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Neural Feedback for Instantaneous Spatiotemporal Modulation of Afferent Pathways in Bi-Directional Brain-Machine Interfaces

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IEEE TRANSACTIONS ON NEURAL systems AND REHABILITATION ENGINEERING 2011年第5期19卷 521-533页

作者： Liu, Jianbo Khalil, Hassan K. Oweiss, Karim G. Michigan State Univ Dept Elect & Comp Engn E Lansing MI 48823 USA Michigan State Univ Neurosci Program E Lansing MI 48823 USA

In bi-directional brain-machine interfaces (BMIs), precisely controlling the delivery of microstimulation, both in space and in time, is critical to continuously modulate the neural activity patterns that carry information about the state of the brain-actuated device to sensory areas in the brain. In this paper, we investigate the use of neural feedback to control the spatiotemporal firing patterns of neural ensembles in a model of the thalamocortical pathway. Control of pyramidal (PY) cells in the primary somatosensory cortex (S1) is achieved based on microstimulation of thalamic relay cells through multiple-input multiple-output (MIMO) feedback controllers. This closed loop feedback control mechanism is achieved by simultaneously varying the stimulation parameters across multiple stimulation electrodes in the thalamic circuit based on continuous monitoring of the difference between reference patterns and the evoked responses of the cortical PY cells. We demonstrate that it is feasible to achieve a desired level of performance by controlling the firing activity pattern of a few "key" neural elements in the network. Our results suggest that neural feedback could be an effective method to facilitate the delivery of information to the cortex to substitute lost sensory inputs in cortically controlled BMIs.

关键词： Bi-directional brain-machine interface (BMI) feedback control multichannel microstimulation multiple-input multiple-output systems spatiotemporal activity thalamocortical networks

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A power scaling analysis of norm-based antenna selection techniques

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第8期7卷 3140-3149页

作者： Smith, Peter J. King, Timothy W. Garth, Lee M. Dohler, Mischa Univ Canterbury Dept Elect & Comp Engn Christchurch 1 New Zealand BAE Syst Adv Syst & Technol Div Merrimack NH 03054 USA Telecommun Technol Ctr Catalonia Barcelona 08860 Spain

In this paper we consider transmit and receive selection methods designed to achieve high channel capacities in a single-user MIMO link. A variety of radio channels are considered, including i.i.d. Rayleigh, correlated Rayleigh and Ricean fading environments. Also considered is the presence of imperfect channel state information (CSI) and a simplified waterfilling scheme. In all cases, we evaluate the performance of optimal selection, simple norm-based selection and other benchmark selection techniques. The major contribution is a general approach to analyzing the capacity of the norm-based selection schemes via a simple power scaling factor. We are able to assess the impact of different channels, imperfect CSI and power allocation using this power scaling factor. Furthermore, the analysis is valid for all scenarios: transmit selection, receive selection and joint transmit-receive selection. Results are shown which compare the capacity performance over a wide range of cases. A notable conclusion is that optimal selection, which is computationally intensive, is outperformed at low signal-to-noise-ratios by the simple norm-based approach with power allocation.

关键词： multiple-input multiple-output systems antenna selection techniques Rayleigh fading Ricean fading

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Performance analysis of adaptive DFE using set-membership binormalized data-reusing LMS algorithm for frequency selective MIMO channels

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AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS 2017年 77卷 91-99页

作者： Mishra, Ramesh Chandra Bhattacharjee, Ratnajit Indian Inst Technol Guwahati Dept Elect & Elect Engn Gauhati Assam India

This paper addresses the concern of complexity involved with adaptive equalization in wireless systems operating over time-varying and frequency selective multiple-input multiple-output (MIMO) channels. Here, we propose a decision feedback equalizer using binormalized data-reusing least mean square (BNLMS) algorithm with set-membership filtering for MIMO channels. The performance of the equalizer is investigated for a MIMO receiver in a multi-path fading environment as experienced in the indoor and pedestrian environment. The equalizer performance is also studied for channels having higher delay and Doppler spread. The convergence issues, BER performance and tracking capabilities are examined through computer simulations. Moreover, the computational complexity issue for this MIMO equalizer is compared with other existing data-selective algorithm based techniques. (C) 2017 Elsevier GmbH. All rights reserved.

关键词： Binormalized data-reusing least mean square Data-selective Decision feedback equalizer multiple-input multiple-output systems

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Improved Perfect Space-Time Block Codes

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IEEE TRANSACTIONS ON INFORMATION THEORY 2013年第12期59卷 7927-7935页

作者： Srinath, K. Pavan Rajan, B. Sundar Indian Inst Sci Dept Elect Commun Engn Bangalore 560012 Karnataka India

Perfect space-time block codes (STBCs) are based on four design criteria-full-rateness, nonvanishing determinant, cubic shaping, and uniform average transmitted energy per antenna per time slot. Cubic shaping and transmission at uniform average energy per antenna per time slot are important from the perspective of energy efficiency of STBCs. The shaping criterion demands that the generator matrix of the lattice from which each layer of the perfect STBC is carved be unitary. In this paper, it is shown that unitariness is not a necessary requirement for energy efficiency in the context of space-time coding with finite input constellations, and an alternative criterion is provided that enables one to obtain full-rate (rate of complex symbols per channel use for an transmit antenna system) STBCs with larger normalized minimum determinants than the perfect STBCs. Further, two such STBCs, one each for 4 and 6 transmit antennas, are presented and they are shown to have larger normalized minimum determinants than the comparable perfect STBCs which hitherto had the best-known normalized minimum determinants.

