Orthogonal frequency-division multiplexing (OFDM) is highly sensitive to carrier frequency offset (CFO), which not only causes intercarrier interference (ICI) among subcarriers but introduces complex multiplicative distortion (CMD) to all detected subcarrier symbols as well. Due to unknown CFO, both ICI and CMD are time variant, thus complicating the data demodulation at the receiver. In conjunction with a training-prefixed data frame structure, a concatenated precoder that is constructed by concatenating an outer modified correlative precoder with an inner reduced Hadamard precoder is proposed in this paper to process data symbols prior to OFDM modulation and to enable joint estimation on channel multipath and constant CMD (CCMD), time-variant CMD (TCMD) estimation and compensation, and ICI suppression at the receiver in the presence of CFO. Simulation results show that the proposed system provides much better error performance than conventional signal coding approaches in the presence of CFO and multipath fading.Index Terms-Carrier frequency offset (CFO), correlative code, Hadamard code, intercarrier interference (ICI), orthogonal frequency-division multiplexing (OFDM).
Taiwan is surrounded by sea; therefore, coastal hazards might become severe due to climate change. The analysis of wave climate characteristics at different time scales (long-term historical period, seasonal prediction, and future prediction) can be used as a reference for the impact of climate change on coastal environments. This model associates the significant wave height with the atmospheric predictor defined by the sea level pressure (SLP) field. We applied SLP based on the outputs of a global climate model (GCM) under two possible future scenarios (RCP4.5 and RCP8.5) in the Fifth Assessment Report, AR5 (IPCC, 2014), then used the historical data of the predictor (sea level pressure) and predictand (sea-state parameters) from reanalysis databases to calibrate the model. The recent historical atmospheric conditions responsible for the swell wave component at the target site are included in the predictor definition. The 18 days sea level pressure fields are used as a predictor by utilizing the evaluation of source and travel-time of wave energy reaching a local area (ESTELA) method. The verification proves the model’s skill to reproduce the seasonal and interannual variability of monthly sea state parameters and can be used to further evaluate the wave climate change around Taiwan under different climate change scenarios. The prediction of wave climate on weather types provides a physical explanation for the relationship between the multivariate wave climate characterization and atmospheric forces. Through the analysis of the similarity and consistency between GCM data and reanalysis data, we can evaluate the suitability of GCM for wave climates in the Taiwan sea area. It shows how the weather type statistical method can be used to quantify the wave climate prediction results of each GCMs and to evaluate their differences and uncertainties, which will improve the estimation of the impact of wave climate change on Taiwan’s coast.
A sparse-training-sequence-aided orthogonal frequency division multiplexing system is proposed to enable channel estimation and data detection without being affected by carrier frequency offset (CFO) effect. With the aid of the sparse training sequence, an approximate maximum likelihood estimation on CFO effect and channel response is developed to retrieve the CFO and channel response information from the received signal, and then facilitate the corresponding CFO effect compensation during channel estimation and data detection. Simulation results show that the proposed approach provides similar error performance to that with perfectly known CFO and channel response.
Spasticity, a common stroke complication, can result in impairments and limitations in the performance of activities and participation. In this study, we investigated the effectiveness of a new dynamic splint on wrist and finger flexor muscle spasticity in chronic stroke survivors, using a randomized controlled trial. Thirty chronic stroke survivors were recruited and randomly allocated to either an experimental or control group; 25 completed the 6-week intervention program. The participants in the experimental group were asked to wear the dynamic splint at least 6 h/day at home, for the entire intervention. The participants in the control group did not wear any splint. All the participants were evaluated 1 week before, immediately, and after 3 and 6 weeks of splint use, with the modified Ashworth scale and the Fugl−Meyer assessment for upper extremity. User experience was evaluated by a self-reported questionnaire after the 6-week intervention. The timed within-group assessments showed a significant reduction in spasticity and improvements in functional movements in the experimental group. We found differences, in favor of the experimental group, between the groups after the intervention. The splint users indicated a very good satisfaction rating for muscle tone reduction, comfort, and ease of use. Therefore, this new splint can be used for at-home rehabilitation in chronic stroke patients with hemiparesis.
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