Bit rate

The data transmission rate (including data transfer rate, data rate, or colloquially transmission speed, connection speed, and not entirely accurate, "bandwidth" or "capacity" referred to ) means the collection of digital data that is transmitted within a time unit over a transmission channel.

The maximum data transmission rate that can be transmitted error-free over a channel is called the channel capacity., Together with the latency time ( response delay ) is a measure of the performance of a channel. A channel may for example be a compound in the computer network, the connection to the ISP or the interface to a data store.

Dimensions of the data transfer rate

The data transfer rate is measured by counting data units per unit time ( throughput of data). The smallest unit is the bit, which is why the transmission rate is often given as bit rate in units of bits per second (bit / s, short b / s in English bps).

Multiples of this unit can be formed with unit resolutions, for example, is 1 kbit / s to 1000 bit / s With data transfer rates, the unit 's resolutions are traditionally used in their SI -compliant decimal significance. So for example transmits Gigabit Ethernet at 125 Mbps through the 5 -PAM modulation method with 2 bits per symbol and pair via four pairs 1,000,000,000 bits / s The same applies to data rates of audio signals (audio CD: 44.1 kHz with two channels, each with 16 bits = 1.4112 million bit / s, MP3 128 kbit / s = 128,000 bit / s). Chance of unit prefixes are used in a hybrid binary / decimal importance in recent times. Designated specifying 768 kbit / s ADSL transmission rate of 768,000 bit / s, so is the term 6 Mbit / s for ADSL frequently, but not consistently for 6291456 bit / s ( = 6 × 1.024 × 1.024 ).

In areas where the parallel data transmission is used ( especially when access to the data memory via a data bus ), the transmission rate also commonly used in bytes per second ( bytes / sec, short- B / s in English bps) provided, which is usually a multiple of 8 bits are meant per second; so you need to pay attention to whether a transfer rate eg 1 MB / s or 1 Mbit / s is specified (the former specification corresponds exactly eight times the speed of the latter).

An indication in Baud, however, is wrong, because this is the unit for the " pace " and " Symbol Rate" ( baud rate).

Relationship between data rate, bandwidth, and walking speed

There is a fixed relationship which is defined by the Shannon - Hartley Act and sometimes referred to as news cuboid communications technology between bandwidth and maximum data transfer rate ( channel capacity ). For a transmission channel with bandwidth B and the signal to noise ratio SNR with additive white Gaussian noise, the maximum attainable, error-free data transmission rate C is available in the following context:

It is essential that this law only applies to white noise whose amplitudes are normally distributed. This disturbance is referred to as additive white Gaussian noise in the additive White Gaussian Noise, or AWGN English. Transmission channels, which have only these disorders and can be characterized by the above equation are therefore also referred to as the AWGN channel. In other interference with the distribution of the noise spectrum, this relationship no longer holds.

If the signal to noise ratio (SNR) is allowed, digital modulation techniques may be used in which more than two states per symbol are possible, for example, QAM or QPSK. The transmission rate is then obtained as the product of the symbol rate and the dual logarithm of the per symbol M possible states.

Typically receives a digital signal on two states, which can be described as "0" and "1". This is called binary. Three states are denoted by ternary. For the same bit rate, and three states for the parameter signal, the bandwidth required is only 63 % of the bandwidth (see Nyquist bandwidth with Shannon's law: ), which is required for binary transmission.

Signal to noise ratio and bandwidth are complementary. A predetermined data transfer rate can be achieved in both a transmission channel with a large signal to noise ratio and a low range as well, in such a lower signal to noise ratio but correspondingly greater bandwidth.

Examples of data transfer rates

Wired

• ATA / ATAPI ( IDE ) to 1064 Mbit / s
• DVB-C 4-5 Mbit / s ( MPEG-2 video coding )
• DVB- C2: 5-8 Mbit / s ( MPEG-4 for video coding )
• FireWire: FireWire 400: 400 Mbit / s, FireWire 800: 800 Mbit / s (another backward-compatible with the previous standards, specification S Firewire 3200 reached the same 9-pin plug type as FW 800 up to about 3, 2 Gbit / s and will be further developed and used) primarily for professional applications in audio and TV area
• I ² C: 0.1 / 0.4 / 1.0 / 3.4 Mbit / s
• SCSI: 40 Mbit / s to 2.5 Gbit / s depending on the type
• Serial ATA Serial ATA: 1.5 Gbit / s Serial ATA revision 2.x: 3 Gbit / s Serial ATA revision 3.x: 6 Gb / s External Serial ATA (eSATA ) 3 Gb / s

