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研究生:王喜文
研究生(外文):Hsi-Wen Wang
論文名稱:分碼多工技術對無線區域網路之介質擷取控制協定之影響
論文名稱(外文):The Effects of CDM on MAC Protocols in Wireless Local Area Networks
指導教授:呂忠津
指導教授(外文):Chung-Chin Lu
學位類別:碩士
校院名稱:國立清華大學
系所名稱:電機工程研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:1994
畢業學年度:82
語文別:中文
論文頁數:70
中文關鍵詞:分碼多工時槽式ALOHA協定擷取點遠端單元服侍區重合服侍區之干擾
外文關鍵詞:code-division multiplexingslotted-ALOHAaccess pointremote
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分碼多重擷取技術因其應用在無線通訊上的優點,已獲得廣泛的注意。在
分碼多重擷取技術中,每一位使用者皆被指定一特殊的碼用來展頻以及聚
頻,然而,暨有好的自相關函數且享有特別的交互相關函數的碼組的數目
,實為有限。因此,如要簡化系統且維持良好的性能,碼組的分配便得慎
行其事。取而代之的,分碼多工技術便被選用來運作在一個基架型無線區
域網路中的各個不同的侍服區,所有經由同一個擷取點服侍的遠端單元皆
使用相同的上傳碼來完成向上傳送,其方式乃採用時槽式ALOHA協定(
slotted-ALOHA)做為向上傳輸的介質擷取控制方式。然而,擷取點的基本
服務範圍之間的重疊現象是維持服務連續不中斷的前題下,無可避免的安
排。任何遠端單元皆可能坐落在其他非其註冊的擷取點以外的擷取點涵蓋
之服侍範圍,因此可能對這些擷取點封包的接收產生影響。這種由註冊於
其他擷取點,且坐落在本擷取點之服侍範圍內的遠端單元所產生的干擾,
稱為重合服侍區之干擾,雖然重合服侍區之干擾可利用分碼多工技術來降
低錯誤率至某些程度,但在無線區域網路的應用上,其作用因來自多數同
時正進行傳送所累加起來、強烈的重合服侍區之干擾訊號而變得不可忽視
。在本論文中,我們主要探索重合服侍區之干擾對建構於分碼多工技術之
時槽式 ALOHA 協定操作的性能所造成的影響。

Code-division multiple access (CDMA) techniques have been
receiving great attention especially in wireless
communications due to some promising good advantages of
using them. In CDMA, each user is assigned a unique code to
spread and despread signals. However, the number of codes which
have good autocorrelation as well as crosscorrelation
properties is limited. As a result, in order to simplify
the implementation of real systems while maintaining good
performance , the assignment of a set of codes with good
crosscorrelation properties should be properly managed. Instead
of CDMA, code-division multiplexing (CDM) is considered to
operate among different cells in an infrastructured wireless
local area network (LAN). All remote units served by the same
access point use the same preassigned code for uplink
transmission. And each cell operates with slotted ALOHA as its
uplink transmission medium access control. Nonetheless, the
basic service areas of access points are inevitable to overlap
one another for the sake of continuation in service. A remote
unit registered to some certain cell may possibly lie in the
coverage areas of other access points and has some influence on
the packet reception in these other access points. The
interference produced by remote units which lie in the joint
region of two cells is called joint-cell interference. Although
joint-cell interference can be suppressed with CDM to some
degree, it can not be totally neglected in a wireless LAN
application because of the strong summing signal transmitted
from a large number of active remote units simultaneously in a
period of time. In this thesis , we investigate the effects of
the joint-cell interference on the performance of slotted ALOHA
protocol with CDM.

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