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Run-length Limited
Run-length limited (RLL) is a line coding technique that is used to send arbitrary data over a communications channel with bandwidth limits. RLL codes are defined by four main parameters: ''m'', ''n'', ''d'', ''k''. The first two, ''m''/''n'', refer to the rate of the code, while the remaining two specify the minimal ''d'' and maximal ''k'' number of zeroes between consecutive ones. This is used in both telecommunication and storage systems that move a medium past a fixed recording head. Specifically, RLL bounds the length of stretches (runs) of repeated bits during which the signal does not change. If the runs are too long, clock recovery is difficult; if they are too short, the high frequencies might be attenuated by the communications channel. By modulating the data, RLL reduces the timing uncertainty in decoding the stored data, which would lead to the possible erroneous insertion or removal of bits when reading the data back. This mechanism ensures that the boundaries b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line Code
In telecommunications, a line code is a pattern of voltage, current, or photons used to represent digital data transmission (telecommunications), transmitted down a communication channel or written to a storage medium. This repertoire of signals is usually called a constrained code in data storage systems. Some signals are more prone to error than others as the physics of the communication channel or storage medium constrains the repertoire of signals that can be used reliably. Common line encodings are Unipolar encoding, unipolar, Polar encoding, polar, Bipolar encoding, bipolar, and Manchester code. Transmission and storage After line coding, the signal is put through a physical communication channel, either a transmission medium or data storage medium.Karl Paulsen"Coding for Magnetic Storage Mediums".2007. The most common physical channels are: * the line-coded signal can directly be put on a transmission line, in the form of variations of the voltage or current (often us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Error Correcting Codes
In computing, telecommunication, information theory, and coding theory, forward error correction (FEC) or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels. The central idea is that the sender encodes the message in a redundant way, most often by using an error correction code, or error correcting code (ECC). The redundancy allows the receiver not only to detect errors that may occur anywhere in the message, but often to correct a limited number of errors. Therefore a reverse channel to request re-transmission may not be needed. The cost is a fixed, higher forward channel bandwidth. The American mathematician Richard Hamming pioneered this field in the 1940s and invented the first error-correcting code in 1950: the Hamming (7,4) code. FEC can be applied in situations where re-transmissions are costly or impossible, such as one-way communication links or when transmitting to multiple receivers in mu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bit Slip
In digital transmission, bit slip is the loss or gain of a bit or bits, caused by clock driftvariations in the respective clock rates of the transmitting and receiving devices. One cause of bit slip is overflow of a receive buffer that occurs when the transmitter's clock rate exceeds that of the receiver. This causes one or more bits to be dropped for lack of storage capacity. One way to maintain timing between transmitting and receiving devices is to employ an asynchronous protocol such as start-stop. Alternatively, bit slip can be prevented by using a self-clocking signal (such as a signal modulated using OQPSK) or using a line coding such as Manchester encoding. Another cause is "losing count", as on a hard drive: if a hard drive encounters a long string of 0s, without any 1s (or a string of 1s without 0s), it may lose track of the frame between fields, and suffer bit slip. When a pulse of N consecutive zero bits are sent, clock drift may cause the hardware to app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
8b/10b Encoding
In telecommunications, 8b/10b is a line code that maps 8-bit words to 10-bit symbols to achieve DC balance and bounded disparity, and at the same time provide enough state changes to allow reasonable clock recovery. This means that the difference between the counts of ones and zeros in a string of ''at least'' 20 bits is no more than two, and that there are not more than five ones or zeros in a row. This helps to reduce the demand for the lower bandwidth limit of the channel necessary to transfer the signal. An 8b/10b code can be implemented in various ways with focus on different performance parameters. One implementation was designed by K. Odaka for the DAT digital audio recorder. Kees Schouhamer Immink designed an 8b/10b code for the DCC audio recorder. The IBM implementation was described in 1983 by Al Widmer and Peter Franaszek. IBM implementation As the scheme name suggests, eight bits of data are transmitted as a 10-bit entity called a ''symbol'', or ''charac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RLL Example 10110010
