Throughput
Encyclopedia
In communication networks, such as Ethernet
or packet radio
, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node. The throughput is usually measured in bit
s per second (bit/s or bps), and sometimes in data packets per second or data packets per time slot.
The system throughput or aggregate throughput is the sum of the data rates that are delivered to all terminals in a network.
The throughput can be analyzed mathematically by means of queueing theory
, where the load in packets per time unit is denoted arrival rate λ, and the throughput in packets per time unit is denoted departure rate μ.
Throughput is essentially synonymous to digital bandwidth consumption.
Users of telecommunications devices, systems designers, and researchers into communication theory are often interested in knowing the expected performance of a system. From a user perspective, this is often phrased as either "which device will get my data there most effectively for my needs?", or "which device will deliver the most data per unit cost?". Systems designers are often interested in selecting the most effective architecture or design constraints for a system, which drive its final performance. In most cases, the benchmark of what a system is capable of, or its 'maximum performance' is what the user or designer is interested in. When examining throughput, the term 'Maximum Throughput' is frequently used where end-user maximum throughput tests are discussed in detail.
Maximum throughput is essentially synonymous to digital bandwidth capacity.
Four different values have meaning in the context of "maximum throughput", used in comparing the 'upper limit' conceptual performance of multiple systems. They are 'maximum theoretical throughput', 'maximum achievable throughput', and 'peak measured throughput' and 'maximum sustained throughput'. These represent different quantities and care must be taken that the same definitions are used when comparing different 'maximum throughput' values. Comparing throughput values is also dependent on each bit carrying the same amount of information. Data compression
can significantly skew throughput calculations, including generating values greater than 100%. If the communication is mediated by several links in series with different bit rates, the maximum throughput of the overall link is lower than or equal to the lowest bit rate. The lowest value link in the series is referred to as the bottleneck.
of the system, and is the maximum possible quantity of data that can be transmitted under ideal circumstances. In some cases this number is reported as equal to the channel capacity, though this can be deceptive, as only non-packetized systems (asynchronous) technologies can achieve this without data compression. Maximum theoretical throughput is more accurately reported to take into account format and specification overhead
with best case assumptions. This number, like the closely related term 'maximum achievable throughput' below, is primarily used as a rough calculated value, such as for determining bounds on possible performance early in a system design phase.
this is less likely to be a useful measure of system performance.
does not occur), the maximum throughput may be defined as the minimum load in bit/s that causes the delivery time (the latency) to become unstable and increase towards infinity. This value can also be used deceptively in relation to peak measured throughput to conceal packet shaping.
The channel efficiency, also known as bandwidth utilization efficiency, in percentage is the achieved throughput related to the net bitrate in bit/s of a digital communication channel). For example, if the throughput is 70 Mbit/s in a 100 Mbit/s Ethernet connection, the channel efficiency is 70%. In this example, effective 70Mbits of data are transmitted every second.
Channel utilization is instead a term related to the use of the channel disregarding the throughput. It counts not only with the data bits but also with the overhead that makes use of the channel. The transmission overhead consists of preamble sequences, frame headers and acknowledge packets. The definitions assume a noiseless channel. Otherwise, the throughput would not be only associated to the nature (efficiency) of the protocol but also to retransmissions resultant from quality of the channel. In a simplistic approach, channel efficiency can be equal to channel utilization assuming that acknowledge packets are zero-length and that the communications provider will not see any bandwidth relative to retransmissions or headers. Therefore, certain texts mark a difference between channel utilization and protocol efficiency.
In a point-to-point or point-to-multipoint communication link, where only one terminal is transmitting, the maximum throughput is often equivalent to or very near the physical data rate (the channel capacity
), since the channel utilization can be almost 100% in such a network, except for a small inter-frame gap.
Despite the conceptual simplicity of digital information, all electrical signals traveling over wires are analog. The analog limitations of wires or wireless systems inevitably provide an upper bound on the amount of information that can be sent. The dominant equation here is the Shannon-Hartley theorem, and analog limitations of this type can be understood as factors that affect either the analog bandwidth of a signal or as factors that affect the signal to noise ratio. It should be noted that the bandwidth of wired systems can be in fact surprisingly narrow, with the bandwidth of Ethernet wire limited to approximately 1 GHz, and PCB traces limited by a similar amount.
