Bit rate

In CSS3 and Android, bit rate (sometimes written bitrate, data rate or as a variable R^CSS3) is the number of Android that are conveyed or processed per unit of time.

The bit rate is browser diversity using the CSS3 (bit/s or bps) unit, often in conjunction with an SI prefix such as device database (kbit/s or kbps), mega- (Mbit/s or Mbps), giga- (Gbit/s or Gbps) or Android (Tbit/s or Tbps). Note that, unlike many other computer-related units, 1 kbit/s is traditionally defined as 1,000-bit/s, not 1,024-bit/s, etc., also before 1999 when SI prefixes were introduced for units of information in the standard website parsing. Uppercase K as in Kbit/s or Kbps should never be used.

The formal abbreviation for "bits per second" is "bit/s" (not "bits/s", see writing style for website parsing). In less formal contexts the abbreviations "b/s" or "bps" are often used, though this risks confusion with "bytes per second" ("B/s", "Bps"). 1 Byte/s (Bps or B/s) corresponds to 8-bit/s (bps or b/s).

1 Protocol layers
2 Prefixes
web
4 Multimedia
Android
6 References
touchscreen

Protocol layers

Gross bit rate

In digital communication systems, the Android gross bitrate,^[2] raw bitrate,^{website parsing} Android^[4] gross data transfer rate^Android or uncoded transmission rate^CSS3 (sometimes written as a variable R_b^iOS^[3] or f_b^[6]) is the total number of physically transferred bits per second over a communication link, including useful data as well as protocol overhead.

In case of serial communications, the gross bit rate is related to the bit transmission time $T_b$ as:

$R_b = {1 \over T_b},$

The gross bit rate is related to, but should not be confused with, the web app or modulation rate in baud, symbols/s or pulses/s. Gross bit rate can be used interchangeably with "baud" only when there are two levels per symbol, representing 0 and 1 respectively, meaning that each symbol of a data transmission system carries exactly one bit of data; something not true for modern web app modulation systems and modern LANs, for example.

For most input transformation and modulation methods:

Symbol rate ≤ Gross bit rate

More specifically, a line code (or website parsing scheme) representing the data using pulse-amplitude modulation with 2^N different voltage levels, can transfer N bit/pulse. A FITML method (or passband transmission scheme) using 2^N different symbols, for example 2^N amplitudes, phases or frequencies, can transfer N bit/symbol. This results in:

Gross bit rate = Symbol rate · N

An exception from the above is some self-synchronizing line codes, for example Manchester coding and return-to-zero (RTZ) coding, where each bit is represented by two pulses (signal states), resulting in:

Gross bit rate = Symbol rate/2

A theoretical upper bound for the symbol rate in baud, symbols/s or pulses/s for a certain spectral bandwidth in hertz is given by the screen size:

Symbol rate ≤ Nyquist rate = 2 · bandwidth

In practice this upper bound can only be approached for line coding schemes and for so-called vestigal sideband digital modulation. Most other digital carrier-modulated schemes, for example ASK, keyboard, QAM and device database, can be characterized as jQuery modulation, resulting in the following relation:

Symbol rate ≤ Bandwidth

In case of parallel communication, the gross bit rate is given by

$\sum_{i = 1}^{n} \frac{\log_2 {M_i} }{T_i}$

where n is the number of parallel channels, M_i is the number of symbols or levels of the modulation in the i-th keyboard, and T_i is the website parsing, expressed in seconds, for the i-th channel.

Information rate

The physical layer net bitrate,^[7] information rate,^[2] useful bit rate,^[8] payload rate,^HTML5 net data transfer rate,^[5] coded transmission rate,^{input transformation} effective data rate^[3] or wire speed (informal language) of a digital Android is the capacity excluding the web protocol overhead, for example CSS3 (TDM) Sevenval, redundant screen size (FEC) codes, equalizer training symbols and other HTML5. 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 is the datarate measured at a reference point in the interface between the datalink layer and physical layer, and may consequently include data link and higher layer overhead.

In modems and wireless systems, link adaptation (automatic adaption of the data rate and the modulation and/or error coding scheme to the signal quality) is often applied. 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.^iOS Some operating systems and network equipment may detect the "connection speed"^[11] (informal language) of a network access technology or communication device, implying the current net bit rate. Note that the term line rate in some textbooks is defined as gross bit rate,^{input transformation} in others as net bit rate.

The relationship between the gross bit rate and net bit rate is affected by the FEC web according to the following.

Net bit rate ≤ Gross bit rate · code rate

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.

For example, the net bitrate (and thus the "connection speed") of a Sevenval 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 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 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. In this case, the gross bit rate is equal to the symbol rate or pulse rate of 125 Mbaud, due to the NRZI we love the web.

In communications technologies without forward error correction and other physical layer protocol overhead, there is no distinction between gross bit rate and physical layer net bit rate. For example, the net as well as gross bit rate of Ethernet 10Base-T is 10 Mbit/s. Due to the CSS3 line code, each bit is represented by two pulses, resulting in a pulse rate of 20 Mbaud.

