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HDSL2
High-bit-rate digital subscriber line 2 (HDSL2) is a standard developed by the American National Standards Institute (ANSI) Committee T1E1.4 and published in 2000 as ANSI T1.418-2000. Like its predecessor HDSL, HDSL2 provides a symmetric data rate of 1,544 kbit/s in both the upstream and downstream directions at a noise margin of 5-6 dB. Its primary purpose was also to provision a T-1 line, only this technology relies on fewer wires - two instead of four - and therefore costs less to set up. The modulation technique used in HDSL2 is TC-PAM, which is also used in G.SHDSL, as opposed to 2B1Q Two-binary, one-quaternary (2B1Q) is a line code used in the U interface of the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) and the high-bit-rate digital subscriber line (HDSL). 2B1Q is a four-level pulse-amplitude modul ... in HDSL. Spectral shaping is applied to increase compatibility with ADSL and HDSL2 on the same bundle. HDSL4 provides the same bitrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HDSL
High-bit-rate digital subscriber line (HDSL) is a telecommunications protocol standardized in 1994. It was the first digital subscriber line (DSL) technology to use a higher frequency spectrum over copper, twisted pair cables. HDSL was developed to transport DS1 services at 1.544 Mbit/s and 2.048 Mbit/s over telephone local loops without a need for repeaters. Successor technology to HDSL includes HDSL2 and HDSL4, proprietary SDSL, and G.SHDSL. Standardization HDSL was developed for T1 service at 1.544 Mbit/s by the American National Standards Institute (ANSI) Committee T1E1.4 and published in February 1994 as ANSI Technical Report TR-28. This American variant uses two wire pairs with at a rate of 784 kbit/s each, using the 2B1Q line code, which is also used in the American variant of the ISDN U interface. First products were developed in 1993. A European version of the standard for E1 service at 2.048 Mbit/s was published in February 1995 by the Europea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TC-PAM
Trellis-coded pulse-amplitude modulation (TC-PAM) is the modulation format that is used in HDSL2 and G.SHDSL. It is a variant of trellis coded modulation (TCM) which uses a one-dimensional pulse-amplitude modulation (PAM) symbol space, as opposed to a two-dimensional quadrature amplitude modulation (QAM) symbol space.Johannes Huber"Multilevel-Codes: Distance Profiles and Channel Capacity" Compared to the 2B1Q scheme used in the older HDSL and SDSL standards, TC-PAM improves range at a given bit-rate and provides enhanced spectral compatibility with ADSL. TC-PAM is also known as 4B1H, because it uses 16 levels to represents a 4 digit binary, 4 Binary 1 Hexadecimal Hexadecimal (also known as base-16 or simply hex) is a Numeral system#Positional systems in detail, positional numeral system that represents numbers using a radix (base) of sixteen. Unlike the decimal system representing numbers using ten symbo .... References Quantized radio modulation modes {{telecom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
American National Standards Institute
The American National Standards Institute (ANSI ) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organization also coordinates U.S. standards with international standards so that American products can be used worldwide. ANSI accredits standards that are developed by representatives of other standards organizations, government agencies, consumer groups, companies, and others. These standards ensure that the characteristics and performance of products are consistent, that people use the same definitions and terms, and that products are tested the same way. ANSI also accredits organizations that carry out product or personnel certification in accordance with requirements defined in international standards. The organization's headquarters are in Washington, D.C. ANSI's operations office is located in New York City. The ANSI annual operating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alliance For Telecommunications Industry Solutions
The Alliance for Telecommunications Industry Solutions (ATIS) is a standards organization that develops technical and operational standards and solutions for the ICT industry, headquartered in Washington, D.C. The organization is accredited by the American National Standards Institute (ANSI). It is the North American Organizational Partner for the 3rd Generation Partnership Project (3GPP), a member of and major U.S. contributor to the International Telecommunication Union ( ITU), as well as a member of the Inter-American Telecommunication Commission ( CITEL). ATIS has 165 member companies, including various telecommunications service providers, equipment manufacturers, and vendors. The organization encompasses numerous industry committees and fora, which discuss, evaluate, and author guidelines concerning such topics as 5G, illegal robocall mitigation, quantum computing, artificial intelligence-enabled networks, distributed ledger technology, non-terrestrial networks, IoT, cybe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upstream (networking)
In computer networking, upstream refers to the direction in which data can be transferred from the client to the server ( uploading). This differs greatly from downstream not only in theory and usage, but also in that upstream speeds are usually at a premium. Whereas downstream speed is important to the average home user for purposes of downloading content, uploads are used mainly for web server applications and similar processes where the ''sending'' of data is critical. Upstream speeds are also important to users of peer-to-peer software. ADSL Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over Copper wire, copper telephone lines than a conventional voiceband modem ... and cable modems are asymmetric, with the upstream data rate much lower than that of its downstream. Symmetric connections such as Symmetric Digital Subscriber Line (SDSL) and T1, h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Downstream (networking)
In a telecommunications network or computer network, downstream refers to data sent from a network service provider to a customer. One process sending data primarily in the downstream direction is downloading. However, the overall download speed depends on the downstream speed of the user, the upstream speed of the server, and the network between them. In the client–server model The client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Often clients and servers communicate ov ..., ''downstream'' can refer to the direction from the server to the client. References Data transmission Orientation (geometry) {{Network-stub nl:Downstream ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Signal-to-noise Ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. SNR is an important parameter that affects the performance and quality of systems that process or transmit signals, such as communication systems, audio systems, radar systems, imaging systems, and data acquisition systems. A high SNR means that the signal is clear and easy to detect or interpret, while a low SNR means that the signal is corrupted or obscured by noise and may be difficult to distinguish or recover. SNR can be improved by various methods, such as increasing the signal strength, reducing the noise level, filtering out unwanted noise, or using error correction techniques. SNR also determines the maximum possible amount of data that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Signal 1
Digital Signal 1 (DS1, sometimes DS-1) is a T-carrier signaling scheme devised by Bell Labs. DS1 is the primary digital telephone standard used in the United States, Canada and Japan and is able to transmit up to 24 multiplexed voice and data calls over telephone lines. E-carrier is used in place of T-carrier outside the United States, Canada, Japan, and South Korea. DS1 is the logical bit pattern used over a physical T1 line; in practice, the terms ''DS1'' and ''T1'' are often used interchangeably. Overview T1 refers to the primary digital telephone carrier system used in North America. T1 is one line type of the PCM T-carrier hierarchy. T1 describes the cabling, signal type, and signal regeneration requirements of the carrier system. The signal transmitted on a T1 line, referred to as the DS1 signal, consists of serial bits transmitted at the rate of 1.544 Mbit/s. The type of line code used is called Alternate Mark Inversion (AMI). Digital Signal Designation is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2B1Q
Two-binary, one-quaternary (2B1Q) is a line code used in the U interface of the Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) and the high-bit-rate digital subscriber line (HDSL). 2B1Q is a four-level pulse-amplitude modulation (PAM-4) scheme without redundancy, mapping two bits (2B) into one quaternary symbol (1Q). Symbol rate is half of data rate. A competing encoding technique in the ISDN basic rate U interface, mainly used in Europe, is 4B3T. Encoding To minimize error propagation, bit pairs ( dibits) are assigned to voltage levels according to a Gray code, as follows: If the voltage is misread as an adjacent level, this causes only a 1-bit error in the decoded data. 2B1Q code is not DC-balanced In signal processing, when describing a periodic function in the time domain, the DC bias, DC component, DC offset, or DC coefficient is the mean value of the waveform. A waveform with zero mean or no DC bias is known as a ''DC balanced'' or ''DC .... ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
