scholarly journals Improved ISR for IEEE 802.11ah Nonlinearity Compensation via Adjustable Constellation Borders

Electronics ◽  
2021 ◽  
Vol 10 (13) ◽  
pp. 1573
Author(s):  
Li Cho ◽  
Cheng-Yu Chen ◽  
Chau-Yun Hsu
Keyword(s):  
Computational Complexity ◽  
Internet Of Things ◽  
Bit Error Rate ◽  
Power Efficiency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Receiver Side ◽  
Channel Quality ◽  
Ieee 802.11Ah

Iterative subcarrier regularization (ISR) has been recently proposed as a receiver-side remedy for orthogonal frequency division multiplexing (OFDM) nonlinearity. It allows the power amplifier of OFDM transmitters to operate at a lower input back-off for more efficient uplinks. However, the compensation ability cannot align with increasing channel quality, because the standard quadrature amplitude modulation (QAM) used in ISR may eliminate compensation due to erroneous decisions. To solve this issue, an improved version of ISR was proposed to flexibly adjust the constellation borders of QAM and numerically optimize it based on IEEE 802.11ah (hereinafter referred to as 802.11ah) specifications. Simulations show that the proposed scheme not only improves the converged bit error rate of ISR but also accelerates its own convergence, especially in a high channel quality, thereby achieving better power efficiency for Internet of Things clients without additional computational complexity.

scholarly journals Performance on ICI Self-Cancellation in FFT-OFDM and DCT-OFDM System

2015 ◽  
Vol 2015 ◽  
pp. 1-7
Author(s):  
Shilpi Gupta ◽  
Upena Dalal ◽  
Vishnu Narayan Mishra
Keyword(s):  
Bit Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
The Other ◽  
Frequency Division Multiplexing ◽  
Intercarrier Interference ◽  
Frequency Division ◽  
Ofdm System ◽  
Awgn Channel ◽  
Energy Compaction ◽  
Carrier To Interference Ratio

In orthogonal frequency division multiplexing (OFDM) system, the existence of frequency offset in AWGN channel affects the orthogonality among the subcarriers and consequently introduces the intercarrier interference (ICI). The paper investigates new ICI self-cancellation technique to mitigate the effect of ICI in FFT-OFDM and compares it to DCT based OFDM system in terms of bit error rate (BER) and carrier to interference ratio (CIR). The proposed method for group size three results in a significant 20 dB improved CIR in FFT-OFDM. In terms of BER, proposed ICI self-cancellation technique outperforms the other self-cancellation techniques in FFT-OFDM. Also, this paper investigates outperforming BER and CIR improvement by using DCT-OFDM without applying self-cancellation techniques, due to its energy compaction property.

scholarly journals APR Reduction Technique based on OFDM Pilot Filter Bank Limiting for Satellite Mobile Communications

2018 ◽  
Vol 246 ◽  
pp. 03002
Author(s):  
Tianfang Dai
Keyword(s):  
Mobile Communications ◽  
Bit Error Rate ◽  
Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Filter Bank ◽  
Hardware Implementation ◽  
Reduction Technique ◽  
Papr Reduction ◽  
Frequency Division Multiplexing ◽  
Frequency Division

Combined with OFDM (Orthogonal Frequency Division Multiplexing), satellite mobile communications will effectively achieve on-demand communication in areas with an ultra-low density of users. With OFDM multiple access optimization, the bandwidth utilization efficiency can be increased by 5 to 10 times. However, satellites are power-constrained systems, so higher PAPR requires greater power backoff, resulting in a decline in satellite transmission capacity. To use OFDM technology in satellites, there are problems such as reduced transmission capacity resulted from high PAPR, complication of lowering PAPR, and difficulty in hardware implementation. In order to deal with the problem of high bit error rate and hardware implementation difficulties in PAPR reduction technique of non-orthogonal frequency division multiplexing, this paper proposes a limiting PAPR reduction technique with OFDM pilot filter banks for satellite mobile communications. Firstly, the applicability of OFDM in satellite mobile communications is analyzed, and the influence of high PAPR on satellite power utilization and the influence of frequency shift sensitivity on inter-satellite communication interference are obtained. Then design the PAPR reduction technique based on the pilot filter bank. By setting the tunable filter bank to the pilot, the sideband power suppression in the OFDM frequency domain is realized, and the PAPR of the OFDM signal is reduced. Finally, the experimental results show that the PAPR performance is improved by 3dB without reducing the bit error rate.

