In this case, the gross bit rate is equal to the symbol rate or pulse rate of 125 megabaud, due to the NRZI line code. The net bit rate of the Ethernet 100BASE-TX physical layer standard is 100 Mbit/s, while the gross bitrate is 125 Mbit/second, due to the 4B5B (four bit over five bit) encoding. The net bit rate of ISDN2 Basic Rate Interface (2 B-channels + 1 D-channel) of 64+64+16 = 144 kbit/s also refers to the payload data rates, while the D channel signalling rate is 16 kbit/s. The connection speed of a technology that involves forward error correction typically refers to the physical layer net bit rate in accordance with the above definition.įor example, the net bitrate (and thus the "connection speed") of an IEEE 802.11a wireless network is the net bit rate of between 6 and 54 Mbit/s, while the gross bit rate is between 12 and 72 Mbit/s inclusive of error-correcting codes. The relationship between the gross bit rate and net bit rate is affected by the FEC code rate according to the following. The term line rate in some textbooks is defined as gross bit rate, in others as net bit rate. Some operating systems and network equipment may detect the " connection speed" (informal language) of a network access technology or communication device, implying the current net bit rate. ![]() In that context, the term peak bitrate denotes the net bitrate of the fastest and least robust transmission mode, used for example when the distance is very short between sender and transmitter. In modems and wireless systems, link adaptation (automatic adaptation of the data rate and the modulation and/or error coding scheme to the signal quality) is often applied. The physical layer net bitrate is the datarate measured at a reference point in the interface between the data link layer and physical layer, and may consequently include data link and higher layer overhead. Error-correcting codes are common especially in wireless communication systems, broadband modem standards and modern copper-based high-speed LANs. The physical layer net bitrate, information rate, useful bit rate, payload rate, net data transfer rate, coded transmission rate, effective data rate or wire speed (informal language) of a digital communication channel is the capacity excluding the physical layer protocol overhead, for example time division multiplex (TDM) framing bits, redundant forward error correction (FEC) codes, equalizer training symbols and other channel coding. Where n is the number of parallel channels, M i is the number of symbols or levels of the modulation in the i-th channel, and T i is the symbol duration time, expressed in seconds, for the i-th channel. ![]() In case of serial communications, the gross bit rate is related to the bit transmission time T b In digital communication systems, the physical layer gross bitrate, raw bitrate, data signaling rate, gross data transfer rate or uncoded transmission rate (sometimes written as a variable R b or f b ) is the total number of physically transferred bits per second over a communication link, including useful data as well as protocol overhead. The International Standard ( IEC 80000-13) specifies different abbreviations for binary and decimal (SI) prefixes (e.g., 1 KiB/s = 1024 B/s = 8192 bit/s, and 1 MiB/s = 1024 KiB/s). = 1 Tbit/s (one terabit per second, i.e., one trillion bits per second)īinary prefixes are sometimes used for bit rates. = 1 Gbit/s (one gigabit per second, i.e., one billion bits per second) = 1 Mbit/s (one megabit per second, i.e., one million bits per second) = 1 kbit/s (one kilobit per second, i.e., one thousand bits per second) = 1 mbit/s (one millibit per second, i.e., one bit per thousand seconds) When quantifying large or small bit rates, SI prefixes (also known as metric prefixes or decimal prefixes) are used, thus: 0.001 bit/s In most computing and digital communication environments, one byte per second (symbol: B/s) corresponds to 8 bit/s. The non-standard abbreviation bps is often used to replace the standard symbol bit/s, so that, for example, 1 Mbps is used to mean one million bits per second. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction with an SI prefix such as kilo (1 kbit/s = 1,000 bit/s), mega (1 Mbit/s = 1,000 kbit/s), giga (1 Gbit/s = 1,000 Mbit/s) or tera (1 Tbit/s = 1,000 Gbit/s). ![]() In telecommunications and computing, bit rate ( bitrate or as a variable R) is the number of bits that are conveyed or processed per unit of time. For disk drives, see data transfer rate (disk drive).
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