Telecommunications Technology

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ATM - Asychronous Transfer Mode, a communication protocol that is well suited to the various xDSL family members because of its speed capabilities.

STM - Sychronous Transfer Mode(Module), (CCITT)a communication protocol that is used for SONET family members because of its speed capabilities and continuous connection.

STS - Sychronous Transfer Signal, (ANSI)a communication protocol that is used for SONET family members because of its speed capabilities and continuous connection.

DS-0 - A 0.064 Mbps communications standard that is a Digital Signal level, a separate voice line.

DS-1 - A 1.544 Mbps communications standard that generally is 24 separate voice lines.

DS-3 - A 44.736 Mbps telephone backbone still in use by many. Generally a frame relay technology. Equals the optical carrier(OC) bandwidth.

T-1 - A 1.544 Mbps copper wire connection usually used for data. Can be split into multiple connections and pieces and called fractional.

T-3 - A 45 Mbps telephone connection that is generally the fastest implemented on copper lines.

E-1 - A 2.048 Mbps communications standard generally associated with Europe.

Frame Relay - A communication protocol that packetizes information in units referred to as frames. Popular for ISDN transmissions.

SONET - Synchronous Optical NETwork currently runs on many OC backbones, an ANSI standard.

SDH - Synchronous Digital Hierarchy currently runs on many OC backbones, a CCITT standard.

TDM - Time Division Multiplexing uses timimg to differentiate informatiom on OC backbones. Permanent connection at the physical layer that does not use packets for communications.

WDM - Wavelength Division Multiplexing the use of 2 to 4 different wavelengths to pack more informatiom on OC backbones. Spacing between wavelegths is broad for inexpensive equipment and accuracy.

CWDM - Coarse Wavelength Division Multiplexing the use of 4 to 8 different wavelengths to pack more informatiom on OC backbones. Spacing between wavelegths is closer requiring more expensive equipment to maintain accuracy.

DWDM - Dense Wave Division Multiplexing the use of 8 or more wavelengths to pack more informatiom on OC backbones. Spacing between wavelegths is closer still requiring expensive equipment and cooling to maintain accuracy.

OC - Optical Carrier fiber-optic telphone backbone that has two ANSI- approved terminologies (SONET-Synchronous Optical Network and OC) and one CCITT standard (SDH- Sychronous Digital Hierarchy.)

OC-1 - A 51.84 Mbps telephone backbone.

OC-3 - A 155.52 Mbps telephone backbone.

OC-12 - A 622.08 Mbps fiber-optic telephone backbone with ATM technology.

OC-24 - A 1,244.16 Mbps fiber-optic telephone backbone.

OC-48 - A 2,488.8 Mbps fiber-optic telphone backbone for WANs and MANs.

OC-192 - High speed backbone at almost 10 Gpbs.

OC-256 - High speed backbone at 13.271 Gpbs.

OC-768 - Top speed backbone at almost 40 Gbps.

OC-1536 - Proposed speed backbone at almost 80 Gbps.

OC-3072 - Proposed speed backbone at almost 160 Gbps.



Telecom Standards Matrix

STS/OC/DS3
(ANSI)		 ITU(CCITT)
SDH		 DS0s DS1s Overhead/Mbps Speed/Mbps
OC-1   672 28 1.728* 51.840*
OC-3 STM-1 2,016 84 5.184* 155.520*
OC-6 STM-2 4,032 168   311.040*
OC-9 STM-3 6,048 252   466.56
OC-12 STM-4 8,064 336 20.736* 622.080*
OC-18 STM-6 12,096 504   933.12
OC-24 STM-8 16,128 672   1,244.16
OC-36 STM-12 24,192 1,008   1,866.24
OC-48 STM-16 32,256 1,344 82.944* 2,488.320*
OC-96 STM-32 64,512 2,688   4,976.00
OC-192 STM-64 129,024 5,376 331.766* 9,953.280*
OC-256         13,271
OC-384 STM-128       19,906.56
OC-768 STM-256     1327.104* 39,813.12
OC-1536         79,626.24†
OC-3072 STM-1024       159,252.48†
* Verified speeds
†Proposed standard speeds

