The high throughput of the cryptographic hash function has become an important aspect of the hardware implementation of security system design. There are several methods that can be used to improve the throughput performance of MD5 design. In this paper, four types of MD5 design were proposed: MD5 iterative design, MD5 unfolding design, MD5 unfolding with 4 stages of pipelining design and MD5 unfolding with 32 stages of pipelining design. The results indicated that MD5 unfolding with 32 stages pipelining of design provides a high throughput compared with other MD5 designs. By using an unfolding transformation factor of 2, the number of cycles of MD5 design was reduced from 64 to 32. All the proposed designs were successfully designed using Verilog code and simulated using ModelSim. The throughput of MD5 unfolding with 32 stages of pipelining design was increased significantly to 137.97 Gbps, and the power of this MD5 unfolding with 32 stages of pipelining was 750.99 mW. Therefore, it is suggested that an unfolding transformation with a high performance pipelining are applied to MD5 hash function design in order to produce an embedded security system design. This paper is expected to be for improving the maximum frequency and the throughput of MD5 design. Thus, by increasing the number of stages in MD5 unfolding design, the performance of MD5 designs can be improved significantly.
To process increasing data traffic, one of the most effective solutions is data offloading. Processing data traffic in heterogeneous networks (HetNets) based on loaded traffic conditions improves the user throughput. In this case, user traffic needs to be divided taking account of the difference in the transmission rate among networks. When a macro base station (BS) provides wireless resources for user equipment (UE) of good channel quality near the macro BS, higher user throughput is expected. However, at the macro cell edge, the transmission performance of UEs in a micro cell deteriorates. To reduce this inconvenience, by processing the loaded traffic appropriately using a macro BS and micro BS, we can obtain higher user throughput. This paper proposes wireless resource allocation based on loaded traffic conditions and the position of BSs with ON-OFF switching according to the channel quality in HetNets. Simulation results show the effectiveness of the proposed method, especially when the data loss ratio of the macro cell is low and that of micro cells is high. The proposed method is effective for a damage-resistant system against natural disasters and an automatic driving system in an intelligent transport system (ITS).
Smartphones with Bluetooth low energy (BLE, marketed as Bluetooth Smart) have been widely used. The BLE is a part of Bluetooth 4.0. It utilizes the 2.4 GHz band known as the industrial, scientific, and medical (ISM) band. The IEEE802.11 wireless local area network (WLAN) utilizes the same ISM band as BLE. Therefore, radio-frequency interference may arise with BLE and WLAN coexistence. In this paper, we focus on the interference between the WLAN beacon and the BLE advertising packet. We evaluate the bit error rate (BER) of the WLAN signal on the direct sequence spread spectrum (DSSS) modulation caused by interference with the BLE signal on the Gaussian minimum shift keying (GMSK) modulation by computer simulation. Additionally, we focus on the difference in frequency to investigate the effect of overlapping channels. Furthermore, we examine BER estimation by using the signal-to-interference ratio (SIR) assuming that the BLE signal is modeled as an additive white Gaussian noise (AWGN). Concerning the characteristic of the difference in frequency, we confirm the validity of these simulation results by experimental evaluation in the coexistence of the WLAN beacon and the BLE advertising packet. These results of simulation and experiment have shown that the difference in frequency is correlated with the interference of the BLE signal on the WLAN signal. Moreover, we have verified that the estimation of BER characteristics considering the difference in frequency by using SIR is possible.
In this paper, we propose a novel channel allocation scheme, i.e., the asymmetrically paired repeated unequally spaced (APRUS) scheme, for the dense wavelength division multiplexing (DWDM) transmission system. The APRUS scheme is capable of virtually eliminating the four-wave mixing (FWM) noise in the DWDM system, thus effectively addressing the FWM problem plaguing the conventional equally spaced (ES) channel allocation scheme. The APRUS allocation scheme was simulated and validated on four performance metrics; the number of FWM frequencies, total FWM power, total FWM efficiency and bit error rate. The simulation results revealed that the APRUS scheme outperforms the conventional ES regime on all four metrics. In addition, the FWM noise under the APRUS scheme is negligible such that no optical filters are required to filter out the noise at the DWDM's receiving end. Moreover, an extra signal channel is accommodated under the APRUS allocation scheme, which is equivalent to a gain of 10Gbit/s data transfer rate.
