• Title/Summary/Keyword: DSSS

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A Study on the Design and Implementation of a DSSS-based MODEM for a Right Termination System(FTS) (대역확산방식 비행종단시스템의 모뎀설계와 구현에 관한 연구)

  • Lim Keumsang;Kim Jaehwan;Cho Hyangduck;Kim Wooshik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.2C
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    • pp.175-183
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    • 2006
  • This letter proposes a Direct Sequence Spread Spectrum (DS-SS)-based Flight Termination System(FTS) and show the simulation results and implements the system using FRGAs. The DS-SS FTS has immunity interference signals and the influence of jamming signal. Moreover, a DS-SS FTS can provides effects on an authentication and encryption with spread codes. And the system uses more less power than an analog FM system. We used Reed-Solomon (32, 28) code and triple Data Encryption Standard(3DES) for error correction and data encryption. Also we used counter algorithm for unauthenticated device's attack The spread codes of In-phase channel and Quadrature channel were generated by Gold sequence generators. The system was implemented in Altera APEX20K100E FPGA for the ground system and EPF10K100ARC240-3 for the airborne system.

Study for trial project of Intelligent Train Control System (MBS) at Korail Bundang Line (분당선 지능형열차제어시스템 (MBS) 시범설비구축 사업에 관한 고찰)

  • Kim, Yun-Bae;Yoon, Ho-Sok
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.339-342
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    • 2008
  • In this paper, the lessons and learns are introduced from the result of the trial project which is the first CBTC(Communication Based Train Control System) at Korail Bundang Line. This project has started end of 2002 and finished recently by Samsung SDS. The main purpose of this project was that new technology was seek for next generation of railway signal control system adapted in Korea. In 2002, there was no any revenue service system using Radio Frequency CBTC in the world at that time. Just a few trial project was on going in USA and EU. In well developed cities, the metro system have been built and old enough therefore they have to be considering re-signalling their existing system with advanced system for increasing availabilities of line usage and safety. This Bundang Line Trial Project was the first Korean CBTC project for above reasons. Most sub systems have been developed using local technology such as Electronics Controlled Interlocking System and Track Circuit Systems etc. Specially, in this project the RF-Communication devices are developed by local technology using DSSS(Direct Sequency Spread Spectrum) instead of FHSS(Frequency Hopping Spread Spectrum). This project has lasted for more than five years originally planned for three years because it was only accessible only night time in the main line from Ori to Suseo about 20km long. Each night only 2 and half hours are available to use the main line. Now the trial project has been done successfully with meet the customer's requirement, therefore the upgrade the mainline of Bundang line and another extension area up to Wangsipli to make revenue service using this new technology. This paper shows this result of the trial project and the strategy of upgrade and extension project as well.

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Performance Analysis on the Impact of Mutual Interference and the Interference Suppression Method for CBTC System in the Presence of WPAN System (CBTC시스템과 WPAN시스템의 상호간섭영향 및 간섭신호 억제방안에 대한 성능분석)

  • Kim, Seong Cheol
    • Journal of the Korean Society for Railway
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    • v.15 no.5
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    • pp.454-458
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    • 2012
  • The CBTC(Communication based Train Control) and WPAN(Wireless Personal Area Network) systems employed on 2.4GHz ISM band wireless networks provide complementary service within the same environment. Coexistence between the networks will be impaired if the mutual packets are uncertainty associated the timing or gaussian distance. This paper analyzes the impact of the mutual interference and proposed method to minimize the effect of the WPAN system signals on CBTC system. The performance analysis is illustrated by examining the symbol error rate versus signal to noise interference ratio in terms of carrier frequency offset. The method contributes to reduce the symbol error rate drastically. However it can't be a fundamental solution for the impact on the interference problem. It may be needed for railway only frequency after checking the problems of the current railway frequency.

