Presents a recurrent neural network for solving the Sylvester equation with time-varying coefficient matrices. The recurrent neural network with implicit dynamics is deliberately developed in the way that its trajectory is guaranteed to converge exponentially to the time-varying solution of a given Sylvester equation. Theoretical results of convergence and sensitivity analysis are presented to show the desirable properties of the recurrent neural network. Simulation results of time-varying matrix inversion and online nonlinear output regulation via pole assignment for the ball and beam system and the inverted pendulum on a cart system are also included to demonstrate the effectiveness and performance of the proposed neural network.

A novel transmission scheme called fully generalised spatial modulation (FGSM) is proposed for underwater communication, where any subset of available transmitting antennas (N t) is activated at a time instant to transmit the data constellation symbol and the index of the active antenna is also harnessed to carry information. The FGSM offers better energy efficiency (EE) than previous spatial modulation (SM) and generalised SM systems. The proposed FGSM system is tested in an acoustic underwater multipath channel. Simulation results show that it can significantly improve the average bit error rate (ABER) as well as EE.

In past decades, there has been a growing interest in the discussion and study of using underwater acoustic channel as the physical layer for communication systems, ranging from point-to-point communications to underwater multicarrier modulation networks. A series of review papers were already available to provide a history of the development of the field until the end of the last decade. In this paper, we attempt to provide an overview of the key developments, both theoretical and applied, in the particular topics regarding multicarrier communication for underwater acoustic communication such as the channel and Doppler shift estimation, video and image transmission throw multicarrier techniques, etc. This paper also includes acoustic propagation properties in seawater and underwater acoustic channel representation.

This novel method to assess the morphological parameters of PTFJ in MRI is reproducible. These parameters are associated with knee radiographic and MRI-based OA-related structural abnormalities, suggesting clinical construct validity. Its predictive validity needs to be examined in future longitudinal studies.

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Performanceof underwater acoustic communication system is influenced on channel characteristic. Especially, an important feature of the underwater acoustic communication is multipath propagation and Doppler spread cause by the surface and bottom reflections. In this paper, we study the application of high speed image transmission using multi-carrier modulation, where this capability can enable the next generation of undersea expeditions. We use Hierarchical Quadrature Amplitude Modulation (HQAM) as Zero-padded (ZP) orthogonal frequency division multiplexing (OFDM) mapper to be unequal error protection for the transmitted bit stream. We proved capability of ZP-OFDM multi-carrier modulation based on HQAM mapper with Reed Solomon channel coder in sensitive bit error reduction without receiver equalizer. Proposed scheme evaluated using different types of images for different values of the modulation parameter and underwater channel physical parameters.

A novel transmission scheme called zero-pseudorandom noise training sequence orthogonal frequency division multiplexing (ZPN-OFDM) is proposed, where the frame structure of dual-pseudorandom noise (PN) padding time domain synchronous OFDM is modified by replacing the first PN sequence by a zero sequence. The new ZPN-OFDM system offers better energy efficiency than previous OFDM systems. The ZPN-OFDM system is tested for significant tap delay multipath channels. Simulation results show that ZPN-OFDM can provide significant bit error rate improvement as well as energy efficiency improvement.Introduction: There are three basic types of orthogonal frequency division multiplexing (OFDM): cyclic prefix OFDM (CP-OFDM), zero padding OFDM (ZP-OFDM) and time domain synchronous OFDM (TDS-OFDM). The popular CP-OFDM utilises a CP as a guard interval to alleviate inter-block-interference (IBI) in multipath channels. The CP is replaced by a ZP in ZP-OFDM to tackle the problem of channel transmission zeros. Unlike CP-OFDM or ZP-OFDM, TDS-OFDM adopts a known pseudorandom noise (PN) sequence as a guard interval as well as a training sequence (TS) for synchronisation and channel estimation. Consequently, it does not require any frequency-domain pilots as usually used in CP-OFDM and ZP-OFDM, leading to a better spectrum and energy efficiency [1].However, TDS-OFDM suffers from IBI due to the mutual interference between the PN TS and OFDM data block. To address this issue, a DPN-OFDM scheme has been proposed with two periodical PN sequences, where the second PN sequence is not affected by the IBI from the previous OFDM data block, and hence can be used for accurate channel estimation [1,2]. Because of its simplicity and good performance, DPN-OFDM is currently under extensive investigation and hardware implementation for the evolution standard of digital television terrestrial broadcasting (DTMB) [1][2][3].In multipath channels with significant tap delays, such as in underwater acoustic (UWA) channels, ZP-OFDM is preferred to the CP-OFDM because it consumes less transmission energy [4,5]. In this Letter, a novel transmission scheme called zero-PN-OFDM (ZPN-OFDM) for a significant tap delay multipath channel with good energy efficiency is proposed.

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