This paper proposes an adaptive modulation (AM) and a transmit power control (TPC) on frequency symbol spreading (FSS) based orthogonal frequency division multiplexing (OFDM) relay system with considering the mobility of relay node. Wireless communications often suffer from large propagation loss due to shadowing and multipath fading. As a solution to this problem, relay communications, which forward data messages from a source to a destination via intermediate station(s), have been focused on. It can obtain the space diversity and expand the area coverage. In the situation where relay node has mobility, propagation channel fluctuates and communication quality is deteriorated. This paper presents a whole system design of FSS-OFDM employing AM and TPC. Exploiting a good match of AM and FSS, throughput performance can be significantly improved even in high mobility environment. In addition to this, utilizing TPC, the most suitable AM is enabled and leads to a further performance enhancement. Computer simulation verifies its effectiveness and reveals the proposed system is the most valuable means which realizes the flexible relay node deployment.

Noise level estimation is important to improve the performance of different image-processing algorithms. Among the different noise level estimation methods, a block-based approach is one of the most effective approaches for estimating the noise level. A noise level estimation method based on a weak-texture patch using the image power spectrum sparsity in the frequency domain is proposed in this paper. A weaktexture image patch is first selected according to the value of image power spectrum sparsity. From the selected weak-texture image patch, the noise variance is estimated by selecting the frequency regions where the image frequency parts are not concentrated. It is observed that the proposed noise level estimation method is effective, especially for images with a rich texture. Furthermore, the proposed method provides a shorter computational time than the conventional methods.

In order to improve tracking capability for fast time-varying channels, this paper proposes maximum-likelihood sequence estimation (MLSE) based on channel prediction employing soft-output Viterbi algorithm (SOVA) for differential space-time coding, e.g., differential encoding and per transmit antenna differential mapping (PADM). Although QPSK is generally demodulated based on LLR (log-likelihood ratio) for its soft decisions, it is difficult for JD (joint detection), which does not explicitly estimate channel state information, to derive LLR. This paper proposes soft decisions for PSP (per-survivor processing), which correspond to metrics difference between the two paths in the VA (Viterbi algorithm) of PSP, where PSP is JD based on the VA. The proposed scheme can improve tracking capability for time-varying channels without an increase of computational complexity. Finally, computer simulation results confirm that the proposed schemes can track four times larger maximum Doppler frequency in fading than the conventional schemes.

This paper discusses an off-line underwater acoustic software modem for multiple differential detection employing per-survivor processing (PSP-MDD) with channel prediction. Underwater acoustic communications (UWACs) suffer from severe time and frequency selective channels, i.e., doubly-selective channels. For doubly-selective channels, the authors have evaluated multiple single carrier (MSC) modulation scheme and joint detection schemes employing channel prediction. This paper discusses MSC modulation schemes employing PSP-MDD with channel prediction. In addition, this paper proposes an off-line underwater acoustic software modem employing commercial acoustic electronic devices. Due to off-line operation, the proposed software modem has the following features: 1) it can evaluate actual acoustic environment using the same program of a performance simulator, 2) it can compare performances of several demodulation schemes using the same received signals recorded in actual acoustic environment. This paper evaluates that performance of MSC modulation schemes employing PSP-MDD with channel prediction by using the proposed software modem in an anechonic tank simulating doubly-selective channels.

Circuit theory can be applied to the Schrödinger equation, and the circuit elements obtained from the Schrödinger equation are of symmetric circuits. In contrast, protons, neutrons, and electrons have a physical property of the spin 1/2 and are considered to express asymmetric circuit elements. In this session, we will apply the method of extending equations explained in Session 16 to the Schrödinger equation and obtain asymmetric circuit elements as equivalent circuit elements.