Analog Decoding Method for Simplified Short-Range MIMO Transmission

Ryochi KATAOKA  Kentaro NISHIMORI  Takefumi HIRAGURI  Naoki HONMA  Tomohiro SEKI  Ken HIRAGA  Hideo MAKINO  

IEICE TRANSACTIONS on Communications   Vol.E97-B   No.3   pp.620-630
Publication Date: 2014/03/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.620
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Antennas and Propagation
short-range MIMO transmission,  zero forcing,  unitary matrix,  90-degree phase shifter,  optimal element spacing,  

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A novel analog decoding method using only 90-degree phase shifters is proposed to simplify the decoding method for short-range multiple-input multiple-output (MIMO) transmission. In a short-range MIMO transmission, an optimal element spacing that maximizes the channel capacity exists for a given transmit distance between the transmitter and receiver. We focus on the fact that the weight matrix by zero forcing (ZF) at the optimal element spacing can be obtained by using dividers and 90-degree phase shifters because it can be expressed by a unitary matrix. The channel capacity by the proposed method is next derived for the evaluation of the exact limitation of the channel capacity. Moreover, it is shown that an optimal weight when using directional antennas can be expressed by using only dividers, 90-degree phase shifters, and attenuators, regardless of the beam width of the directional antenna. Finally, bit error rate and channel capacity evaluations by both simulation and measurement confirm the effectiveness of the proposed method.