scholarly journals Interference Cancellation Using Replica Signal for HTRCI-MIMO/OFDM in Time-Variant Large Delay Spread Longer Than Guard Interval

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Yuta Ida ◽  
Chang-Jun Ahn ◽  
Takeshi Kamio ◽  
Hisato Fujisaka ◽  
Kazuhisa Haeiwa
Keyword(s):  
Interference Cancellation ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
Delay Spread ◽  
High Time Resolution ◽  
Large Delay ◽  
Guard Interval ◽  
Maximum Delay ◽  
Mimo Ofdm

Orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) are generally known as the effective techniques for high data rate services. In MIMO/OFDM systems, the channel estimation (CE) is very important to obtain an accurate channel state information (CSI). However, since the orthogonal pilot-based CE requires the large number of pilot symbols, the total transmission rate is degraded. To mitigate this problem, a high time resolution carrier interferometry (HTRCI) for MIMO/OFDM has been proposed. In wireless communication systems, if the maximum delay spread is longer than the guard interval (GI), the system performance is significantly degraded due to the intersymbol interference (ISI) and intercarrier interference (ICI). However, the conventional HTRCI-MIMO/OFDM does not consider the case with the time-variant large delay spread longer than the GI. In this paper, we propose the ISI and ICI compensation methods for a HTRCI-MIMO/OFDM in the time-variant large delay spread longer than the GI.

scholarly journals Optimization for Interference Cancellation in MIMO-OFDM System using Modified Bat Algorithm (MBA)

2019 ◽  
Vol 8 (4) ◽  
pp. 24-31
Keyword(s):  
Interference Cancellation ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Bat Algorithm ◽  
Ofdm Systems ◽  
Broadband Wireless ◽  
Multiple Input ◽  
Mimo Ofdm ◽  
Signal Channel ◽  
Modified Bat Algorithm

The intervention has to be negated deprived of humiliation of the spectral effectiveness In broadband wireless communication systems. The intrusive overthrow of the parallel OFDM systems are called as MIMO-OFDM (Multiple Input Output Orthogonal Frequency Division Multiplexing) is brought together in our projected effort. The representation of AWGN within the signal channel and improved by the value of MSE minimum factor is chosen. Thus, the optimization is prepared for the operation of the MBA (Modified Bat Algorithm). Our proposed concepts with its results are evaluated in the platform of MATLAB.

scholarly journals Improved Efficiency of Data Transmission in Wireless Communication Systems with Orthogonal Frequency Multiplexing

2021 ◽  
pp. 15-18
Author(s):  
Olga Safonova ◽  
◽  
Elena Arepyeva ◽  
Nadezhda Ermakova ◽  
◽  
...  
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
Signal To Noise Ratio ◽  
Radio Channel ◽  
Radio Communication ◽  
Software Model ◽  
Radio Broadcasting ◽  
Mimo Ofdm ◽  
Frequency Multiplexing

The active introduction of Orthogonal Frequency Division Multiplexing (OFDM) technology is now beginning to be widely used in wireless transmission systems, television, radio communication, and radio broadcasting. The efficiency of using a dedicated frequency band at a constant high transmission rate allows you to combat interference arising from the transmission of a useful information on the radio channel. A method of improving quality of information transmission in communication systems with orthogonal frequency multiplexing is described. It is shown that with an increase in the number of receiving and transmitting antennas, the noise immunity increases significantly. An experiment was carried out to change the number of receiving-transmitting antennas and the signal-to-noise ratio, and the dependence of the appearance of an error on the number of transmitting antennas was obtained. The work investigated the software model of MIMO OFDM (modulators and demodulators). As a result of the analysis, the dependence of the appearance of the error frequency on the probability of the error was obtained. This showed that the use of OFDM and MIMO places increased demands on channel estimation.

Time Domain Replica Signal Based Interference Compensation for SP-MIMO/OFDM with Large Delay Spread Channel

2014 ◽  
Vol 5 (4) ◽  
pp. 1-17
Author(s):  
Taichi Sakaue ◽  
Chang-Jun Ahn ◽  
Tatsuya Omori ◽  
Ken-Ya Hashimoto
Keyword(s):  
Mobile Communications ◽  
Time Domain ◽  
Delay Spread ◽  
Impulse Responses ◽  
Channel State ◽  
Large Delay ◽  
Guard Interval ◽  
Interference Compensation ◽  
Mimo Ofdm ◽  
The Time Domain

In mobile communications, MIMO-OFDM transmission performance suffers severe degradation caused by the large delay spread channel greater than guard interval (GI). This is because the excess delay results in considerable inter-symbol interference (ISI) between adjacent symbols and inter-carrier-interference (ICI) among subcarrier in the same symbol. In case of scattered pilot (SP), the interference of pilot signals causes the deterioration of channel estimation. To mitigate this problem, in this paper, we propose the interference compensation scheme using the time domain replica signals. We make the time domain replica signals from detected signals and the excess channel impulse responses over GI. After compensation of the time domain replica signals and the received signals, we recalculate the channel state information (CSI) and the CSI is updated. Finally, we carry out the channel compensation with updated CSI for obtaining accurate compensated signals.