RLL may refer to: * Run Length Limited, an encoding scheme for disk drives * Relay Ladder Logic, a programming language for industrial control * Radio Local Loop, same as Wireless Local Loop (WLL) * Rahal Letterman Lanigan Racing Rahal Letterman Lanigan Racing (RLL) is an auto racing team that has participated in the WeatherTech SportsCar Championship and the IndyCar Series. Headquartered in Zionsville, Indiana and Hilliard, Ohio, it is co-owned by 1986 Indianapolis 50 ..., an auto racing team in the WeatherTech SportsCar Championship * ''right lower lobe'', see List of medical abbreviations: R {{disambiguation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IrDA
IrDA is a wireless standard designed for exchanging data using infrared (IR). Infrared ports for this purpose have been implemented in portable electronic devices such as mobile telephones, laptops, cameras, printers, and medical devices. The main characteristics of this kind of wireless optical communication are physically secure bidirectional data transfer, line-of-sight and very low bit error rate, using point-and-shoot principles. IrDA has been made dormant by newer improved technologies like Bluetooth. History and usage The protocols and specifications of the standard were developed by the Infrared Data Association (abbreviated IrDA, giving the name to the standard itself), an industry-driven interest group that was founded in 1994 by around 50 companies. IrDA was popular on PDAs, laptops and some desktops from the late 1990s through the early 2000s. However, it has been displaced by other wireless technologies such as Bluetooth, and Wi-Fi, favored because they don't ne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differential Manchester Encoding
Differential Manchester encoding (DM) is a line code in digital frequency modulation in which data and clock signals are combined to form a single two-level self- synchronizing data stream. Each data bit is encoded by a presence or absence of signal level transition in the middle of the bit period, followed by the mandatory level transition at the beginning. The code is insensitive to an inversion of polarity. In various specific applications, this method is also called by various other names, including biphase mark code (CC), F2F (frequency/double frequency), Aiken biphase, and conditioned diphase. Definition Differential Manchester encoding is a differential encoding technology, using the presence or absence of transitions to indicate logical value. An improvement to Manchester coding which is a special case of binary phase-shift keying, it is not necessary to know the initial polarity of the transmitted message signal, because the information is not represented by the ab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compact Disc
The compact disc (CD) is a Digital media, digital optical disc data storage format co-developed by Philips and Sony to store and play digital audio recordings. It employs the Compact Disc Digital Audio (CD-DA) standard and was capable of holding of uncompressed stereo audio. First released in Japan in October 1982, the CD was the second optical disc format to reach the market, following the larger LaserDisc (LD). In later years, the technology was adapted for computer data storage as CD-ROM and subsequently expanded into various writable and multimedia formats. , over 200 billion CDs (including audio CDs, CD-ROMs, and CD-Rs) had been sold worldwide. Standard CDs have a diameter of and typically hold up to 74 minutes of audio or approximately of data. This was later regularly extended to 80 minutes or by reducing the spacing between data tracks, with some discs unofficially reaching up to 99 minutes or which falls outside established specifications. Smaller variants, such ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM PC Compatible
An IBM PC compatible is any personal computer that is hardware- and software-compatible with the IBM Personal Computer (IBM PC) and its subsequent models. Like the original IBM PC, an IBM PC–compatible computer uses an x86-based central processing unit, sourced either from Intel or a second source like AMD, Cyrix or other vendors such as Texas Instruments, Fujitsu, OKI, Mitsubishi or NEC and is capable of using interchangeable commodity hardware such as expansion cards. Initially such computers were referred to as PC clones, IBM clones or IBM PC clones, but the term "IBM PC compatible" is now a historical description only, as the vast majority of microcomputers produced since the 1990s are IBM compatible. IBM itself no longer sells personal computers, having sold its division to Lenovo in 2005. " Wintel" is a similar description that is more commonly used for modern computers. The designation "PC", as used in much of personal computer history, has not meant "pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
