• Title/Summary/Keyword: In-Wi

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An Improved DSA Strategy based on Triple-States Reward Function (Triple-state 보상 함수를 기반으로 한 개선된 DSA 기법)

  • Ahmed, Tasmia;Gu, Jun-Rong;Jang, Sung-Jeen;Kim, Jae-Moung
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.11
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    • pp.59-68
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    • 2010
  • In this paper, we present a new method to complete Dynamic Spectrum Access by modifying the reward function. Partially Observable Markov Decision Process (POMDP) is an eligible algorithm to predict the upcoming spectrum opportunity. In POMDP, Reward function is the last portion and very important for prediction. However, the Reward function has only two states (Busy and Idle). When collision happens in the channel, reward function indicates busy state which is responsible for the throughput decreasing of secondary user. In this paper, we focus the difference between busy and collision state. We have proposed a new algorithm for reward function that indicates an additional state of collision which brings better communication opportunity for secondary users. Secondary users properly utilize opportunities to access Primary User channels for efficient data transmission with the help of the new reward function. We have derived mathematical belief vector of the new algorithm as well. Simulation results have corroborated the superior performance of improved reward function. The new algorithm has increased the throughput for secondary user in cognitive radio network.

A Performance Evaluation of MB-OFDM UWB System Considering the Domestic DAA Regulation (국내 DAA 기술 기준을 고려한 MB-OFDM UWB 성능 평가)

  • Shin, Cheol-Ho;Choi, Sang-Sung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.9
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    • pp.1000-1009
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    • 2008
  • The purpose of this paper is to analyze the performance of MB-OFDM UWB system when the interference signal that can be WIMAX signal or 4 G system signal is received by detection limit of -80 dBm/MHz proposed in Korea for DAA(Detect And Avoid) to permit UWB in $3.1{\sim}4.8$ GHz. MB-OFDM UWB system supports two transmission modes; one is TFI(Time frequency Interleaving) mode that transmits OFDM symbols using different carrier frequency from symbol to symbol according to Time Frequency(TF) codes, the other is FFI(Fixed Frequency Interleaving) mode that transmits OFDM symbols using a specific carrier frequency. In this paper, we considered the TX average power and the synchronization structure to reflect the effect of frequency hopping according to TFC. Interference analysis results show that the WiMAX system is fenced thoroughly from UWB interference in domestic DAA regulation, but the performance of MB-OFDM UWB system is degraded seriously by an interference signal with the DAA detection limit even in frequency Hopping mode that can get frequency diversity effect.

Design of Broadband Polarization Diversity Antenna for Mobile Base Stations (이동 통신 기지국용 광대역 편파 다이버시티 안테나 설계)

  • Seo, In-Jong;Cho, In-Ho;Lee, Cheon-Hee;Jung, Jin-Woo;Lee, Hyeon-Jin;Lim, Yeong-Seog
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.9
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    • pp.1023-1029
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    • 2010
  • In this paper, we proposed the broadband polarization diversity antenna operating in the PCS, WCDMA and WiBro band for mobile base station. We designed the antenna using the dipole antenna of the square loop type and microstrip feeding structure. Additionally, we used the choke box to remove the distortion of radiation patterns by the reflector structure when operating broadband. The simulation was performed using MWS in a commercial tool of CST company and the antenna was fabricated on a teflon substrate with 3.33 of the relative permittivity. The proposed antenna has the bandwidth of 640 MHz(from 1.75 to 2.39 GHz) when VSWR is below 1.5. At the operating bands, the interisolation between the cross-pair radiators is less than -25 dB and the maximum gains for PCS, WCDMA and WiBro band are 8.9, 8.2 and 8.6 dBi, respectively.

Analysis of Frequency Sharing Performance using Guard Band and User Device Density in a Urban Environment (도심 환경에서 보호대역과 단말밀도를 이용한 주파수 공유성능 분석)

  • Cho, Ju-Phil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.16 no.9
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    • pp.1864-1869
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    • 2012
  • We make an interference analysis to obtain a critical ctiteria for coexisting availability of WLAN and WiBro between adjacent channels can be used in TVWS(TV White Space). To meet this analysis, we set the various transmission parameters including the emission and blocking mask, antenna height and gain, transmission power and bandwidth, channel model etc. And, based on these parameters, we analyze on performances according to a variation of guard band, a number of service user and allowable transmit power of the user operating in the adjacent channels. In this paper, we consider a urban environment and apply a Extended Hata-SRD for WLAN and an interference link and Extended Hata model for WiBro, respectively. With these results, we can see how each system can be shared in an adjacent channel.

