Fractionally Spaced Frequency Equalization Method for Orthogonal Frequency Division Multiplexing (OFDM) Jointing with Modified Pilot Sequences

2012 ◽  
Vol 198-199 ◽  
pp. 1569-1572
Author(s):  
Ye Cai Guo ◽  
Qu Chen ◽  
Jun Guo ◽  
Xiao Li Miao
Keyword(s):  
Frequency Domain ◽  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
High Efficiency ◽  
Interpolation Method ◽  
Linear Interpolation ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
Single Carrier ◽  
Frequency Domain Response

In order to obtain accurate and high-speed data transmission, the orthogonal frequency division multiplexing(OFDM) technology is introduced and it is a kind of a multi-carriers modulation technology with high efficiency in the use of frequency band and characteristics of strong anti-interference ability. The fractionally spaced OFDM frequency domain equalization algorithm based on modified pilot sequences is proposed. In this proposed algorithm, one-dimensional linear interpolation method is used to estimate the frequency domain response of all subcarriers by part of the subcarriers’ frequency domain response with reducing the number of transmitted pilot sequences, and received signals are oversampled to acquire more detailed channel information. The computer simulations in underwater acoustic channel show that the performance of proposed method outperforms the single-carrier system and traditional OFDM system.

A Novel Reconfigurable Orthogonal Frequency Division Multiplexing Transceiver

2019 ◽  
Vol 16 (2) ◽  
pp. 430-435
Author(s):  
N. Girinath
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
High Speed ◽  
Frequency Division Multiplexing ◽  
Path Delay ◽  
Frequency Division ◽  
Channel Fading ◽  
High Data ◽  
Digital World ◽  
Single Carrier ◽  
Selective Mapping

As the world moves toward 3G/4G there is a need for high data rate and relatively wide bandwidths. OFDM (Orthogonal Frequency Division Multiplexing) a form of multicarrier modulation technique is widely used to achieve high speed efficient data transmission at the rate of several Mbps. It is used in Wi-Fi standards like 802.11a, 802.11n, 802.11ac, broadcast standards like Digital Video Broadcast (DVB) and cellular telecommunications standard LTE. The main advantage of OFDM compared to single carrier modulation is their robustness to channel fading in wireless environment, high baud rates and less inter symbol interference. One major disadvantage is its High PAPR. PTS partial transmit sequences (PTS) and selective mapping are proposed to reduce it. Since FFT is core block of OFDM it must be able to adapt itself to ever changing digital world. A function specific reconfigurable 2k SDF (Single path delay feedback) FFT is proposed. It utilizes less power and can be configured for different FFT sizes ranging from 16-point to 1024-point. The validity and efficiency of the architecture have been verified by simulation in hardware description language VERILOG and targeted on Virtex-6 device. Finally PAPR is estimated by MATLAB simulation.

scholarly journals Performance analysis of OFDMA and SC-FDMA

2017 ◽  
Vol 8 (2) ◽  
pp. 113-116 ◽  
Author(s):  
M. Al-Rawi
Keyword(s):  
Carrier Frequency ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
High Speed ◽  
Minimum Mean Square Error ◽  
Frequency Division ◽  
International Telecommunication Union ◽  
Single Carrier ◽  
Main Challenge ◽  
Better Than

The main challenge in any high-speed digital communication system is how to maximize the data rate with minimizing the bit error rate. Several techniques have been developed to achieve this point. Some of these techniques are orthogonal frequency division multiplexing (OFDM), single-carrier frequency domain equalization (SC-FDE), orthogonal frequency division multiple access (OFDMA), and single-carrier frequency division multiple access (SC-FDMA). These four techniques are described briefly in this paper. Also, the paper measures the performances of OFDMA and SC-FDMA systems over international telecommunication union (ITU) vehicular-A channel using minimum mean square error (MMSE) equalization. Simulation results show that the performances with interleaved mapping outperform that with localized mapping. Also, the performances with quadrature phase shift keying (QPSK) are better than that with 16-ary quadrature amplitude modulation (16QAM). In addition, the performance of SC-FDMA is better than that of OFDMA, when QPSK is used, but the latter is little bit better than that of SC-FDMA when 16QAM is used.

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 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>

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