The Receiving Method Based on Signal Separation by Spread Spectrum in the Cooperative System with Step Direct Channel

2014 ◽  
Vol 513-517 ◽  
pp. 3107-3110
Author(s):  
Zhang You Peng ◽  
Xu Liu ◽  
Xue Xia Zhong ◽  
Jian Wang ◽  
Yang Liu
Keyword(s):  
Bit Error Rate ◽  
Spread Spectrum ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Step Change ◽  
Signal Separation ◽  
Frequency Division Multiplexing ◽  
Direct Channel ◽  
Frequency Division ◽  
Cooperative System

In high-speed mobile Orthogonal Frequency Division Multiplexing (OFDM) cooperative system, direct channel signal presents a step change due to carriage loss, which interferes with signal reception. In the proposed system, spread spectrum is adopted at relay to separate the receiving mixed signals. Subsequently, the fading coefficient threshold of direct channel is obtained by simulating outage probability of direct channel. Finally, separated direct channel signal is selectively received based on the ratio relationship between its current fading coefficient and the obtained threshold. The proposed receiving strategy reduces Bit Error Rate compared with other receiving methods. Moreover, throughput of the proposed system increases when the fading coefficient is higher than threshold.

scholarly journals Research of the Influence of the Quadrature Components Mismatch on the Noise Immunity of OFDM and UFMC Signals

2021 ◽  
Vol 24 (1) ◽  
pp. 71
Author(s):  
A. Yu. Belousov ◽  
V. V. Khvorenkov
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Orthogonal Frequency Division Multiplexing ◽  
Noise Immunity ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Error Vector Magnitude ◽  
Error Vector ◽  
Vector Magnitude

Метод непосредственной модуляции с использованием комплексных сигналов применяется при реализации сигнальных трактов передатчиков в базовых станциях систем сотовой связи. В процессе модуляции возникают рассогласования коэффициента усиления и фазы квадратурных составляющих сигнала. Рассогласование ухудшает модуль вектора ошибки (Error Vector Magnitude, EVM) в приемнике, что, в свою очередь, приводит к повышению частоты появления ошибочных битов (Bit Error Rate, BER). Качество принимаемого сигнала выражается в частоте появления битовых ошибок. Рассогласование амплитуды и фазы квадратурных составляющих является одним из важнейших факторов, вносящих наибольший вклад в амплитуду вектора ошибки, который необходимо исследовать.В статье приведено исследование влияния рассогласования квадратурных составляющих сигналов технологий OFDM (Orthogonal frequency-division multiplexing) и UFMC (universal filtered multi-carrier). Разработана модель передатчика, канала связи и приемника для сигналов OFDM и UFMC. Модель построена в програм­мной среде MatLab при помощи языка MatLab и представляет собой программную модель m-script.В ходе работы путем исследования имитационной модели изучена зависимость помехоустойчивости технологий путем изменения параметров канала связи, таких как амплитудное и фазовое рассогласование квадратурных составляющих сигнала, а также отношение сигнал/шум. Проведен сравнительный анализ таких параметров сигналов, как занимаемая полоса частот, пик-фактор, частота появления битов с ошибкой. По результатам исследования получены графики зависимости вероятности ошибки и пик-фактора сигнала от рассогласования квадратурных составляющих для двух технологий – OFDM и UFMC. Проведенное исследование позволяет выделить преимущества технологии UFMC, которые выражаются в спектральной эффективности, помехоустойчивости и уровне пик-фактора сигнала.

scholarly journals An identification of the tolerable time-interleaved analog-to-digital converter timing mismatch level in high-speed orthogonal frequency division multiplexing systems

