scholarly journals [Paper] A Novel Multicarrier CDMA Scheme With Interference Free Performance in Very Large Delay Spread

2014 ◽  
Vol 2 (4) ◽  
pp. 362-369 ◽  
Author(s):  
Ainiwan Abudoukeremu ◽  
Shinya Matsufuji ◽  
Yuta Ida ◽  
Takahiro Matsumoto
Keyword(s):  
Delay Spread ◽  
Multicarrier Cdma ◽  
Large Delay

Doppler Estimation, Synchronization with HFM Signals for Underwater Acoustic Communications

2012 ◽  
Vol 198-199 ◽  
pp. 1638-1645 ◽  
Author(s):  
Lan Zhang ◽  
Xiao Mei Xu ◽  
Wei Feng ◽  
You Gan Chen
Keyword(s):  
Multipath Propagation ◽  
Delay Spread ◽  
Underwater Acoustic Communication ◽  
Good Prospect ◽  
Underwater Acoustic Communications ◽  
Frame Synchronization ◽  
Large Delay ◽  
Underwater Acoustic ◽  
Moving Platforms ◽  
Testing Performance

This paper presents the application of the hyperbolic frequency modulated (HFM) signal to acoustic propagation in order to improve the performance of underwater acoustic (UWA) communications. Due to the large delay spread caused by multipath propagation and the severe Doppler Effect of the channel, we propose the using of double HFM signals as preambles for Doppler estimation, frame synchronization in UWA communications. A theoretical analysis about Doppler-invariability of HFM signals was provided firstly, then some numerical simulations about Doppler estimation were implemented, and experiments on testing performance of double-HFM preambles for frame synchronization in the pool were carried out as well. The simulation and experimental results show that using double-HFM signals as preambles has the capability to take an explicit Doppler estimation and retiming for frame synchronization, demonstrating that it has a good prospect in underwater acoustic communication system, especially for moving platforms.

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.

Turbo Equalized Double Window Cancellation and Combining Robust to Large Delay Spread Channel

2009 ◽  
Vol E92-B (2) ◽  
pp. 517-526
Author(s):  
JunHwan LEE ◽  
Tomoaki OHTSUKI ◽  
Masao NAKAGAWA
Keyword(s):  
Delay Spread ◽  
Large Delay

scholarly journals A hybrid equalizer/Rake receiver for the Wideband CDMA Downlink in large delay spread channels

2008 ◽  
Vol 6 ◽  
pp. 107-112 ◽  
Author(s):  
C. Buchacher ◽  
M. Zimmermann ◽  
S. Paul ◽  
M. Huemer
Keyword(s):  
Computational Complexity ◽  
Code Division Multiple Access ◽  
Minimum Mean Square Error ◽  
Rake Receiver ◽  
Delay Spread ◽  
Wideband Cdma ◽  
Large Delay ◽  
Hybrid Solution ◽  
Classic Approach ◽  
Code Division Multiple

Abstract. Signals transmitted over a multi-path propagation channel exhibit Inter-Path Interference (IPI) and fading. The receiver has to employ measures to mitigate these effects or it will incur severe performance degradation. A classic approach in Code Division Multiple Access (CDMA) communications is the Rake receiver. Alternatively, a Linear Minimum Mean Square Error (LMMSE) equalizer can further improve performance. This paper compares performance and computational complexity of these two algorithms. A hybrid solution will be introduced in order to decrease computational complexity while retaining most of the interference suppression capabilities of the LMMSE equalizer.

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.

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