American National Standards Institute

European Telecommunications Standards Institute

International Standards Organization

International Telecommunications Union

International Telecommunications Union, Also



CAP
Carrierless Amplitude and Phase modulation is a transmission introduced by Bell Laboratories at the advent of ISDN in the 1970's. Used in Europe widely, it benefits from low power consumption from the central office as it is powered by the loop. It is licensed to Globe Span Tchnologies who is the only producer of the chip sets to implement it.
DMT
Discrete Multi-Tone modulation is a newer technology more immune to noise and to causing interference, but at a higher power cost requirement.
QAM
Quadrature Amplitude Modulation is a newer technology combined with CAP to make it more immune to noise.
DSL
Digital Subscriber Line is the original product in this line, dating back to the advent of ISDN; it is also the slowest by far.
ADSL
Asymmetric Digital Subscriber Line gets its name from the fact that its downstream speed far exceeds its upstream speed and implemented with either CAP or DMT. Currently it receives the most coverage in the press. Up to 9 Mbps downstream and up to 1 Mbps upstream.
CDSL
Consumer Digital Subscriber Line, an invention of Rockwell Semiconductors describes a cost-effective chip set and technology competing with k56 modems in price. Up to 1 Mbps downstream and 160 kbps upstream. The benefit for the telcos and the customer consists in the fact that it requires no equipment at the central office nd no switch box on the outside of the customer's premise. Higher speed xDSL requires the switch box and a card in the PC, often an Ethernet NIC, and some require another box inside the premise.
HDSL
High data rate Digital Subscriber Line sees its greatest use now to provide T1(1.544Mbps), E1(2.048Mbps) or DS1(1.544Mbps) by the telcos. You may notice that T1 and DS1 have the same speed; T1 can generally provide bandwidth based on need and DS1 has twenty-four voice channels. Generally it requires two twisted pairs(four wires) to implement. Speeds of 1.544 Mbps or 2.048 Mbps.
HDSL2
High data rate Digital Subscriber Line 2 provides the function of HDSL, but only uses one twisted pair(two wires) with exceptional noise immunity and higher speeds possibly available later. The newest of the proposed standards, it was first introduced to ANSI in January, 1997 and again by three more proponents at the end of June.
IDSL
ISDN-enabled Digital Subscriber Line is basically only ISDN with a bit more flexibility since it is generally run into a router that may actually be hooked up to a T1 or E1 line. Speeds of 64 kbps or 128 kbps in both directions.
MDSL
Multi-rate Digital Subscriber Line a DSL technology that sounds much the same as many others, but supported by Level 1.
RADSL
Rate Adaptive Digital Subscriber Line tests the line for best possible speed and adapts to that. It also offers the ability to adapt to slower speeds based on current needs and the customer is billed by bandwidth used. Speeds of up to ADSL depending on line conditions.
SDSL
Symmetric Digital Subscriber Line is basically HDSL and telephone service. The name comes from the fact that it can give the speed of ADSL in either direction; not at the same time, but can adapt to need for speed and configure itself by changing in the chips internally. Speeds of 160 kbps to 2.084 Mbps in both directions.
S-HDSL
Single line High data rate Digital Subscriber Line has few followers and is implemented only in CAP.
UDSL
Unidirectional high data rate Digital Subscriber Line has one proponent in Europe and little interest.
VADSL
Very high speed Asymmetric Digital Subscriber Line is a higher speed ADSL that uses technology associated with ADSL but delivers speeds that make it a subset of VDSL.
VDSL
Very high data rate Digital Subscriber Line delivers the promise of speeds necessary for video over telephone service. It also provides the impetus for fiber optic cable in what is called "fiber to the curb" and "fiber to the building" because of its short effective reach and rapid degradation associated with distance, shortest range of all varieties, less than a mile. Speeds up to 52 Mbps downstream and up to 2.3 Mbps upstream.


xDSL Speeds

Type Downstream Upstream
ADSL 1.5 to 9 Mb/s 16 to 640 kb/s
CDSL 128 to 1000 kb/s 16 to 384 kb/s
HDSL (T1) 1.544 Mb/s 1.544 Mb/s
HDSL (E1) 2.048 Mb/s 2.048 Mb/s
IDSL 160 kb/s 160 kb/s
MDSL 272 to 1168 kb/s 272 to 1168 kb/s
RADSL To 7 Mb/s To 1 Mb/s
VDSL 13 t0 52 Mb/s 500 to 2300 kb/s