The Effect of Electromagnetic Noise on the Wireless LAN Using Direct Sequence Spread Spectrum (DSSS 방식용 무선 LAN에 대한 전파 잡음의 영향)

  • Kim, Che-Young;Park, Jeung-Keun;Park, Seng-Keun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.6
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    • pp.630-639
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    • 2008
  • In this paper, we investigate the cause of throughput degradation on the wireless local area network(WLAN) and the reason of interference level change attributed to the spanned frequency in the presence of electromagnetic interference. We also measured and quantified the electric field strength of interference which yields the abrupt change of the throughput. Two units of WLAN and one unit of AP(Access Point) are configured to maintain the radio link. As the sources of interference, both the co-channel and adjacent-channel interference are considered and the critical values of electric field are provided for each case. Our experimental observations show that the signal strength generated from these interference sources is at most less than 54 dBuV/m @3 m in order to coexist between WLANs and other low power radio devices without any noticeable throughput decreases. Based on our empirical results, as far as 802.11b WLAN is concerned, we believe that the current domestic limit of the signal strength for an extremely low power radio device, 30.9 dBuV/m @3 m, can be increased as much as 23.1 dB.

Location error analysis of a real time locating system in a multipath environment (다중경로 환경에서 실시간 위치추적 시스템의 위치 오차 분석)

  • Myong, Seung-Il;Mo, Sang-Hyun;Lee, Heyung-Sub;Park, Hyung-Rae;Seo, Dong-Sun
    • Journal of IKEEE
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    • v.14 no.1
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    • pp.25-32
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    • 2010
  • In this paper, we analyze the location accuracy of real-time locating systems (RTLS) in multipath environments, where the RTLS complies with an ISO/IEC 24730-2 international standard. RTLS readers should have an ability not only to recover the transmitted signal but also provide arrival timing information from the received signal. In the multipath environments, in general, the transmitted signal goes through both direct and indirect paths, and then it becomes some distorted form of the transmitted signal. Such multipath components have a critical effect on deciding the first arrival timing of the received signal. To analyze the location error of the RTLS in the multipath environments, we assume two multipath components without considering an additive white Gaussian noise. Through the simulation and real test results, we confirm that the location error does not occur when the time difference between two paths is more than 1.125Tc, but the location error of about 2.4m happens in case of less than 0.5Tc. In particular, we see that the resolvability of two different paths depends largely on the phase difference for the time difference of less than 1Tc.

A Study on a Conceptualization-oriented SDSS Model for Landscape Design (조경설계를 위한 공간개념화 지향의 공간의사결정지원시스템 모델에 대한 연구)

  • Kim, Eun Hyung
    • Spatial Information Research
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    • v.22 no.6
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    • pp.55-65
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    • 2014
  • By combining the role of current GIS technology and design behaviors from the cognitive perspective, spatial conceptualization can be extended efficiently and creatively for ill-structured problems. This study elaborates the model of a conceptualization-oriented SDSS(Spatial Decision Support System) for a landscape design problem. Current information-oriented GIS technology plays a minor role in planning and design. The three attributes in planning and design problems describe how the deficiencies of current GIS technology can be seen as a failure of the technology. These are summarized: (1) Information Explosion/Information Ignorance (2) Dilemma of Rigor and Relevance (3) Ill-structured Nature of planning and Design. In order to implement the conceptualization idea in the current GIS environment, it will be necessary to shift from traditional, information-oriented GISs to conceptualization-oriented SDSSs. The conceptualization-oriented SDSS model reflects the key elements of six important theories and techniques. The six useful theories and techniques are as follows; (1) Human Information Processing (2) Tool/Theory Interaction (3) The Sciences of the Artificial and Epistemology of Practice (4) Decision Support Systems (DSSs) (5) Human-Computer Interaction (HCI) (6) Creative Thinking. The future conceptualization-oriented SDSS can provide capabilities for planners and designers to figure out some "hidden organizations" in spatial planning and design, and develop new ideas through its conceptualization capability. The facilitation of conceptualization has been demonstrated by presenting three key ideas for the framework of the SDSS model: (1) bubble-oriented design support system (2) prototypes as an extension of semantic memory, and (3) scripts as an extension of episodic memory in a cognitive pschology perspective. The three ideas can provide a direction for the future GIS technology in planning and design.