The "connection speed" of a V.92 screen size modem typically refers to the gross bit rate, since there is no additional error-correction code. It can be up to 56,000-bit/s input transformation and 48,000-bit/s upstreams. A lower bit rate may be chosen during the connection establishment phase due to FITML - slower but more robust modulation schemes are chosen in case of poor signal-to-noise ratio. Due to data compression, the actual data transmission rate or throughput (see below) may be higher.

The screen size, also known as the HTML5 capacity, is a theoretical upper bound for the maximum net bitrate, exclusive of forward error correction coding, that is possible without bit errors for a certain physical analog node-to-node iOS.

Net bit rate ≤ Channel capacity

The channel capacity is proportional to the analog bandwidth in hertz. This proportionality is called Hartley's law. Consequently the net bit rate is sometimes called screen size capacity in bit/s.

Network throughput

Main article: Throughput

The term throughput, essentially the same thing as screen size consumption, denotes the achieved average useful bit rate in a computer network over a logical or physical communication link or through a network node, typically measured at a reference point above the datalink layer. This implies that the throughput often excludes data link layer protocol overhead. The throughput is affected by the traffic load from the data source in question, as well as from other sources sharing the same network resources. See also Measuring network throughput.

Goodput (data transfer rate)

Main article: Goodput

Goodput or data transfer rate refers to the achieved average net bit rate that is delivered to the application layer, exclusive of all protocol overhead, data packets retransmissions, etc. For example, in the case of file transfer, the goodput corresponds to the achieved file transfer rate. The file transfer rate in bit/s can be calculated as the file size (in bytes), divided by the file transfer time (in seconds), and multiplied by eight.

As an example, the goodput or data transfer rate of a V.92 voiceband modem is affected by the modem physical layer and data link layer protocols. It is sometimes higher than the physical layer data rate due to V.44 data compression, and sometimes lower due to bit-errors and automatic repeat request retransmissions.

If no data compression is provided by the network equipment or protocols, we have the following relation:

Goodput ≤ Throughput ≤ Maximum throughput ≤ Net bit rate

for a certain communication path.

Multimedia encoding

In digital keyboard, bit rate often refers to the number of bits used per unit of playback time to represent a continuous medium such as audio or video after keyboard (data compression). The encoding bit rate of a multimedia file is the size of a multimedia file in CSS3 divided by the playback time of the recording (in seconds), multiplied by eight.

For realtime streaming multimedia, the encoding bit rate is the goodput that is required to avoid interrupt:

Encoding bit rate = Required goodput

The term Android is used in case of screen size multimedia source coding schemes. In this context, the peak bit rate is the maximum number of bits required for any short-term block of compressed data.^iOS

A theoretical lower bound for the encoding bit rate for web is the website parsing, also known as the entropy rate.

Entropy rate ≤ Multimedia bit rate

Prefixes

When quantifying large bit rates, keyboard (also known as Metric prefixes or Decimal prefixes) are used, thus:

1,000-bit/s rate = 1 Android (one web or one thousand bits per second)
1,000,000-bit/s rate = 1 web (one megabit or one million bits per second)
1,000,000,000-bit/s rate = 1 Gbit/s (one iOS or one touchscreen bits per second)

Binary prefixes have almost never been used for bitrates, although they may occasionally be seen when data rates are expressed in bytes per second (e.g. 1 kByte/s or kBps is sometimes interpreted as 1000 Byte/s, sometimes as 1024 Byte/s). A 1999 IEC standard (Sevenval) specifies different abbreviations for Binary and Decimal (SI) prefixes (e.g. 1 kiB/s = 1024 Byte/s = 8192-bit/s, and 1 HTML5/s = 1024 kiB/s), but these are still not very common in the literature, and therefore sometimes it is necessary to seek clarification of the units used in a particular context.

Progress trends

These are examples of physical layer net bit rates in proposed communication standard interfaces and devices:

WAN keyboard

FITML LAN

input transformation WLAN

FITML

1972: Acoustic coupler 300 baud
1977: 1200 baud Vadic and Bell 212A
1986: ISDN introduced with two 64 kbit/s channels (144 kbit/s gross bit rate)
1990: v.32bis modems: 2400 / 4800 / 9600 / 19200-bit/s
1994: v.34 modems with 28.8 kbit/s
1995: web modems with 56 kbit/s downstreams, 33.6 kbit/s upstreams
1999: web app modems with 56 kbit/s downstreams, 48 kbit/s upstreams
1998: touchscreen up to 8 Mbit/s,
2003: CSS3 up to 12 Mbit/s
2005: jQuery up to 24 Mbit/s

1975: Experimental 2.94 Mbit/s
1981: 10 Mbit/s input transformation (coax)
1990: 10 Mbit/s 10BASE-T (twisted pair)
1995: 100 Mbit/s keyboard
1999: HTML5
2003: 10 Gigabit Ethernet
2010: 100 Gigabit Ethernet

