We propose a multi-stage adaptive equalizer for the demodulation of an optical aggregated 16QAM. A successful demodulation of the 100Gbps class 16QAM signal was demonstrated without an OSNR penalty when the input PAM4 signals to the optical aggregation were not symbol-synchronized.

In 5G vehicular communications, beamforming technologies for vehicles, which compensate for large propagation losses at high carrier frequencies, are being considered. However, because the deflected beamforming loss degrades the communication quality, an accurate beam tracking system that follows the movement of the vehicle is required. In conventional schemes using a periodic codebook, the main lobe often deviates from the direction of the base station owing to fast movement. Therefore, in this study, a scheme for adaptively generating beam candidates using beam selection logs and the steering angle of the vehicle is proposed. Numerical results show that the scheme has high accuracy.

This paper proposes a frequency-division multiplexed vibrotactile signal transfer system on conductive textiles for implementing wearable tactile suits. For multiplexing, many carrier frequencies are in one-to-one correspondence with many receivers. Each carrier signal is frequency-modulated with analog vibrotactile waveforms, and each receiver demodulates it and drives its built-in actuator. The analog waveform transmission achieves multi-channel real-time vibrotactile actuation, which is suitable for applications such as virtual reality (VR) games. A commercially available frequency modulation (FM) radio receiver chip achieves high sensitivity and superior channel selectivity. Carrier frequencies can be located in a 32MHz bandwidth, from 76MHz to 108MHz, every 200kHz, and 160 channels of vibrotactile waveforms can be transmitted simultaneously.

We propose a rolling-shutter-sensor-based visible light communication (RS-VLC) system using a cross-screen filter suitable for intelligent transport system (ITS) scenarios. The proposed system uses a cross-screen filter to diffuse the received light in the scanning direction of the rolling-shutter sensor, thus improving the intensity of the received signal and increasing the communication range. The experimental results show that the proposed system can improve the communication range. We also show that the proposed system is capable of multi-user communication and positioning.

In current cellular networks, Spatial Modulation with Orthogonal Frequency Division Multiplexing (SM OFDM) is a newly designed transmission method that substitutes Multiple Input Multiple Output (MIMO) OFDM transmission. In practical frameworks, estimation of the channel is vital for recovering the transmitted data. In a conventional DFT-based channel estimation algorithm, impact of noise is reduced in the time domain. It retains the significant values with some sort of threshold value equal to the Cyclic Prefix (CP) length that differentiates the signal values and noise terms of Channel Impulse Response (CIR), thereby improving the performance in OFDM systems. Here we require information on CIR length in advance. But this results in performance degradation if the path delays are less for a channel. Hence this work proposes improved DFT-based channel estimation where the threshold value is set equal to the estimated CIR length using RMS delay spread approximation in SM OFDM systems. Symbol Error Rate (SER) and Mean Square Error (MSE) are the performance metrics considered in Rayleigh fading channel employing ITU- Vehicular A channel model for 16 QAM SM OFDM systems. Simulation output shows performance improvement of SER and MSE by the implementation of improved DFT-based channel estimation. At an SNR of 40 dB, the proposed method can enhance SER performance by about 2.8 dB and MSE performance about 4dB compared with conventional DFT estimation.

This paper proposes a technique of sampling-rate retrieval using multi-cameras with a lower frame rate than the symbol rate on an optical camera communication (OCC) with a clock divider. This proposed technique applies the characteristics of the integral sampling method that occurs when an image sensor-based camera receives the optical signal. The technique realizes the demodulation of the optical signal having a larger bit rate than the frame rate of the camera. Employing the proposed technique can achieve the transmission capacity of the number of cameras times frame rate per camera.

This letter investigates the performance and the design of fully-digitized, uplink multiuser massive multiple-input multiple-output (MIMO) systems with low-resolution analog-to-digital converters (ADCs). We analyze the effects of quantization errors when low-resolution ADCs are applied to uplink multiuser massive MIMO systems for reducing power consumption. We derive appropriate decoding parameters to estimate channel bit log-likelihood ratios (LLRs) by taking the power of quantization errors and channel estimation errors into account. The simulation results reveal that lower bit error rates (BERs) can be achieved by enhancing the number of receiving antennas and reducing the number of quantization bits for given spatial correlation matrices.

Bioequivalent phantoms are used to evaluate the effects of the human body in electromagnetic waves propagation for small wireless communication devices such as smart phones and wearable devices used in close proximity to the human body. The conventional phantom fabrication process requires fabrication skills and experience to avoid air bubbles in the phantom that affect the electrical characteristics. This letter proposes a new phantom fabrication method using ultrasonic vibrations for degassing to stabilize the electrical constants of the fabricated phantom and demonstrates its effectiveness by experiments.

Centralized RAN, which connects a centralized base band unit (BBU) to multiple remote radio units (RRUs), is one of the promising architectures because it enables the BBU to coordinate with distributed RRUs by using multiple-input multiple-output (MIMO) processing without control signaling among RRUs. However, fronthaul traffic between the BBU and RRUs increases and fronthaul link capacity is to be under strain due to increasing the number of RRUs in a same fronthaul network segment. In this paper, we propose a direct constellation mapping method to reduce the fronthaul traffic. And it is also shown that our proposed method can drastically reduce the required fronthaul link capacity with slight downlink throughput degradation by Monte-Carlo computer simulation.

This letter proposes a practical transmission datarate adaptation (TDA) scheme using Q-learning applicable to IEEE 802.11ax wireless local area networks. In the proposed scheme, each basic service set (BSS) selects an appropriate transmission datarate according to the buffer statuses of adjacent BSSs which are periodically collected and the transmission results of DATA frames in the BSS. Then, the BSS conducts underlay transmissions based on the framework of spatial reuse defined in IEEE 802.11ax. The performance of the proposed scheme is evaluated through system-level computer simulation assuming downlink full-buffer traffic. It is confirmed that the proposed scheme can achieve higher average area throughput than conventional TDA schemes such as Robust Rate Adaptation Algorithm (RRAA) and adaptive modulation and coding (AMC) based on the received power.

This letter presents the derivation for the steady-state bias errors of a tracking filter using a coordinated turn (CT) model for tracking a target moving at a constant velocity as a tracking performance index of maneuvering target. The analysis of the tracking filter using the CT model indicates bias errors due to differences between the model-assumed motion (constant angular velocity) and target motion (constant velocity). We derive this bias error in the closed-form as expressed by the filter design parameters. Then, numerical simulations show that the derived bias errors are correct and can be efficiently used for filter design.