DEFINITION
Cable modem is a tool that provides access to high-speed Internet through cable television network. Similar to the response of a traditional analog modem, cable modem has the benefits of a more strength, is able to transmit data more quickly is approximately 500 times.
AREA OVERVIEW
This paper explains the ability to access high-speed cable modem from tehnologi clearly, with the stress of this type of operation, network architecture, alternative technologies, and security.
TOPIC
1. HOW WORK KABEL MODEM
Access the Internet through a modem flow 28.8-, 33.6-or 56-kbps modem tehnologi known as "voiceband". Like voiceband modems, cable modem and demodulasi data modulation signal. However, the combination of cable modem service to more functional with a high speed internet. On the network cable, data from the network to the user as the "downstream", where user data to the network as is "Upstream." The views of users, cable modem is a 64/256 QAM FM recipient is able to transmit data more than 30 up to 40 Mbps in a 6 MHz cable. This is 500 times more quickly from the 56 Kbps modem. Data from the user is sent to the network flexible and terprogram monitored from the "headend". Data modulation transmitter using QPSK/16 QAM levels with data from 320 Kbps - 10 Mbps. Levels of data Upstream and downstream may be configured for use with flexible cable modem.
Our customers can continue to the recipient when the recipient's cable television on the cable modem data transfer to personal computer (PC) with the help of "simple one-to two-splitter." Data service offered by cable modem may be divided more than 16 users on a local area network configuration (LAN).
Figure 1. Cable modem subscribers at the location
Because some of the network cable is very good for local television services, cable modem may use a standard phone line or modem QPSK/16QAM offer two-way cable system to transmit data Upstream from the user's location to the network. When the phone lines using a combination of one-way broadcast network, cable data system is used as the system telephony return interface (TRI). In this type, network or satellite television without cable can also be used as a data network.
At the end of the cable-edge, from the data filtered by the user demodulasi Upstream (or telephone-return system, as the withdrawal) to be processed further by the end of the cable modem system (CMTS-Cable Modem Termination System). CMTS is a switching system, usually designed to route data from most cable modem users through multiplexed network interface. CMTS receives data from the internet provider and to route data on the user's cable modem. Data from the network to be sent to the user group 64/256 QAM modulation. The result is the modulation of data users over 6 MHz perchannel, the allocation of spectrum for which the cable television channel for broadcasting as ABC, NBC or TBS to all users
Figure 2. System last transmission cable modem & cable headend
Combination edge-end of the cable between the downstream data channel with the video, pay per-view, audio, and local advertising program that will be received by the television. Then a combination of signals transmitted akan cable distribution network. In place of the user, the signal received by the television "set-stop-box", while the user data received separately by the cable modem and sent to the PC.
CMTS is a new element which is very important to support the merging of data communication service Upstream and downstream data over a network cable. Number of Upstream and downstream channel in the CMTS can be classified based on the service area, the number of consumers, the data levels are offered on each user and a different spectrum.
Other important element in the management and operation of day-to-day from the cable data system is "Element Management System (EMS). EMS is a system designed specifically to prepare and combine the CMTS and cable modem pelangganan. Including the operation of the task requirements, administration of day-to-day, monitoring, alarm, and test of various components of the CMTS. From the central network operations center (NOC), an EMS can support multiple systems in a single CMTS the geographic area.
Figure 3. Operation and Management of the Cable Data Systems
2. Specialties SYSTEM OF DATA KABEL
In addition to modulation and demodulasi, cable modem Inc. has several purposes, among which is to expand the network to broadcast communication "Wide-Area Network (WANs). Layer network is selected as the Internet Protocol (IP) to support Internet and network service world wide. Relationship (link) data layer was divided into 3 parts: a logical link control, link security, and Media Access Control (MAC) is very good for cable system operations. Flow system in the form of a cable modem using the internet for transmission of data Upstream and downstream channel data. Each channel of data Upstream and Upstream data integration on the network cable to expand the Internet network WAN. Number of additional operational cable channel can reproduce the data Upstream and downstream bandwidth to support the request on the network data cable. From above description, the growth of cable data network that the new method can be applied in the same growth in internet LANs which is a legal environment.
Link security that allowed divided into 3 parts: Baseline privacy interface (BPI), security system interface (SSI), and a removable security module interface (RSMI). BPI provides a cable modem where the confidentiality of the data across the network by cable lalulintas user data between the cable modem and CMTS. Operation conducted by the EMS allows a CMTS to map the identity to pay for cable modem customers and allow customers to access services into the network data. Confidentiality and security requirements to protect the user data as well as prevent theft of cable data services.
Discussion early in the Institute of Electrical and Electronic Engineers (IEEE) agreed to offer the use of asynchronous transfer mode (ATM) network through a data cable to provide various facilities including telephone, data and video, all of which is supported by the cable modem. Although the current standard cable modem Inc. internet using cable modem, is the extent of providing standardization in order to support ATM or other protocol data units. IP-telephony network is supported through a data cable which is expected to be the value of services in the new few years.
3. Architecture KABEL DATA NETWORK
Cable data network architecture is the same as the office LAN. CMTS provides network expansion to the Internet through WAN reach more than 100 miles. Cable data network may be able to be fully operation by the local cable. Other alternative, all operations may be conducted simultaneously in the main regional data to obtain a more economical scale. The division of geography or the metropolitan area may have a small location where the cable television linked together by fiber links. Operating day-to-day management and the cable data network may be incorporated in a single location, such as "super hub", while the other end of the location can be more easily managed as the basic axis (see figure 4).
