Friday, September 11, 2009

Broadband technologies



Broadband Internet access, which widely called broadband is more faster and reliable than Dial-Up internet access.

There isn't a registered or accurate explenation for Broadband, the speed ranging up from 64 kbit/s up to 8 Mbit/s and more. the 2006 OECD report is typical by defining broadband as having download data transfer rates equal to or faster than 256 kbit/s, while the United States (US) Federal Communications Commission (FCC) as of 2009, defines "Basic Broadband" as data transmission speeds exceeding 768 kilobits per second (Kbps).

Data rates are defined in terms of maximum download because several common consumer broadband technologies such as ADSL are "asymmetric"—supporting much slower maximum upload data rate than download.

"Broadband penetration" is now treated as a key economic indicator.

Although ISPs advertised about their bandwidth, customer/user can't get the actual bandwidth which ISP tells because of the overselling the bandwidth and the quality of the equipments.



Broadband technologies :


  • Mainly consists of DSL and Cable modems.

  • In some areas where DSL or Cable modems didn't available, there are wireless internet connecting options like Wi-Fi, HSDPA, EV-D0 and WiMax.


DSL ( Digital subscriber line )

Digital subscriber line, or DSL, is more expensive than dialup, but provides a faster

connection. DSL also uses telephone lines, but unlike dialup access, DSL provides a

continuous connection to the Internet. This connection option uses a special high-speed

modem that separates the DSL signal from the telephone signal and provides an Ethernet

connection to a host computer or LAN.


Digital Subscriber Line (DSL) technology is a modem technology that uses existing twisted-pair telephone lines to transport high-bandwidth data.

xDSL technologies

  • ADSL

  • SDSL

  • HDSL

  • HDSL-2

  • G.SHDL

  • IDSL

  • VDSL



xDSL is drawing significant attention from implementers and service providers because it promises to deliver high-bandwidth data rates to dispersed locations with relatively small changes to the existing telco infrastructure.

xDSL services are

  • dedicated

  • point-to-point



public network access over twisted-pair copper wire on the local loop (last mile) between a network service provider's (NSP) central office and the customer site, or on local loops created either intrabuilding or intracampus.




ADSL-Asymmetric Digital Subscriber Line

Allows more bandwidth downstream—from an NSP's central office to the customer site—than upstream from the subscriber to the central office. This asymmetry, combined with always-on access (which eliminates call setup)



Advantages:

  • Could use phone line and ADSL line at the same time

  • Could use to view videos, listen to songs, download files and for many purpose.

  • More than 6Mbps bandwidth available.

  • Continuous connection / Stable

  • can be purchased with various speed ranges and capabilities

  • Bandwidth is unlimited in some countries

  • can use existing phone line



Disadvantages:

  • Limited to 4Km radius from the nearest telephone exchange.

  • Have to buy a ADSL modem or router.

  • Expensive in some countries.

  • Not available in some areas

  • receiving data is faster than sending data



An ADSL circuit connects an ADSL modem on each end of a twisted-pair telephone line, creating three information channels:

  • a high-speed downstream channel

  • a medium-speed duplex channel

  • a basic telephone service channel



ADSL modems accommodate Asynchronous Transfer Mode (ATM) transport with variable rates and compensation for ATM overhead, as well as IP protocols.



ADSL uses two pieces of equipment, one on the customer end and one at the Internet service provider, telephone company or other provider of DSL services. At the customer's location there is a DSL transceiver, which may also provide other services. The DSL service provider has a DSL Access Multiplexer (DSLAM) to receive customer connections.




The DSLAM at the access provider is the equipment that really allows DSL to happen.



SDSL

  • Symmetric Digital Subscriber Line (SDSL) allows equal bandwidth downstream from an NSP's central office to the customer site as upstream from the subscriber to the central office.

  • SDSL supports data only on a single line and does not support analog calls.

  • The symmetry that SDSL offers, combined with always-on access (which eliminates call setup)

  • Because traffic is symmetrical, file transfer, web hosting, and distance-learning applications can effectively be implemented with SDSL.

