Nowadays, requirements of communication in special channel environments are increasing such as underwater, underground, and biological tissues which have a high permittivity characteristic. The conventional radio frequency (RF) communication, which is based on the principle of electromagnetic radiation, is not suitable in these channel environments due to a high path loss problem. Magnetic communication systems are not affected by the permittivity of channel environments. Therefore, the magnetic communication systems have attracted attention as an alternative communication in these channels. However, the magnetic communication has limitations such as a low data-rate, a short communication range and a sensitive in misalignment between transmit antennas and receiver antennas. Many research teams have tried to overcome these problems by various approaches. In this paper, we realize the magnetic MIMO communication test bed using the heterogeneous multi-pole loop antenna array to obtain the higher data rate and the enhancement of bit error rate (BER) performance in misalignment cases using various signal processing schemes. The proposed antenna array can satisfy a same BER performance of the conventional antenna array at the further distance. Furthermore, to obtain the enhanced BER performance in various misalignment cases, we apply signal processing schemes, which are used in the conventional RF communication, to the proposed test bed, such as maximum likelihood (ML), zero forcing (ZF), minimum mean square error (MMSE) and singular value decomposition (SVD). We verify to overcome the misalignment problems that magnetic communication can overcome the misalignment problem using the signal processing schemes. The SVD shows the lowest BER performance in large misalignment with a perfect channel information, and ML shows the best BER performance without the channel information. Other signal processing schemes present a same BER performance due to a high SNR channel condition. ⓒ 2017 DGIST
Table Of Contents
Ⅰ. Introduction 1 -- Ⅱ. Near field magnetic communication 3 -- 2.1 Magnetic communication and applications 3 -- 2.2 Limitation and related research 4 -- 2.2.1 To expend the communication distance 4 -- 2.2.2 To robust to misalignment 5 -- 2.2.3 To robust to misalignment 5 -- Ⅲ. Magnetic MIMO communication System 7 -- 3.1 Concept of magnetic MIMO 7 -- 3.2 Misalignment in MIMO antenna array 8 -- Ⅳ. Misalignment insensitive communication system test bed 12 -- 4.1 Hardware configuration 12 -- 4.2 Software configuration 14 -- 4.3 MIMO signal processing schemes 17 -- 4.3.1 Singular value decomposition (SVD) based estimator 18 -- 4.3.2 Maximum likelihood (ML) detector 19 -- 4.3.3 Zero forcing (ZF) receiver 20 -- 4.3.4 Minimum mean square error (MMSE) receiver 21 -- Ⅴ. Misalignment experimental results 22 -- 5.1 Experiment setup 23 -- 5.2 BER performance results 24 -- Ⅵ. Conclusion 29