关键词： Cyclic division algebras Galois group multiple-input multiple-output systems nonvanishing determinant shaping criterion space-time block codes

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Exact bit error probabilities and packet error statistics for SVD transmission over time-varying dual-branch MIMO systems obtained by a Markov model

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AEU-INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATIONS 2013年第2期67卷 113-122页

作者： Ivanis, Predrag N. Stojnic, Milena M. Drajic, Dusan B. Univ Belgrade Fac Elect Engn Belgrade 11001 Serbia

Using a finite state Markov channel model, we develop an analytical method for evaluation of the packet error structure in multiple-input multiple-output (MIMO) systems based on singular value decomposition (SVD). We consider dual-branch MIMO systems, with either two transmit and arbitrary number of receive antennas, or arbitrary number of transmit and two receive antennas. The corresponding Markov model parameters are obtained using a novel closed-form expressions for probability density function and level crossing rate of the signal-to-noise ratio at the output of eigenchannels in a MIMO system, derived for a case of Rayleigh propagation, imperfect channel state information and any fixed power allocation. The exact bit error rate for the transmission of quadrature amplitude modulated (QAM) symbols through the eigenchannels is derived in polynomial closed form. Furthermore, by using the developed Markov model, the packet error statistics in the corresponding eigenchannels are determined, and the closed-form analytical expression for the system throughput is derived when 'go-back-N' automatic repeat request procedure is applied in time-varying eigenchannels. The analytical results are validated by using Monte Carlo simulations. (C) 2012 Elsevier GmbH. All rights reserved.

关键词： Automatic repeat request Beamforming Bit error rate Markov model multiple-input multiple-output systems Packet error structure Singular value decomposition

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QOSTBC coded MIMO system with reduced complexity and optimised decoding for rank deficient channels

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IET COMMUNICATIONS 2020年第4期14卷 646-654页

作者： Gupta, Bhasker Balyan, Vipin Saini, Davinder S. CCET ECE Dept Sect 26 Chandigarh India Cape Peninsula Univ Technol EEC Dept Cape Town South Africa

In multiple-input multiple-output (MIMO) systems, rank deficient channels are the most common and key areas of research. In these channels, the number of transmit antennas (M-Tx) is higher than receive antennas (M-Rx) and subsequently the unknown variables are more than the number of equations. In such situations, the conventional sphere decoder (SD) fails due to the presence of zero diagonal elements in Cholesky decomposition. This study analyses the quasi-orthogonal space-time block code (QOSTBC) of symbol rate-2 for M-Tx = 4 with modified double-layer SD detection to overcome rank deficiency problem. The first half of transmitted symbols is detected using two partially dependent SDs with optimised search radii. The remaining half is detected by employing single symbol maximum likelihood detection. Simulation and analytical results indicate that the proposed detection scheme reduces bit error rate and complexity compared to existing techniques.

关键词： channel coding space-time block codes maximum likelihood detection decoding transmitting antennas MIMO communication receiving antennas error statistics antenna arrays communication complexity search problems rank deficient channels multiple-input multiple-output systems transmitting antennas sphere decoder zero diagonal elements quasiorthogonal space-time block code symbol rate-2 modified double-layer SD detection rank deficiency problem single symbol maximum likelihood detection bit error rate QOSTBC coded MIMO system search radii optimisation receiving antennas Cholesky decomposition

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MIMO capacity of antenna arrays evaluated using radio channel measurements, reverberation chamber and radiation patterns

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IET MICROWAVES ANTENNAS & PROPAGATION 2007年第6期1卷 1160-1169页

作者： Garcia-Garcia, L. Lindmark, B. Jalden, N. Orlenius, C. Univ Politecn Madrid Dept SSR E-28040 Madrid Spain KTH Sch Elect Engn Stockholm Sweden Chalmers Univ Technol Dept Electromagnet S-41296 Gothenburg Sweden Bluetest AB S-41296 Gothenburg Sweden

We compare different methods of evaluating arrays for multiple-input multiple-output (MIMO) systems through calculation of the MIMO capacity of a compact antenna array for mobile or WLAN applications at 1766 MHz and comparing it to a reference array of four mono-poles. Three different methods were used: evaluation using radiation patterns and a channel model, measurements in a reverberation chamber and simultaneous measurement of radio channel data using the two arrays. We conclude that all methods give very similar relative results and that the main difference in the two arrays is the 1.3 dB lower radiation efficiency of the compact array. The channel measurements also show that the arrays provide between 80% and 90% of the capacity of a 4 x 4 MIMO system.