On Adaptive Narrowband Interference Cancellers for Direct-Sequence Spread-Spectrum Communication Systems (주파수대역 직접 확산 통신시스템에서 협대역 간섭 신호 제거를 위한 적응 간섭제거기에 관한 연구)

  • 장원석;이재천
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.10C
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    • pp.967-983
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    • 2003
  • In wireless spread-spectrum communication systems utilizing PN (pseudo noise) sequences, a variety of noise sources from the channel affect the data reception performance. Among them, in this paper we are concerned with the narrowband interference that may arise from the use of the spectral bands overlapped by the existing narrowband users or the intentional jammers as in military communication. The effect of this interference can be reduced to some extent at the receiver with the PN demodulation by processing gain. It is known, however, that when the interferers are strong, the reduction cannot be sufficient and thereby requiring the extra use of narrowband interference cancellers (NIC's) at the receivers. A class of adaptive NIC's are studied here based on different two cost functions. One is the chip mean-squared error (MSE) computed prior to the PN demodulation and used in the conventional cancellers. Since thses conventional cancellers should be operated at the chip rate, the computational requirements are enormous. The other is the symbol MSE computed after the PN demodulation in which case the weights of the NIC's can be updated at a lot lower symbol rate. To compare the performance of these NIC's, we derive a common measure of performance, i.e., the symbol MSE after the PN demodulation. The analytical results are verified by computer simulation. As a result, it is shown that the cancellation capability of the symbol-rate NIC's are similar or better than the conventional one while the computational complexity can be reduced a lot.

Optimum Rake Processing for Multipath Fading in Direct-Sequence Spread-Spectrum Communication Systems (주파수대역 직접확산 통신시스템에서 다중경로 페이딩 보상을 위한 최적 레이크 신호처리에 관한 연구)

  • 장원석;이재천
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.10C
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    • pp.995-1006
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    • 2003
  • It is well know that in the wireless communication systems the transmitted signals can suffer from multipath fading due to the wave propagation characteristics and the obstacles over the paths, resulting in serious reduction in the power of the received signals. However, it is possible to take advantage of the inherent diversity imposed in the multipath reception if the underlying channel can be properly estimated. One of the diversity reception methods in this case is Rake processing. In this paper we study the Rake receivers for the direct-sequence spread-spectrum communication systems utilizing PN (pseudo noise) sequences to achieve spread spectrum. A conventional Rake receiver can use the finite-duration impulse (FIR) filter followed by the PN sequence demodulator, where the FIR filter coefficients are the reverse-ordered complex conjugate values of the fading channel impulse response estimates. Here, we propose a new Rake processing method by replacing the aforementioned PN code sequence with a new set of optimum demodulator coefficients. More specifically, the concept of the new optimum Rake processing is first introduced and then the optimum demodulator coefficients are theoretically derived. The performance obtained using the new optimum Rake processing is also calculated. The analytical results are verified by computer simulation. As a result, it is shown that the new optimum Rake processing method improves the MSE performance more than 10 dB over the conventional one using the fixed PN sequence demodulator. It is also shown that the new optimum Rake processing method improves the MSE performance about 10 dB over the Adaptive Correlator that performs the combining of the multipath components and PN demodulation concurrently. And finally, the MSE performance of the optimum Rake demodulator is very close to the MSE performance of OPSK demodulator under the AWGN channel.

