56k modems are voiceband In electronics, voiceband means the typical human hearing frequency range that is from 20 Hz to 20 kHz. In telephony, it means the frequency range normally transmitted by a telephone line, generally about 200–3600 Hz. Frequency-division multiplexing in telephony normally uses 4 kHz carrier spacing. The roll-off rate, or rate at which the modems A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog nominally capable of download speeds up to 56 kbit/s (56,000 bits per second). At the beginning of the 21st Century, most personal computers contained one[citation needed], but their use is declining as broadband technologies such as DSL Digital Subscriber Line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term Digital Subscriber Line is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly and UMTS Universal Mobile Telecommunications System is one of the third-generation (3G) mobile telecommunications technologies, which is also being developed into a 4G technology. The first deployment of the UMTS is the release99 (R99) architecture. It is specified by 3GPP and is part of the global ITU IMT-2000 standard. The most common form of UMTS uses W-/HSDPA High-Speed Downlink Packet Access is an enhanced 3G (third generation) mobile telephony communications protocol in the High-Speed Packet Access (HSPA) family, also dubbed 3.5G, 3G+ or turbo 3G, which allows networks based on Universal Mobile Telecommunications System (UMTS) to have higher data transfer speeds and capacity. Current HSDPA gain wider availability.
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Speed
The 56 kbit/s theoretical speed is only possible when the system being dialed into has a digital connection to the telephone system, such as DS0 Digital Signal 0 is a basic digital signaling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel. The DS0 rate, and its equivalents E0 and J0, form the basis for the digital multiplex transmission hierarchy in telecommunications systems used in North America, Europe, Japan, and the rest of the world, for service. By the time 56k modems came into use, most of the telephone system beyond the local loop In telephony, the local loop is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the carrier or telecommunications service provider's network. At the edge of the carrier access network in a traditional PSTN (Public Switched Telephone Network) scenario, the local loop terminates in a was already digital, so the new 56k protocols took advantage of this.
If both calling party The calling party is a person who (or device that) initiates a telephone call over the public switched telephone network, usually by dialing a telephone number and called party The called party is a person who (or device that) answers a telephone call. The person who (or device that) initiates a telephone call is the calling party have an analog connection, the voiceband signal will be converted from analog to digital and then back to analog. Each conversion adds noise, and there will be too much noise from the second conversion for 56k to work. The modem's negotiation processes will fall back to the less demanding 33.6 kbit/s mode. Other local loop conditions, such a certain antiquated pair gain In telephony, pair gain is a method of transmitting multiple POTS signals over the twisted pairs traditionally used for a single traditional subscriber line in telephone systems. Pair gain has the effect of creating additional subscriber lines. This is typically used as an expedient way to solve subscriber line shortage problems by using existing systems, may have similar results.
In 8-N-1 8-N-1 is a common shorthand notation for a serial port parameter setting or configuration in asynchronous mode, in which there are eight data bits, no (N) parity bit, and one (1) stop bit connections (1 start bit, 8 data bits, No parity bit, 1 stop bit), which were typical before LAPM became widespread, the actual throughput is a maximum of 5.6 kilobytes per second, since ten bits are used for every byte The byte is a unit of digital information in computing and telecommunications. It is an ordered collection of bits, in which each bit denotes the binary value of 1 or 0. Historically, a byte was the number of bits (typically 5, 6, 7, 8, 9, or 16) used to encode a single character of text in a computer and it is for this reason the basic, although effective throughput can be increased as high as 32 kbytes/s using internal compression, or 100 kbytes/s using ISP-side compression.
Effective throughput People are often concerned about measuring the maximum data throughput rate of a communications link or network access. A typical method of performing a measurement is to transfer a 'large' file and measure the time taken to do so. The throughput is then calculated by dividing the file size by the time to get the throughput in megabits, kilobits, will vary, depending on framing protocols, noise, data compression In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits than an unencoded representation would use, through use of specific encoding schemes, and other factors. See V.42 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces and Comparison of synchronous and asynchronous signalling article for more detail.