HDSL

  • Originally developed by Bellcore, high bit-rate DSL (HDSL)/T1/E1 technologies have been standardized by ANSI (two-pair T1 transmission, with a data rate of 784 kbps on each twisted pair ) in the United States and by ETSI ( two-pair E1 system, with each pair carrying 1168 kbps, and a three-pair E1 system, with 784 kbps on each twisted pair ) in Europe.

  • T1 service can be installed by installing HDSL modems at each end of the line.

  • HDSL is heavily used in cellular telephone buildouts.

  • HDSL does have drawbacks. First, no provision exists for analog voice because it uses the voice band. Second, ADSL achieves better speeds than HDSL because ADSL's asymmetry deliberately keeps the crosstalk at one end of the line. Symmetric systems such as HDSL have crosstalk at both ends.

HDSL-2

  • HDSL-2 is an emerging standard and a promising alternative to HDSL. The intention is to offer a symmetric service at T1 speeds using a single-wire pair rather than two pairs.

  • The biggest advantage of HDSL-2, which was developed to serve as a standard by which different vendors' equipment could interoperate, is that it is designed not to interfere with other services. However, HDSL-2 is full rate only, offering services only at 1.5 Mbps.

ISDN Digital Subscriber Line

  • is a cross between ISDN and xDSL

  • Unlike ISDN, ISDL does not connect through the voice switch. A new piece of data communications equipment terminates the ISDL connection and shuts it off to a router or data switch.

  • This is a key feature because the overloading of central office voice switches by data users is a growing problem for telcos.

  • The limitation of ISDL is that the customer no longer has access to ISDN signaling or voice services. But for Internet service providers, who do not provide a public voice service, ISDL is an interesting way of using POTS dial service to offer higher-speed Internet access, targeting the embedded base of more than five million ISDN users as an initial market.

VDSL

transmits high-speed data over short reaches of twisted-pair copper telephone lines, with a range of speeds depending on actual line length.

The maximum downstream rate under consideration

  • 51 and 55 Mbps over lines up to 1000 feet (300 m) in length.

  • 13 Mbps over lengths beyond 4000 feet (1500 m) are also common.





ISDN ( Integrated Service Digital Network )

Integrated Service Digital Network (ISDN) is one of the oldest broadband digital access method which is a telephone data service standard.


A basic rate ISDN line is an ISDN line with 2 data "bearer" channels (DS0 - 64 kbit/s each). Using the ISDN bonding technology, we can get 256 kbps or more bandwidth.


Advantages :

  • Constant data rate at 64 kbit/s for each DS0 channel.

  • Two way broadband symmetric data transmission, unlike ADSL.

  • One of the data channels can be used for phone conversation without disturbing the data transmission through the other data channel.

  • Call setup is very quick.

  • Low latency

  • ISDN Voice clarity is unmatched by other phone services.

  • Caller ID is available.

  • Maximum distance from the central office is much greater than it is for DSL.

  • When using ISDN-BRI, there is the possibility of using the low-bandwidth 16 kbit/s "D" channel for packet data and for always on capabilities.


Disadvantages


  • ISDN offerings are dwindling in the marketplace due to the widespread use of faster and cheaper alternatives.

  • ISDN routers, terminal adapters ("modems"), and telephones are more expensive than ordinary POTS equipment, like dial-up modems.

  • ISDN provisioning can be complicated due to the great number of options available.

  • ISDN users must dial in to a provider that offers ISDN Internet service, which means that the call could be disconnected.

  • ISDN is billed as a phone line, to which is added the bill for Internet ISDN access.

  • "Always on" data connections are not available in all locations.

  • Some telephone companies charge unusual fees for ISDN, including call setup fees, per minute fees, and higher rates than normal for other services.







Satellite Internet


Is the most expensive way to use the Internet. But availability and bandwidth is greater than other technologies because Satellites can cover any place on the earth by using 3 separate satellites.


Advantages:

  • True global broadband Internet access availability

  • Mobile connection to the Internet

  • High bandwidth


Disadvantages:


  • High latency compared to other broadband services, especially 2-way satellite service

  • Unreliable: drop-outs are common during travel, inclement weather, and during sunspot activity .