Wireless

Radio signals:

• Mars probe Mariner 4 (1964 ): 8.3 bit / s
• GSM: 9.6 kbit / s
• IrDA 1.0 ( = infrared interface ): 9.6 kbit / s to 115 kbit / s
• IrDA 1.1: 4 Mbit / s
• IrDA 1.3: 16 Mbit / s
• GPRS: 53.6 kbit / s (theoretically up to 171.2 kbit / s)
• Mercury Mariner 10 (1973 ): 100-150 kbit / s
• EDGE 260 kbit / s for downloads and 220 kbit / s for uploads
• BGAN (Internet via Satellite): up to 420 kbit / s
• DECT: 800 kbit / s
• UMTS: 384 kbit / s
• HSDPA: 3.6 / 7.2 Mbit / s
• Digital Radio Mondiale: 11-26 kbit / s
• DRM : 35-185 kbit / s
• DMB: 1-2 Mbit / s
• Bluetooth 2.0 EDR 3 Mbit / s
• DTT: 2-3 Mbit / s ( MPEG-2 video coding )
• DVB-S 4-5 Mbit / s ( MPEG-2 video coding )
• DVB- S2: 5-20 Mbit / s ( MPEG-4 for video coding )
• WiMAX: 40-100 Mbit / s
• 3GPP (LTE): 75-300 Mbit / s
• WLAN: 1-1300 Mbit / s
• ZigBee: 250 kbit / s

Display in the mobile phone display ː see mobile phone standard

Computer network

Computer Networks:

• ARCNET: 2.5 Mbit / s, 20 Mbit / s
• Token Ring: 4 Mbit / s, 16 Mbit / s
• Ethernet: 10 Mbit / s
• Fast Ethernet 100 Mbit / s
• Gigabit Ethernet: 1 Gbit / s
• PowerLAN: 14/85/200/500 Mbit / s
• Fibre Channel: 4 Gb / s, 8 Gb / s
• 10 Gigabit Ethernet: 10 Gbit / s
• InfiniBand 60 Gbit / s ( 12 -channel connection)
• Record for a single optical fiber without frequency division multiplexing ( about 160 km): 107 Gbit / s
• Intercontinental fiber optic bundle: 1 Tbit / s
• World record for the fastest data transfer on a laser: 32.5 Tbit / s

Internet

When accessing the Internet:

• Modem: up to 56 kbit / s
• ISDN: 64 kbit / s, 128 kbit / s when using both B- channels, 2 Mbit / s primary rate access
• ADSL: 384 kbit / s downstream and 64 kbit / s upstream (DSL "light" ) to 25 Mbit / s downlink and 3.5 Mbit / s upstream ( ADSL2 )
• VDSL: 25 Mbit / s to 52 Mbit / s, sometimes up to 100 Mbit / s downstream and 5 Mbit / s to 20 Mbit / s upstream
• DOCSIS ( cable TV ): 1.60 Gbit / s downstream
• Fibre to the Home (FTTH, fiber): 1 Gb / s downstream

Video and audio signals

• Telephone conversation quality ( about 3.1 kHz bandwidth): 64 Kbit / s (ISDN - with practically no techniques irrelevancy and redundancy - reduction ( " compression " ) may be used. )
• Compressed Music File: usually between about 24 kbit / s ( streaming audio through analog telephone modem) and 9.8 Mbit / s ( maximum data rate for lossless multi-channel tracks an SACD / DVD -A)
• Lossless compressed file: between 320 kbit / s and 1411 kbit / s depending on the source ( Flac )
• Audio CD: approx 1411 kbit / s, sampling rate 44.1 kHz, 16 bits and two channels ( with virtually no irrelevance and redundancy reduction)
• SD television picture ( MPEG-2 compressed): about 3 Mbit / s
• DVD ( MPEG-2 compressed): about 6 Mbit / s
• SD video ( 576p 50 Hz uncompressed): 400 Mbit / s
• HD video (720p 60 Hz 24b/px uncompressed): about 1.3 Gbit / s
• Full HD video (1080p 60 Hz 24b/px uncompressed): about 3 Gbit / s

Higher data transfer rates provide a higher bandwidth and are increasingly made ​​possible by new technologies.