scholarly journals Iterative Interference Cancellation for Multi-Carrier Modulation in MIMO-DWT Downlink Transmission

2021 ◽  
Vol 9 (4) ◽  
pp. 75-87
Author(s):  
Yahya Harbi ◽  
ALI AL-JANABI ◽  
Hayder Almusa ◽  
Marwa Chafii ◽  
Alister Burr
Keyword(s):  
Interference Cancellation ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Minimum Mean Square Error ◽  
Multiple Input Multiple Output ◽  
Multipath Channel ◽  
Discrete Wavelet ◽  
Ldpc Decoder ◽  
Mimo Ofdm ◽  
Iterative Interference Cancellation

The Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) scheme represents the dominant radio interface for broadband multicarrier communication systems. However, with insufficient Cyclic Prefixes (CP), Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) occur due to the time-varying multipath channel. This means that the performance of the system will be degraded. In this paper, we investigate the interference problem for a MIMO Discrete Wavelet Transform (MIMO-DWT) system under the effect of the downlink LTE channel. A Low-Density Parity-Check (LDPC) decoder is used to estimate the decoded signal. The proposed iterative algorithm uses the estimated decoded signal to compute the components required for ICI/ISI interference reduction. In this paper, Iterative Interference Cancellation (IIC) is employed to mitigate the effects of interference that contaminates the received signal due to multiple antenna transmission and a multipath channel. An equalizer with minimum mean square error is considered. We compare the performance of our proposed algorithm with the traditional MIMO-OFDM scheme in terms of bit error probability under insufficient CP. Simulation results verify that significant improvements are achieved by using IIC and MIMO-IIC for both systems.

scholarly journals Covert Communication in MIMO-OFDM System Using Pseudo Random Location of Fake Subcarriers

2016 ◽  
Vol 4 (1) ◽  
pp. 150-163 ◽  
Author(s):  
Rizky Pratama Hudhajanto ◽  
I Gede Puja Astawa ◽  
Amang Sudarsono
Keyword(s):  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Random Sequence ◽  
Multiple Input Multiple Output ◽  
Ofdm System ◽  
Transmission Scheme ◽  
Sensitive Data ◽  
Input Multiple Output ◽  
Mimo Ofdm ◽  
Random Location

Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) is the most used wireless transmission scheme in the world. However, its security is the interesting problem to discuss if we want to use this scheme to transmit a sensitive data, such as in the military and commercial communication systems. In this paper, we propose a new method to increase the security of MIMO-OFDM system using the change of location of fake subcarrier. The fake subcarriers’ location is generated per packet of data using Pseudo Random sequence generator. The simulation results show that the proposed scheme does not decrease the performance of conventional MIMO-OFDM. The attacker or eavesdropper gets worse Bit Error Rate (BER) than the legal receiver compared to the conventional MIMO-OFDM system.

scholarly journals A Comprehensive Review on Channel Estimation in OFDM System

2019 ◽  
Vol 5 (3) ◽  
pp. 6 ◽  
Author(s):  
Neha Dubey ◽  
Ankit Pandit
Keyword(s):  
Channel Estimation ◽  
Mean Square Error ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
Minimum Mean Square Error ◽  
Estimation Method ◽  
Least Square ◽  
Estimation Methods ◽  
Mean Square ◽  
Mimo Ofdm

In wireless communication, orthogonal frequency division multiplexing (OFDM) plays a major role because of its high transmission rate. Channel estimation and tracking have many different techniques available in OFDM systems. Among them, the most important techniques are least square (LS) and minimum mean square error (MMSE). In least square channel estimation method, the process is simple but the major drawback is it has very high mean square error. Whereas, the performance of MMSE is superior to LS in low SNR, its main problem is it has high computational complexity. If the error is reduced to a very low value, then an exact signal will be received. In this paper an extensive review on different channel estimation methods used in MIMO-OFDM like pilot based, least square (LS) and minimum mean square error method (MMSE) and least minimum mean square error (LMMSE) methods and also other channel estimation methods used in MIMO-OFDM are discussed.

scholarly journals Multipath Pipelined Polyphase Structures for FIR Interpolation and Decimation in MIMO OFDM Systems

2011 ◽  
Vol 2011 ◽  
pp. 1-4 ◽  
Author(s):  
Zhen-dong Zhang ◽  
Bin Wu ◽  
Yu-mei Zhou
Keyword(s):  
Data Streams ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Finite Impulse Response ◽  
Multiple Input Multiple Output ◽  
Ofdm Systems ◽  
Silicon Area ◽  
Multiple Data ◽  
Mimo Ofdm ◽  
Multiple Data Streams

The combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency-division multiplexing (OFDM) technique is one favored solution in wireless communication systems for enhancing data rate. However, the computational complexity is also linear increased with the number of data streams. Generally, multiple finite impulse response (FIR) interpolations and decimations are added to solve the multiple data streams in a MIMO OFDM system, which cause a large increase in the hardware cost. In this paper, two multipath pipelined polyphase structures for FIR interpolation and decimation to efficiently deal with the simultaneous multiple data streams are proposed. According to the proposed structures, M simultaneous data streams can be supported in the M-component polyphase interpolation or decimation with only one set of computation units. Implementation examples show that up to 56% reduction of silicon area can be obtained over the traditional polyphase structures.