Generation methods of the optical zero-correlation zone (ZCZ) sequence set with ZCZ 1, 4z - 2 and 2z have been proposed, where z is a natural number. However, the code generator for the sequence with ZCZ 2z has not been considered. In this paper, we propose a new construction of a code generator without ROM. The proposed code generator can suppress the circuit size and operate faster than the conventional code generator with ROM. In addition, the conventional and proposed code generators for the sequences with the ZCZ sizes of 2, 4, and 8 are implemented on a field-programmable gate array (FPGA) and compared. As a result, the proposed code generator can reduce the circuit size and operate faster than the conventional code generator.
The quasi-synchronous direct sequence code division multiple access system can realize fast frame acquisition and interference-free performance if a shift orthogonal code is used as a spreading sequence set, and synchronization among users is quickly established within a permissible time interval. In this paper, we presents high-speed synchronization acquisition methods, which can be established by the correlation handling of one received data frame. They utilize one of the spreading sequences in the shift orthogonal code as a synchronization control sequence, and a matched filter bank that provides all the correlation functions between a received signal and any sequence. The effectiveness of the proposed methods, in which output is close to an impulse function, is shown by the synchronization error rate over the additive white Gaussian noise and Rayleigh fading channels.
Satellite data has often been used to investigate damage from natural disasters (e.g., flood, drought, forest fire and volcano eruption) close to real-time. In particular, Terra/MODIS and Aqua/MODIS have been widely used for retrieving information on natural disasters and land cover changes because of their advantage of good ground resolution (maximum 250 m) and daily availability (full daily coverage of the Earth). However, the observation of areas covered by clouds using optical sensors does not work. Although the composite method is widely used to reduce the influence of clouds, clouds are likely to remain in some compositing periods. This paper presents the White Object Index (WOI), used for estimating the cloud fraction of a pixel in satellite imagery. The WOI was obtained from differences in reflectance of visible and short-wave infrared spectral bands using a mixture model. The efficiency of the WOI was tested by comparing the maximum value composite (MVC) method with MOD35 using time series data. As a result, WOI was confirmed to be an efficient tool for estimating the influence of clouds within a pixel.
In this paper, we develop a nonlinear observer by applying a pseudo-formal linearization method of the polynomial type to both state and measurement equations for nonlinear systems. The given nonlinear system is linearized into an augmented linear system by pseudo-formal linearization based on the Taylor expansion. Furthermore, an augmented measurement vector that consists of polynomials of measurement data is introduced and is transformed into an augmented linear one by the pseudo-formal linearization. A linear system theory is applied to these linearized systems to design a new nonlinear observer. Numerical experiments indicate that the performance of the presented method is more improved than by the previous method.
The slow slip event (SSE) is an aseismic transient slip on a fault, and is an important seismological event in the subduction zone. In the field of seismology, a method is needed to accurately estimate the spatio-temporal slip distribution and duration of the SSE using crustal deformation data around the ground. However, conventional methods for estimating the spatio-temporal slip distribution and duration have been developed separately, and have employed models that cannot accurately capture the spatio-temporal behavior of the SSE. We propose a method for estimating the spatio-temporal slip distribution and duration of the SSE simultaneously by introducing a switching model that takes three forms corresponding to three periods. In the first and third periods, the fault is fixed, and in the second period, the fault is slipping slowly. The time points at which the model changes as well as the parameters of the switching model are estimated by the maximum likelihood method using the Expectation-Maximization algorithm. The proposed method thus improves the estimation accuracy of the slip distribution and duration of the SSE by applying appropriate models for specific situations. We compare the method to conventional approaches by applying each to synthetic data and real strain data.