关键词： multiple-input multiple-output systems antenna radiation patterns radio channel measurement MIMO capacity radiation patterns Radio links and equipment UHF antennas reverberation chamber wireless channels antenna arrays radio channel data frequency 1766 MHz Antenna arrays MIMO communication

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Subcarrier Intensity Modulated MIMO Optical Communications in Atmospheric Turbulence

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JOURNAL OF OPTICAL COMMUNICATIONS AND NETWORKING 2013年第9期5卷 1001-1009页

作者： Song, Xuegui Cheng, Julian Univ British Columbia Sch Engn Kelowna BC Canada

We investigate spatial diversity techniques for subcarrier phase-shift keying (PSK)-modulated optical wireless communication links over the Gamma-Gamma channels. Both repetition code and the Alamouti-type orthogonal space-time block code (OSTBC) are considered. Highly accurate series error rate expressions are derived by using a moment generating function approach with a series expansion of the modified Bessel function. Truncation error analyses and asymptotic error rate analyses are also presented. Our asymptotic analyses show that the diversity order of the studied system depends only on the effective number of small-scale cells of the scattering process in the atmosphere. Our performance analyses confirm that the repetition code outperforms OSTBC for subcarrier PSK-based systems over the Gamma-Gamma channels. The asymptotic performance loss of the Alamouti-coded system with respect to the repetition-coded system is also quantified analytically.

关键词： Alamouti code Atmospheric turbulence multiple-input multiple-output systems Optical wireless communication

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Parameterised codebook design based on channel statistics for efficient multi-rank MIMO transmission

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IET COMMUNICATIONS 2018年第15期12卷 1880-1890页

作者： Shin, Sungin Lee, Hyukjun Kim, Changhyeon Sung, Wonjin Park, Jonghyun Sogang Univ Dept Elect Engn Seoul 04107 South Korea LG Elect Adv Standard R&D Lab Seoul 07336 South Korea

As the number of antenna elements increases in multiple-input multiple-output (MIMO) systems, an efficient feedback and beamforming strategy becomes more important to achieve the desired bandwidth efficiency required by the next-generation wireless systems. The authors investigate the statistical characteristics of the MIMO channel generated by the three-dimensional spatial channel model to recognise some of the limitations inherent in the existing codebooks adopted by the current third generation partnership project specifications. Such limitations include unnecessary co-phasing combinations for cross-polarised (X-pol) antenna arrays and, in particular, long-term codevector selections, which are not best suited to the channel distributions. In this study, the observed shortcomings are improved by proposing a new multi-rank codebook applicable to the X-pol array of antenna elements supporting up to the quadruple rank. The proposed beamforming codevectors are presented using variable parameters so that they can be adapted to changing channel characteristics. The efficiency of the proposed codebook is further improved by eliminating redundant co-phasing values. The performance of the proposed codebook is evaluated using the TR 36.873 urban macro environment and its effectiveness is demonstrated by quantifying its gain over the existing codebooks.

关键词： MIMO communication wireless channels channel capacity array signal processing antenna arrays parameterised codebook design channel statistics efficient multirank MIMO transmission antenna elements increases multiple-input multiple-output systems channel state information beamforming strategy next-generation wireless systems statistical characteristics MIMO channel three-dimensional spatial channel model current third generation partnership project specifications unnecessary co-phasing combinations cross-polarised antenna arrays long-term codevector selections channel distributions X-pol array quadruple rank beamforming codevectors

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On the error probability of Alamouti scheme with transmit antenna selection for CPM-MIMO systems

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IET COMMUNICATIONS 2017年第18期11卷 2743-2750页

作者： Lei Guowei Liu Yuanan Xiao Xuefang Jimei Univ Sch Sci Xiamen Peoples R China Beijing Univ Posts & Telecommun Sch Elect Engn Beijing Peoples R China Xiamen Univ Technol Sch Optoelect & Commun Engn Xiamen Peoples R China

Up to now, some related results on the upper bounds of error probability have been concluded for some linear modulations with orthogonal space-time block codes in multiple-input and multiple-output (MIMO) systems. For instance, the performance of MIMO systems with antenna selection (AS) has been investigated widely, whereas in non-linear modulations, i.e. continuous phase modulation (CPM), there are few relevant literatures found to this date. With this motivation, this study derives upper bound of the error probability of Alamouti scheme with transmit AS (TAS) in CPM-MIMO systems. First, a new form of signal matrix for CPM-MIMO system is given. Then, the pair wise probability conditioned on fading channel statistics is written availably by computing the difference of signal matrix. Moreover, the probability distribution function is obtained by employing order statistics theory. Furthermore, the tight upper bounds of the frame error rate are derived. Finally, simulated results verify the accuracy of the theoretical analysis.

关键词： pair wise probability multiple-input multiple-output systems Alamouti scheme error probability error statistics Codes probability fading channels orthogonal space-time block codes CPM-MIMO systems orthogonal codes probability distribution function order statistics theory transmitting antennas transmit antenna selection nonlinear modulations Antenna arrays continuous phase modulation space-time block codes Radio links and equipment signal matrix fading channel statistics MIMO communication Other topics in statistics

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