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What Is CMTS And CMTS Architecture For Digital Headend

cmts design


Cable Tv companies are increasing their number of services. Initially they were providing Analog Tv channels after upgradation of Analog Headend with the Digital Headend they started to provide Digital Tv channels and then High Definition Television Channels.

Now they are providing various services like Video On Demand , Switched Digital Video , Digital Tv Services and Radio services. There is one more service which is called Internet Broadband Service. This service establishes more the business of MSOs as well as Cable Operators.

So it have became necessary for Cable Tv Companies to provide various kinds of services. In which Internet Broadband Service have became common which results use of CMTS.

What Is CMTS

CMTS stands for Cable Modem Termination System. CMTS is  Headend Equipment responsible for High Speed Data Services. These high speed data services are VOIP (Voice Over Internet Protocol) and Cable Internet Service. It provide functions like DSLAM.

CMTS enables Broadband Internet services for cable tv subscribers. It is located inside Digital Headend.

Working Of CMTS And CMTS Architecture

As shown below in the figure there are three parts of CMTS architecture which follows three process in it.  There are two interface of CMTS system. first Eth Out and second one is RF Out. The Eth Out interface contains the IP packets which are sent to the other router in the network. Thus in this interface the data is in the form of IP packets which are write on Layer 2. While on the other hand at RF Out the IP packets are in the form of MPEG frames.

CMTS Architecture

RF Out port have the coaxial cable which further goes into the combiner then this mixed signal goes to the subscriber end. While the medium for Eth Out can be Optical Fiber Cable. This filter is traffic shaper. It is used to control the upstream traffic for each subscriber.

Implementation Of CMTS In Digital Headend System

As shown below in the figure CMTS is implemented in Digital Headend System. In the figure at subscriber end voice defines the telephone and data defines request comes threw laptop or computers for internet access. Third point define the request comes from Set Top Box or STB.

cmts implementation IN digital headend system CMTS Architecture

So when a subscriber request for data , voice and tv service then request for these things goes into the Cable Modem. This cable modem then modulate the information. This information goes to the combiner located at Digital Headend System. This combiner is used to mix RF from cable Tv system and CMTS system. Cable Tv request from STB goes to the RF of Cable TV.

After that this request (data+voice) goes to the CMTS system. This requested information is demodulated and then send to the next router. Here in this section voice request send to the gateway which forward it to the Public Telephone Network. Data request from this big router goes to internet section as shown in the figure to fulfill the data request.

As shown above in the figure there is medium between combiner and cable modem. This medium is combination of Optical Fiber Cable and Coaxial Cable. The output of combiner is coaxial. Then we use the Optical Transmitters to send this signal at long distance. This transmitter have the RF input from Combiner and give Optical Output for transmission of signal.


CMTS is Headend Equipment which is located at Digital Headend. CMTS is used to provide the data and voice services to the cable tv subscribers. RF output from CMTS is mixed with the RF of cable tv services. A cable modem is installed at the subscriber end to provide these service to the subscriber.

Thus this is all about What Is CMTS And CMTS Architecture.

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