Background: Social frailty (SF) is associated with multiple adverse health outcomes, yet there has been an inadequate focus on social frailty. The convoy model portrays the social networks through the perspective of the life course, thus providing a framework to explain the occurrence of social frailty. This study aimd to figure out the prevalence of social frailty and loneliness among community-dwelling older adults and to explore their correlations based on convoy model. Methods: This was a cross-sectional study, and 295 older adults from 10 communities of Zhengzhou in Henan Province participated in the study. Social frailty and loneliness were assessed separately with the Social Frailty Scale and University of California at Los Angeles-Loneliness Scale. The scores of social frailty of the older adults in different characteristic communities were compared by independent sample t-test and single factor analysis of variance. The influencing factors of social frailty were analysed by multiple stepwise linear regression and the structural equation model. The correlation between social frailty and loneliness was analysed by Pearson correlation analysis. Results: The total scores of social frailty and loneliness of the older adults in the community were (2.09 ± 1.53) and (43.19 ± 8.91), respectively. There was a moderate positive correlation between social frailty and loneliness (r = 0.621, P < 0.01). The results of multiple stepwise linear regression analysis showed that age, living styles, balance of payments, and loneliness were the main influencing factors of the social frailty of older adults in the community (F = 27.180, P < 0.001). The structural equation model of social frailty fitted well (χ² = 47.292, df = 26, χ²/df = 1.819, P = 0.007; RMSEA = 0.053, 95%CI (0.028, 0.076), P = 0.359; GFI = 0.971; AGFI = 0.939; NFI = 0.904; IFI = 0.955; TLI = 0.918; CFI = 0.953; SRMR = 0.0466). Conclusions: The convoy model had certain applicability in explanation of the relationship between loneliness and social frailty among older adults in community. The incidence of social frailty among the older adults in the community was high, and loneliness was at a medium level. It is necessary to strengthen the intervention of social frailty and loneliness of the older adults in the community, improve the quality of life of the older adults, and promote the development of healthy aging.

A 60-GBaud intensity modulation and direct detection discrete Fourier transform spread (DFT-S) discrete multi-tone (DMT) transmission system employing low-density parity check- (LDPC-) encoded probabilistic shaping 16-ary quadrature amplitude modulation (PS-16QAM) is proposed and experimentally demonstrated. In contrast to classical probability-oriented PS schemes such as arithmetic distribution matching (ADM) and constant composition distribution matching (CCDM), the proposed one is performed based on a novel bit-weighted distribution matching (BWDM) algorithm having the advantage of simpler operations along with lower computation and hardware complexity, which merely relies on bit-class processing. As the key content of the BWDM, the bit weight intervention operation is utilized to enlarge the probability of bit `0' in the first two out of four serial binary sequences before PS-16QAM mapping. Different from the labels indicating probability distribution in ADM and CCDM, the end product of the BWDM is a group of bits mapped from input data source, which can be seamlessly compatible with the following LDPC-based forward error correction. In our experiments, system performance is respectively investigated with three LDPC code rates (3/4, 5/6, and 9/10) as well as three PS parameter values (k = 4, 5, and 7), which leads to various symbol probability distribution. Compared with standard uniformly-distributed 16QAM, up to 0.407-dB shaping gain can be achieved to approach Shannon limit in the low signal-to-noise ratio region. Moreover, the experimental results show that appreciable receiver power sensitivity improvement can be obtained by the PS-16QAM DMT based on BWDM over 2-km standard single-mode fiber for short-reach optical interconnection. Additionally, the reference-based pre-equalization is equipped to compensate for the high frequency loss by ultra-wide signal bandwidth.

In cognitive radio or military communications systems, the receiver usually needs to blindly identify which LDPC code has been adopted by the transmitter. Existing methods for blind LDPC code identification suffer from high computational complexity. This paper proposes a deep learning based LDPC code identification algorithm. According to the algorithm, the received LDPC encoded sequence is treated as a text sentence, and a special convolutional neural network (CNN), TextCNN, is utilized to understand the sequence and infer which code is adopted. Two types of LDPC codes, namely quasi-cyclic LDPC and spatially coupled LDPC, are considered. Simulation results show that, the proposed algorithm is able to accurately identify both types of LDPC codes no matterwhether an extra convolution code exists or not.

In this letter, an adaptive decoding algorithm with a variable sliding window for joint source-channel coding (JSCC) scheme based on double spatially coupled low-density parity-check (DSC-LDPC) codes is investigated. For the traditional sliding window decoding (SWD) algorithm, one or more errors occurring in a decoding window may affect the decoding of the next window, which will trigger error propagation. To mitigate the effects, a window extension algorithm based on average log-likelihood ratios (LLRs) will be proposed, but the implement of extension implies higher decoding complexity. In order to trade-off the error rate performance and complexity, the source and channel threshold that determines the window extension are analyzed. In the simulation, the proposed SWD algorithm with acceptable complexity has better error rate performance in the water fall region and the error floor region.

A 5 × 60 Gb/s low-density parity-check (LDPC) coded WDM-PON using 8-level pulse amplitude modulation (PAM8) signals with probabilistic shaping (PS) over 20-km standard single-mode fiber (SSMF) with direct detection is proposed and experimentally demonstrated. Each optical carrier at the optical line terminal (OLT) carries a 20-Gbaud probabilistically-shaped LDPC-coded PS-PAM8 signal from a conventional uniform PAM16 signal following a designed approximate Gaussian distribution (AGD). A LDPC-based bit-interleaved coded modulation scheme with iterative decoding (BICM-ID) is utilized to recover the inherently overlapped symbols due to the proposed PS mapping. Combining decision-directed least-mean-squares (DD-LMS) and constant modulus algorithm (CMA), a blind feedback pre-equalizer is adopted to reduce the frequency loss of the signal owing to imperfect electro-optical components in experiment. As for experimental verification and application, 1.48-dB superior receiver power sensitivity and 1.7-dB launch fiber power optimization are gained respectively by using LDPC-coded PS-PAM8 signals in WDM-PON, which can bring higher spectral efficiency and power loss budget for the optical distribution networks.

We introduce a probabilistic shaping (PS) 44-ary quadrature amplitude modulation (44QAM) based on many-to-one (MTO) mapping into a discrete multi-tone wavelength division multiplexing passive optical network (DMT-WDM-PON) with maximum shaping gain of 0.46 dB. A low-density parity-check (LDPC) based bit-interleaved coded modulation and iterative decoding system is proposed to generate and transmit the PS-44QAM DMT signal without any extra PS redundancy. An extrinsic information (EI) is iteratively used between LDPC decoder and PS demapper to retrieve the PS-44QAM DMT signal including overlapped/ambiguous symbols. The experimental results show that the PS-44QAM DMT signal with improved receiver power sensitivity and system fiber nonlinear effect tolerance can be obtained in the power splitter based WDM-PON. Thus, the corresponding system loss budget can be significantly enlarged in the optical distribution network for the purpose of serving more optical network units.