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Efficient Complex Matrix Inversion for MIMO OFDM Systems
Zhi Quan,Jie Liu 한국통신학회 2017 Journal of communications and networks Vol.19 No.6
The use of orthogonal frequency-division multiplexing(OFDM) greatly simplifies receiver design in multiple-inputmultiple-output (MIMO) wireless systems when the channel is frequencyselective. Since complex-valued matrix manipulations, suchas matrix inversion, are normally required in MIMO-OFDM systems,the receiver complexity is much higher than that of singleinputsingle-output and single-carrier systems. In this paper, theauthors propose a low-complexity version of matrix inversion byusing the dichotomous coordinate descent (DCD) algorithm forMIMO-OFDM systems. The idea is for the DCD algorithm to separatelyobtain the individual columns of the inverse of the matrix. Owing to the low-complexity hardware implementation of the individualDCD algorithm, a block of DCD processors can be adoptedto obtain the columns of the inverse of the channel correlation matrixin parallel with low hardware occupation.
Zhiquan Wang,Jianjun Li,Xuejun Jiang,Xuejun Jiang,Neng Wang,Shimin Wang 대한의학회 2009 Journal of Korean medical science Vol.24 No.1
The effects of the antiarrhythmic drug propafenone at c-type kv1.4 channels in Xenopus laevis oocytes were studied with the two-electrode voltage-clamp techinique. Defolliculated oocytes (stage V-VI) were injected with transcribed cRNAs of ferret Kv1.4△N channels. During recording, oocytes were continuously perfused with control solution or propafenone. Propafenone decreased the currents during voltage steps. The block was voltage-, use-, and concentration- dependent manners. The block was increased with positive going potentials. The voltage dependence of block could be fitted with the sum of monoexponential and a linear function. Propafenone accelerated the inactivate of current during the voltage step. The concentration of half-maximal block (IC50) was 121 μM/L. With high, normal, and low extracellular potassium concentrations, the changes of IC50 value had no significant statistical differences. The block of propafenone was PH- dependent in high-, normal- and low- extracellular potassium concentrations. Acidification of the extracellular solution to PH 6.0 increased the IC50 values to 463 μM/L, alkalization to PH 8.0 reduced it to 58 μM/L. The results suggest that propafenone blocks the kv1.4 N channel in the open state and give some hints for an intracellular site of action.
A Novel M-ary Code-Selected Direct Sequence BPAM UWB Communication System
Zhiquan Bai,곽경섭 한국전자통신연구원 2006 ETRI Journal Vol.28 No.1
In this letter, a novel M-ary code-selected direct sequence (DS) ultra-wideband (UWB) communication system is presented. Our purpose is to achieve a high data rate by an M-ary code-selected direct sequence bipolar pulse amplitude modulation (MCSDS-BPAM) scheme. In this system, a particular DS code sequence is selected by the log2M/2 bits from the DS gold code set. This scheme can accomplish both a high data rate without increasing the system bandwidth or changing the pulse shape and improve the BER with an increase of modulation level M even at a lower signal-to-noise ratio (SNR). The receiver signal processing algorithm is given for an MCSDS-BPAM UWB system over an ideal AWGN channel and correlation receivers.