• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.50-58
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• 2009

Fourth generation mobile communication network have the technology of extensive form include basic service technology and it has been developed from the radio access technology and network topology. Not only fourth generation mobile communication network have basically done new highspeed radio access technology which is suitable to high and low speed environment of transfer, but also it is possible that they have been made for freely vertical handover. ETRI also has made fourth generation mobile communication network which is WiNGS(Wireless Initiative for Next Generation Service) satisfied that demand. This paper is made by lossless handover method through the local retransmission ARQ agent that is one of the main technology of fourth generation mobile communication network. Lossless handover method through local retransmission ARQ agent has been basically made by WiNGS and it was better than original local retransmission of layer by simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.1
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• pp.48-59
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• 2009

Next generation mobile communication system will have various access networks and provide seamless multimedia data service to mobile nodes. The WiNGS system, one of these access network, has superior RAT(Radio Access Technology) and network connectivity other than previous ones. In this paper, we propose link-layer SR-ARQ between mobile node and WAGW to solve packet re-ordering problem during handover. In the proposed scheme, we apply the adaptive timer at the SR-ARQ sender to reduce unnecessary packet retransmission during handoff and delayed NAK algorithm at the SR-ARQ receiver for delaying NAK response due to temporary out-of-sequenced frames. We evaluate the performance of the proposed scheme by implementing the new SR-ARQ protocol at the link-layer using ns-2 simulator, and show the handover performance is improved greatly by preventing unnecessary retransmission.

• Journal of Korean Neurosurgical Society
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• v.29 no.7
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• pp.899-903
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• 2000

Objective : Object : A 7-year retrospective clinical and MRI study was reviewed to evaluate the characteristics of pineal cyst. We evaluated results of clinical and radiologic change of pineal cyst during follow up period. Patients and Methods : From 1992 to 1999, 50 patients with pineal cyst were visited for evaluation. Follow up clinical information was obtained from patients or clinical record through phone conversation. also radiologic findi-ngs of pineal cyst in mid-sagittal MRI were reviewed in detail. Results : Pineal cysts were usually asymptomatic and detected incidentally during evaluation of other diseases. Sagittal MRI is the most useful diagnostic test. The radiologic findings of pineal cyst were isointensity on T1WI comared to CSF and slightly high signal intensity on T2WI. Cyst wall was variably enhanced on Gad-enhanced T1WI. The average size of cyst was $13.9{\times}13.0mm$. The pineal cyst was classified into five groups according to previous report. Long term behavior of these lesions are not apparent, but in our study they showed no specific changes in clinical and radiological aspects during 25 months. Conclusion : Although long-term follow up results are needed, the pineal cyst are considered as normal variants. In our 25 months follow up results, there was no rapid change of cyst both clinically and radiologically. Therefore, frequent radiologic evaluation seems unnecessary except type III pineal cyst.