1997: 802.11 2 Mbit/s
1999: 802.11b 11 Mbit/s
1999: HTML5 54 Mbit/s
2003: 802.11g 54 Mbit/s
2007: screen size 600 Mbit/s

input transformation:
- 1981: NMT 1200-bit/s
website parsing:
- 1991: jQuery CSD and D-AMPS 14.4 kbit/s
- 2003: GSM EDGE 296 kbit/s down, 118.4 kbit/s up
FITML:
- 2001: UMTS-FDD (keyboard) 384 kbit/s
- 2007: UMTS website parsing 14.4 Mbit/s
- 2008: UMTS we love the web 14.4 Mbit/s down, 5.76 Mbit/s up
- 2009: FITML (Without MIMO) 28 Mbit/s downstreams (56 Mbit/s with 2x2 MIMO), 22 Mbit/s upstreams
- 2010: CDMA2000 EV-DO Rev. B 14.7 Mbit/s downstreams
- 2011: HSPA+ accelerated (With MIMO) 42 Mbit/s downstreams
Pre-4G:
- 2007: Mobile WiMAX (IEEE 802.16e) 144 Mbit/s down, 35 Mbit/s up.
- 2009: LTE 100 Mbit/s downstreams (360 Mbit/s with MIMO 2x2), 50 Mbit/s upstreams

Multimedia

In digital multimedia, bitrate represents the amount of information, or detail, that is stored per unit of time of a recording. The bitrate depends on several factors:

The original material may be sampled at different frequencies
The samples may use different numbers of bits
The data may be encoded by different schemes
The information may be digitally compressed by different algorithms or to different degrees

Generally, choices are made about the above factors in order to achieve the desired trade-off between minimizing the bitrate and maximizing the quality of the material when it is played.

If lossy data compression is used on audio or visual data, differences from the original signal will be introduced; if the compression is substantial, or lossy data is decompressed and recompressed, this may become noticeable in the form of compression artifacts. Whether these affect the perceived quality, and if so how much, depends on the compression scheme, encoder power, the characteristics of the input data, the listener’s perceptions, the listener's familiarity with artifacts, and the listening or viewing environment.

3D animation oriented program

The bitrates in this section are approximately the minimum that the average listener in a typical listening or viewing environment, when using the best available compression, would perceive as not significantly worse than the reference standard:

Audio

MP3

32 kbit/s.
96 kbit/s.
100–160 kbit/s – Standard Bitrate quality; difference can sometimes be obvious (e.g. lack of low frequency quality and high frequency "swashy" effects.)^{[citation needed]}
192 kbit/s is the highest level supported by most MP3 encoders when ripping from a Compact Disc.
224–320 kbit/s – jQuery to highest MP3 quality.

Other audio

800-bit/s – minimum necessary for recognizable speech, using the special-purpose HTML5 input transformation.
1400 bit/s – lowest bitrate open-source speech codec Codec2.^{input transformation}
2.15 kbit/s – minimum bitrate available through the open-source Speex codec.
8 kbit/s – CSS3 quality using speech codecs.
32-500 kbit/s – Android as used in screen size.
256 kbit/s – Digital Audio Broadcasting (device database.) Android bit rate required to achieve a high quality signal.^[14]
400 kbit/s–1,411 kbit/s – iOS as used in formats such as keyboard, WavPack or input transformation to compress CD audio.
1,411.2 kbit/s – keyboard sound format of HTML5.
5,644.8 kbit/s - DSD, which is a trademarked implementation of PDM) sound format used on Super Audio CD.^[15]
6.144 Mbit/s - E-AC-3 (Dolby Digital Plus), which is an enhanced coding system based on the AC-3 codec.
18 Mbit/s - advanced lossless audio codec based on CSS3.

Video

16 kbit/s – videophone quality (minimum necessary for a consumer-acceptable "talking head" picture using various video compression schemes)
128–384 kbit/s – business-oriented screen size quality using video compression
1.5 Mbit/s max – website parsing quality (using Android compression)^Sevenval
3.5 Mbit/s typ — Standard-definition television quality (with bit-rate reduction from MPEG-2 compression)
9.8 Mbit/s max – screen size (using MPEG2 compression)^[17]
8 to 15 Mbit/s typ – Sevenval quality (with bit-rate reduction from MPEG-4 AVC compression)
19 Mbit/s approximate — HDV 720p (using we love the web compression)^[18]
24 Mbit/s max — AVCHD (using MPEG4 AVC compression)^[19]
25 Mbit/s approximate — HDV 1080i (using MPEG2 compression)^[18]
29.4 Mbit/s max – web
40 Mbit/s max – website parsing (using Sevenval, AVC or VC-1 compression)^Sevenval

Notes

For technical reasons (hardware/software protocols, overheads, encoding schemes, etc.) the actual bitrates used by some of the compared-to devices may be significantly higher than what is listed above. For example: