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Introduction to MIMO Systems
Published in Brijesh Kumbhani, Rakhesh Singh Kshetrimayum, MIMO Wireless Communications over Generalized Fading Channels, 2017
Brijesh Kumbhani, Rakhesh Singh Kshetrimayum
Fading causes severe degradation in the performances of wireless communication systems, the most important being erroneously received data (compare BER curves of Figure 1.2 without fading and Figure 1.3 with fading). The most commonly studied methods to overcome the effect of fading are the diversity combining schemes such as spatial diversity scheme, temporal diversity scheme, spectral diversity scheme, polarization diversity scheme, etc. of which spatial diversity techniques are the most commonly used and highly studied diversity techniques. Spatial diversity techniques take advantage of spatial variation in the signal strength due to multipath components and combine them accordingly using multiple antennas at the receiver. Thus, diversity systems can be categorized as single-input multiple-output (SIMO) systems. Implementing a diversity system requires no extra frequency band (except in frequency diversity), no added latency (except in time diversity), etc. The commonly used spatial diversity combining schemes are: selection combining (SC), equal gain combining (EGC) and maximal ratio combining (MRC). Each of these combining techniques is discussed in brief as follows.
MIMO for WirelessMAN
Published in Yan Zhang, Hsiao-Hwa Chen, Mobile Wimax, 2007
Xiaopeng Fan, Steven Y. Lai, Yuan Zheng, Jiannong Cao
MIMO is an important technology for WiMAX-based WirelessMAN. In this chapter we briefly introduced the WiMAX and IEEE 802.16 standard. For MIMO, we focused on system capacity, which is approximately proportional to the number of antennas. We generalized the discussion on capacity to cases that encompass transmitters having some prior knowledge of a channel. Our discussion covered a fading channel with additive white Gaussian noise and a low flat Rayleigh fading channel. When discussing MIMO in WiMAX, we analyzed the capacity of a multiuser system model. Space-time coding is one of the schemes for the transmission of signals via MIMO systems. We introduced Alamouti transmission because the Alamouti code is applied in WiMAX for IEEE 802.16-2004 OFDM-256. We also described various diversity schemes for enhancing the performance of wireless channels. Space diversity is an effective scheme for combating multipath fading.
Basics on the Theory of Fading Channels and Diversity
Published in Athanasios G. Kanatas, Konstantina S. Nikita, Panagiotis Mathiopoulos, New Directions in Wireless Communications Systems, 2017
Vasileios M. Kapinas, Georgia D. Ntouni, George K. Karagiannidis
The negative impact of fading on signal transmission can be summarized in two major effects: the distortion of the signal due to intersymbol interference (ISI) and the signal-to-noise ratio (SNR) penalty in the error performance compared to the additive white Gaussian noise (AWGN) channel. These problems need to be efficiently tackled in order to guarantee robust communication with high availability. Diversity schemes can improve the transmission reliability by proper utilization of multiple communication channels with different characteristics. Interestingly, diversity has been proved to be one of the most common and efficient techniques for combating the detrimental effects of fading, interference, and error bursts for over a century now in the history of wireless systems.
Multivariate η−μ fading distribution with arbitrary correlation model
Published in International Journal of Electronics, 2018
Wireless communication channel suffers from time-varying transmission environment, where the channel becomes very unreliable due to multipath fading. Different diversity schemes can be used to improve the quality and reliability of a wireless channel. However, if space or spatial diversity is used, the receiver can use two or more replicas of the information signal which have been subjected to different fading mechanisms. Due to insufficient spaces between receiving antennas, the diversity branches may be correlated. This correlation reduces diversity gain, and system performance deteriorates as the correlation coefficients parameter increase.
Maritime cognitive radio spectrum sensing based on multi-antenna cyclostationary feature detection
Published in International Journal of Electronics, 2020
Jingbo Zhang, Feng Ran, Da Liu
In (Sadeghi & Azmi, 2008), a multi-antenna receiver diversity scheme using SUM-MSDF algorithm is proposed. This scheme first makes independent soft decisions on each antenna, and then converts the decision results of each antenna into a yield problem for fusion decision. The results show that the scheme can improve the reliability of PU signal detection. Since each individual antenna unit needs to adopt a multi-cycle detection algorithm, the implementation complexity of the scheme is relatively high.