-
Using DS-CDMA to Realize Bi--direction
Communications in CATV Network
< br>直接使用码分多址序列实现双方向通信有
线电视网络
Abstract
：
In
this paper
，
a new scheme
using DS-CDMA to
realize
Bi
—
Direction
communications
in
CATV
network
is
addressed
．
As
a
colusion
，
we
can
find
that
this
is
an
economical
realization
of
access
network
，
having
good
performances
compared with some other
schemes
．
文摘
:
在这篇文章中
,
一个新的
计划在有线电视使用码分多址实
现双向通信网络解决。作为一个解决方案
,
我们可以发现这是一个经
济的实现访问网络
,
与其他方案相比具有良好的性能。
1
．
Introduction
1.
介绍
With
the development
of modern
communications,
the access
network
technology
is
showing
its
great
importance
day
by
day.
随着现代通信的发展
,
接入网技术正显示出其重视。
The
access network technology can be divided into four
categories
：
advanc
ed cotton cable technology
，
FITL system
，
CATV network and
WLL system
．
接入网技术
可分为四类
:
先进的棉花电缆技术
,<
/p>
光纤环路系统、
有
线电视网络和系统广泛
分布有线电视网络。
The
popularly
distributed
CATV
network
，
for
its
relatively
low
price and good broad
band transport
characteristics
，
may be
the
most
prospective
media
to
realize
multi-
service
communications including
voice
，
data and moving
picture
．
因其相对较低的价
格和良好的宽带运输特点
,
可能是最准媒体实现多
业务通信包括语音
,
数据和移动图像。
In
this
paper
，
a
new
scheme
using
DS
—
CDMA
to
realize
Bi-
Direction communications in CATV network is
addressed
．
在本文使用码
分多址的新方案在有线电视网络实现双向通信地址。
As
a
colusion
，
we
can
find
that
this
is
economical
and
with
good
performances compared with some other
schemes
．
作为一个解决方案
,
我们可以发现这是经济和与其他方案相比具有良
好的性能。
2
．
Existing CATV
Network
2.
现有的有线电视网络
The CATV network is a hierarchical
and single-direction
system
，
as we can
see from
Fig
．
1
，
composed of three parts
：
front
end
part
，
transportation
part
and
user
distribution
part.
In the tranportation
lines
，
there are many
equipments such as
amplifiers
，
branches and distributors
．
<
/p>
有线电视网络层次和发展性系统
,
从图<
/p>
1
中我们可以看到
,
由三
部分组成
:
前端部分
,
运输和用户分配部分。交通运输线路
,
有很多设
备如放大器、分支机构和分销商。
-direction
System Design
3.
双向系统设计
In order to make
Bi
—
direction communication
available
，
we
divide the whole bandwidth into twos
：
0
—
50 MHz as the
upward passway and 50-400 MHz as the
downward passway
．
It is
also
needed
to
change
the
existing
single
direction
equipments
in transportation lines into Bi-
direction equipments
，
Just
As
Fig
．
2
．
为了提供双向的沟通
,
我们将整个带宽
分为两个
:0-50
MHz
的上
行通道和
50 - 400
MHz
下行通道。它也需要改变现有的单一方向的
设备在运输到
Bi -
方向行设备
,
如图
2
所示。
4
．
Features of
Spread Spectrum Communication
4.
特性的扩频通信
In
the
spread
spectrum
communication
systems
，
the data
is
applied
to
a
narrow-band
modulator
and
the
resulting
narrow-band signal
is widely spread using the spreading code
(always the PN code) at the
transimter
．
在扩频通信
系统中
,
数据是应用于窄带调制和由此产生的窄带信
号被广泛传播使用传播代码
(
总是
PN
码
)
晶体管。
The transmitted spread signal
with interferring signals
and
noise
is
despread
by
the
same
spreading
code
and
the
resulting
narrow-band signal is demodulated at the
receiver
．
传播信号干涉信
号和噪声是由相同的传播代码解扩和由此产生
的窄带信号在接收机解调处理。
Because the spread signal can be
demodulated even in the
presence
of
noise
and
interferring
signals
with
higher
spectrum
densisties
than
the
signal
，
it
means
that
the
spread
signal
has
resistance to interferring signals and
interception
．
因为可
以解调的信号传播甚至在噪声的存在和干涉信号频谱密
度高于信号
,
这意味着传播信号抗干涉信号并拦截。
By
using
PN
codes
to
spread
the
narrow-band
signal
，
it
can
support
simutaneous
digital
communication
among
a
large
community
of relatively uncoordinated
users
．
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