The upload speed is 33.6 kbit/s if an analog voiceband modem is used (V.90 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces), or 48.0 kbit/s using a digital modem (V.92 V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90, that establishes a modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates. With V.92 PCM is used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream data). Due to the design of public telecommunications The public switched telephone network also referred to as the Plain Old Telephone Service (POTS) is the network of the world's public circuit-switched telephone networks. It is a worldwide net of telephone lines, fiberoptic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables connected networks, higher speed dialup modems are unlikely to ever appear. Also, depending on the quality of the line conditions, the user may not be able to reach this maximum speed. While faster communications such as DSL Digital Subscriber Line is a family of technologies that provides digital data transmission over the wires of a local telephone network. DSL originally stood for digital subscriber loop. In telecommunications marketing, the term Digital Subscriber Line is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly and cable modems A cable modem is a type of network bridge and modem that provides bi-directional data communication via radio frequency channels on a HFC and RFoG infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a HFC and RFoG network. They are commonly became widely available to urban consumers in the early 2000s in the United States, dial-up Internet access Dial-up Internet access is a form of Internet access that uses telephone lines. The user's computer or router uses an attached modem connected to a telephone line to dial into an Internet service provider's node to establish a modem-to-modem link, which is then used to route Internet Protocol packets between the user's equipment and hosts remains common, since high speed rural Internet Rural Internet is the access to the Internet from rural areas , which are settled places outside towns and cities. Inhabitants live in villages, hamlets, on farms and in other isolated houses connections are often scarce and because people may still use it to send faxes A fax is a document sent over a telephone line. Fax machines have existed, in various forms, since the 19th century (see "History" below), though modern fax machines became feasible only in the mid-1970s as the sophistication of technology increased and cost of the three underlying technologies dropped. Digital fax machines first became.
History
Initially there were two rival 56k modem systems. One was K56flex from Rockwell Rockwell International was a major American manufacturing conglomerate in the latter half of the 20th century, involved in aircraft, the space industry, both defense-oriented and commercial electronics, automotive and truck components, printing presses, valves and meters, and industrial automation. It was the ultimate incarnation of a series of and Lucent Lucent Technologies was a technology company composed of what was formerly AT&T Technologies, which included Western Electric and Bell Labs. It was spun off from AT&T on September 30, 1996. The other was X2 from US Robotics. In February 1998 the International Telecommunication Union The International Telecommunication Union is the eldest organization in the UN family still in existence. It was founded as the International Telegraph Union in Paris on 17 May 1865 and is today the leading United Nations agency for information and communication technology issues, and the global focal point for governments and the private sector (ITU) drafted a 56 kbit/s standard called V.90 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces which was carefully designed to allow both types of modem to be converted to it by a firmware upgrade. This was formally approved during September 1998.
K56flex
K56flex (a combination of Rockwell's K56Plus and Lucent's V.Flex2 proposals) was a proprietary modem A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog chipset A chipset, PC chipset or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product from Rockwell and Lucent Lucent Technologies was a technology company composed of what was formerly AT&T Technologies, which included Western Electric and Bell Labs. It was spun off from AT&T on September 30, 1996 that gave users the possibility of receiving data on ordinary phone lines at 56 kbit/s as opposed to the previous maximum of 33.6 kbit/s.
K56flex is a combination of two competitors' efforts at 56k technology. Lucent developed the K56 protocol, while Rockwell developed the 56flex protocol. This occasionally led to incompatibilities between Lucent and Rockwell chipsets as their implementation of K56flex differed.
X2
X2 was a 56 kbit/s In telecommunications, bit rate or data transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system. This is typically measured in multiples of the units bit per second or byte per second modem protocol developed by U.S. Robotics U.S. Robotics is a company that makes computer modems and related products. It sold high-speed modems in the 1980s, and had a reputation for high quality and compatibility.[citation needed] With the reduced usage of voiceband modems in North America in the early 21st century, USR is now one of the few modem companies left in that market. It now. The protocol used V.34 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces+ to upload at 33.6 kbit/s, and downloaded under PCM at 56 kbit/s. X2 was found to consistently have a lower top end speed, yet overall performance was faster than K56flex.[citation needed] The incompatibilities experienced between variant Lucent and Rockwell chipsets in K56flex were also avoided as there was only one X2 standard.
V.90
V.90 is an ITU-T recommendation for a modem A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog, allowing 56 kbit/s PCM Pulse-code modulation is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a numeric (usually binary) code. PCM has been used in digital telephone systems and 1980s-era electronic musical keyboards.[clarification needed] It is also the download and 33.6 kbit/s analog-modulated upload. It replaced two vendor standards (K56flex and X2) and was designed to allow modems from both prior standards to be flash upgraded to support it. It was developed between March 1998 and February 1999. It is also known as V.Last as it was anticipated to be the last standard for modems operating near the channel capacity of POTS Plain old telephone service is the voice-grade telephone service that remains the basic form of residential and small business service connection to the telephone network in most parts of the world. The name is a retronym, and is a reflection of the telephone service still available after the advent of more advanced forms of telephony such as ISDN, lines to be developed. A follow-on standard, V.92 V.92 is an ITU-T recommendation, titled Enhancements to Recommendation V.90, that establishes a modem standard allowing near 56 kbit/s download and 48 kbit/s upload rates. With V.92 PCM is used for both the upstream and downstream connections; previously 56K modems only used PCM for downstream data, was developed later in 1999 to replace V.90.
