• Journal of Communications and Networks
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• v.6 no.2
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• pp.123-132
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• 2004

The various challenges to realize a fixed wireless ATM network are discussed and some solutions for these challenges are presented. In this paper, the capacity allocation in wireless ATM, the wireless link impact on ATM traffic, and the optimum utilization of the wireless network resonrces for a line of sight (LOS) winless ATM link are studied. An adaptive MQAM modulator is introduced to provide a suitable solution to these issues. The modulator level is adjusted using a unique QoS metric in a wireless network. The metric, termed modified effective bandwidth, takes into account the bandwidth demand, QoS requirements, and outage conditions of the wireless ATM link. A performance study using VBR MPEG-l video traffic in a fixed wireless channel (Ricean channel) demonstrates the advantages of the proposed system.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2093-2095
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• 2002

Nowadays, there are actually lots of changes in wireless communications of Korea. But it is not an exact PTP(Peer to Peer) Communication. In other words, a mobile station which can find fixed station can be connected with wireless internet server or other services, oppositely fixed station cannot approach to mobile station. Even though it exists, it is difficult to communicate with full duplex. We can service using CDMA 1X techniques such as cellular based SMS (Short Message Service) service or very simple MPRG Services. In this paper, we propose a system, using DirectX based mobile/fixed station stand alone program, depending on bandwidth of wireless service provider, tranceiving high resolution moving picture or reliable data regularly by a fixed connection each other.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.104-114
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• 2005

This work presents a concept and the related analysis of the traffic performance for a wireless broadband system based on fixed relay stations acting as wireless bridges. The analysis focuses on the important performance indicators end-to-end throughput and delay, taking into account the effects of an automated repeat request protocol. An extension to a MAC frame based access protocol like IEEE 802.11e, 802.15.3, 802.16a, and HIPERLAN2 is outlined and taken as basis for the calculations. The system is intended for both dense populated areas as an overlay to cellular radio systems and to provide wide-area broad-band coverage. The two possible deployment scenarios for both dense urban and wide-area environments are introduced. Analytical and validating simulation results are shown, proving the suitability of the proposed concept for both of the mentioned scenarios. It is established that the fixed relaying concept is well suited to substantially contribute to provide high capacity cellular broad-band radio coverage in next generation (NG) cellular wireless broadband systems.

• Journal of Broadcast Engineering
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• v.13 no.4
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• pp.479-487
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• 2008

The method to determine allowable interference criteria is required due to new digital FWSs(Fixed Wireless Systems) adding to allowable frequency bands, besides current FWSs and digital FWSs. In this paper, we suggested a method to define allowable interference between digital FWSs. Types of interference for FWS were defined and channel characteristics were analyzed. Allowable interference criteria were analyzed using the suggested method for M-ary QAM modulations, which is typical modulation technique of digital FWS.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.8
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• pp.443-451
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• 2003

Many attempts have been made for the health and lives of patients at a remote site. but little attention has been given to emergency system using wireless or other intelligent networks. In this paper, shown is a remote emergency system which can be used in an ambulance. It possibly gives a great help to the patients who may lose their lives, in other words, gives pre-hospital cure to them being sent to the hospital. Doctors or specialists are able to give a quick help which may give a new life to patients. This system deal with very important patient's data-ECG, SpO$_2$, blood pressure, biomedical signal data etc. - as other emergency system. A good performance better than other system is many but shortly spoken as follows. First, this system is user friendly system activated in windows 2000 environment. Second, MPEG4 and ECG data sent to the other station for specilists can give a pre-hospital cure to patients in advance. Third, there exist effective algorithms to operate this system. Fourth, this system has been made with software mostly, so this system can be easily embedded in IBM compatible computer. In addition to this performance, for the better and reliable system, various tests were proceeded and recursively tested. Tests were made in EV-DO wireless network and Local Area Network. This mobile-fixed remote emergency system using wireless network like EV-DO network will give a great usage to needed area.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.1
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• pp.40-47
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• 2013