Ganbar 4. Distribution of "Hub" Basic
Distribution is a basic relationship with the network configuration that minimize the data that is used more than the tip of the cable television. Khususdilengkapi edge and the recipient of the satellite, fiber connection kelokasi end of the regional and other RF upsteam recipient to pay-per-view and data service. Configuration data network system including CMTS can transport as Upstream and downstream data and IP routing to the location to contact the super hub (see image 5).
Figure 5. Super Hub
Super hub is the location of the ends of the cable with additional facilities to house temperature control degan various server computers, which are necessary to run the cable data network. Including sending a file server, using the rights and bookkeeping, control log (syslog), IP address, and administration (DHCP server), DNS server, and data over cable service interface spesifications (DOCSIS) server control.
User data from the primary location and super hub is a recipient of the regional data center for the unity and further distribution through the network. Super hub is supported by dynamic host configuration protocol (DHCP), DNS (domain name server), and server logs that are important to control the administration of the network cable data.Pusat regional data linked to the internet and world wide network and server Farms also needed to support services internet. The server includes an e-mail, Web hosting, news, chat, proxy, caching, streaming media server.
Figure 6. Regional Data Center
In the addition to the wired network data, network data center may also be supported by the service dial-up modem (56-kbps service) and business-to-business internet service. Swithing network, routing is done on the server and the regional data center for the dial-up at the same time, high speed, internet service and busines.
Super hub and regional data centers can be made into one location and is set as a business entity. Super hub is set by the cable television service provider (TCI), while a regional data center is set sepreti separate business and free (@ home). In one area, the existence of the Internet Service Provider (ISP) to provide support to regional data centers where the origin and location of super hub is set by the cable networks and provider of data independently.
Regional data centers are linked with regional data centers that use the other network "backbone" national. In addition, each regional data center is also connected to the internet and world wide service network. Traffic between regional networks, the Internet and the other regional networks is through the regional data center.
4. STANDARD KABEL DATA NETWORK
Cable data system consists of various technologies and different standards. Memasyarakatkan for cable modem products from different vendors can be operated.
To meet the requirements of the system can be operated, the cable television operator in North America form a limited partnership, Multimedia Cable Network System (MCNS), and developed an initial set of requirements cable modem (DOCSIS). Equipment vendors must comply to the regulations DOCSIS test capabilities and operation of the certification program conducted by CableLabs.
Physical Layer
Data channel downstream
At the level of physical experiment, the channel downstream data specifications should be based on digital video, and North America based on the following characteristics:
o 64 and 256 QAM
o 6-MHZ spectrum used side by side with other signals in the main cable
o The block of code Reed-Solomon code and Trellis, support the operation in increasing percentage of cable Main North America.
o "variable length interleaving supports", the second service data "latency-sensitive and latency-insensitive"
Data Upstream Channels
Upstream channel data must follow the characteristics as follows:
o Format QPSK and 16 QAM
o Multiple symbol rates
o Delivery of data from 320kbps to 10 Mbps
o Flexible and cable modem that can be programmed under the supervision of CMTS
o Frequency wiliness
o Multiple access time-division
o Supported by the second protocol data unit: "fixed-frame and variable-length"
o Can be programmed into a block of Reed-Solomon
MAC Layers
MAC provides a level of global requirements for cable modem subscribers to share channels for Upstream data transmissions to the network. Terms include detection "collision" and the transmission balikan. The amount of area that can be reached from the data network cable causing a special problem as a result of the time delay between transmission of the user closer to the headend from a remote user that headend. To eliminate loss-loss cable and a delay caused by distance, there is a restriction levels of the MAC, in which each cable modem can access the time delay is transmitted to the headend. Increase the levels of MAC time synchronization., Placement bandwidth to cable modem on the CMTS control, error detection, control and improvement of error, the procedure for registration of a new cable modem.
Privacy
Confidentiality of user data received by using a data-link layer between the cable modem and CMTS. The setting of parameters, including the security data given to the cable modem by the security association (SA). All transmissions from the cable modem Upstream run across a single channel of data Upstream and received by the CMTS. At the CMTS downstream channel data must select the correct SA based on the destination address of the target cable modem.
Network Layer
Network cable to use IP for data communication from the cable modem to the network. The Internet Engineering Task Force (IETF) form the basis for all DHCP IP assignment pegalamatan and administration of the network cable. System network translation (NAT) can be used to place multiple computers using a single access via high-speed cable modem.
Transport Layer
Cable network using the data transmission control protocol (TCP) and user datagram protocol (UDP) as transport layer.
Application Layer
All applications are internet-relationships improved. Applications include e-mail, ftp, TFTP, http, news, chat, and signaling network management protocol (SNMP). The use of SNMP management for the very good from the CMTS and cable modem.
Operations System
The operations support system interface (OSSI) requirements of DOCSIS specify how a network of cable data set. As a note, the provisions allowed in the RF MIB. This system lets the seller to make the EMS to support spectrum management, customer management, billing, and other operations.
1. CONCLUSION
Tehnologi cable modem offers high-speed access to the internet and world wide service network. Network cables combine data elements that are important for the progress of modern technology that is coming and provides several benefits such as confidentiality, security, data network, internet access and feature quality-of-service. Network architecture end-to-end cable modem allows users to connect to the CMTS, in turn, connect to the regional data center for access to the internet service. Thus, through the system from a network connection, the network data cable allows users to connect to other users anywhere in the global network.
Source:
Cable Modems - Cadant - The International Engineering Consortium
By:
Arief Hamdani Gunawan - RisTI Division, PT. Telekomunikasi Indonesia
Kurniawan Abadi Andrik - FTE, Maranatha Christian University
Henky Prasetyo - FTE, Maranatha Christian Universit