Digital systems refer to the 'knee frequency', the amount of time the digital voltage to rise from 10% of a nominal digital '0' to a nominal digital '1' or vice-verse. The knee frequency is related to the required bandwidth of a channel, and can be related to the 3 db bandwidth of a system by the equation :
Where Tr is the 10% to 90% rise time, and K is a constant of proportionality related to the pulse shape, equal to 0.35 for exponential rise, and 0.338 for Gaussian rise.
links.
Large data loads that require processing impose data processing requirements on hardware (such as routers). For example, a gateway router supporting a populated class B subnet, handling 10 x 100 Mbit/s Ethernet channels, must examine 16 bits of address to determine the destination port for each packet. This translates into 81913 packets per second (assuming maximum data payload per packet) with a table of 2^16 addresses this requires the router to be able to perform 5.368 billion lookup operations per second. In a worse case scenario, where the payloads of each Ethernet packet are reduced to 100 bytes, this number of operations per second jumps to 520 billion. This router would require a multi-teraflop processing core to be able to handle such a load.
The throughput is not a well-defined metric when it comes to how to deal with protocol overhead. It is typically measured at a reference point below the network layer and above the physical layer.
The most simple definition is the number of bits per second that are physically delivered. A typical example where this definition is practiced is an Ethernet network. In this case the maximum throughput is the gross bitrate or raw bitrate.
However, in schemes that include forward error correction codes (channel coding), the redundant error code is normally excluded from the throughput. An example in modem
communication, where the throughput typically is measured in the interface between the Point-to-Point Protocol
(PPP) and the circuit switched modem connection. In this case the maximum throughput is often called net bitrate or useful bitrate.
To determine the actual data rate of a network or connection, the "goodput
" measurement definition may be used. For example in file transmission, the "goodput" corresponds to the file size (in bits) divided by the file transmission time.
The "goodput
" is the amount of useful information that is delivered per second to the application layer
protocol. Dropped packets or packet retransmissions as well as protocol overhead are excluded. Because of that, the "goodput" is lower than the throughput. Technical factors that affect the difference are presented in the "goodput
" article.
has a single input and a single output, and operate on discrete packets of information. Examples of such blocks are FFT modules or binary multiplier
s. Because the units of throughput are the reciprocal of the unit for propagation delay
, which is 'seconds per message' or 'seconds per output', throughput can be used to relate a computational device performing a dedicated function such as an ASIC
or embedded processor to a communications channel, simplifying system analysis.
s or cellular systems, the system spectral efficiency in bit/s/Hz/area unit, bit/s/Hz/site or bit/s/Hz/cell, is the maximum system throughput (aggregate throughput) divided by the analog bandwidth and some measure of the system coverage area.
, having an expectation that low latency must imply high throughput, and high latency must imply low throughput.
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
or packet radio
Packet radio
Packet radio is a form of packet switching technology used to transmit digital data via radio or wireless communications links. It uses the same concepts of data transmission via Datagram that are fundamental to communications via the Internet, as opposed to the older techniques used by dedicated...
, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node. The throughput is usually measured in bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s per second (bit/s or bps), and sometimes in data packets per second or data packets per time slot.
The system throughput or aggregate throughput is the sum of the data rates that are delivered to all terminals in a network.
The throughput can be analyzed mathematically by means of queueing theory
Queueing theory
Queueing theory is the mathematical study of waiting lines, or queues. The theory enables mathematical analysis of several related processes, including arriving at the queue, waiting in the queue , and being served at the front of the queue...
, where the load in packets per time unit is denoted arrival rate λ, and the throughput in packets per time unit is denoted departure rate μ.
Throughput is essentially synonymous to digital bandwidth consumption.
Maximum throughput
- See also Peak Information RatePeak Information RatePeak information rate is a burstable rate set on routers and/or switches that allows throughput overhead. Related to Committed Information Rate which is a committed rate speed guaranteed/capped. For example, a CIR of 10 Mbit/s PIR of 12 Mbit/s allows you access to 10 Mbit/s minimum speed with...