By virtue of Rec. ITU-R P.1546 and geography information system, interference analysis for the fixed wireless system and radar has been presented based upon the frequency-distance rules with minimum coupling loss, and a comprehensive methodology for assessing interoperability between systems was examined in terms of received signal, protection ratio, frequency dependent rejection. Also to find the antenna gain from a discrimination angle, a useful S-I plane was introduced based on signal and interference vectors derived from the real map with geographic information. To show some computational results, geography information on the map was taken for the given area, and field strength and path profile were illustrated for the radar and fixed wireless system operating at 2.7 GHz, for convenience. In addition the interference effect of receiver was also checked as a function of radar beam direction including protection ratio and frequency dependent rejection. The developed interference analysis can be actually applied to evaluate interoperability for wireless systems in the VHF and UHF bands.

• International Journal of Contents
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• v.12 no.1
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• pp.65-69
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• 2016

Wireless communication chipsets have fixed transmission rate and communication distance. Although there are many kinds of chipsets with throughput and distance purpose, they cannot support various types of wireless applications. This paper provides theoretic research results in order to support various wireless applications requiring different throughput, delayed quality-of-service (QoS), and different communication distances by using a wireless communication chipset with fixed rate and transmission power. As a performance metric, the probability for a data frame that successfully receives at a desired receiver is adopted. Based on this probability, the average number of transmission in order to make a successful frame transmission is derived. Equations are utilized to analyze the performance of a single-hop with channel coding and a dual-hop without error correction matter transmission system. Our results revealed that single-hop transmission assisted by channel coding could extend its communication distance. However, communication range extending effect of the single-hop system was limited. Accordingly, dual-hop transmission is needed to overcome the communication distance limit of a chipset.

• Journal of Communications and Networks
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• v.6 no.2
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• pp.163-172
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• 2004

Ultra Wide Bandwidth (UWB) spread-spectrum techniques will playa key role in short range wireless connectivity supporting high bit rates availability and low power consumption. UWB can be used in the design of wireless local and personal area networks providing advanced integrated multimedia services to nomadic users within hot-spot areas. Thus the assessment of the possible interference caused by UWB devices on already existing narrowband and wideband systems is fundamental to ensure nonconflicting coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. In this paper, we study the coexistence issues between an indoor UWB-based system (hot-spot) and outdoor point to point (PP) links and Fixed Wireless Access (FWA) systems operating in the 3.5 - 5.0 GHz frequency range. We consider a realistic UWB master/slave system architecture and we show through computer simulation, that in all practical cases UWB system can coexist with PP and FWA without causing any dangerous interference.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.103-109
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• 2003

We have proposed the 4-Dimensional Multiple-Subcarrier Modulation with fixed bias in Optical Wireless Communications. Here, the 4-D signal vectors are derived from the optimization technique of signal waveforms maximizing the minimum distance between signal points in an n-dimensional Euclidean sphere. The resulting vectors are used in generating the output amplitude of impulse generator in a Multiple-Subcarrier Modulation scheme. We have achieved that the normalized power requirement of the proposed system is maximum 3 dB and 3.3 dB smaller than those of normal QPSK, Reserved Subcarrier, and Minimum Power scheme, respectively. Also, in the range of 1.125 ∼ 1.25 of the normalized bandwidth, the proposed system has maximum 3 dB, 2 ∼ 4 dB, 0 ∼ 3 dB smaller bandwidth requirement compare to normal QPSK, Res. Subcarrier, Min. Power schemes, respectively.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.527-530
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• 2002

The frequencies for HAPS used in fixed wireless access are allocated in the millimeter wave bands. The systems using these frequencies can have a serious impact on the radio communication qualities due to rain. In this paper, we compare the specific rain attenuation using CM(combined) raindrop size distribution with those using different sevral raindrop size distributions for the frequency bands 28/48㎓. The rain attenuations using CM raindrop size distribution for the path between the earth and HAPS platform according to the elevation angle are described.