Adaptive Spatial Mode Of Space–Time And Spacefrequency OFDM System Over Fading Channels

2012 ◽  
Author(s):  
Nor K. Noordin ◽  
Borhanuddin M. Ali ◽  
S. S. Jamuar ◽  
Tharek A. Rahman ◽  
Mahamod Ismail
Keyword(s):  
Fading Channels ◽  
Channel Coding ◽  
Orthogonal Frequency Division Multiplexing ◽  
Multipath Fading ◽  
Individual Performance ◽  
Space Time ◽  
Delay Spread ◽  
Spatial Mode ◽  
Time Space ◽  
Space Frequency

Dalam kertas kerja ini kami membentangkan skema mod ruang (ASM) adaptif 2 menghantar 1 menerima (2 Tx : 1 Rx) menggunakan kaedah ruang–masa (ST) dan ruang frekuensi (SF) multiplekskan pembahagian frekuensi ortogonal (OFDM). Pada nilai nisbah isyarat ke hingar yang rendah kami menggunakan ST–OFDM dan menukar kepada mod SF–OFDM pada nilai ambang yang telah ditentukan. Nilai ini ditentukan berdasarkan titik silang antara lengkuk prestasi kedua–dua mod. Keputusan simulasi menunjukkan gandaan banyak 9 dB (pada kadar ralat bit 10–3) diperolehi dengan menggunakan mod ruang adaptif (ASM) berbanding dengan ST–OFDM tanpa kod, lebih kurang 6 dB berbanding SF–OFDM, 4 dB berbanding ST–OFDM terkod dan gandaan sebanyak 2 dB berbanding SF–OFDM terkod, pada rebak lengah 700 ns. Kata kunci: OFDM, ruang–masa, ruang–frekuensi, pengekodan saluran dan saluran pemudaran berbilang laluan In this paper we present a 2 transmit 1 receive (1 Tx : 1 Rx) adaptive spatial mode (ASM) of space–time (ST) and space–frequency (SF) orthogonal frequency division multiplexing (OFDM). At low signal to noise ratio (SNR) we employ ST–OFDM and switch to SF–OFDM at a certain SNR threshold. We determine this threshold from the intersection of individual performance curves. Results show a gain of 9 dB (at a bit error rate of 10–3) is achieved by employing adaptive spatial mode compared to a fixed ST–OFDM, almost 6 dB to fixed SF–OFDM, 4 dB to Coded ST–OFDM and 2 dB to a fixed coded SF–OFDM, at a delay spread of 700 ns. Key words: OFDM, space–time, space–frequency, channel coding and multipath fading channels

scholarly journals Performance of OFDM System under Different Fading Channels and Channel Coding

2017 ◽  
Vol 6 (1) ◽  
pp. 54-61
Author(s):  
Pratima Manhas ◽  
M. K. Soni
Keyword(s):  
Fading Channels ◽  
Channel Coding ◽  
Orthogonal Frequency Division Multiplexing ◽  
Mobile Station ◽  
Multipath Fading ◽  
Ofdm System ◽  
Angle Of Arrival ◽  
Multiple Reflections ◽  
Multipath Fading Channels ◽  
Base Transceiver Station

Orthogonal frequency division multiplexing (OFDM) is a type of multicarrier modulation (MCM) technique in which larger bandwidth is divided into parallel narrow bands each of which is modulated by different subcarriers. All the subcarriers are orthogonal to each other and hence it reduces the interference among various subcarriers. OFDM technique is an efficient modulation technique used in certain wired and wireless application.In a wireless communication channel, the transmitted signal can travel from transmitter to receiver over multiple reflective paths. This results to multipath fading which causes fluctuations in amplitude, phase and angle of arrival of the received signal. For example, the signal which is transmitted from BTS (base transceiver station) may suffer multiple reflections from the buildings nearby, before reaching the mobile station. Such multipath fading channels are classified into slow fading/fast fading and frequency-selective/flat fading channels. This paper discusses the performance of OFDM system using various fading channels and channel coding. The parameter which is known as Bit error rate (BER) is calculated under different fading channels (AWGN, Rayleigh and Rician) for different digital modulation (BPSK, QPSK and QAM) and Channel coding (linear/Cyclic coding). Matlab Simulink tool is used to calculate the BER parameter.

