This paper proposes a novel distributed Raman amplification (DRA) scheme for long-haul optical fiber transmission systems. The scheme utilizes two fibers for the bidirectional transmission links, and each fiber is counter-pumped by a second-order pump source. The first-order pump lights are generated in the ring cavity consisting of two fibers, and amplify the optical signal. This scheme enables both co-pumping and counter-pumping from the generated first-order pump lights by using only second-order counter-pumping. The amplification performance of the proposed scheme is examined in the long-haul transmission experiments using dual-polarization QPSK signal, and the proposed scheme is confirmed to improve the transmission performance compared with the conventional first-order counter-pumping DRA.

The instantaneous throughput is evaluated based on the communication traffic volume per unit time. Although the method can roughly evaluate that throughput within a unit time, it is difficult to evaluate the communication situation of each packet in detail. Therefore, the authors have proposed the method of deriving instantaneous throughput based on the occupied duration in individual UDP transmission. In the method, not only instantaneous throughput per packet but also that of other signals such as beacon signals can be evaluated. In this paper, we define and extend the occupied duration in individual TCP transmission, and show an example of analysis compared with the conventional methods.

Generally, a monitoring system has tradeoff between network fee and monitoring precision. If the system user wants to monitor a something target from a remote office precisely, the network fee becomes higher because of taking lots of monitoring packets (i.e., video frame). Here, I propose an extractive streaming system to address this problem. The proposed system is installed for both the video sender and receiver. The sender system extracts the pre-determined target area (e.g., license plate) with high quality from a video frame, and sends both roughly compressed entire video frame (e.g., encoded H.264) and the extract area to the receiver in parallel. Subsequently, the receiver system overlays the extracted area on the entire video frame. Through these process, the user can monitor a target area (i.e., focused area) precisely with low network fee. I evaluated the proposed system and investigated the extent to which additional latency and communication traffic was incurred by the proposed system and conducted that the system results in reduced network traffic with decreased latency.

We investigated the cross-phase modulation (XPM) and phase-noise compensation capability of our proposed polarization-multiplexed and intensity-modulated pilot-carrier scheme. Theoretically, the proposed scheme can completely compensate for the effects of XPM as well as self-phase modulation (SPM) and the phase noise of the light source. The performance was evaluated by numerical simulation of optical fiber transmission of wavelength-division-multiplexed (WDM) 16-ary quadrature amplitude modulation (16QAM) signals. The compensation performance was confirmed by changing the transmission distance and the optical input power to the optical fiber.

This paper considers designing hybrid beamformer (HBF) to enhance communication performance and reduce inter-cell interference for massive MIMO system. The goal is minimizing the transmission power under individual signal-to-interference-plus-noise ratio (SINR) and sidelobe level (SLL) constraints, which is a non-convex optimization problem. To tackle the SLL over continuous intervals, we convert it into a finite number of constraints. Then we give the optimal solution of the problem for different RF chain to user number ratio. Simulation results show proposed algorithm not only effectively reduce inter-cell interference but also exhibits high numerical stability in multiuser massive MIMO system.

This letter presents improved maximum cyclic autocorrelation selection (MCAS) based spectrum sensing techniques with multiple antennas. The improved MCAS based spectrum sensing employs two types of statistic; one includes an information of target signals and another one is for the comparison with the former one. These statistics are computed from a cyclic autocorrelation function (CAF) at only one cyclic frequency. In this letter, we attempt to enhance the performance of signal detection by selecting a receive antenna element with a minimum statistic for the comparison. The presented results are compared with some conventional results. Numerical examples are shown to validate the effectiveness of the presented technique and the performance of the presented technique is superior to the conventional technique.

As the allowable antenna power of amateur stations is higher than that of smartphones, the specific absorption rate (SAR) is expected to increase. However, to date, there has been limited research on handheld FM transceivers and SAR for amateur stations. Therefore, this study focuses on the 1.2-GHz band, which is the highest frequency of all commercially available handheld FM transceivers, and proposes a monopole antenna with a reflector to reduce SAR. The finite-difference time-domain method was employed to conduct simulations using a brain-equivalent simple model and a real numerical human body model. It is confirmed that by installing a reflector, SAR can be reduced without significantly changing the antenna characteristics.

In this article, we propose a frequency-domain feature clustering scheme for a machine-learning based object detection utilizing channel state information (CSI) in wireless local area network (WLAN) systems with multiple antennas where CSI frames are captured from nearby wireless devices. In this scheme, all subcarriers (their CSI) are divided into multiple clusters in an interleaved manner and the existence of object is detected by integrating majority decision of cluster-by-cluster machine-learning results. Simulation results show that the proposed interleaved clustering scheme achieves better object detection probability than cases with a localized clustering scheme and without clustering in an indoor propagation environment.