Delay-sensitive applications over cellular networks, such as road traffic collision avoidance, usually have a deadline constraint within which the data must be delivered. Model-based network resource management may miss the deadline due to model uncertainties of the cellular networks. This letter proposes a deadline-aware resource management method based on maximum bit rate (MBR) control with a feedback controller for delay-sensitive applications. The proposed method treats the model uncertainties as disturbances. The feedback controller maintains the effective throughput at a target level to meet the deadline even if disturbances exist. Numerical simulations demonstrate that the proposed method improves the success rate of data delivery within the deadline constraint in the presence of disturbances.
This paper presents a basic consideration of complex impedance projection. We start by recalling the traditional Smith chart. The well-known standing wave ratio is revisited by its natural logarithm, which brings Poincaré metric to geometrical distance on the chart. We then replace the distance by its double to observe the Beltrami-Klein disk model from the aspect of RF engineering. To give fundamental locus examples, we formulate how lumped-constant elements behave on hyperbolic coordinates, and find that they draw their constant-R and -X contours in straight lines or vertical ellipses. For higher frequency applications, we also formulate the behavior of transmission lines to show what trajectories they exhibit on the disk.
Radar is one of the technologies that can detect drones. We have previously proposed to use an ultra-wideband (UWB) radar, which uses quasi-millimeter wave band (24/26 GHz) or millimeter wave band (60/79 GHz), for drone detection. The radar cross section (RCS) of a radar target is an important factor related with the radar performance such as detection, tracking, and classification. This paper experimentally investigates the RCS patterns of five types of drones with different shapes, sizes, and the number of rotor blades (Phantom 3, Bebop Drone, 3DR Solo, Mavic Pro, and Matrice 600). RCS measurements were conducted at 24 GHz for two polarizations, H-H and V-V. As a result, we have confirmed that the mean RCS values of the drones vary from -8.1 dBsm to -19.1 dBsm depending on body size, shape, and polarization.
In this paper, we propose a real-time detection system for smartphone zombie (smombie) base on machine learning. The feature of this study is that it does not use cameras and external devices, which are often seen in studies focused on smombie. The proposed system uses brightness, acceleration, gyro and motion sensors. We find the effectiveness of the proposed system by experiments for 10 examinees. We show it can detect smombie with 93% accuracy.
In wireless communication systems, simplification of the receiver circuits is an important issue. In particular, an analog-to-digital converter (ADC) is one of the most important circuit blocks. To deal with this issue, a low-resolution ADC utilizing hysteresis-based simple negative feedback (SNF) technique (hysteresis-based SNF-ADC) was proposed to mitigate nonlinear distortion. In this article, we investigate a recursive channel estimation technique for single carrier modulation with one-bit resolution hysteresis-based SNF-ADC. Simulation results clarify that the channel estimation accuracy is improved by using hysteresis-based SNF-ADC and bit error rate (BER) performance is improved compared to cases with only a comparator.
5G wireless communications use electromagnetic (EM) waves in the 28GHz band, and the EM waves radiated from high-directivity (gain) antennas are hence scattered in a specular direction by walls. If there are obstructions between the transmitting and receiving antennas, the wireless communication quality is deteriorated since the receiver can receive neither direct waves nor reflected waves. In this paper, an EM scattering wall is designed by applying array antenna theory to improve the wireless communication quality. Moreover, the optimum configuration of the EM scattering wall is designed by using the genetic algorithm without a large amount of calculation by an EM simulator.
This paper proposes a novel polarization crosstalk canceller (PCC) based on receiver digital signal processing (DSP) in polarization division multiplexed digital coherent transmission utilizing forward-pumping distributed Raman amplification (DRA). The PCC consists of 1-tap adaptive filters with a butterfly configuration controlled by the recursive least square algorithm. The PCC offsets the crosstalk between two polarization tributaries caused by the time-varying polarization fluctuation due to the relative intensity noise of the forward-pumping sources. The proposed PCC is applied to the long-haul dual-polarization QPSK transmission experiment with forward-pumping DRA, and confirmed to improve the transmission performance.
We have proposed an information acquisition method with detecting the reflector code on roadside by using infrared laser range scanner. The scanner on vehicle scans the reflector code on roadside while traveling. However, we cannot change the code pattern according to the road information, GPS location and so on. Hence, we propose an adaptive reflector code by switching infrared LED to express appropriate information. Through some experiments, we show that the vehicle can obtain different information from roadside according to the use case.
Rolling-shutter (RS) optical camera communication (OCC) is effective to increase symbol rate in indoor OCC from LED lamp to smartphones’ built-in camera. However, exposure time of RS camera is longer than the line interval of the camera. Symbol error rate deteriorates as the symbol rate increases owing to inter-symbol interference (ISI). To reduce ISI, dual camera is adapted. Ensemble averaging in number of decision pixels per symbol with dual camera suppresses ISI. Error-free symbol rate was increased with dual camera more than that with a single camera. The reason for increase in symbol rate is elucidated with the correlation coefficient.
