臺灣博碩士論文加值系統

摘要在同步光纖網路中,塞取多工機是一個相當重要的網路元件.塞取多工
機可從輸入的高速連線中取出數個子通道,再將這些資訊輸出到低速的連
線.相對的,塞取多工機也可將低速連線輸入的資訊組合成數量相當的子通
道,再將它們組合成高速連線的輸出.非同步傳輸模式是一種結合了通路交
換與封包交換之優點的新傳輸技術,可適用於各種的數位服務.為了要在網
路骨幹的傳輸中使用非同步傳輸模式,必須使它能支援通路交換的數位服
務.針對具有延遲限制的定速率數位服務,非同步傳輸模式適應層的第一型
具備了準同步數位訊號的傳輸能力.此一功能稱之為非同步傳輸模式網路
中的通路模擬.結合了非同步傳輸模式與其第一型的適應層,可設計出類似
於同步光纖網路之塞取多工機的非同步傳輸模式之塞取多工機.就同步光
纖網路之塞取多工機而言,每個子通道的資訊以位元組為單位,在其適當的
位置,加入或移出同步光纖傳輸訊框.而就非同步傳輸模式之塞取多工機而
言,雖然其實體層是建立在同步光纖網路之上,每個子通道,在此稱之為非
同步傳輸模式的虛擬通道,是以非同步傳輸模式之細胞作為塞取的單位;每
個細胞的標頭處具有表示連結的標識.因為非同步傳輸模式之細胞本身就
是一個傳輸訊框,所以不會有同步光纖網路時槽交換的問題.在本設計中,
使用了四個高速的連結,其規格為155.52MHz的STS-3c/STM-1之光介面.高
速的傳輸介面命名為SO150,具有塞取64路E1(2.048MHz) 信號的能力.負責
通路模擬的CE2低速板共有十六片,每個低速板可以處理4路的E1信號.而由
SCU實現整體的控制與管理的功能.整個初版的非同步傳輸模式之塞取多工
機已經初步完成,進入系統整合語與測試的階段.

Abstract In SONET/SDH network, add/drop multiplexer (ADM) is a
key network element. It drops several sub-channels of a high-
speed link as outputs of low-speed links, and adds up to the
same number of sub-channels to the high-speed link from the
inputs of the low-speed links. Asynchronous Transfer Mode (ATM)
is a new transfer technology, which combines the advantages of
circuit-switching and flexibility of packet-switching. It is
possible for ATM to transmit almost all kinds of services. To
use ATM as the backbone network of transmission, it must be
support existing circuit-switched services. For constant bit
rate (CBR) service with delay constraint, ATM adaptation layer
type 1 (AAL1) is used to transmit asynchronous digital signals
from plesiosynchronous digital hierarchy (PDH). It is called
circuit emulation to transport an asynchronous digital through
ATM network. With ATM transport technology and adaptation of
AAL1, an ATM ADM similar to SONET/SDH ADM is designed. In SONET/
SDH ADM, each sub-channel is byte-multiplexed with regards to
reference position to SONET/SDH transmission framing. In ATM
ADM, although its physical medium is based on SONET/SDH, each
sub-channel, termed virtual channel in ATM, is a cell-
multiplexed with a label in the cell header to indicate the
connection. The cell is self-supported, so there is no TSI
problem. In the design, there are four high-speed 155.52 MHz
STM-1/STS-3c link called SO150. SO150 can add/drop up to 64
lines of E1 signal (2048KHz). There are 16 CE2 boards each
handling 4 E1 tributaries for circuit emulation. The SCU board
is designed for control and management functions. The minimal
ATM ADM system can be built for system integration and testing.