This paper proposes a method of using a blockchain to solve the privacy problem and forgery of black box image data, which plays an essential role in determining the responsibility for traffic accidents and preventing accidents. Blockchain that can operate inside vehicle black box IoT or connected car is used, and for this purpose, the size is reduced for operation in low-power, low-capacity devices. By enabling consensus, security problems can be solved through a lightweight blockchain that can operate inside a black box device. As a result of the experiment, it was confirmed that the IPFS upload and download delay time increased linearly, and the proposed consensus algorithm decreased 63% compared to PBFT.

Low-complexity overhead and very small side information (SI) are virtues of the low peak-to-average-power ratio (PAPR) filter bank multicarrier [Low PAPR FBMC (LP-FBMC in short)], which has been recently proposed. However, the SI is an annoying burden because it needs a complicated system design, irrespective of its size. In this paper, we propose an SI-embedded LP-FBMC that does not separately transmit SI but embeds it in the transmitted signal in a specific way while preserving the PAPR and bit error rate (BER) performance. The approach is motivated by a property of the LP-FBMC where demodulation by even an incorrect SI does not change the signal constellation. We embed the SI in the intentional phase rotation of the constellation without additional energy or bandwidth. The phase rotation differs according to the SI and is common to all data symbols in each LP-FBMC subframe. In the receiver, we remove data symbol-dependent phase terms of the decision variables (DVs) by taking the fourth power and detect the SI embedded in the remaining phase term. Simulation results reveal that the BER of the SI-embedded LP-FBMC is almost the same as that of the perfect SI case when there are an acceptable number of data symbols for SI estimation. We also devised a complexity-reduced implementation for the additional processing required for the proposed SI embedding and detection schemes.

Recently, Low PAPR FBMC (LP-FBMC) was proposed to resolve high peak-to-average power ratio (PAPR) issue of filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM). The LP-FBMC has very small side information (SI) burden (two bits per subframe). However, irrespective of SI size, SI itself is a very annoying burden because sending and reception of SI demands complicated system design and very high reliability. In this paper, we propose a modified version of LP-FBMC which gets rid of necessity of sending SI while preserving BER performances. We embed SI information in the phase term throughout the subframe without additional energy or bandwidth. The receiver detects the SI by checking the phase offset of the decision variables with a fractional increase of computational complexity. Simulation results reveal that if the number of data symbols for SI detection is practically large, SI detection error is negligible and the BER is close to the case of perfect SI. In addition, as the modified LP-FBMC is free from SI burden, we can set the LP-FBMC subframe size to minimum, i.e., 1, which maximizes PAPR reduction gain of LP-FBMC.

To further enhance frequency-asynchronous distributed Alamouti-coded (FADAC) orthogonal frequency division multiplexing (OFDM), we propose a new scheme which combines the partial maximum likelihood detection (PMLD) to the residual intercarrier interference cancellation (RIC). In order to decrease the performance gap from intercarrier interference- (ICI-) free level after single time iteration of the RIC, the final stage of the proposed scheme performs the PMLD limited to the symbols of less-reliable decision variables. We show that with the practically acceptable candidate symbol set size, a single iteration for RIC is enough to achieve the ICI-free performance. Moreover, the proposed scheme substantially expands the allowable ranges of the three undesirable terms, i.e., the timing and frequency offsets between the transmit antennas and the multipath delay spreads.

Unlike single carrier-frequency division multiple access (SC-FDMA), just combining discrete Fourier transform (DFT) spreading and filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) results in only marginal peak to average power ratio (PAPR) reduction. To utilize the single carrier effect of DFT spreading, a special condition of the coefficients at each subcarrier's in-phase and quadrature-phase (IQ) channels should be satisfied. As a starting point, we first derive this condition, which we call the identically-time-shifted-multicarrier (ITSM) condition. Then, based on this condition, we propose a new type of FBMC for low PAPR. The main features of the proposed scheme are summarized as follows. First, in order to further enhance the amount of PAPR reduction, we generate the four candidate versions of the DFT-spread and ITSM-conditioned FBMC waveform and select the one with minimum peak power. Even with multiple candidate generation, the major computation parts, such as DFT and IDFT are shared and need to be performed only once, unlike the conventional side information (SI)-based PAPR reduction schemes. Consequently, with a fractional complexity overhead compared with the previous DFT-spread FBMC, the proposed scheme achieves a PAPR reduction comparable to that of SC-FDMA. Second, the proposed scheme transmits only two bit SI per data block consisting of multiple FBMC-OQAM symbols. Hence, the SI overhead is significantly low compared with the usual SI-based schemes, such as selective mapping or partial transmit sequence.