  • The narrow-beam highly directional antenna must be accurately pointed to the satellite orbiting overhead

  • One-way satellite service requires a data uplink connection .

  • Satellite dishes are very large.




Cellular broadband / Wireless Internet


  • Cellular phone towers are very widespread, and as cellular networks move to third generation (3G) networks they can support fast data; using technologies such as EVDO, HSDPA and UMTS. These can give broadband access to the Internet, with a cell phone, with Cardbus, ExpressCard, or USB cellular modems, or with cellular broadband routers, which allow more than one computer to be connected to the Internet using one cellular connection.


  • Wi-fi and WiMax technology which provides mobility and connectivity as well as the more bandwidth than Dial-Up.







3G technology

  • A technology which used for mobile telephony, data, video, voice

  • speed differs from 384 kbps to 14.4 Mbps for downlink and till 5.8 Mbps for uplink.


HSDPA ( High-Speed Downlink Packet Access )

  • is a 3G technology

  • Downlink available from 1.8 Mbps , 3.6 Mbps, 7.2 Mbps and 14.4 Mbps.

  • Uplink till 5.8 Mbps


WiMax ( Worldwide Interoperability for Microwave Access )

  • a telecommunications technology that provides wireless transmission of data using a variety of transmission modes, from point- to-multipoint links to portable and fully mobile internet access

  • Provides speed up to 72 Mbps.

  • Based on IEEE 802.16 standard.

uses:

  • Connecting Wi-Fi hotspots to the Internet.

  • Providing a wireless alternative to cable and DSL for "last mile" broadband access.

  • Providing data and telecommunications services.

  • Providing a source of Internet connectivity as part of a business continuity plan.

  • Providing portable connectivity.


Wi-Fi

  • transmit at frequencies of 2.4 GHz or 5 GHz.The higher frequency allows the signal to carry more data.

  • use 802.11 networking standards, which come in several flavors (802.11a, 802.11b , 802.11g, 802.11n

  • allows local area networks (LANs) to be deployed without wires for client devices

  • High mobility

  • Security problems occurs


Advantages of wireless technologies:

  • more bandwidth than Dial-Up.

  • Mobility.

  • Availability.

  • Could use for media steaming, VoIP and many.

  • Easy to connect

  • Speed.



Disadvantages of wireless technologies:

  • Due to the 3G technology is a shared bandwidth service , bandwidth available from one tower could be shared among many users. So, it'll be slower than usual at sometimes.

  • Some service provider's shares single IP address among many users. So, it could make some problems with identity.

  • Service fees could be high.

  • Limited data bundle will be available to use. ( most service provider's don't provide unlimited data bundles )

  • Sometimes , it will have some issues with 3G connectivity although there is a tower nearby.

  • Security problems occurs because it hasn't security features by default.

  • Due to the radio signals, health problems could occur.



Now it's time to compare Dial-Up internet access with Broadband Internet access.


Differences between Dial-Up internet access and Broadband Internet access.

  • In Dialup we can use normal PSTN phone line to access to the Internet if there is a modem available. But we can't use normal PSTN phone line with a Modem or Router without configuring the telephone line for ADSL broadband.

  • Dial-Up internet technology is a lower speed with lower bandwidth and Broadband is not like that.

  • Dial-Up is suitable for light usage and broadband is suitable for heavy usage.

  • Dialup is a low cost method to access the Internet than broadband.

  • Dialup charges for Internet usage and for the time we used to surf the web because it make a call to connect to the Intenet and in Broadband it charges flat rate for a data bundle or for the time.

  • We can't make calls using the phone while browsing, but we can answer to the calls while browsing with broadband technologies.

  • Dialup can't use for VoIP and media streaming but broadband can.

  • When we use Dial-Up , there is a possibility to drop the connection more than Broadband.

  • Dial-Up can't used for mobile workers if there isn't a PSTN line. But some broadband technologies provide mobility.


Posted by K. W. Roshan Herath [ roshan herath ]



Source:

Broadband technologies

    accessed on 08th September, 2009


Digital Subscriber Line

accessed on 08th September, 2009


accessed on 08th September, 2009



Wireless technology


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