• Title/Summary/Keyword: Node Grouping

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Distance-Based Channel Assignment with Channel Grouping for Multi-Channel Wireless Mesh Networks (멀티채널 무선 메쉬 네트워크에서의 채널 그룹을 이용한 거리 기반 채널 할당)

  • Kim, Sok-Hyong;Suh, Young-Joo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.12B
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    • pp.1050-1057
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    • 2008
  • Wireless Mesh Networks (WMNs) have recently become a hot issue to support high link capacity in wireless access networks. The IEEE 802. I 1 standard which is mainly used for the network interface technology in WMNs supports up to 3 or 12 multiple channels according to the IEEE 802.11 specification. However, two important problems must be addressed when we design a channel assigmnent algorithm: channel dependency problem and channel scanning delay. The former occurs when the dynamic channel switching of an interface leads to the channel switching of other interfaces to maintain node connectivity. The latter happens per channel switching of the interface, and affects the network performance. Therefore, in this paper, we propose the Distance-Based Channel Assigmnent (DB-CA) scheme for multi-channel WMNs to solve such problems. In DB-CA, nodes just perform channel switching without channel scanning to communicate with neighboring nodes that operate on different channels. Furthermore, DB-CA minimizes the interference of channels being used by nodes near the gateway in WMNs. Our simulation results show that DB-CA achieves improved performance in WMNs.

A Clinicopathologic Analysis of Neck Masses (경부 종괴의 임상 및 병리학적 고찰)

  • Km Jeong-Ho;Oh Sang-Hoon;Kim Sang-Hyo
    • Korean Journal of Head & Neck Oncology
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    • v.13 no.1
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    • pp.51-57
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    • 1997
  • A mass appearing in the anterior or lateral side of neck often can be a diagnostic challenge. Differential diagnosis of the neck mass covers a broad spectrum of diseases and the proper evaluation and management of a neck mass requires an impressive amount of anatomic and pathologic information. Because improper diagnosis and management may convert a potentially curable malignant metastasis into incurable disease, a differential diagnosis must be considered in all patients who present with a neck mass. Authors reviewed 2,148 cases of neck mass who were diagnosed by surgical resection, biopsy or aspiration during the period between October 1982 to December 1993, excluding those with thyroid and parathyroid disease. The evaluated characteristics were age, sex, site of lesion, and pathologic diagnosis. The results were as follows: Of 2,148 cases of neck mass, the overall ratio of benign to malignant tumor was 3 : 1. In 1,603 cases of benign mass lesion, the most common disease was lymphadenitis(non-specific and tuberculosis) showing 53% incidence, the second was salivary gland tumor(13%), and the third was congenital lesion(12%). The minor problems such as lipoma and sebaceous cyst were 21 %. In the age distribution of benign lesion, tuberculous lymphadenitis showed peak incidence in second decade, non-specific lymphadenitis was main disease of childhood, salivary gland tumor was peak in fourth decade, and most of congenital lesions were diagnosed at the age below 15. In 545 malignant tumors, the most common lesion was metastatic cancer to cervical lymph nodes yielding 71 % incidence(head and neck primary 52%, infraclavicular primary 42%, unknown primary 5%), the second common disease was lymphoma(19%), and the third was salivary gland cancer(9%). In the age incidence of malignant tumor, 60% of them developed in the fifth and sixth decade, head and neck primary was more common in the fifth decade than sixth, however lymphoma showed higher incidence in sixth decade. In the analysis of mass location according to lymph node level grouping(I - V), lymphadenitis developed mostly in level V nodes, the next common occurring site was level IV in tuberculous lymphadenitis and level II in non-specific lymphadenitis. The majority of metastatic cancers were found in level IV and III, and common occurring site of lymphoma was in level II and IV. Pathologic diagnosis of neck masses were made by fine needle aspiration cytology 80 cases, incisional biopsy 533 cases, excisional surgery 1,399 cases, and neck dissection 116 cases. For the proper management of neck mass, a proper diagnostic modality should be selected from imaging techniques, cytology, biopsy or neck dissection, with the consideration of patient's age, history and clinical findings. The scapel biopsy could be used freely in the inflammatory disease or inoperable metastatic cancer, but it should be reserved in the curable metastatic cancer or clinically possible malignancy.

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