• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.45-50
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• 2011

In this paper, the encoding time delay of FH/TDD(Frequency Hopping/Time Division Duplex) based Motion JPEG image compression CODEC is analyzed for radio video transmissions of multi-camera systems in a vehicle. And, Synchronized connection of minimum channel collision is designed with synchronized shift and access according to channel status for Motion JPEG based FH/TDD multiple access.

• Journal of electromagnetic engineering and science
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• v.6 no.3
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• pp.176-181
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• 2006

Signal distortion due to the path loss, shadow, and multi-path fading is very serious in radio channel. In this paper, we propose CDMA-OFDM cooperative communication system based on DFP(Decode and Forward Protocol) to overcome these phenomena using spread spectrum technique, orthogonal sub-carrier, and the space diversity. We simulated proposed system under Rayleigh flat fading channel environment. A variety of simulation results reveal the cooperation can provide performance gain of up to 12 dB over direct communications in ideal inter-user case at BER of $10^{-3}$. And we can also confirm variation of diversity effect as channel environment changes.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.2 s.5
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• pp.1-8
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• 2004

Characteristics of digital broadcasting are multi-channel, high-definition and multi-function. especially, multi-function is enable us to do a variety of services except for an image and a voice. This paper, therefore, is analyzed propagation environment in Busan into ETRI model application about 지상파 DMB service. It takes to be simulated in Busan area around the mountains area and high building. So it measures the electric field strength in standards. Distribution pattern are similar with mutually in the 이론 and real measurement. Even areas are almost the same, but urban areas and mountains are different with mutually. Therefore, we conclude that ETRI propagation model and theoretical modeling in a free space in Busan area is not suitable.

• Journal of Industrial Technology
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• v.21 no.A
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• pp.189-198
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• 2001

In recent years, the predominant part in telecommunications is mobile communications. The next generation network is extending today's voice-only mobile networks to multi-service networks. ATM Network is possible to carry such multi-media traffic and it will be expect to use wireless ATM for the future mobile access network. One of manly important aspects for the performance of wireless ATM is the Medium Access Control (MAC) protocol. The MAC protocol must be able to satisfyingly handle the different ATM services (CBR, VBR, ABR and UBR) with their radically different performance requirements. Additionally, the MAC protocol must be able to cope with the complex radio environment where fading, multi-path propagation interference and burst-errors further complicate the situation. In this paper, a dynamic slot allocation algorithm in wireless ATM is proposed for an efficient channel sharing/media access at the MAC layer. We use equivalent capacity in the allocation of slots for VBR traffic which is variable along the time. It is simple and effective slot allocation method for VBR service. In particular, we consider the slot allocation of a session consisted of several connections for requirement of multimedia traffic. Simulation shows that the cell loss ratio is reduced by re-allocation of extra slots in Mobile Terminal (MT).

• ETRI Journal
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• v.43 no.3
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• pp.400-413
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• 2021

This paper theoretically and empirically explores the reliability gain that can be obtained by installing multiple antennas in on-vehicle broadcasting receivers. Analytical derivations reveal that maximal-ratio-combining-based diversity allows a multi-antenna receiver (MR) to achieve significantly better coverage probability than a single-antenna receiver (SR). In particular, the notable MR gains for low-power reception and high-throughput services are highlighted. We also discuss various aspects of mobile MRs, including geometric coverage, volume of the users served, and impact of receiver velocity. To examine the feasibility of MRs in the real world, extensive field experiments were conducted, particularly with on-air ATSC 3.0 broadcast transmissions. Relying on the celebrated erroneous second ratio criterion, MRs with two and four antennas were verified to achieve notable reliability gains over SRs in practice. Furthermore, our results also prove that layered-division multiplexing can cope better with receiver mobility than traditional time-division multiplexing when multiple services are intended in the same radio frequency channel.

• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.17-23
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• 2004

The mobile radio channel can be simulated as a complex-valued random process with narrow-band spectrum. This paper describes a real-time implementation of that process using a INS320C6414 digital signal processor and XC2VP30 Virtex FPGA. The simulator presented here is not only a comprehensive model of the flat fading but also frequency selective fading mobile channel conditions. To replicate the statistical characteristics of the multipath fading environment with the minimum computational burden, multi-rate techniques are employed to resolve practical problems such as variable sampling rate. The simulator produces accurate and consistent results due to digital implementation. It is very flexible and simple to program for various field conditions in mobile communications with a graphical user interface.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.811-814
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• 2009

The HF band maritime communication is have developing to digital methode that techniques should be readied the automatic link establishment of 1:N by coast station to many ship station. Because can use way by polling simply that communication environment calls particular station wicked fellow HF communication states which is much redundancy times for coast station to set link. In amateur radio particular station selective calling do to be using ALE(Automatic Link Establishment) controller by 1:1 automatic link setting way, but expect 1:N link setting by these way in maritime communication very difficult. That is difficult to avoid collision by traffic overload to induce calling of ship stations. Because HF communication considers channel special quality traffic state radio link should be established, and should be applied automatically secures stability of channel as accommodative at traffic overload. In this paper is studied the new radio protocol by 3 step sequency driving of free access, group free access and polling access using multi-tone in single channel.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.3
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• pp.11-17
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• 2010

Multi-standard, multi-band, multi-service system to ensure a flexible interface between the SDR (Software Defined Radio) technology for the implementation of the Stability and Low-Power, Low-Calcualrion DDC (Digital Down Conversion) technology is essential. DDC technology consists of a digital channel filter. This is a typical digital filter because of the limited fisheries are vulnerable to overflow and rounding errors are drawbacks. In this paper, we overcome this disadvantage, we propose the structure of the DDC. The way WDF (Wave Digital Filter) Structural rounding error due to the structural resistance to noise. Therefore, This is the useful structure when the filter coefficients's word length is short. In addition, since IIR filters based on FIR filters based on the amount of computation is reduced because fewer than filter's tap. The proposed structure is used in DDC that CIC (Cascaded Integrator Comb) filter, WDF, IFOP (Interpolated Fourth-Order Polynomials) were analyzed with respect to, the results were confirmed by computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1281-1288
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• 2012

This paper presents the design and implementation of a multi-mode mobile broadcasting Emergency Warning System (EWS) transmission and reception system which enables the propagation of disaster information using the encoding and transmission, reception and decoding methods specified in diverse mobile broadcasting standards. The implemented system supports global mobile broadcasting standards such as Terrestrial Digital Multimedia Broadcasting (T-DMB), Digital Video Broadcasting-Handheld (DVB-H), Integrated Services Digital Broadcasting-Terrestrial (ISDB-T), and the Digital Radio Mondiale (DRM) digital radio standard. The system consists of two key part: an encoding/transmission part and a reception/decoding part. The multi-mode mobile broadcasting EWS encoding and transmission system generates EWS data according to each broadcasting specification. The generated EWS data is then transmitted through a channel interface which meets the commercial broadcasting equipment specification. The receiver system receives and decodes the EWS data on a single hardware platform and can display the results on screen. Verification and conformity testing has been carried out on the implemented system by transmitting emergency data for each mode in real-time and displaying the received information in text on the receiver display.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1370-1378
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• 2008

In the system necessary for safety such as the train control system, to make train control information be sent correctly is very important. In the case of the system such as RF-CBTC(Radio Frequency-Communication Based Train Control), sometimes failure in correctness of train controlling information may happen because the information is sent throughout wireless transmission between on-board system of a train and wayside transmitter, and then, it is exposed to noises. Of RF-channel interference, there are various forms. Under the environment of mobile telecommunications, adjacent-channel interference and Co-channel interference are in trouble, and under the environment of the wireless LAN, inter-symbol interference is in trouble. Also, the system of the cellular CDMA mobile telecommunication is affected on the RF-channel interference such as Doppler effect, multi-cell interference, and other users' intervention. In this paper, we analyzed the effect of the train control information related to fading, intervention and other noises made in the underground interval and explained the transmission characteristics numerically. Furthermore, we calculated the mean of the error terms by increasing users in the system of the cellular CDMA. As the method for decrease the error term of sent information, we represented the way adjusting the arrangement of antennas, and we did the model related to the system of RF-CBTC in which the location of an antenna is calculated with really measured value of the transmission characteristics and the way confirming reliability of the wireless transmission.