Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
In the past years, light fidelity (Li-Fi) has been gaining popularity in the research. However, many researches have done only offline transmission with laboratory instruments. As a result, it is not practical to be used in commercial product, due to its cost and size. Therefore, the objective of this paper is to address problems that arise from the real-time implementation of Li- Fi system using the commercial off-the-shelf components. The implementation was developed on a low-cost system-on-chip (SoC) field-programmable gate array (FPGA). The implementation supports orthogonal frequency division multiplexing (OFDM) modulation including time synchronization. In order to build a system that is more practical to be used in commercial product, the network stack that supports TCP and ICMP was also developed. As a result, the user client can easily access the Internet using the available web browsers. The results showed that the system is functionally verified enabling it for real-time transmission to be used to access the Internet. According to the result, our baseband processor can transfer data with a maximum throughput of 1 Mbps at 125 Mhz of FPGA....
The importance of translation services has become increasingly prominent with the acceleration of economic globalization. Compared with human translation, machine translation is cheaper and faster, and therefore more suitable for the current era. The current mainstream machine translation method is neural machine translation, which employs machine methods to train on parallel corpora and create translation models. Research into neural machine translation has yielded a wealth of information. Learning and generalization abilities of neural networks have substantially enhanced the effectiveness of neural machine translation. This work applies machine learning and wireless network technology to build an online translation system for real-time translation. First, this work proposes a multigranularity feature fusion method based on a directed acyclic graph, which uses a directed acyclic graph to fuse different granularities as input and obtain a position representation. Secondly, this paper improves the Transformer model and proposes multigranularity position encoding and multigranularity self-attention. Then, on the basis of multigranularity features as input, this work introduces dynamic word vectors to improve the word embedding module, and uses the ELMo model to obtain dynamic word vector embeddings. Finally, this work builds a multigranularity feature-dynamic word vector machine translation model with above strategy, deploys it on server. Users can upload the content to be translated and download the translated content through the wireless network and realize an online translation system based on machine learning and wireless network....
This paper presents estimation of harvested RF energy by means of measurement survey and rectifier circuit simulation. The survey was done in an indoor environment in Bangkok, Thailand using a low-cost in-house developed measurement system. From the survey, channel power distribution of a signal with 950MHz center frequency and 20MHz bandwidth was created. The maximum time averaged channel power is -7.6 dBm whereas the mean value with maximum signal statistic is -11.1 dBm. A single stage rectifier is simulated with 5 different nominal values of RF input power which is used to optimize the rectifier for maximum RF-to-DC power conversion efficiency. The rectifier composes a Schottky diode, a matching network and a simple load consisting of a resistor and a storage capacitor. Parameters of the simplified LC matching network have been varied to match the rectifier’s input impedance to 50Ω for various nominal values of the RF input power. In addition, the load resistance was varied according to the nominal RF input power for an optimal power conversion efficiency of the rectifier. The rectifier delivers the highest harvested RF energy with a nominal RF input power of -9 dBm which is a value between the maximum and the mean values from the survey. The DC energy converted from ambient RF energy by the rectifier can be estimated. With this information, it can be assessed what type of applications based on available RF energy can be applied for the test area. This rectifier optimization strategy can be applied to any kind of RF signal since it is based on actual measurement results. Moreover, the proposed rectifier can be designed for reconfigurability regarding nominal RF input power at the location of interest by varying the matching network parameters and the load resistance. In practical applications, the reconfigurable rectifier can maintain a high level of power conversion efficiency over a wide range of RF input power. This can be done by optimizing the rectifier’s input matching network and the load resistance for the highest possible power harvested from the environment where the rectifier is located....
At present, the dynamic nature and unstable network connections in the deployment environments of Wi-Fi-based smart home devices make them susceptible to component damage, crashes, network disconnections, etc. To solve these problems, researchers have used various fault detection methods, such as alarming when monitored fault parameters exceed the preset values, modelbased mathematical methods, device signal processing-based methods, and artificial intelligence-based methods. However, these methods require large numbers of fault parameters, the model are complex, and their fault detection accuracy is relatively poor. To more quickly and accurately detect faults in smart home devices and ensure the continuity of people’s daily work and lives, this paper analyzes both the Wi-Fi traffic characteristics of smart home devices and the complexity and difficulty of traditional fault detection methods and proposes a fault detection method based on TDD (Throughput and Delay Distribution). This method obtains throughput and data packet delay distribution by capturing Wi-Fi communication and sending test data. By dividing the throughput into heartbeat data and command information, we can calculate the real-time throughput and further calculate the similarity between the real-time throughput and the throughput in database. Also, the resulting delay distribution is compared with the probability distribution of delay in the database. When the throughput values are sufficiently similar and the delays are all in the normal range, the smart home secure devices are functioning properly. The experimental results show that the proposed TDD method can detect faults in household devices in real time and that it achieves high recall and good detection accuracy in Wi-Fi communication environment....
Mobile Internet Protocol v6 (MIPv6) is a protocol that allows a mobile node (MN) to transparently maintain connections while moving from one subnet to another. Using the route optimization (RO) method in MIPv6 gives optimized routing and helps avoid triangular routing. In real-time applications such as video conference applications, quality of service (QoS) issues will increase especially in the handover process between subnets. This study investigates the performance of MIPv6 handover in IEEE802.11e standard in wireless environments. The investigation considers that handover for the MN moves between 2 home agents (HA). The system model’s fundamental performance limits are measured by packet delay variation, HA binding delay, and wireless local area network (WLAN) media access delay analysis metrics in video conference applications. According to the results of real-time simulations, network performance during the handover process can be effectively improved as the packet lost during handover decreased significantly from 43% in IEEE802.11b distributed coordination function (DCF) to 36% in IEEE802.11e hybrid coordination function (HCF). Furthermore, experimental results prove that IEEE802.11e connects to new HA roughly 20% quicker than IEEE802.11b, and IEEE802.11b has 100 times more time delay than IEEE802.11e. In addition to this, the WLAN media access delay of IEEE802.11b often reaches 0.00011 s as compared to 0.000005 s of IEEE802.11e. Thus, it is evident that the performance of IEEE802.11e in terms of packet delay variation, HA binding delay, and WLAN media access delay is better than IEEE802.11b. Likewise, it is noted that network speed during the handover process in IEEE802.11e can be considerably improved in a MIPv6 scenario....
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