This paper presents a non-codebook based Multiple User Multiple Input Multiple Output (MU-MIMO) test-bed system for Time Division Duplex (TDD) Long Term Evolution-Advanced (LTE-A). The system was implemented for verifying the performance of a dynamic precoding procedure that selects the most appropriate precoder among a given set of precoding techniques. Using two parameters, the propagation path gain and the condition number of the channel matrix, the proposed MU-MIMO system can adaptively switch the precoding software to guarantee that the upper bound Bit Error Rate (BER) is maintained with a minimum computational burden. This paper also presents a novel procedure for accurately and simply calibrating the multiple Radio Frequency (RF) paths of the multiple antennas and RF transceivers of the MU-MIMO system. From various experimental measurements obtained from the implemented test-bed system, the upper bound BER, which was arbitrarily set to 10-3 in this paper, can be maintained with the simplest precoder, Zero Forcing (ZF), unless the propagation path gain becomes less than 0.25. It was also found in the experimental tests that, as the distance between 2 handsets becomes shorter than 1 meter, which causes the condition number of the channel matrix to be larger than 17, the precoder should be switched from Lattice Reduction (LR) to Tomlinson-Harashima Precoding (THP) when the minimum distance between base-station and each handset maintained is set to at least 6 meters.

Recently, filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) has received increasing attention from researchers, owing to its merits and superior spectral efficiency. High peak-to-average power ratio (PAPR) occurs in approximately all multicarrier systems, including FBMC/OQAM, and may cause bit-error-rate (BER) degradation if not appropriately handled. Conventional PAPR reduction methods for orthogonal frequency division multiplexing (OFDM), such as partial transmit sequence (PTS), selective mapping (SLM), and discrete Fourier transform (DFT) spreading, are ineffective in FBMC/OQAM because of the different structure of the symbols. This study proposes a novel method combining DFT spreading and PTS methods to reduce the PAPR of FBMC/OQAM systems with reasonable computational complexity. Numerical results obtained from various computer simulations show that the proposed method achieves a noticeable enhancement in the PAPR performance of the FBMC/OQAM signal compared to other existing methods without affecting the BER performance. Further, the computational complexity analysis and BER performance of the proposed method are presented in comparison to typical existing methods. From our computer simulations, the proposed method reduces the PAPR by approximately 32.8% compared to that of the conventional methods, and the BER performance is improved by 25% with a high-power amplifier effect.

In state-of-the-art mobile devices (MDs), non-radio contexts (i.e., non-real-time data) provided by various sensors have been excluded in determining the modem configuration because of the problems in applying them in real-time modem operations. This paper presents a reconfiguration procedure and hardware implementation of a European Telecommunications Standards Institute (ETSI)-standard reconfigurable MD with a multi-antenna system. Borrowing the ETSI-standard architecture, the proposed MD can exploit a high-level abstraction of configuration-related operations, which consequently provides its application processor operating in non-real-time domain a uniform way of managing the multi-antenna-related hardware platform operating in real time. The configuration of the proposed MD is determined in accordance with non-radio and radio context information for opportunistically utilizing multiple antenna resources. From an implemented multi-antenna MD system operating in an indoor layout and computer simulations of the multi-antenna MD operating in a modeled outdoor layout, we verify that the MD configuration can be optimized in accordance with radio and non-radio contexts not only for fixed indoor but also for mobile outdoor environments. This enables the multi-antenna MD to efficiently utilize its antenna resources, such that the throughput maximization and/or power consumption minimization can be achieved.

Backward compatibility is one of the key issues for radio equipment that supports IEEE 802.11, which is a typical communication protocol for wireless local area networks (WLANs). For achieving successful packet decoding with backward compatibility, frame format detection is the core precondition. In this study, we present a novel, deep-learning-based frame format detection method for IEEE 802.11 WLANs. Considering that the detection performance of conventional methods is mainly degraded because of poor performance in symbol synchronization and/or channel estimation in environments with a low signal-to-noise ratio, we propose a novel detection method based on a deep learning network to replace conventional detection procedures. The proposed deep-learning network method achieves robust detection directly from the received (Rx) data. Through extensive computer simulations performed in multipath fading channel environments (modeled by Project IEEE 802.11 Task Group ac), we confirmed that the proposed method exhibits significantly higher frame format detection performance than that of the conventional method.

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC/OQAM) is an attractive alternative to orthogonal frequency division multiplexing, as it yields a higher spectral efficiency and robustness to frequency dispersion; however, FBMC/OQAM suffers from multipath interference owing to the absence of the cyclic prefix, especially in the signal environments of widely spread multipaths. Although conventional techniques such as multiple‐input multiple‐output along with equalization can combat multipath fading, these techniques do not effectively resolve the multipath interference unless each subcarrier channel can be assumed to be of a flat fading. This article presents a systematic procedure of applying a receive antenna array to FBMC/OQAM systems that removes the multipath interferences using a nicely‐shaped beam pattern for each of the multipaths associated with a severe frequency selectivity. The performance of the proposed array system has been demonstrated in terms of its bit error rate in the adverse multipath‐spread environment of the Extended Typical Urban model of the 3rd Generation Partnership Project, in which each subcarrier channel suffers from a severe frequency‐selective fading. Using various computer simulations, we found that the proposed array system can completely resolve multipath interferences with an array of N = 10, 16, and 22 when Δθ = 15°, 10°, and 5°, respectively, where N and Δθ denote the number of antennas in each subarray and the interpath direction of arrival difference, respectively. In addition, the proposed array system also provides a signal‐to‐noise ratio gain that is proportional to N, once the multipath interferences are successfully resolved.

This paper presents a reconfigurable base-station platform that supports the wide variety of evolution of network services required for 5G mobile communications. The new technology is based on Radio Virtual Machine concept which resolves the problem of portability between the various network service software and base-station platform hardware. Using the proposed method, base-station is capable of adopting the various network services required for the 5G mobile systems.

This paper assumes an inevitable necessity for reconfigurable vehicular communication platforms to cope with the evolution of communication standards. In spite of the keen requirement of the software reconfigurability, however, the conventional Software Defined Radio (SDR) technology that is based on Software Communication Architecture (SCA) suffers from a critical hindrance of the inefficient software portability for commercial applications. This paper presents a novel technology of resolving the problem of portability between the Radio Application (RA) software and communication platform hardware. The new technology is based on Radio Virtual Machine (RVM) about which the related protocols and interfaces have been published as a standard of European Telecom. Standard Institute (ETSI).

This paper presents a non-codebook based Multiple User Multiple Input Multiple Output (MU-MIMO) test-bed system for Time Division Duplexing (TDD) Long Term Evolution-Advanced (LTE-A), which has been implemented for verifying the performance of a dynamic precoding procedure. Using the parameter of propagation path gain, the proposed MU-MIMO system can adaptively switch the precoder to guarantee that the upper bound BER is maintained with a minimum computational burden.