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參數(shù)資料
| 型號： | MT8972 |
| 廠商： | Mitel Networks Corporation |
| 英文描述： | () |
| 中文描述： | （） |
| 文件頁數(shù)： | 3/5頁 |
| 文件大小： | 27K |
| 代理商： | MT8972 |
Application Sheet
MSAS-42
A-3
connected to the F0i of the next DNIC, you could
multiplex several DNIC streams onto a single ST-
BUS link.
19. How is the DNIC powered
The DNIC can be powered from the telephone line.
Since it is a low power CMOS device with a typical
power draw of only 50 mW, it can be continuously
powered from the central office battery.
20. Is there a power down mode on the DNIC
No. Once the DNIC loses power, the contents of the
RAM are lost. On power up, the RAM must first
settle before meaningful data can be transmitted.
21. With reference to the ISDN model, where
does the DNIC fit it
The DNIC transfers basic rate data (2B+D) over a
single twisted pair by employing full duplex echo-
cancellation techniques, thus corresponding to the
U-interface reference point of the ISDN model. The
DNIC uses a differential bi-phase line code rather
than the ANSI defined 2B1Q line code. DNIC
provides a simpler and cheaper basic rate
transmission scheme for proprietary applications.
For a fully compatible U-interface device refer to the
MT8910 Digital Subscriber Line Interface Circuit.
22. What are the advantages of Echo
Cancellation over TCM (ping-pong)
Echo cancellation is a full duplex solution in that it
transmits data continuously in both directions at the
same time. TCM only transmits in one direction at a
time. Therefore in order to get the same effective
data rate, the TCM system must transmit at over
twice the baud rate. This has the effect of increasing
the frequency content of the signal, making it prone
to increased crosstalk, attenuation and other
interference. The increased spectrum also results in
a larger amount of radiated energy, which can be
quite disruptive to any other transmission schemes
operating in the same binder group. It seems that
TCM is limited ultimately by loop delay, which is a
physical limitation and is difficult to overcome. Efforts
to overcome this may result in substantial
degradation of customer service.
23. What are the advantages of Biphase over
other line codes
There are several advantages inherent with the
Biphase line code. Since it is a two level code, it has
an extra 6dB of SNR over a three level code (e.g.
AMI). Differential encoding makes the transmission
insensitive to wiring crossover. Furthermore, the
nature of the PSD graph enables the signal to be
effectively bandlimited without losing the major
portion of the signal content. The guaranteed zero-
crossing in each baud makes data and clock
extraction
much
more
Equalization for Biphase is much less complex than
for other codes such as AMI and 4B3T, as these
require very complex adaptive equalizers to operate
properly. The adaptive equalizer adds to the cost
geometry and complexity of the interface solution.
reliable
and
robust.
24. How long does the DNIC take to achieve
synchronization after power up
The time before valid data transmission begins is a
function of the data rate, the line condition, and the
initial value of the RAM. The majority of the
activation time is taken up by the settling of the RAM
to the appropriate line value. Synchronization is
achieved concurrently with the settling of the RAM.
Therefore, by the time the RAM has settled, the
DNIC will have achieved synchronization.
25. Why is the data scrambled before being
transmitted
The data stream is scrambled in order to ensure
orthogonality of transmission, i.e. the transmitted
and received data should not be correlated in any
way. Another reason for scrambling is to ensure that
every RAM location is accessed and iterated down to
the correct value in the initialization sequence.
26. What is the training sequence for the DNIC
on power up
The DNIC does not require a specific training
sequence to achieve synchronization on power up.
The scramblers in the DNIC ensure that random data
is put on the line, thus guaranteeing convergence.
Synchronization is achieved from the received data
stream, and is independent of the actual transmitted
data.
27. What kind of echo cancelling scheme does
the DNIC use
The echo cancelling scheme is referred to as “RAM
based echo cancelling, using the sign bit algorithm”.
The process of echo cancelling is as follows. An
estimate of the echo resulting from a particular
transmit data sequence is stored in RAM. The value
in RAM is a digital representation of the echo
estimated to be reflected from the line. The RAM
value is passed through a D/A converter into a
summer. The summer subtracts the echo estimate
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MT8976 | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| MT8976 | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| MT8976AC | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| MT8976AE | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
| MT8976AP | Ultraframer DS3/E3/DS2/E2/DS1/E1/DS0 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MT8972B | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS ST-BUS⑩ FAMILY Digital Subscriber Interface Circuit Digital Network Interface Circuit |
| MT8972BC | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS ST-BUS⑩ FAMILY Digital Subscriber Interface Circuit Digital Network Interface Circuit |
| MT8972BE | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS ST-BUS⑩ FAMILY Digital Subscriber Interface Circuit Digital Network Interface Circuit |
| MT8972BP | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO2-CMOS ST-BUS⑩ FAMILY Digital Subscriber Interface Circuit Digital Network Interface Circuit |
| MT8976 | 制造商:MITEL 制造商全稱:Mitel Networks Corporation 功能描述:ISO-CMOS ST-BUS⑩ FAMILY T1/ESF Framer Circuit |
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