• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.7
• /
• pp.2047-2066
• /
• 2024

In order to improve the coverage and achieve massive spectrum access, non-orthogonal multiple access (NOMA) technology is applied in millimeter wave massive multiple-input multiple-output (mMIMO) communication network. However, the power assumption of active sensors greatly limits its wide applications. Recently, Intelligent Reconfigurable Surface (IRS) technology has received wide attention due to its ability to reduce power consumption and achieve passive transmission. In this paper, spectral efficiency maximum problem in the millimeter wave mMIMO-NOMA system with IRS is considered. The sparse RF chain antenna structure is designed at the base station based on continuous phase modulation. Furthermore, a joint optimization problem for power allocation, power splitting, analog precoding and IRS reconfigurable matrices are constructed, which aim to achieve the maximum spectral efficiency of the system under the constraints of user's quality of service, minimum energy harvesting and total transmit power. A three-stage iterative algorithm is proposed to solve the above mentioned non-convex optimization problems. We obtain the local optimal solution by fixing some optimization parameters firstly, then introduce the relaxation variables to realize the global optimal solution. Simulation results show that the spectral efficiency of the proposed scheme is superior compared to the conventional system with phase shifter modulation. It is also demonstrated that IRS can effectively assist mmWave communication and improve the system spectral efficiency.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.2
• /
• pp.7-14
• /
• 2011

Numerical simulations were performed for the evaluation of wave and current loads on a fixed cylindrical substructure model for an ocean wind turbine using the ANSYS-CFX package. The numerical wave tank was actualized by specifying the velocity at the inlet and applying momentum loss as a wave damper at the end of the wave tank. The Volume-Of-Fluid (VOF) scheme was adopted to capture the air-water interface. An accuracy validation of the numerical wave tank with a truncated vertical circular cylinder was accomplished by comparing the CFD results with Morison's formula, experimental results, and potential flow solutions using the higher-order boundary element method (HOBEM). A parametric study was carried out by alternately varying the length and amplitude of the wave. As a meaningful engineering application, in the present study, three kinds of conditions were considered, i.e., cases with current, waves, and a combination of current and progressive waves, passing through a cylindrical substructure model. It was found that the CFD results showed reasonable agreement with the results of the HOBEM and Morison's formula when only progressive waves were considered. However, when a current was included, CFD gave a smaller load than Morison's formula.

• Proceedings of the KSPS conference
• /
• 2000.07a
• /
• pp.166-177
• /
• 2000

The purpose of this study was to create letters for of nonliterary Pulang tribe in Thailand those who immigrant from China. illiterate Pulang tribe hand down their tradition by primary oral culture therefore their tradition can't initiate and keep, moreover, it may disappear throughout history. So it is expected to crusade against unlettered people. The scheme of research adopted in this study was a minority race who habitate at the northern Machan, Chiangrai in Thailand. It is not only analysis of language but also the eradication of literacy and the research based on linguistic, ethnolinguistic, and primary oral culture. Five Pulang people who live in that area were chosen for creating letters. By using the I. P. A., after each word was listen to their pronunciation one by one it was described and repeated this process several times; the material words and humanbody were pointed in front of them while other words were described by gesture. For final description, number of people were in the lineup for listening the sound of words and phrases to sentences. In the first stage, it was an analysis segmental of Pulang: vocoid, contoid and diphthong were described with each sample syllables and words. The suprasegmental were studied with intonation and juncture of the words in the second stage. Two words were compared and different meanings within their intonation and juncture were shown. At the end of this part, each case of phonemic or morphophonemics representation described the juncture in the words. In the third stage, minimal pairs were analyzed with vowels and consonants and described in free variation based on words. In the last stage, syllable structure in open syllable and closed syllable was studied and then each syllable of its structure was analyzed with samples. There were thirty-two phonemes in apong Pulang as follows: seven vocoids; a, i, e, o, u, ${\ae}$, and $\wedge$, one diphthong; wu, 24 contoids; b, c, d, f, g, h, j, k, k, 1, m, n, ${\eta}, {\;}p^{h}$, p, p, r, s, s, sh, t, t, w, and y. Their pronunciations of p, s, d, $p^{h}$, j, and t are frequently used in speech and are unique in triphthong. Moreover, most of the words used initial and final consonant cluster.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.16 no.11
• /
• pp.3738-3760
• /
• 2022

Due to increasing spectrum demand for new wireless devices applications, cooperative spectrum sensing (CSS) paradigm is the most promising solution to alleviate the spectrum shortage problem. However, in the interweave cognitive radio (CR) system, the inherent nature of CSS opens a hole to Byzantine attack, thereby resulting in a significant drop of the CSS security and efficiency. In view of this, a weighted differential sequential single symbol (WD3S) algorithm based on MATLAB platform is developed to accurately identify malicious users (MUs) and benefit useful sensing information from their malicious reports in this paper. In order to achieve this, a dynamic Byzantine attack model is proposed to describe malicious behaviors for MUs in an interweave CR system. On the basis of this, a method of data transmission consistency verification is formulated to evaluate the global decision's correctness and update the trust value (TrV) of secondary users (SUs), thereby accurately identifying MUs. Then, we innovatively reuse malicious sensing information from MUs by the weight allocation scheme. In addition, considering a high spectrum usage of primary network, a sequential and differential reporting way based on a single symbol is also proposed in the process of the sensing information submission. Finally, under various Byzantine attack types, we provide in-depth simulations to demonstrate the efficiency and security of the proposed WD3S.

• Journal of Communications and Networks
• /
• v.18 no.5
• /
• pp.784-795
• /
• 2016

In this paper, we investigate the resource allocation problem in time-varying heterogeneous wireless networks (HetNet) with multi-homing user equipments (UE). The stochastic optimization model is employed to maximize the network utility, which is defined as the difference between the HetNet's throughput and the total energy consumption cost. In harmony with the hierarchical architecture of HetNet, the problem of stochastic optimization of resource allocation is decomposed into two subproblems by the Lyapunov optimization theory, associated with the flow control in transport layer and the power allocation in physical (PHY) layer, respectively. For avoiding the signaling overhead, outdated dynamic information, and scalability issues, the distributed resource allocation method is developed for solving the two subproblems based on the primal-dual decomposition theory. After that, the adaptive resource allocation algorithm is developed to accommodate the timevarying wireless network only according to the current network state information, i.e. the queue state information (QSI) at radio access networks (RAN) and the channel state information (CSI) of RANs-UE links. The tradeoff between network utility and delay is derived, where the increase of delay is approximately linear in V and the increase of network utility is at the speed of 1/V with a control parameter V. Extensive simulations are presented to show the effectiveness of our proposed scheme.