Performance of Drip Irrigation System in Banana Cultuivation - Data Envelopment Analysis Approach

  • Kumar, K. Nirmal Ravi;Kumar, M. Suresh
    • Agribusiness and Information Management
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    • v.8 no.1
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    • pp.17-26
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    • 2016
  • India is largest producer of banana in the world producing 29.72 million tonnes from an area of 0.803 million ha with a productivity of 35.7 MT ha-1 and accounted for 15.48 and 27.01 per cent of the world's area and production respectively (www.nhb.gov.in). In India, Tamil Nadu leads other states both in terms of area and production followed by Maharashtra, Gujarat and Andhra Pradesh. In Rayalaseema region of Andhra Pradesh, Kurnool district had special reputation in the cultivation of banana in an area of 5765 hectares with an annual production of 2.01 lakh tonnes in the year 2012-13 and hence, it was purposively chosen for the study. On $23^{rd}$ November 2003, the Government of Andhra Pradesh has commenced a comprehensive project called 'Andhra Pradesh Micro Irrigation Project (APMIP)', first of its kind in the world so as to promote water use efficiency. APMIP is offering 100 per cent of subsidy in case of SC, ST and 90 per cent in case of other categories of farmers up to 5.0 acres of land. In case of acreage between 5-10 acres, 70 per cent subsidy and acreage above 10, 50 per cent of subsidy is given to the farmer beneficiaries. The sampling frame consists of Kurnool district, two mandals, four villages and 180 sample farmers comprising of 60 farmers each from Marginal (<1ha), Small (1-2ha) and Other (>2ha) categories. A well structured pre-tested schedule was employed to collect the requisite information pertaining to the performance of drip irrigation among the sample farmers and Data Envelopment Analysis (DEA) model was employed to analyze the performance of drip irrigation in banana farms. The performance of drip irrigation was assessed based on the parameters like: Land Development Works (LDW), Fertigation costs (FC), Volume of water supplied (VWS), Annual maintenance costs of drip irrigation (AMC), Economic Status of the farmer (ES), Crop Productivity (CP) etc. The first four parameters are considered as inputs and last two as outputs for DEA modelling purposes. The findings revealed that, the number of farms operating at CRS are more in number in other farms (46.66%) followed by marginal (45%) and small farms (28.33%). Similarly, regarding the number of farmers operating at VRS, the other farms are again more in number with 61.66 per cent followed by marginal (53.33%) and small farms (35%). With reference to scale efficiency, marginal farms dominate the scenario with 57 per cent followed by others (55%) and small farms (50%). At pooled level, 26.11 per cent of the farms are being operated at CRS with an average technical efficiency score of 0.6138 i.e., 47 out of 180 farms. Nearly 40 per cent of the farmers at pooled level are being operated at VRS with an average technical efficiency score of 0.7241. As regards to scale efficiency, nearly 52 per cent of the farmers (94 out of 180 farmers) at pooled level, either performed at the optimum scale or were close to the optimum scale (farms having scale efficiency values equal to or more than 0.90). Majority of the farms (39.44%) are operating at IRS and only 29 per cent of the farmers are operating at DRS. This signifies that, more resources should be provided to these farms operating at IRS and the same should be decreased towards the farms operating at DRS. Nearly 32 per cent of the farms are operating at CRS indicating efficient utilization of resources. Log linear regression model was used to analyze the major determinants of input use efficiency in banana farms. The input variables considered under DEA model were again considered as influential factors for the CRS obtained for the three categories of farmers. Volume of water supplied ($X_1$) and fertigation cost ($X_2$) are the major determinants of banana farms across all the farmer categories and even at pooled level. In view of their positive influence on the CRS, it is essential to strengthen modern irrigation infrastructure like drip irrigation and offer more fertilizer subsidies to the farmer to enhance the crop production on cost-effective basis in Kurnool district of Andhra Pradesh, India. This study further suggests that, the present era of Information Technology will help the irrigation management in the context of generating new techniques, extension, adoption and information. It will also guide the farmers in irrigation scheduling and quantifying the irrigation water requirements in accordance with the water availability in a particular season. So, it is high time for the Government of India to pay adequate attention towards the applications of 'Information and Communication Technology (ICT) and its applications in irrigation water management' for facilitating the deployment of Decision Supports Systems (DSSs) at various levels of planning and management of water resources in the country.