What Is Cable Modem Or Cable Modem Working And Installation For CMTS

cable modem


As we all knows cable tv industry is growing day by day. It is also providing internet solution to their subscribers. Cable tv connected to each and every house so this makes easy to provide internet connection to each subscriber. Cable services are provided by co axial cable. In which trunk line is connected with RG 11 and branches are connected with RG 6 coaxial cables.

To provide broadband services we need to extend our Digital Headend. Because we need to install additional equipments in headend like CMTS (Cable Modem Termination System) which enable subscriber for internet service. The download bandwidth for internet is upto 27 Mbps and upload bandwidth is 2.5 Mbps in cable tv line. While earlier in telephone modem the speed was 56 kbps. It is very slow speed for internet access.

We need to install a Cable Modem at subscriber end.

What Is Cable Modem

cable modem arris motorola

Cable Modem is a hardware device which communicates with CMTS to provide internet broadband services to cable tv subscribers.

In other words Cable Modem enable broadband internet service for their subscribers.

Cable Modem is installed at the cable tv subscriber’s house. So that threw one co axial cable a subscriber can have two services simultaneously Cable Tv Service as well as Internet Broadband Service.

There are various kinds of Cable Modems available like,

Arris Motorola SB6141

Arris Motorola SB6121

Netgear CM400

D-Link DCM-301

Zoom 5341J


LinkSys DPC3008

Each subscriber have its own registered cable modem installed at his home. Subscriber need to pay rent for cable modem if he get it from service provider. Subscriber can also purchase his own personal cable modem to avoid cable modem monthly rental. If subscriber installs his own cable modem then he needs to provide his cable modem serial number with its MAC (Machine Access Code) address to cable service provider for registration. There are name of companies which provide cable services,

Time Warner

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Cable One

What Is OTT Headend

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Cable Modem Installation

To better understand Cable Modem Installation diagram is shown below. In the figure this is subscriber end setup for cable modem. Where a splitter have two output one for STB and second one is for Cable Modem.

Thus output of STB gives HDMI which connect further to the Television for cable tv services.


A cable modem have the coaxial input also known as RF (Radio frequency ) input. So we need to connect this RF cable to the cable modem input port. Now we need to connect the CAT 6 cable to the RJ 45 port of cable modem. This RJ 45 port acts as the output of cable modem.

This output goes into the local router installed at subscriber end. The function of this local router is to deliver internet services to various devices like Personal Computer , Laptop , Tablet and Mobile.

You can also connect your personal computer to the cable modem directly via with RJ 45 port by using CAT 6 cable. But in this way only one PC can access the internet only.

Cable Modem Working

Cable Modem working is, to do the modulation between digital and analog signals. It provides high speed internet connection.

cable modem working

As shown above in the figure cable modem have RF input port and RJ 45 output port. A personal computer can directly connected to the RJ 45 port. Then a subscriber makes a request threw pc or laptop. This request goes into the Cable modem. Then this cable modem modulate the request and forward it to the CMTS. This CMTS is installed at the Digital headend.

CMTS then demodulate the request and forward it other router. So when the CMTS receive the resolved request then it sends to the cable modem. Then further cable modem forward it to the device from which request was made.


Cable Modem is a device which communicates with CMTS to provide internet service to cable tv subscribers. CMTS is installed at headend whereas  Cable Modem is installed at subscriber end. So only from one cable line subscriber can get two services like Broadband Internet and Cable Tv. Cable tv have large bandwidth to provide internet service.

Cable modem Working is complex than regular telephone modem. A PC can directly connected to cable modem to provide internet service. If you want to run internet on various wireless device then you need to install a local router.

Thus this is all about what is cable and cable modem working.

Know More About   What Is CMTS And CMTS Working

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  1. Kunal Kapoor says:

    this is the case when operator is providing only cable tv and internet but what will be the architecture if a operator is giving 3play services like Cable Tv, BB and Telephone as well


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