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Various offshore structures such as FPSO, FSO, Semi-submersible, TLP and Spar are operated to develop offshore oil and gas fields. Most of the offshore structures shall be operated over 20 years under the harsh environments at sites so that the offshore structures should be designed to endure the harsh environments. In this study, the effect of the impact load (so called slapping load) by the steep waves acting on the FPSO bow is investigated through the model test. For measurement of the impact pressures on the frontal area, a bow-shaped panel was fabricated, and installed the pressure sensors on the bow starboard side of the model FPSO. During the model test campaign, the impact load was investigated using the steep waves with Hs/λ greater than 1/16 of the representative wave condition. Consequently, it is confirmed through the model test that the impact loads acting on the FPSO bow are significantly increased with the steep waves (Hs/λ > 1/16) than the representative wave conditions of a maximum significant wave height and a pitch forcing period. Therefore, for safe design of North Sea FPSO, it is necessary to consider the steep waves in addition to the representative wave conditions and to be applied as proper structural load. Also, the effect of random seeds in irregular waves should be considered to build the safe FPSO.

Filter bank multiple carrier (FBMC) technology is one of the alternative solutions for multicarrier modulation. FBMC does not need cyclic prefix (CP) and guard band utilized for orthogonal frequency division multiplexing (OFDM) and CP and guard band cause loss of spectral efficiency. FBMC features offset QAM (OQAM) and band-limited filtering on each subcarrier, which eliminate the need of CP and guard band. FBMC filtering could maintain the orthogonality in a real signal domain by using well localized filter. Meanwhile layer division multiplexing (LDM) is also introduced to increase the spectral efficiency. In LDM, low density parity check (LDPC) coded multi signals are transmitted simultaneously with different power levels in same frequency band and these signals form signal layers. Combination of FBMC and LDM techniques can maximize the spectral efficiency. In this paper, LDM system which adopts FBMC is proposed. The LDM system has both OFDM and FBMC modulated layers. To apply FBMC to LDM system, log-likelihood ratio (LLR) calculation scheme for FBMC is needed for LDPC decoding. Three scenarios for LDM system are considered and BER performance of each scenario is analyzed to find proper scenario.

This paper presents a new block iterative/adaptive frequency-domain channel estimation scheme, in which a channel frequency response (CFR) is estimated iteratively by the proposed weighted element-wise block adaptive frequency-domain channel estimation (WEB-CE) scheme using the soft information obtained by a soft-input soft-output (SISO) decoder. In the WEB-CE, an equalizer coefficient is calculated by minimizing a weighted conditional squared-norm of the a posteriori error vector with respect to its correction term. Simulation results verify the superiority of the WEB-CE in a time-varying typical urban (TU) channel.