This letter presents a device identification method based on the distortion of a power amplifier (PA). The distortion of PA is measured by a logarithmic swept sine, which can distinguish harmonic distortion for each order. In this letter, we propose a new feature extraction utilizing each harmonic distortion to accurate device identification in a multipath environment. The proposed method can reduce computational complexity because it requires no calculation of the pseudoinverse matrix and iterative calculation. Experimental results show that the proposed method can achieve a higher identification ratio in an indoor environment.
High reliability will be required even in Internet of Things (IoT) communications in the near future for control purposes. To enhance reliability, both uplink (UL) and downlink (DL) communication quality must be considered. In this paper, we focus on the improvement of DL physical layer communication. To enhance the reliability of DL, the use of spatial diversity is a promising technique. We deal with two transmit diversity (TD) techniques, space-time block coding (STBC) and cyclic delay diversity (CDD), which are evaluated by experimentations in real environments. From the results of the experiments, we confirmed that STBC and CDD could improve frame error ratio (FER). CDD can achieve almost the same performance as STBC by setting the amount of cyclic shift (ACS) appropriately. For example, in a non-line-of-sight (NLOS) area where shadowing happens due to hillock, FER could be improved from 5.11×10-2 to 1.59×10-2 in STBC and 1.00×10-2 in CDD.
This contribution describes a fingerprint position estimation using RSSI (Received Signal Strength Indicator) of wireless LAN Access Points (APs) that employs Neural Network (NN). We propose position estimation using the weighted intermediate point to estimate the exact position. In this method, RSSI of UD (User Data) is collated with the RSSI in DB (data base). RSSI of DB was measured on coordinates in advance. Therefore, one of the coordinates is selected as the estimation result. The coordinate closest to correct point is selected in case of estimation at the intermediate point of the coordinates. In this study, we propose to estimate the intermediate point using weighting with the existence probability distribution of limited coordinate output from NN. The accuracy of proposed position estimation method was verified using three-layer NN based on measured data.
Collaborated multiple-input multiple-output reception is studied in this letter. This system employs multiple mobile stations (MSs) to receive signals from a base station, and then share their received signals among collaborated MSs. One of important research topic for this system is MS selection for collaboration. This letter presents the relation between the error rate performance of this system and antenna arrangements of the MS side in actual environments. The results suggest that MSs in collaboration can remain the same in terms of long-term average performance.
We propose a simple technique for measuring the differential group delays (DGDs) between two different modes in a few-mode fiber (FMF) using an interferometric technique. We also experimentally demonstrate that the DGD between the two modes in the FMF with four modes can be successfully and simultaneously measured using the proposed technique.
The IEEE 802.11ay channel models have been developed based on the quasi-deterministic (Q-D) channel modeling that considers environment specific property of millimeter-wave (mm-wave) propagation by representing multi-path channels as superposition of deterministic (called D-ray) and random clusters (called R-ray). Based on the Q-D model, this letter presented the inter-cluster parameters of the random clusters which were obtained from the double-directional channel measurement in an indoor entrance hall environment. Comparison between the parameters obtained in this study and those of the existing IEEE 802.11ay/MiWEBA model showed that both are reasonable values inferred from each corresponding environment.
In private information retrieval (PIR) from coded storage servers, consider the case where some of servers are Byzantine adversaries and unresponsive. There have been proposed several specialized schemes guaranteeing that the user can correctly obtain the desired message even in the adversarial situation. However, to the best of our knowledge, such resistance to the adversaries in PIR schemes based on arbitrary codes have been not precisely characterized. In this paper, we reveal that the exact resistance to Byzantine and unresponsive servers is expressed in terms of the coset distance of linear codes in linear PIR schemes based on arbitrary storage code.
This letter proposes approximated zero forcing precoding with a threshold in molecular communication (MC). Frequency domain precoding for channel equalization is investigated. Owing to the restriction of a transmitter in MC the main part of an equalized waveform is extracted and a corresponding rectangular waveform is transmitted. In the proposed equalization scheme, the frequency component of the transmit signal is suppressed if a threshold exceeds the channel coefficient in the proposed scheme. Numerical results obtained through computer simulation show that approximation by a single rectangular waveform achieves almost the same performance as that with rectangular approximation that suppresses inter-symbol interference with the proposed precoding technique.
For high-density wireless LAN environment, the interference among overlapped basic service sets (OBSSs) is a serious problem. To address this issue, we have proposed distributed smart antenna system (D-SAS) for wireless LAN, which suppresses the interference among OBSSs and improves the throughput. We have also developed the prototype of wireless LAN access point (AP) with D-SAS and demonstrated the system throughput with stadium environment. In this letter, we evaluate the performance of the developed wireless LAN AP with D-SAS on a train environment and describe that throughput with D-SAS is superior to that with the conventional centralized antennas. It was found that the developed D-SAS AP provides twice system throughput larger than the conventional AP with centralized antennas.
A rerouting technique using a time aware shaper is proposed for Internet of Things traffic in a Layer-2 network to accommodate time division duplex (TDD) based mobile front-haul. Experimental results showed that a low latency of 40us and a high throughput near line rate could be attained at any time by avoiding the route with the reserved transfer window.