Adaptive Transmission Mode Switching in Interference Alignment Based Clustered Wireless Network

Abstract In this paper, the design of adaptive transmission mode switching (TMS) to maximize the sum rate for the downlink multiple-input-single-output based non-orthogonal multiple access (MISO-NOMA) systems is investigated. Firstly, the colsed-form expressions of the boundary of achievable rate region of two candidate transmission mode, i.e., NOMA-based maximum ratio transmission (NOMA-MRT) and minimum mean square error beamforming (MMSE-BF), are obtained. By obtaining the outer boundary of the union of the achievable rate regions of the two transmission mode, an adaptive switching method is developed to achieve a larger rate region. Secondly, based on the idea that the solution to the problem of weighted sum rate (WSR) optimization must be on the boundary of achievable rate region, the optimal solutions to the problem of WSR optimization for NOMA-MRT and MMSE-BF are obtained, respectively. Subsequently, by exploiting the optimal solutions aforementioned for two transmission modes and the high efficiency of TMS, a low-complexity Joint User pairing and Power Allocation algorithm (JUPA) is proposed to further improve sum-rate performance for the multi-user case. Compared with the Exhaustive Search based user Pairing and Power Allocation algorithm (ES-PPA), the proposed JUPA can enjoy a much lower computation complexity and only suffer a slight sum-rate performance loss, whereas outperforms other traditional schemes. Finally, numerical results are provided to validate the analyses and the proposed algorithms.

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Active Frequency Selective Surface with Simultaneous Absorption/Transmission Mode Switching and Frequency Tuning Characteristic

2019 8th Asia-Pacific Conference on Antennas and Propagation (APCAP) ◽

10.1109/apcap47827.2019.9471904 ◽

2019 ◽

Author(s):

Ratanak Phon ◽

Sungjoon Lim

Keyword(s):

Frequency Tuning ◽

Frequency Selective Surface ◽

Transmission Mode ◽

Mode Switching ◽

Simultaneous Absorption ◽

Tuning Characteristic ◽

Frequency Selective

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Dynamic Spatiotemporal Restructuring of Visual Receptive Fields through Selective Attention: A Model

Perception ◽

10.1068/v970246 ◽

1997 ◽

Vol 26 (1_suppl) ◽

pp. 375-375

Author(s):

K Suder ◽

K Funke ◽

F Woergoetter

Keyword(s):

Selective Attention ◽

Positive Feedback ◽

Signal Transmission ◽

Receptive Fields ◽

Transmission Mode ◽

Mode Switching ◽

Feedback Mechanisms ◽

Low Threshold ◽

Winner Takes All ◽

Cortical Receptive Fields

Cells in the lateral geniculate nucleus (LGN) strongly change their behaviour covarying with different EEG states. During sleep and drowsiness (synchronised alpha, delta-wave EEG) short transient responses prevail whereas during a desynchronised ‘alert’ EEG (beta-waves) long-lasting tonic responses are observed. We propose that this is part of a mechanism used to restructure the spatial and temporal characteristics of the receptive fields in LGN and cortex reflecting changing states of selective attention. To this end we present a model of the primary visual pathway using integrate-and-fire neurons to simulate the afferent signal flow (retina, LGN, V1). The model also implements excitatory topographically arranged lateral intracortical and corticofugal connections which act as a positive feedback and trigger spatial winner-takes-all (WTA) mechanisms enhanced by lateral inhibition at both levels. Furthermore, the LGN membrane characteristic can switch from phasic (hyperpolarised) low-threshold Ca2+ bursting mode to tonic (depolarised) signal-transmission mode. Switching is triggered by feedback and amplified by intracellular intrinsic positive-feedback mechanisms in the model LGN. All positive-feedback mechanisms are subject to damping such that they remain ineffective below a certain threshold. Salient stimuli which ‘attract attention’ will push the system above threshold and a self-amplifying process is started which sharpens the cortical receptive fields spatially (by spatial WTA) and drives the winners in the LGN into signal transmission mode (by intrinsic intracellular mechanisms). These results predicted by the model are in accordance with LGN cell behaviour. In addition, the model predicts that cortical receptive fields should be wider during synchronised EEG than during desynchronised EEG.

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