scholarly journals Generalized Spatial Modulation in Highly Correlated Channels

2019 ◽  
Author(s):  
Majed Saad ◽  
Feyiz Chris Lteif ◽  
Ali Chamas Al Ghouwayel ◽  
Hussein Hijazi ◽  
Jacques Palicot ◽  
...  
Keyword(s):  
Spatial Modulation ◽  
Correlated Channels ◽  
Highly Correlated

scholarly journals Determinants of synaptic strength vary across an axon arbor

2012 ◽  
Vol 107 (9) ◽  
pp. 2430-2441 ◽  
Author(s):  
Xiaoyu Peng ◽  
Thomas D. Parsons ◽  
Rita J. Balice-Gordon
Keyword(s):  
Synaptic Vesicles ◽  
Hippocampal Neurons ◽  
Synaptic Strength ◽  
Pool Size ◽  
Spatial Modulation ◽  
Readily Releasable Pool ◽  
Single Axon ◽  
Individual Vesicle ◽  
Highly Correlated ◽  
Vesicle Pool

We used synaptophysin-pHluorin expressed in hippocampal neurons to address how functional properties of terminals, namely, evoked release, total vesicle pool size, and release fraction, vary spatially across individual axon arbors. Consistent with previous reports, over short arbor distances (∼100 μm), evoked release was spatially heterogeneous when terminals contacted different postsynaptic dendrites or neurons. Regardless of the postsynaptic configuration, the evoked release and total vesicle pool size spatially covaried, suggesting that the fraction of synaptic vesicles available for release (release fraction) was similar over short distances. Evoked release and total vesicle pool size were highly correlated with the amount of NMDA receptors and PSD-95 in postsynaptic specialization. However, when individual axons were followed over longer distances (several hundred micrometers), a significant increase in evoked release was observed distally that was associated with an increased release fraction in distal terminals. The increase in distal release fraction can be accounted for by changes in individual vesicle release probability as well as readily releasable pool size. Our results suggest that for a single axon arbor, presynaptic strength indicated by evoked release over short distances is correlated with heterogeneity in total vesicle pool size, whereas over longer distances presynaptic strength is correlated with the spatial modulation of release fraction. Thus the mechanisms that determine synaptic strength differ depending on spatial scale.

scholarly journals The Role of Correlation in the Performance of Massive MIMO Systems

2021 ◽  
Vol 4 (3) ◽  
pp. 54
Author(s):  
Marwah Abdulrazzaq Naser ◽  
Mustafa Ismael Salman ◽  
Muntadher Alsabah
Keyword(s):  
Channel Model ◽  
Mimo Systems ◽  
Multiple Input Multiple Output ◽  
Interference Management ◽  
Base Station ◽  
Rectangular Array ◽  
High Data ◽  
Correlated Channels ◽  
Physical Channel ◽  
Highly Correlated

Massive multiple-input multiple-output (m-MIMO) is considered as an essential technique to meet the high data rate requirements of future sixth generation (6G) wireless communications networks. The vast majority of m-MIMO research has assumed that the channels are uncorrelated. However, this assumption seems highly idealistic. Therefore, this study investigates the m-MIMO performance when the channels are correlated and the base station employs different antenna array topologies, namely the uniform linear array (ULA) and uniform rectangular array (URA). In addition, this study develops analyses of the mean square error (MSE) and the regularized zero-forcing (RZF) precoder under imperfect channel state information (CSI) and a realistic physical channel model. To this end, the MSE minimization and the spectral efficiency (SE) maximization are investigated. The results show that the SE is significantly degraded using the URA topology even when the RZF precoder is used. This is because the level of interference is significantly increased in the highly correlated channels even though the MSE is considerably minimized. This implies that using a URA topology with relatively high channel correlations would not be beneficial to the SE unless an interference management scheme is exploited.

scholarly journals Selective Feature Generation Method Based on Time Domain Parameters and Correlation Coefficients for Filter-Bank-CSP BCI Systems

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3769 ◽  
Author(s):  
Yongkoo Park ◽  
Wonzoo Chung
Keyword(s):  
Time Domain ◽  
Filter Bank ◽  
Correlation Coefficients ◽  
Channel Selection ◽  
Classification Performance ◽  
Selection Methods ◽  
Common Spatial Pattern ◽  
Correlated Channels ◽  
Fisher Ratio ◽  
Highly Correlated

This paper presents a novel motor imagery (MI) classification algorithm using filter-bank common spatial pattern (FBCSP) features based on MI-relevant channel selection. In contrast to existing channel selection methods based on global CSP features, the proposed algorithm utilizes the Fisher ratio of time domain parameters (TDPs) and correlation coefficients: the channel with the highest Fisher ratio of TDPs, named principle channel, is selected and a supporting channel set for the principle channel that consists of highly correlated channels to the principle channel is generated. The proposed algorithm using the FBCSP features generated from the supporting channel set for the principle channel significantly improved the classification performance. The performance of the proposed method was evaluated using BCI Competition III Dataset IVa (18 channels) and BCI Competition IV Dataset I (59 channels).

scholarly journals Diagonal Space Time Block Coded Spatial Modulation

2018 ◽  
Vol 2019 (1) ◽  
Author(s):  
Nguyễn Tiến Đông ◽  
Trần Xuân Nam ◽  
Lê Minh Tuấn
Keyword(s):  
Design Procedure ◽  
Space Time ◽  
Spatial Modulation ◽  
Time Block ◽  
Time Code ◽  
Spatially Correlated ◽  
Correlated Channels ◽  
Spatially Correlated Channels ◽  
Antenna Configuration ◽  
Simulation Results

In this paper, a new Spatial Modulation (SM) scheme, called Diagonal Space Time Coded Spatial Modulation (DS-SM), is designed by embedding the Diagonal Space Time Code in SM. The DS-SM scheme still inherits advantages of SM while enjoying further benefits from spatial constellation (SC) designs. Based on rank and determinant criteria, a new set of four SC codewords is proposed for the DS-SM system with 4 transmit antennas to achieve the fourth-order diversity. Then a general design procedure for an even number of transmit antennas, larger than 4, is developed by cyclically shifting two rows of the SC codewords. Simulation results show that DS-SM surpasses several existing SM schemes at the same spectral efficiency and antenna configuration. DS-SM also exhibits better performance over the benchmark systems under spatially correlated channels. Complexity of DS-SM is also analyzed and compared with other SM schemes.

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