scholarly journals Dual-Hop OSTBC Transmissions Over Fading Channels under Receiver Phase Noise for Regenerative Systems

2012 ◽  
pp. 22-26
Author(s):  
K. Sujatha ◽  
S. Varadarajan
Keyword(s):  
Fading Channels ◽  
Channel Model ◽  
Spatial Diversity ◽  
Space Time ◽  
Delay Spread ◽  
Frequency Diversity ◽  
Space Time Coding ◽  
Propagation Parameters ◽  
Space Frequency ◽  
Time Coding

Space-time coding for fading channels is a Communication technique that realizes the diversity benefits of multiple transmit antennas. Previous work in this area has focused on the narrowband flat fading case where spatial diversity only is available. In this paper, we investigate the use of space-time coding in OFDM based broadband systems where both spatial and frequency diversity are available. We consider a strategy which basically consists of coding across OFDM tones and will therefore be called space-frequency coding. For a spatial broadband channel model taking into account physical propagation parameters and antenna spacing, we derive the design criteria for space-frequency codes and we show that space-time codes designed to achieve full spatial diversity in the narrowband case will in general not achieve full space-frequency diversity. Specifically, we show that the Alamouti scheme across tones fails to exploit frequency diversity. For a given set of propagation parameters and given antenna spacing, we establish the maximum achievable diversity order. Finally, we provide simulation results studying the influence of delay spread, propagation parameters, and antenna spacing on the performance of Space-frequency codes.

OFDM System Performance Evaluation under Different Fading Channels and Channel Coding using Matlab Simulink

2017 ◽  
Vol 5 (2) ◽  
pp. 260
Author(s):  
Pratima Manhas ◽  
M.K Soni
Keyword(s):  
Fading Channels ◽  
Channel Coding ◽  
Orthogonal Frequency Division Multiplexing ◽  
Mobile Station ◽  
Multipath Fading ◽  
Ofdm System ◽  
Multiple Reflections ◽  
Matlab Simulink ◽  
Base Transceiver Station ◽  
Wireless Application

<p>Orthogonal Frequency Division Multiplexing (OFDM) is a form of Multicarrier Modulation (MCM) technique in which larger bandwidth is divided into parallel narrow bands each of which is modulated by different subcarriers. All the subcarriers are orthogonal to each other and hence it reduces the interference among various subcarriers. OFDM technique is an efficient modulation technique used in certain wired and wireless application. During transmission, the transmitted signal can travel from transmitter to receiver over multiple reflective paths in case of wireless communication system which results to multipath fading and produces variation in amplitude, phase and angle of the received signal. The signal which is transmitted from BTS (base transceiver station) may undergo multiple reflections from the buildings nearby, before reaching the mobile station. This paper discusses the performance of OFDM system using various fading channels and channel coding. The parameter which is known as Bit error rate (BER) is calculated for different fading channels (AWGN, Rayleigh and Rician) for different digital modulation (BPSK, QPSK and QAM) and Channel coding(linear/ Cyclic coding).The tool which is used to evaluate  the BER parameter is Matlab Simulink.</p>

scholarly journals State-Space Estimation for OFDM and SC-FDE Schemes with Strongly Varying Carrier Frequency Offset

1970 ◽  
Vol 4 (1) ◽  
pp. 21-29
Author(s):  
Pedro Pedrosa ◽  
Rui Dinis ◽  
Fernando Nunes
Keyword(s):  
Fading Channels ◽  
Carrier Frequency ◽  
Channel Coding ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Multipath Fading ◽  
Frequency Offset ◽  
Spatial Diversity ◽  
Single Carrier ◽  
Pilot Symbols

Parametric algorithms for the estimation of rapidly-varying Carrier Frequency Offset (CFO) usually employ pilot symbols multiplexed with the data transmission. As the CFO variation rate increases so has to increase the density of pilot symbols transmitted, thus impairing the bandwidth efficiency. In order to reduce the number of pilot symbols used in the estimation of rapidly-varying CFO it was proposed to use a truncated Taylors series to predict the CFO, where the derivatives up to order d-1 are recursively estimated with a d-order Kalman filter (KF).We propose to compare the performance of a fourth-order KF predictor in the most popular block transmission systems: Orthogonal Frequency Division Multiplexing (OFDM) and Single Carrier Frequency-Domain Equalization (SC-FDE). Simulating different transmission scenarios, e.g., channel coding and spatial diversity, our results show that for static multipath fading channels the proposed receiver for the SC-FDE scheme exhibits better Bit Error Rate (BER) performance than that of OFDM.

