• The Journal of the Acoustical Society of Korea
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• v.12 no.1
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• pp.47-54
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• 1993

Performance analysis is very important to transmit the high quality information and to construct the optimal system for the minimze the noise from the channel of spread spectrum system. In this paper the error rate performance is analyzed with computer simulation in noncoherent frequency hopping M-qry frequency shift keying(FH/MFSk) systems with regard to thermal noise under the partial band jamming environments. AS a result, in case the thermal noise is disregarded, bit error probability of system in jamming fraction ρ and Eb/Nj(bit energy to jamming power density) is reduced with the increase of K and in worst case 32FSK system is better than 2FSK system by 3.23dB with the variatio of Eb/Nj. In case thermal noise is considered, bit error probability of system by 3.23dB with the variation of Eb/Nj. In case thermal noise is considered, bit error probability of system are reduced with the increase of K and Eb/No(bit energy to thermal noise density). Bit error probability in connection with worst case ρ is not largely influenced form over the 14dB to K=1 and 8dB to K=5 accordingly thermal noise disregarding. These results may be useful for avoiding the common vulnerabilities when the spread spectrum system is designed.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.1-9
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• 1990

The performance of noncoherent FH/FSK system in the presence of multitone jamming and noise is analyged. Random and the structured jammings are considered as a multitone jamming model. The probability density function is derived and then optimum decision rule is applied to determine error probability of each cases. As a result, error probabilities of random and structured multitone jamming are shown as a function of number of jamming tones, jamming to signal power ratio, jamming signal phase and one jamming tone power to signal power ratio under Worst-case Jamming interference. It is found that error probability is maximam when one jamming tone power to signal power ratio is 1. Also we know that error performance of random and structured jamming is almost equal.

• ETRI Journal
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• v.38 no.3
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• pp.455-462
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• 2016

Frequency hopping (FH) is a common characteristic of a wide variety of communication systems. On the other hand, software-defined radio (SDR) is an increasingly utilized technology for implementing modern communication systems. The main challenge when trying to realize an SDR FH system is the frequency tuning time, that is, the higher the hopping rate, the lower the required frequency tuning time. In this paper, significant universal hardware driver tuning options (within GNU Radio software) are investigated to discover the tuning option that gives the minimum frequency tuning time. This paper proposes an improved SDR frequency tuning algorithm for the generation of a target signal (with a given target frequency). The proposed algorithm aims to improve the frequency tuning time without any frequency deviation, thus allowing the realization of modern communication systems with higher FH rates. Moreover, it presents the design and implementation of an original GNU Radio Companion block that utilizes the proposed algorithm. The target SDR platform is that of the Universal Software Radio Peripheral USRP-N210 paired with the RFX2400 daughter board. Our results show that the proposed algorithm achieves higher hopping rates of up to 5,000 hops/second.

• Transactions of the Society of Information Storage Systems
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• v.6 no.1
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• pp.12-17
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• 2010

Thermally-assisted magnetic recording (TAMR) is a potentially promising approach to increase the storage density of hard disk drive (HDD). However, TAMR has some issues such as temperature effects, media problems, thermal deformation and light delivery. In this research, we focused on light delivery. One of the powerful methods to deliver the light from laser diode to recording medium is the use of an optical fiber and a specially designed prism. However, the TAMR with optical fiber may have some flyability problems induced by the mounted optical fiber and prism. Also, the TAMR suspension using an optical fiber has high vertical and pitch stiffness. Therefore, p-torque is greatly increased by the optical fiber. Also, flying height (FH) of the slider with TAMR suspension can be largely changed by p-torque. Therefore, in this paper, we focus on the pitch static attitude (PSA) tolerance and the FH by PSA of the TAMR suspension. The FH is investigated using various errors and the PSA tolerance for TAMR suspension is proposed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7C
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• pp.666-674
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• 2005

A hybrid multicarrier CDMA/FDM system with a truncated adaptive transmission scheme is analyzed in forward link based on the feedback information from the mobile station. In the single cell environment, the prop(mea scheme outperforms the adaptive FH/DS system as well as the MC DS/CDMA system when orthogonal signature sequences are used. In the multiple cell environment also, the proposed scheme has better performance characteristics than the adaptive FH/DS system when orthogonal and random codes are used as spreading sequences.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.253-265
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• 1988