2022 ◽  
Vol 12 (2) ◽  
pp. 1667
Author(s):  
Vo Trung Dung Huynh ◽  
Linh Mai ◽  
Hung Ngoc Do ◽  
Minh Ngoc Truong Nguyen ◽  
Trung Kien Pham
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Performance Degradation ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Analog To Digital ◽  
Time Interleaved

<span>High-speed Terahertz communication systems has recently employed orthogonal frequency division multiplexing approach as it provides high spectral efficiency and avoids inter-symbol interference caused by dispersive channels. Such high-speed systems require extremely high-sampling <br /> time-interleaved analog-to-digital converters at the receiver. However, timing mismatch of time-interleaved analog-to-digital converters significantly causes system performance degradation. In this paper, to avoid such performance degradation induced by timing mismatch, we theoretically determine maximum tolerable mismatch levels for orthogonal frequency division multiplexing communication systems. To obtain these levels, we first propose an analytical method to derive the bit error rate formula for quadrature and pulse amplitude modulations in Rayleigh fading channels, assuming binary reflected gray code (BRGC) mapping. Further, from the derived bit error rate (BER) expressions, we reveal a threshold of timing mismatch level for which error floors produced by the mismatch will be smaller than a given BER. Simulation results demonstrate that if we preserve mismatch level smaller than 25% of this obtained threshold, the BER performance degradation is smaller than 0.5 dB as compared to the case without timing mismatch.</span>

scholarly journals Transceiver Design for GFDM with Hexagonal Time–Frequency Allocation Using the Polyphase Decomposition

Electronics ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 1862
Author(s):  
Evren Catak ◽  
Arild Moldsvor ◽  
Mohammad Derawi
Keyword(s):  
Energy Consumption ◽  
Computational Complexity ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Channel Model ◽  
Low Latency ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Next Generation ◽  
Time Frequency

Generalized frequency division multiplexing (GFDM) is a waveform for the next-generation communication systems to succeed in the drawbacks of orthogonal frequency division multiplexing (OFDM). The symbols of users are transmitted with the time- and frequency-shifted versions of a prototype filter. According to filtering operation, the computational complexity and processing load are high for the devices that suffer from energy consumption. The communication systems are required to support the new generation devices that need low energy consumption and low latency issues. Motivated by such demands of the next-generation communication system, we propose a novel GFDM waveform that we call hexagonal GFDM. The contributions of the hexagonal GFDM are that it: (i) supports short transmission time based on its hexagonal time–frequency allocations; and (ii) provides low latency communication with low computational complexity manner. Furthermore, we design a transmitter and receiver structure in a less complicated way with mathematical derivation by using polyphase decomposition and Fourier transform (FT) transformation. The proposed systems are realized analytically and investigated over Rayleigh fading channel model through computer simulations.

scholarly journals Analysis of the PAPR Behavior of the OFDM Passband Signal

2019 ◽  
Author(s):  
Frank Andrés Eras ◽  
Italo Alexander Carreño ◽  
Thomás Borja ◽  
Diego Javier Reinoso ◽  
Luis Urquiza-Aguiar ◽  
...  
Keyword(s):  
Bit Error Rate ◽  
Communication Systems ◽  
Orthogonal Frequency Division Multiplexing ◽  
Average Power ◽  
Wireless Communication Systems ◽  
Frequency Division Multiplexing ◽  
Power Ratio ◽  
Frequency Division ◽  
Ofdm System ◽  
High Power Amplifier

Orthogonal Frequency Division Multiplexing (OFDM) is a technique widely used in today's wireless communication systems due to its ability to combat the effects of multi-path in the signal. However, one of the main limitations of the use of OFDM is its high Peak-to-Average Power Ratio (PAPR), which reduces the efficiency of the OFDM system. The effects of PAPR can produce both out-of-band and in-band radiation, which degrades the signal by increasing the bit error rate (BER), this occurs in both baseband and bandpass sginals. In this document the effect of the PAPR in a OFDM passband signal is analyzed considering the implementation of a High Power Amplifier (HPA) and the Simple Amplitude Predistortion-Orthogonal Pilot Sequences (OPS-SAP) scheme to reduce the PAPR.

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