Channel Selection Method of Wireless Sensor Network Nodes for avoiding Interference in 2.4Ghz ISM(Industrial, Scientific, Medical) Band (2.4Ghz ISM(Industrial Scientific Medical) 밴드에서 간섭을 회피하기 위한 무선 센서 노드의 채널 선택 방법)

  • Kim, Su Min;Kuem, Dong Hyun;Kim, Kyung Hoon;Oh, Il;Choi, Seung Won
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.10 no.4
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    • pp.109-116
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    • 2014
  • In recent, ISM (Industrial Scientific Medical) band that is 2.4GHz band authorized free of charge is being widely used for smart phone, notebook computer, printer and portable multimedia devices. Accordingly, studies have been continuously conducted on the possibility of coexistence among nodes using ISM band. In particular, the interference of IEEE 802.11b based Wi-Fi device using overlapping channel during communication among IEEE 802.15.4 based wireless sensor nodes suitable for low-power, low-speed communication using ISM band causes serious network performance deterioration of wireless sensor networks. This paper examined a method of identifying channel status to avoid interference among wireless communication devices using IEEE 802.11b (Wi-Fi) and other ISM bands during communication among IEEE 802.15.4 based wireless sensor network nodes in ISM band. To identify channels occupied by Wi-Fi traffic, various studies are being conducted that use the RSSI (Received Signal Strength Indicator) value of interference signal obtained through ED (Energy Detection) feature that is one of IEEE 802.15.4 transmitter characteristics. This paper examines an algorithm that identifies the possibility of using more accurate channel by mixing utilization of interference signal and RSSI mean value of interference signal by wireless sensor network nodes. In addition, it verifies such algorithm by using OPNET Network verification simulator.

Performance Comparison of Autoencoder based OFDM Communication System with Wi-Fi

  • Shiho Oshiro;Takao Toma;Tomohisa Wada
    • International Journal of Computer Science & Network Security
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    • v.23 no.5
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    • pp.172-178
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    • 2023
  • In this paper, performance of autoencoder based OFDM communication systems is compared with IEEE 802.11a Wireless Lan System (Wi-Fi). The proposed autoencoder based OFDM system is composed of the following steps. First, one sub-carrier's transmitter - channel - receiver system is created by autoencoder. Then learning process of the one sub-carrier autoencoder generates constellation map. Secondly, using the plural sub-carrier autoencoder systems, parallel bundle is configured with inserting IFFT and FFT before and after the channel to configure OFDM system. Finally, the receiver part of the OFDM communication system was updated by re-learning process for adapting channel condition such as multipath channel. For performance comparison, IEEE802.11a and the proposed autoencoder based OFDM system are compared. For channel estimation, Wi-Fi uses initial long preamble to measure channel condition. but Autoencoder needs re-learning process to create an equalizer which compensate a distortion caused by the transmission channel. Therefore, this autoencoder based system has basic advantage to the Wi-Fi system. For the comparison of the system, additive random noise and 2-wave and 4-wave multipaths are assumed in the transmission path with no inter-symbol interference. A simulation was performed to compare the conventional type and the autoencoder. As a result of the simulation, the autoencoder properly generated automatic constellations with QPSK, 16QAM, and 64QAM. In the previous simulation, the received data was relearned, thus the performance was poor, but the performance improved by making the initial value of reception a random number. A function equivalent to an equalizer for multipath channels has been realized in OFDM systems. As a future task, there is not include error correction at this time, we plan to make further improvements by incorporating error correction in the future.