V.92
V.92 is an ITU-T The Telecommunication Standardization Sector coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland recommendation, titled Enhancements to Recommendation V.90, that establishes a modem A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog standard allowing 48 kbit/s PCM upload, but at the expense of download rates. For example a 48 kbit/s upstream rate would reduce the downstream as low as 40 kbit/s, due to echo on the telephone line. To avoid this problem, V.92 modems offer the +PIG=1 command to turn off the digital upstream and instead use a 33.6 kbit/s analog connection, in order to maintain a high digital downstream of 50 kbit/s or higher. (See November and October 2000 update at http://modemsite.com/56k/v92s.asp )
V.92 was first presented in August 1999. It was intended to succeed the V.90 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces standards. Like earlier protocol improvements, V.92 was ineffective unless implemented at both ends of the connection. Unlike those, this enhancement was introduced at a time when, due to the spread of broadband Internet access Broadband Internet access, often shortened to just broadband, is a high data rate Internet access—typically contrasted with dial-up access using a 56k modem, dial-up service was declining rather than growing, so Internet service providers An Internet service provider , also sometimes referred to as an Internet access provider (IAP), is a company that offers its customers access to the Internet[citation needed]. The ISP connects to its customers using a data transmission technology appropriate for delivering Internet Protocol Paradigm, such as dial-up, DSL, cable modem, wireless or were buying few new modems, and uptake was low. Some providers such as Netzero NetZero is an Internet service provider based in Woodland Hills, Los Angeles, California. It is a subsidiary of United Online, owner of Juno Online Services and BlueLight Internet Services. The current chairman, president, and CEO of United Online (and thus NetZero) is Mark Goldston offer V.92 lines, but with features like "Modem on Hold" turned off.
- Quick Connect
This reduces negotiation times to around 10 seconds instead of over 20 seconds. Quick connect works by training the client modem on the first call; analog and digital characteristics are stored in a local profile, and then retrieved for future connections.
- "Modem on Hold" (MOH)
This allows the connection to be temporarily severed and then reconnected, reducing the possibility of dropped connections. This is particularly useful for lines that have call waiting so the user can take voice calls.
- V.44 compression
V.44 The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces compression replaces the existing V.42bis The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces compression standards. It generally allows for between 10% and 50% better compression. In most situations the improvement is around 15%. °
See also
- ITU-T V-Series Recommendations The ITU-T V-Series Recommendations on Data communication over the telephone network specify the protocols that govern approved modem communication standards and interfaces
- Dial Up Dial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network to establish a dialled connection to an Internet service provider (ISP) via telephone lines. The user's computer or router uses an attached modem to encode and decode Internet Protocol packets and control information into and from
- List of device bandwidths This is a list of device bit rates, or the physical layer information rates net bit rates or 'useful' bit rates, at which digital devices can communicate over various kinds of buses and networks. The distinction between a bus and a communications network cable (external, between boxes and rarely relying on more than four wires) can be arbitrary
Notes
References
This article was originally based on material from the Free On-line Dictionary of Computing The Free On-line Dictionary of Computing is an online, searchable, encyclopedic dictionary of computing subjects. It was founded in 1985 by Denis Howe and is hosted by Imperial College London. Howe has served as the editor-in-chief since the dictionary's inception, with visitors to the website able to make suggestions for additions or corrections, which is licensed under the GFDL The GNU Free Documentation License is a copyleft license for free documentation, designed by the Free Software Foundation (FSF) for the GNU Project. It is similar to the GNU General Public License, giving readers the rights to copy, redistribute, and modify a work and requires all copies and derivatives to be available under the same license.
External links
- ITU-T Recommendation V.92: Enhancements to Recommendation V.90
- ITU-T Recommendations: Series V
- V92.com
- Brent Townshend
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ITU V-Series | V.92 | K56flex | X2 | MNP | Hayes command set |
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Categories: Computer and telecommunication standards | Modems
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Tue, 27 Jul 2010 07:55:21 GMT+00:00
Bluhalo (blog) ... about the prospect of broadband speeds reaching 10 megabits, sometimes 20 megabits per second, only to receive what feels like 56k dial-up modem speeds. ...
