Fading Mitigation with Diversity Schemes in WCDMA : Technical Review (original) (raw)
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Transmit diversity schemes for WCDMA
Wireless Personal Communications, 2003
Previous work on transmitter antenna diversity has shown that the use of multiple transmitter antennas at the base station results in improved performance due to increase of diversity (path diversity). This happens with no bandwidth cost, even when the signal quality along several paths is poor, but the receiver estimates the channel with accuracy. This paper evaluates the effects of channel estimation errors in the performance of the schemes designated as Space-Time Transmitter Diversity (STTD) and Selective Transmitter Diversity (STD). We consider low to medium signal to noise ratios characteristic of Wideband Code Division Multiple Access (WCDMA) networks. Different fading channel models are considered for comparison between the two schemes. The improvement due to convolutional coding associated with these techniques is also evaluated.
DIVERSITY TECHNIQUES FOR WIRELESS COMMUNICATION
The users of the wireless communication demands for higher data rates, good voice quality and higher network capacity restricted due to limited availability of radio frequency spectrum, Bandwidth, Channel Capacity, physical areas and transmission problems caused by various factors like fading and multipath distortion.
Diversity Technique And Modulation Method Used To Reduce Fading in Wireless Communication Pradeep
— Wireless communication has made everyone's life easy. Wireless network provides high speed mobility for data and voice signal. But wireless communication suffers from a problem namely fading, means multipath propagation of signal. Diversity is the technique used in wireless communication system to improve the performance over a communication channel i.e. used to remove fading from the channel. Space diversity is also known as Antenna Diversity that uses two or more antennas to improve the quality and reliability of a wireless link. MIMO is the most powerful diversity technique used in wireless communication. In this paper we analyzed with several antennas (MIMO i.e. multiple input multiple output) so as to obtain the space diversity. Also there is Architectural Comparison between Conventional MIMO-OFDM receiver design and orthogonal MIMO OFDM design. This paper is focused on the improvements obtained in the quality of data transmission.
Performance Comparison of Various Diversity Techniques using Matlab Simulation
IJITCS, 2013
Due to the time-varying nature of the wireless channel and presence of limited resources for the signal transmission, which faces various detrimental effects such as path-loss, delay spread, Doppler spread, shadowing and interference make it very difficult to achieve sufficient data rates. To combat the effect of multi-path fading in the wireless communication system, the diversity combining mechanism has been introduced. In this paper, we have developed an algorithm for the performance evaluation of various spatial diversity combing techniques by using Matlab simulation. The developed new algorithm combine all three diversity techniques such as maximal ratio combining (MRC), selection combining (SC) and equal gain combing (EGC) techniques The combined diversity techniques algorithm computes and compares the MRC, SC, and EGC combing techniques theoretically by using the Matlab simulation.
Transmit diversity in the WCDMA system
1999
This document presents the transmit diversity concept adopted for the FDD mode of the thirdgeneration WCDMA system in ETSI in 1998. The open-loop mode is based on the space-time block code attaining full diversity order with two transmit antennas. Different feedback modes are speci® ed. They all utilize terminal measurements in controlling the transmit weighting in the transmit antennas. The concept is described in detail for two transmit antennas. It is shown that very limited feedback from the terminal to the base, as de® ned for the FDD mode, can increase downlink performance signi® cantly when compared to single-antenna transmission.
An Overview of Diversity Techniques in Wireless Communication Systems
Fading problem is a major impairment of the wireless communication channel. In this paper we considers different techniques to mitigate the fading problem in wireless channel. The trivial solution for the fading problem would be to add a fading margin at the transmitter. However, this is not an efficient solution at all. One alternate solution is to take advantage of the statistical behavior of the fading channel. Here comes the basic concept of diversity; where two or more inputs at the receiver are used to get uncorrelated signals.
This paper focuses on the use of antenna diversity technique in enhancing the performance of Wideband Code Division Multiple Access network. Several field measurements of received signal strength were obtained from a WCDMA network with the help of spectrum analyzer and global positioning system. In this paper also, the characterization of the propagation environment was done using the pathloss exponent and empirical pathloss model. Results show that the pathloss exponent of the field environment where the network is situated resulted in 3.63.The use of antenna diversity on the same network gave a pathloss exponent of 2.51.
Hybrid Diversity Combining Techniques for Fading Channels
Diversity combining is the effective to way to mitigate the effects of multipath fading. The independent signal paths have low probability of experiencing deep fades simultaneously is the fact exploited by diversity combining. In diversity combining the replicas of same information signal is combined together to obtain high SNR. The Hybrid Diversity combining techniques has been carried out to reduce the effects of fading owing to its good performance and low implementation complexity. Different Hybrid Diversity combining techniques are summarized in this paper.
Diversity Schemes for Wireless Communication- a Short Review
Now-a-days the requirements of wireless communication are to have high voice quality, high data rates, multimedia features, lightweight communication devices etc. But the wireless communication channel suffers from much impairment .One of them is fading which is due to the effect of multiple propagation paths, and the rapid movement of mobile communication devices. In a typical wireless communication environment, multiple propagation paths often exist from a transmitter to a receiver due to scattering by different objects. Signal copies following different paths can undergo different attenuation, distortions, delays and phase shifts. So, this is necessary to reduce the problem of fading, but not at the cost of extra power or additional bandwidth. One effective solution is proposed for wireless system named diversity, with out the requirement of power or extra bandwidth. This paper discusses about the characteristics of fading channels and a broad classification of various diversity ...
International Journal of Research, 2018
This paper indicates that antenna diversity method for the wireless multiple antenna system. In wireless communication fading accumulate in the channel is major apprehension .So the antenna diversity is used to mitigate the the effect of fading over the channel at the relatively less cost. The most commonly antenna diversity technique is space time block code (STBC) provides transmit diversity and maximum ratio combining (MRC) provides receiver diversity in wireless technology is case of multiple-input multiple-output (MIMO) systems. The most commonly employed antenna diversity is Maximal Ratio Receiver Combining (MRRC) in which several uncorrelated replica of the signals with weight values are combined at the receiver in order to achieve improved reconstructed signals. This paper presenting Maximal Ratio Receiver Combining (MRRC) receiver diversity technique to mitigate the effect of Rayleigh fading channel. The simulation result are based on BER performance for systems with sin...