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.

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 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 Anti-Wiretap Spectrum-Sharing for Cooperative Cognitive Radio Communication Systems

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4142
Author(s):  
Peiyuan Si ◽  
Weidang Lu ◽  
Kecai Gu ◽  
Xin Liu ◽  
Bo Li ◽  
...  
Keyword(s):  
Cognitive Radio ◽  
Wireless Communication ◽  
Cooperative Communication ◽  
Communication Systems ◽  
Spectrum Sharing ◽  
Transmission Rate ◽  
Primary System ◽  
Radio Communication ◽  
Sharing Scheme ◽  
Simulation Results

As wireless communication technology keeps progressing, people’s requirements for wireless communication quality are getting higher and higher. Wireless communication brings convenience, but also causes some problems. On the one hand, the traditional static and fixed spectrum allocation strategy leads to high wastefulness of spectrum resources. The direction of improving the utility of spectrum resources by combining the advantages of cooperative communication and cognitive radio has attracted the attention of many scholars. On the other hand, security of communication is becoming an important issue because of the broadcasting nature and openness of wireless communication. Physical-layer security has been brought into focus due to the possibility of improving the security in wireless communication. In this paper, we propose an anti-wiretap spectrum-sharing scheme for cooperative cognitive radio communication systems which can secure the information transmission for the two transmission phases of the cooperative communication. We maximized the secondary system transmission rate by jointly optimizing power and bandwidth while ensuring the primary system achieves its secrecy transmission rate. Useful insights of the proposed anti-wiretap spectrum-sharing scheme are given in the simulation results. Moreover, several system parameters are shown to have a big impact for the simulation results.

scholarly journals Efficient Joint Estimation and Compensation of CFO, Tx/Rx Frequency-Selective I/Q Imbalance, and the MIMO Radio Channel in OFDM Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-20 ◽  
Author(s):  
Jian Luo ◽  
Wilhelm Keusgen ◽  
Andreas Kortke
Keyword(s):  
Carrier Frequency ◽  
Communication Systems ◽  
Complexity Analysis ◽  
Radio Channel ◽  
Direct Conversion ◽  
Joint Estimation ◽  
Ofdm Systems ◽  
Rf Impairments ◽  
Mimo Ofdm ◽  
Frequency Selective

MIMO OFDM is a very promising technique for future wireless communication systems. By applying direct conversion architecture, low-cost, low-power, small size, and flexible implementation of MIMO OFDM systems can be realized. However, the performance of direct conversion architecture-based MIMO OFDM systems can be seriously affected by RF impairments incling carrier frequency offset (CFO) and I/Q-imbalance. While OFDM is sensitive to CFO, direct conversion architecture is sensitive to I/Q imbalance. Such RF impairments aggravate as the carrier frequency becomes higher for example, beyond 60 GHz. To achieve the desired high performance of MIMO OFDM, such RF impairments have to be compensated for. In this paper, the joint compensation of CFO, transmitter and receiver frequency-selective I/Q imbalance, and the MIMO radio channel is investigated. Two preamble-based schemes are proposed for impairment parameter estimation. The proposed preambles are constructed both in time and frequency domains and require much less overhead than the state-of-the-art designs. Furthermore, much lower computational complexity is allowed, enabling efficient implementation. The advantages and effectiveness of both proposed schemes are compared and verified by numerical simulations and complexity analysis.

scholarly journals Turbo Decoder for Low-Power Ultrawideband Communication Systems

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Esam A. Obiedat ◽  
Lei Cao
Keyword(s):  
Computational Complexity ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Signal To Noise Ratio ◽  
Turbo Decoding ◽  
Ofdm Symbol ◽  
Turbo Decoder ◽  
Multicarrier Systems ◽  
Ultrawideband Communication ◽  
Ber Performance

A new method to reduce the computational complexity of the turbo decoding in ultrawideband (UWB) orthogonal frequency division multiplexing (OFDM) system is proposed. Existing stopping techniques for turbo decoding process using constrained decoding assume fixed signal-to-noise ratio (SNR) for all the OFDM symbol bits so they fail to yield an acceptable bit-error rate (BER) performance in multicarrier systems. In this paper, we propose a bit-level stopping technique for turbo decoding process based on the constrained decoding method. In this technique, we combine the cyclic redundancy check (CRC) with an adaptive threshold on the log likelihood ratio (LLR) on each subcarrier to detect for convergence. The threshold is adaptive in the sense that the threshold on the LLR of a bit is determined by the average SNR of the OFDM symbol and the channel gain of the transmission subcarrier. Results show that when the channel state information (CSI) is used to determine the threshold on LLR, the stopping technique can reduce the computational complexity by about 0.5–2.5 equivalent iterations compared to GENIE turbo without degradation in the BER performance.

scholarly journals Joint use of frequency-time division and antinoise coding in radio communication systems with FHSS

2021 ◽  
Vol 9 (4) ◽  
pp. 77-84
Author(s):  
A. A. Paramonov ◽  
Van Zung Hoang
Keyword(s):  
Data Transmission ◽  
Communication Systems ◽  
Error Probability ◽  
Noise Immunity ◽  
Signal To Noise Ratio ◽  
Frequency Division ◽  
Radio Communication ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Time Division

In the context of continuous improvement of radio prospecting and active radio jamming technics along with introduction of automated active countermeasures systems (ACS), the frequency-hopping spread spectrum (FHSS) radio communication systems (RCS) are widely used in order to improve reliability and noise immunity of data transmission. The noise immunity of the RCS affected by unintentional or deliberate interference can be significantly perfected by the combined use of frequency-time division and antinoise coding. This paper explores the case when the interference created by an ACS system with a limited transmitter power covers a part of the RCS frequency range. The receiver gets input mix of the wanted signal, the receiver noise, and probably a deliberate interference also considered as a noise. The article analyzes the noise immunity of signals reception with FHSS in the low-speed radio systems with joint use of frequency-time division of information subsymbols and noise combating codes when the deliberate interference destructively impacts a part of the RCS working band. Dependence of the bit error probability on the signal-to-noise ratio is calculated for the joint use of frequency division of information subsymbols and noise combating codes. It is shown that due to effective use of the frequency-energy resource of a radio line, considering the use of correction codes, a quite high noise immunity of RCS under the influence of deliberate interference can be assured. The indicated dependences of the error probability on the signal-to-noise ratio confirm that the reliability of data transmission can be significantly increased by the proper combination of signal spectrum spreading, applying of correction codes, and frequency division of subsymbols followed by their weight processing.

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 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 Review of the Multicarrier Modulation Techniques used in Modern Wireless Communications

Telecom IT ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 55-66
Author(s):  
I. Grishin ◽  
A. Kalinkina
Keyword(s):  
Communication Networks ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Multicarrier Modulation ◽  
Wireless Communication Networks ◽  
Frequency Division ◽  
Radio Communication ◽  
Modulation Techniques ◽  
Radio Signals

This article provides an overview of the technologies for generating radio signals, such as orthogonal frequency division multiplexing and its modifications: universal filtered multicarrier and filter bank multi-carrier currently used in wireless communication networks. Subject of research: methods of multicar-rier modulation. Main results: Overview of modern methods of forming multicarrier signals in radio communication systems. A number of computational experiments have been performed to compare the characteristics of signal localization, peak-to-average ratios and spurious emissions. Practical implica-tions: the results can be used in choosing the type of modulation in the case of the development of digi-tal radio communication systems.

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