This study was designed to compare the normal head posture group with the extended head posture group in order to investigate the relatinship between head posture and craniofacial morphology. The subjects were devided into two groups; one included 80 children with normal head posture and occlusion, and the other 60 malocclusion patients with extended head posture. Their lateral cephalograms were traced and analysed based on 38 selected items. The following conclusion were reached. 1. The craniocervical angulations in normal group; OPT to SN, CVT to SN, OPT to FH and CVT to FH angles were $101.7^{\circ},\;104.8^{\circ},\;91.7^{\circ}\;and\;100.7^{\circ}$, respectively. 2. Compared with normal group, experimental group showed increase in mandibular plane angle, decrease in facial plane angle, airway space and posterior facial height but, there were insignificant differences in anterior facial height and tongue level between two groups. 3. Of the craniocervical angulations, OPT to FH angle was most highly correlated to the variables of the craniofacial morphology. 4. The effect of craniocervical angulation on craniofacial morphology in experimental group was different from that in comparison of normal group and experimental group.

• Journal of the Korea Society of Computer and Information
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• v.3 no.4
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• pp.78-85
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• 1998

In this paper, we analyzed the performances for FH/CPFSK system with limiter - discriminator detection and integrate-and-dump post-detection filtering under thermal noise and partial-band jamming noise. And, we considered intersymbol interference - related SNR and differential phase parameters for all eight of the possible adjacent bit data patterns, FM noise clicks for evaluating FH/CPFSK and CPFSK systems. In result, the optimum modulation index h was 0.7 and the optimum value of bandwidth-time product D was 1.0. Next, when we considered the thermal noise under the partial-band jamming, the thermal noise significantly influenced the error probability of system below 20dB approximately but could ignore above 20dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1357-1365
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• 1991

This paper proposes the generation of several classes of frequency hopping patterns. which are derived by permutation, for an asynchronous frequency hopping spread spectrum multiple accecss system (FH/SSMA). The first class of hopping patterns is obtained by using a Latin square. The second class of hopping patterns is derived by generalizing the first class which is designed by using a permutation technique. The third class of hopping patterns is designed by using a rotational base of elements. We evaluate the hit property of the proposed classes of hopping patterns when these patterns are nutually shifted in an FH/SSMA system. Compared to the Reed Slolmon sequences generated by the conventional method, the sequence obtained by the permutation technique can reduce the number of hits among hopping frequencies in asynchronous time/frequency shift.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.730-738
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• 1992

This paper alms to analyse the performance of frequency hopping /spread spectrum multiple access system by employing the channel with mixture of AWGN, partial band Jamming, fading and user interference. The performance analysis of FH /SSMA system, taking account of frequency 'hit'(user Interference ) which occurs in the presence of multiple user, produces the following numerical results by computing error probability and throughput of each code in two cases whether the side Information about channel is used or not. The numerical results are as follows : When composite interferences coexist In channel, RS code Is significantly superior to convolutional code in terms of performance. Concatenated code provides the same performance as RS code. The above results show that RS code is pertinent as error-correction code.

• Journal of Information Technology Services
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• v.8 no.1
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• pp.165-177
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• 2009

This paper reviews diverse IP mobility and fast handover mechanisms for seamless Internet services. Especially, fast handover mechanisms for the Proxy Mobile IPv6( PMIPv6) are categorized according to their approaches. Then, a new fast handover PMIPv6(FH-PMIPv6) mechanism is proposed using only L3 signaling message exchange. In the proposed FH-PMIPv6 mechanism, only local mobility anchor(LMA) exchanges L3 signaling messages with mobility access gateways(MAGs) for the fast handover operation. That is, inter-MAG signalling messages are not required for the fast handover operation. Therefore, unlike existing fast handover mechanisms, two relevant neighbouring MAGs need not set up the security association(SA) to protect fast handover related signaling messages and share SA related information. Moreover, the L3 triggering message is defined newly by standard ICMPv6 to trigger promptly the proposed mechanism. Analysis and comparison of the handover latency are performed for the proposed mechanism and existing mechanisms, which shows that the proposed FH-PMIPv6 mechanism has the favorable performance.