scholarly journals Performance Analysis of MIMO STBC System in Flat Fading and Frequency Selective Fading Channels

2019 ◽  
Vol 3 (1) ◽  
pp. 19
Author(s):  
Pebri Yeni Samosir ◽  
Nyoman Pramaita ◽  
I Gst A. Komang Diafari Djuni Hartawan ◽  
Ni Made Ary Esta Dewi Wirastuti
Keyword(s):  
Fading Channels ◽  
System Performance ◽  
Mimo System ◽  
Multipath Fading ◽  
Delay Spread ◽  
Selective Fading ◽  
Frequency Selective Fading ◽  
Flat Fading ◽  
Frequency Selective ◽  
Frequency Selective Fading Channels

Multiple Input Multiple Output (MIMO) technology is a technique that can be used to overcome multipath fading. The multipath fading is caused by signals coming from several paths that experience different attenuations, delays and phases. In a multipath condition, an impulse that sent by the transmitter, will be received by the recipient not as an impulse but as a pulse with a spread width that called delay spread. Delay spread can cause intersymbol interference (ISI) and bit translation errors from the information received. To determine the effect of delay spread on the MIMO system, then MIMO system performance research was performed on flat fading and frequency selective fading channels using the Space Time Block Code (STBC) coding technique. This research was conducted using MatLab 2018a software. The simulation results show that the MIMO STBC system performance on flat fading channels is better than the MIMO STBC system performance on the frequency selective fading channel. This result is analyzed based on the value of BER vs. Eb/No and eye diagram.

scholarly journals Robust Preamble-Based Timing Synchronization for OFDM Systems

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Yun Liu ◽  
Fei Ji ◽  
Hua Yu ◽  
Dehuan Wan ◽  
Fangjiong Chen ◽  
...  
Keyword(s):  
Fading Channels ◽  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Estimation Method ◽  
Multipath Fading ◽  
New Method ◽  
Timing Synchronization ◽  
Ofdm Systems ◽  
Multipath Fading Channels ◽  
Timing Offset

This study presents a novel preamble-based timing offset estimation method for orthogonal frequency division multiplexing (OFDM) systems. The proposed method is robust, immune to the carrier frequency offset (CFO), and independent of the structure of the preamble. The performance of the new method is demonstrated in terms of mean square error (MSE) obtained by simulation in multipath fading channels. The results indicate that the new method significantly improves timing performance in comparison with existing methods.

Joint Angular and Time Diversity of Multi-Antenna CDMA Systems in Wireless Fading Channels

2011 ◽  
Vol 1 (1) ◽  
pp. 1-14
Author(s):  
Feng She ◽  
Hsiao Hwa Chen ◽  
Hongyang Li
Keyword(s):  
Fading Channels ◽  
Performance Improvement ◽  
Multipath Fading ◽  
Antenna System ◽  
Space Time ◽  
Diversity Gain ◽  
Multipath Fading Channel ◽  
Time Diversity ◽  
Time Domains ◽  
Code Division Multiple

In this paper, a multi-antenna based receiver structure for direct sequence code division multiple access (DS/CDMA) system is proposed. The proposed scheme exploits the excellent time resolution of a CDMA RAKE receiver and uses an antenna array beamforming structure to resolve multipath returns in both angular and time domains. A much higher diversity gain than that based only on the time domain diversity can be achieved. This work suggests a new space-time diversity paradigm, namely angular-time diversity, which differs from traditional Alamouti-type space-time coded schemes. The impairments caused by multipath and multiuser interference are analyzed. The performance of the proposed receiver in multipath fading channel is explicitly evaluated. An expression for uncoded system bit error probability is derived. Simulation results show the performance improvement in terms of BER due to the use of multi-antenna in the receiver, and the results illustrate that the multi-antenna based receiver works effectively in resolving multipaths in both angular and time domains to achieve performance improvement due to angular and time diversity gain provided by the multi-antenna system.

Sign in / Sign up

Export Citation Format

Share Document