presented. Simple linear processing ML decoders are derived and presented. The used channel is Rayleigh fading channel MIMO and assumed to behave in a “quasi-static” fashion. Finally, the performances of OSTBC schemes were evaluated and compared in terms of the Bit Error Rate (BER) and Signal to Noise Ratio (SNR). The environment of simulation is MATLAB which is a powerful tool for mathematical calculation and system simulation. The methods of modulations chosen are QPSK, 16QAM, 64QAM, and 128QAM with gray scale mapping
LDPC concatenated space-time block coded system in multipath fading environment: Analysis and evaluation
Irregular low-density parity-check (LDPC) codes have been found to show exceptionally good performance for single antenna systems over a wide class of channels. In this paper, the performance of LDPC codes with multiple antenna systems is investigated in flat Rayleigh and Rician fading channels for different modulation schemes. The focus of attention is mainly on the concatenation of irregular LDPC codes with complex orthogonal space-time codes. Iterative decoding is carried out with a density evolution method that sets a threshold above which the code performs well. For the proposed concatenated system, the simulation results show that the QAM technique achieves a higher coding gain of 8.8 dB and 3.2 dB over the QPSK technique in Rician (LOS) and Rayleigh (NLOS) faded environments respectively
Building Space Time Block Codes with set partitioning for three transmit antennas: application to STTC Codes
Publication in the conference proceedings of EUSIPCO, Florence, Italy, 200
Space-time coding techniques with bit-interleaved coded modulations for MIMO block-fading channels
The space-time bit-interleaved coded modulation (ST-BICM) is an efficient
technique to obtain high diversity and coding gain on a block-fading MIMO
channel. Its maximum-likelihood (ML) performance is computed under ideal
interleaving conditions, which enables a global optimization taking into
account channel coding. Thanks to a diversity upperbound derived from the
Singleton bound, an appropriate choice of the time dimension of the space-time
coding is possible, which maximizes diversity while minimizing complexity.
Based on the analysis, an optimized interleaver and a set of linear precoders,
called dispersive nucleo algebraic (DNA) precoders are proposed. The proposed
precoders have good performance with respect to the state of the art and exist
for any number of transmit antennas and any time dimension. With turbo codes,
they exhibit a frame error rate which does not increase with frame length.Comment: Submitted to IEEE Trans. on Information Theory, Submission: January
2006 - First review: June 200
Performance Analysis Of Amplify And Forward Based Cooperative Diversity with Multiple Transmit Antennas
In todays world,wireless communication has a tremendous impact on the human
civilization.There has been a sea changes in modern day living and the
credit goes to the development in Wireless communication technology.But
Wireless communication is highly challenging due to complex,time varying
propagation medium which causes multi path fading,co-channel interferences,
cross talk,etc..,Diversity techniques are widely used in wireless communication
to mitigate these effects
Recommended from our members
Space time coding in MIMO systems
Multiple-input multiple-output (MIMO) antenna technology is promising
for high-speed wireless communications without increasing the transmission band-
width. Space time coding (STC) is a scheme that employs multiple antennas to
increase transmission rate or to improve transmission quality. STC is used widely
in mobile cellular networks, wireless local area networks (WLAN) and wireless
metropolitan area networks (WMAN). However, there are still many unsolved or
partially solved issues in STC. In this thesis, I propose a new STC design from
cyclic design. I then propose a systematic method to design quasi-orthogonal
space time block codes (QOSTBC) for an arbitrary number of transmit antennas,
and derive the optimal constellation rotation angles to achieve full diversity. I also propose an analytical method to derive the exact error probabilities of orthogonal space time block codes (OSTBC). In order to improve the error performance, I
introduce an adaptive power allocation scheme for OSTBC. Combining STC with
continuous phase modulation (CPM) is an attractive solution for mobile commu-
nications for which power is limited. Thus, I apply OSTBC to binary CPM with
modulation index h = 0.5, and develop a simplified receiver for such scheme. Finally, I present a decoding method to reduce the complexity of QOSTBC without
degrading its error performance
Reducing Multiple Access Interference in Broadband Multi-User Wireless Networks
This dissertation is devoted to developing multiple access interference (MAI) reduction techniques for multi-carrier multi-user wireless communication networks.
In multi-carrier code division multiple access (MC-CDMA) systems, a full multipath diversity can be achieved by transmitting one symbol over multiple orthogonal subcarriers by means of spreading codes. However, in frequency selective fading channels, orthogonality among users can be destroyed leading to MAI. MAI represents the main obstacle to support large number of users in multi-user wireless systems. Consequently, MAI reduction becomes a main challenge when designing multi-carrier multi-user wireless networks. In this dissertation, first, we study MC-CDMA systems with different existing MAI reduction techniques. The performance of the studied systems can be further improved by using a fractionally spaced receivers instead of using symbol spaced receivers. A fractionally spaced receiver is obtained by oversampling received signals in a time domain. Second, a novel circular-shift division multiple access (CSDMA) scheme for multi-carrier multi-user wireless systems is developed. In CSDMA, each symbol is first spread onto multiple orthogonal subcarriers in the frequency domain through repetition codes. The obtained frequency-domain signals are then converted to a time-domain representation. The time-domain signals of different users are then circularly shifted by different numbers of locations.
The time-domain circular shifting enables the receiver to extract signals from different users with zero or a small amount of MAI. Our results show that the CSDMA scheme can achieve a full multipath diversity with a performance outperforms that of orthogonal frequency division multiple access (OFDMA). Moreover, multipath diversity of CSDMA can be further improved by employing the time-domain oversampling. Performance fluctuations due to a timing offset between transmitter and receiver clocks in MC-CDMA and CSDMA systems can be removed by employing the time-domain oversampling. Third, we study the theoretical error performance of high mobility single-user wireless communication system with doubly selective (time-varying and frequency-selective) fading channel under impacts of imperfect channel state information (CSI). Throughout this dissertation, intensive computer simulations are performed under various system configurations to investigate the obtained theoretical results, excellent agreements between simulation and theoretical results were observed in this dissertation
Separable Implementation of L2-Orthogonal STC CPM with Fast Decoding
In this paper we present an alternative separable implementation of
L2-orthogonal space-time codes (STC) for continuous phase modulation (CPM). In
this approach, we split the STC CPM transmitter into a single conventional CPM
modulator and a correction filter bank. While the CPM modulator is common to
all transmit antennas, the correction filter bank applies different correction
units to each antenna. Thereby desirable code properties as orthogonality and
full diversity are achievable with just a slightly larger bandwidth demand.
This new representation has three main advantages. First, it allows to easily
generalize the orthogonality condition to any arbitrary number of transmit
antennas. Second, for a quite general set of correction functions that we
detail, it can be proved that full diversity is achieved. Third, by separating
the modulation and correction steps inside the receiver, a simpler receiver can
be designed as a bank of data independent inverse correction filters followed
by a single CPM demodulator. Therefore, in this implementation, only one
correlation filter bank for the detection of all transmitted signals is
necessary. The decoding effort grows only linearly with the number of transmit
antennas
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