Introduction
Large number of cable tv operators in United States are having HFC network to deliver their cable tv services. Now all of these cable tv operators wants to provide internet services to their customers then it will be very hard for them to shift on fiber network only.
Because to convert the HFC Network into the fiber network is expensive and time consuming task for them. DOCSIS provides a solution to deliver internet broadband with cable tv services over the HFC Network.
Let now discuss about what is DOCSIS , what are types of it & How Does it Work?
What Is Docsis ?
DOCSIS stands for Data Over Cable Service Interface Specification. It was developed by the Cablelabs. Cablelabs is a US company.
DOCSIS is a solution for cable tv service providers to deliver high speed internet with CATV services with the help of CMTS and Cable Modem over HFC Network.
The DOCSIS for Europe is known as EuroDOCSIS which is advanced version of it.
What Are DOCSIS Versions & Improvements ?
| DOCSIS Version | Released | Improvements | Upload | Download |
| DOCSIS 1.0 | 1996 | High Speed Internet Data | 10 Mbps | 40 Mbps |
| DOCSIS 1.1 | 1999 | Addition Of VOIP, Streaming & Gaming | 10 Mbps | 40 Mbps |
| DOCSIS 2.0 | 2001 | Upload Speed Improvement | 30 Mbps | 40 Mbps |
| DOCSIS 3.0 | 2006 | Upload Download Speed Enhancement & IPV6 | 100 Mbps | 1 Gbps |
| DOCSIS 3.1 | 2013 | OFDM With Speed Enhancement | 2 Gbps | 10 Gbps |
| DOCSIS 3.1 Full Duplex | 2017 | Improvements in Upload Speed | 10 Gbps | 10 Gbps |
How Does DOCSIS Work ?
As shown above in the figure there are two device which plays an important role in DOCSIS architecture.
First one is CMTS and second one Cable Modem. Where CMTS needs to install inside the Headend System. Cable Modem needs to install at subscriber home.
as shown, the router’s backbone is connected to the internet. After that this router is connected to switch and then with CMTS. This switch is also connected with DHCP as shown.
The CMTS output goes into the HFC Network. Now at subscriber end we need to install a Cable Modem. This cable modem provides RF output for Set Top Box for TV services. It also have RJ-45 port for Voice and Data services.
DOCSIS is a two way communication known as Downstream & Upstream. When the data is flowing through CMTS to Cable Modem it is called Downstreming of data. While data flowing from Cable Modem to CMTS it is called Upstreaming of data
In delivery of internet broadband the upstreaming speed is always lower than then downstreaming speed. Because users makes a request to access the data which consume less bandwidth over internet. While when user get the respond of request which contains whole request data it consume more space.
For example if you entered in browser Headendinfo.com . Then you requested to access the website. This request consume very less amount of bandwidth over internet.
Now respond for this request contains website data (Text and images) which consume higher bandwidth than Request.
Until the DOCSIS 3.0 the upload speed was down than the download speed. But next version of DOCSIS 3.0 known as DOCSIS Full Duplex made the upstream and downstream speed same at 10 Gbps. Which is very efficient.
DOCSIS 3.0 uses the Upstream frequency between 5 MHz to 85 MHz with 64 QAM. It uses the downstream capacity with 6 MHz & 256 QAM.
One thing keep in mind that there are different Cable Modem for each version of DOCSIS. So we should choose Cable Modem according to DOCSIS Version.
Conclusion
DOCSIS is great solution for CATV Service Providers to provide Data and Voice services with TV Channels over exiting HFC Network.
DOCSIS 3.0 provides low latency, enhance the security and support the Mulitcasts. It also supports IPV6. It uses the AES Encryption.
DOCSIS 3.1 Full Duplex is the latest version it was introduced in 2017.
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reference : cablelabs