PAPR Reduction Using Hybrid Schemes for Satellite Communication System

  • Kim, Jae-Moung;Zhao, Zibin;Li, Hao-Wei;Sohn, Sung-Hwan
    • Journal of Satellite, Information and Communications
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    • v.3 no.2
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    • pp.48-53
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    • 2008
  • In the future, satellite communication systems, such as ISDB in Japan and DVB in Europe, are required to support higher transmission date rate for providing multimedia services including HDTV, high rate data communication etc. Considering the effectiveness of OFDM technique in efficient usage of frequency bandwidth and its robustness to the multi-path fading, several OFDM based standards have been proposed for satellite communication. However, the problem of high Peak to Average Power Ratio is one of the main obstacles for the implementation of OFDM based system. Many PAPR reduction schemes have been proposed for OFDM systems. Among these, the partial transmit sequences (PTS) is attractive as they obtain better PAPR property by modifying OFDM signals without distortion. In this paper, considering the complexity issue, we present a simplified minimum maximum (minimax) criterion and Sub-Optimal PTS algorithm to optimize the phase factor. This algorithm can be dynamically made tradeoff`f between performance and complexity on demand. In addition, we integrate guided scrambling (GS) with this method. Simulation in multiple antenna based OFDM system proves that the proposed Hybrid schemes can get much more PAPR reduction and do not require transmission of side information (SI). Thus it is helpful when implementing OFDM technique in satellite communication system.

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IEEE 802.11 ax optimization design study in XR (eXtended Reality) training room

  • Chae, Yeon Keun;Chae, Myungsin
    • International Journal of Advanced Culture Technology
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    • v.10 no.1
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    • pp.253-264
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    • 2022
  • In the era of the pandemic, the importance of a wireless LAN environment has become increasingly important, especially as the era of smart working and non-face-to-face education has become a universal and daily routine. Smartphones, tablets, laptops, PCs, smart watches, and wearable devices, collective referred to as wireless terminals, can be accessed anytime and anywhere through the internet, allowing for consistent and constant access to offices, factories, warehouses, shopping malls, railways, hotels, hospitals, schools, logistics centers, airports, exhibition halls, etc. This sort of access is currently being used in roads, parks, traditional markets, and ports. Since the release of the IEEE 802.11 Legacy Standard in 1997, Wi-Fi technology has been continuously supplemented and revised, and the standard has been continuously developed. In the era of smart working, the importance of efficient wireless deployment and scientific design has become more important. The importance of wireless in the smart factory, in the metaverse era, in the era of pursuing work and life that transcend time and space by using AR, VR, MR, and XR, it is more urgent to solve the shadow area of Wi-Fi. Through this study, we intend to verify the wireless failure problem of the xr training center and suggest improvement measures.

A Leakage-Based Solution for Interference Alignment in MIMO Interference Channel Networks

  • Shrestha, Robin;Bae, Insan;Kim, Jae Moung
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.2
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    • pp.424-442
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    • 2014
  • Most recent research on iterative solutions for interference alignment (IA) presents solutions assuming channel reciprocity based on the suppression of interference from undesired sources by using an appropriate decoding matrix also known as a receiver combining matrix for multiple input multiple output (MIMO) interference channel networks and reciprocal networks. In this paper, we present an alternative solution for IA by designing precoding and decoding matrices based on the concept of signal leakage (the measure of signal power that leaks to unintended users) on each transmit side. We propose an iterative algorithm for an IA solution based on maximization of the signal-to-leakage-and-noise ratio (SLNR) of the transmitted signal from each transmitter. In order to make an algorithm removing the requirement of channel reciprocity, we deploy maximization of the signal-to-interference-and-noise ratio (SINR) in the design of the decoding matrices. We show through simulation that minimizing the leakage in each transmission can help achieve enhanced performance in terms of aggregate sum capacity in the system.

The Study of Adaptable Plant Species according to Warmth Index using RCP 8.5 Scenarios in Cheonan-Si (RCP 8.5 시나리오를 이용하여 온량지수에 따른 천안시 적응 가능한 식물종 연구)

  • Kong, Seok Jun;Shin, Jin Ho;Yang, Keum Chul
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.16 no.3
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    • pp.19-30
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    • 2013
  • This study was proposed to adaptable species according to climate change using warmth index(WI) in Cheonan-Si. RCP 8.5 was used to estimate change of warmth index(WI) depending on climate change in Cheonan-Si. Climatic change of Cheonan-Si was estimated to change from cool temperate forest central zone to warm temperate forest zone. The following plant species will survive within WI change of Cheonan-Si from 2010 to 2050 : 18 species in the tree layer including Quercus serrata, Q. variabilis, Pinus densiflora, Q. acutissima etc.; 28 species in the shrub layer including Rhus trichocarpa, Lindera obtusiloba, Zanthoxylum schinifolium etc.; 24 species in the herb layer including Oplismenus undulatifolius, Carex lanceolata, etc.; 12 species in the vine plants including Smilax china, Cocculus trilobus, etc.