scholarly journals Precoding Aided Data Correlation Scheme for Channel Estimation Technique in MIMO-OFDM System

2021 ◽  
Vol 16 ◽  
pp. 146-154
Author(s):  
Sidramayya S. Matad ◽  
Ramesha K.
Keyword(s):  
Channel Estimation ◽  
Mean Square Error ◽  
Orthogonal Frequency Division Multiplexing ◽  
Transmission Rate ◽  
Multiple Input Multiple Output ◽  
Blind Channel Estimation ◽  
Mean Square ◽  
Estimation Technique ◽  
Blind Channel ◽  
Mimo Ofdm

Channel estimation is considered as an important phase in Multiple Input Multiple Output – Orthogonal Frequency Division Multiplexing (MIMO-OFDM) networks which can enhances the performance significantly. Channel estimation widely classified as pilot based, blind and semi-blind channel estimation. The pilot-based channel estimation decreases the data transmission rate and spectral efficiency. To overcome these issues of existing schemes, we present a novel blind channel estimation technique. According to proposed scheme, we transmit the data in a block-wise manner. The proposed scheme uses precoding technique to establish the correlation between these blocks. Further, we use channel correlation to solve the diagonal uncertainty of correlation matrix which helps to improve the system performance. We present a comparative analysis study which shows that proposed approach can achieve better performance in terms of Normalized Mean Square Error (NMSE) and Mean Square Error (MSE) when compared with existing techniques.

scholarly journals Algorithm for Evaluating Energy Detection Spectrum Sensing Performance of Cognitive Radio MIMO-OFDM Systems

Sensors ◽  
2021 ◽  
Vol 21 (20) ◽  
pp. 6881
Author(s):  
Josip Lorincz ◽  
Ivana Ramljak ◽  
Dinko Begusic
Keyword(s):  
Cognitive Radio ◽  
Spectrum Sensing ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Detection Threshold ◽  
Operating Parameter ◽  
Energy Detection ◽  
Operating Parameters ◽  
Ofdm Systems ◽  
Mimo Ofdm

Cognitive radio technology enables spectrum sensing (SS), which allows the secondary user (SU) to access vacant frequency bands in the periods when the primary user (PU) is not active. Due to its minute implementation complexity, the SS approach based on energy detection (ED) of the PU signal has been analyzed in this paper. Analyses were performed for detecting PU signals by the SU in communication systems exploiting multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) transmission technology. To perform the analyses, a new algorithm for simulating the ED process based on a square-law combining (SLC) technique was developed. The main contribution of the proposed algorithm is enabling comprehensive simulation analyses of ED performance based on the SLC method for versatile combinations of operating parameter characteristics for different working environments of MIMO-OFDM systems. The influence of a false alarm on the detection probability of PU signals impacted by operating parameters such as the signal-to-noise ratios, the number of samples, the PU transmit powers, the modulation types and the number of the PU transmit and SU receive branches of the MIMO-OFDM systems have been analyzed in the paper. Simulation analyses are performed by running the proposed algorithm, which enables precise selection of and variation in the operating parameters, the level of noise uncertainty and the detection threshold in different simulation scenarios. The presented analysis of the obtained simulation results indicates how the considered operating parameters impact the ED efficiency of symmetric and asymmetric MIMO-OFDM systems.

Modelling and Simulation of IDMA-OFDM for Underwater Acoustic Communication

2015 ◽  
Vol 65 (4) ◽  
pp. 307 ◽  
Author(s):  
Sangram More ◽  
K. Krishna Naik
Keyword(s):  
Time Delay ◽  
Acoustic Signal ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal Transmission ◽  
Simulated Data ◽  
Delay Spread ◽  
Underwater Acoustic Communication ◽  
Long Time ◽  
Multi Access

<p>The Ocean exhibits phenomenon of changing acoustic signal transmission due to its non-stationary nature. Water columns in between transmitter and receiver are not fixed at any point of time. Thus, designing of a wireless communication systems for underwater applications becomes significantly challenging. The speed of sound in water is 1500 m/s which introduces large delay spread in acoustic signal due to multipath phenomenon. The large time delay causes Inter-symbol Interference; this ISI degrades the performance of many receivers. However orthogonal frequency division multiplexing is multi-tone modulation reduces long time delay spreads of acoustic channels. The interleave division multiple access distinguishes each user with the unique random interleaver code. The IDMA-OFDM is superior design for reducing error bursts in multi-access underwater applications. A Simulink based simulation modell of IDMA-OFDM system has been discussed in this paper. Satisfactory performance of the implementation was observed through analysis of BER with respect to SNR. The results have been concluded by comparing simulated data in BER tool of Simulink.</p><p><strong>Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 307-311, DOI: http://dx.doi.org/10.14429/dsj.65.8606</strong></p>

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