This paper proposes a simple timing synchronization method in order to design a timing synchronization circuit with low-complex and low-volume digital signal processing (DSP) for orthogonal frequency division multiplexing (OFDM) packet transmission systems. The proposed method utilizes the subtraction process for acquirement of a timing metric of fast Fourier transform (FFT) window, whereas the conventional methods utilize the multiplication process. This paper adopts the proposed method to a standardized OFDM format, IEEE 802.11a, and elucidates that the proposed one shows good transmission performance as well as the conventional one in fast time-variant multi-path Rayleigh fading channels by computer simulation.

This paper discusses the characteristics of the nonlinearly amplified spread–spectrum (SS) signals. We evaluate the symbol error–rate performance with the conventional receiver, changing the length of the spreading sequence. In addition, we also propose the receiver with MLSE. The configuration of the MLSE for the nonlinearly amplified signals is generally complicated; however we show that the complexity of the MLSE receiver can be reduced, as the number of required reference sequences in the receiver for an SS signal is small. As the result, it is shown that the error rate performance of the nonlinearly amplified SS signal can be improved by this proposed receiver and that the degradation caused by the nonlinear amplification can be made negligibly small with a sufficiently long spreading sequence.

This paper deals with study results on the effect of nonlinear amplification in the CDMA system using offset-QPSK signals bandlimited with a square-root cosine roll-off filter. As a result of the study, it is shown that the nonlinear amplification does not affect bit error rate performance with reasonable out-of-band emission characteristics when the roll-off factor of the transmit filter is one.

This paper discusses the influence of the nonlinearity of analog-to-digital converters (ADCs) on the performance of orthogonal frequency division multiplexing (OFDM) receivers. We evaluate signal constellations and bit error rate performances while considering quantization errors and clippings. The optimum range for an ADC input amplitude is found as a result of the trade-off between quantization error and the effects of clipping. In addition, it is shown that the peak-to-average power ratio (PAPR) of the signal is not a good measure of the bit error rate (BER) performance, since the largest peaks occur only with very low probabilities. The relationship between the location of a subcarrier and its performance is studied. As a result, it is shown that the influence of the quantization error is identical for all subcarriers, while the effects of clipping depend on the subcarrier frequency. When clipping occurs, the BER performance of a subcarrier near the center frequency is worse than that near the edges.

When the automated driving cars are in widespread usage, traffic will coexist with prioritized vehicles (e.g., ambulances, fire trucks, police vehicles) and automated driving cars. Automated driving cars are expected to be safer and lower stress than manual driving vehicles because of passengers paying less attention to driving. However, there are many challenges for automated driving cars to get along with surrounding transport participants. In particular, when an ambulance is driving into an intersection with the red traffic signal, the automated driving car is required to deal with a situation differently from normal traffic situations. In order to continue safe driving, it is necessary to recognize the approach of the ambulance at an earlier time. Possible means of recognizing ambulances include siren sound, rotating red lights and vehicle to vehicle communication. Based on actual traffic data, the authors created a mathematical model of deceleration for giving way and consider the status of suitable behavior by automated driving cars. The authors calculate the detection distance required to take suitable action. The results indicate that there are advantages in vehicle to vehicle communication in detecting ambulances by automated driving cars.