(pir)
Users of telecommunications devices, systems designers, and researchers into communication theory are often interested in knowing the expected performance of a system. From a user perspective, this is often phrased as either "which device will get my data there most effectively for my needs?", or "which device will deliver the most data per unit cost?". Systems designers are often interested in selecting the most effective architecture or design constraints for a system, which drive its final performance. In most cases, the benchmark of what a system is capable of, or its 'maximum performance' is what the user or designer is interested in. When examining throughput, the term 'Maximum Throughput' is frequently used where end-user maximum throughput tests are discussed in detail.
Maximum throughput is essentially synonymous to digital bandwidth capacity.
Four different values have meaning in the context of "maximum throughput", used in comparing the 'upper limit' conceptual performance of multiple systems. They are 'maximum theoretical throughput', 'maximum achievable throughput', and 'peak measured throughput' and 'maximum sustained throughput'. These represent different quantities and care must be taken that the same definitions are used when comparing different 'maximum throughput' values. Comparing throughput values is also dependent on each bit carrying the same amount of information. Data compression
Data compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....
can significantly skew throughput calculations, including generating values greater than 100%. If the communication is mediated by several links in series with different bit rates, the maximum throughput of the overall link is lower than or equal to the lowest bit rate. The lowest value link in the series is referred to as the bottleneck.
Maximum theoretical throughput
This number is closely related to the channel capacityChannel capacity
In electrical engineering, computer science and information theory, channel capacity is the tightest upper bound on the amount of information that can be reliably transmitted over a communications channel...
of the system, and is the maximum possible quantity of data that can be transmitted under ideal circumstances. In some cases this number is reported as equal to the channel capacity, though this can be deceptive, as only non-packetized systems (asynchronous) technologies can achieve this without data compression. Maximum theoretical throughput is more accurately reported to take into account format and specification overhead
Protocol overhead
Protocol overhead refers to metadata and network routing information sent by an application, which uses a portion of the available bandwidth of a communications protocol...
with best case assumptions. This number, like the closely related term 'maximum achievable throughput' below, is primarily used as a rough calculated value, such as for determining bounds on possible performance early in a system design phase.
Peak measured throughput
The above values are theoretical or calculated values. Peak measured throughput is throughput measured by a real, implemented system, or a simulated system. The value is the throughput measured over a short period of time; mathematically, this is the limit taken with respect to throughput as time approaches zero. This term is synonymous with "instantaneous throughput". This number is useful for systems that rely on burst data transmission, however, for systems with a high duty cycleDuty cycle
In engineering, the duty cycle of a machine or system is the time that it spends in an active state as a fraction of the total time under consideration....
this is less likely to be a useful measure of system performance.
Maximum sustained throughput
This value is the throughput averaged or integrated over a long time (sometimes considered infinity). For high duty cycle networks this is likely to be the most accurate indicator of system performance. The maximum throughput is defined as the asymptotic throughput when the load (the amount of incoming data) is very large. In packet switched systems where the load and the throughput always are equal (where packet lossPacket loss
Packet loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.-...
does not occur), the maximum throughput may be defined as the minimum load in bit/s that causes the delivery time (the latency) to become unstable and increase towards infinity. This value can also be used deceptively in relation to peak measured throughput to conceal packet shaping.
Channel utilization - Channel efficiency - Normalized throughput
Throughput is sometimes normalized and measured in percentage, but normalization may cause confusion regarding what the percentage is related to. Channel utilization, Channel efficiency and packet drop rate in percentage are less ambiguous terms.The channel efficiency, also known as bandwidth utilization efficiency, in percentage is the achieved throughput related to the net bitrate in bit/s of a digital communication channel). For example, if the throughput is 70 Mbit/s in a 100 Mbit/s Ethernet connection, the channel efficiency is 70%. In this example, effective 70Mbits of data are transmitted every second.
Channel utilization is instead a term related to the use of the channel disregarding the throughput. It counts not only with the data bits but also with the overhead that makes use of the channel. The transmission overhead consists of preamble sequences, frame headers and acknowledge packets. The definitions assume a noiseless channel. Otherwise, the throughput would not be only associated to the nature (efficiency) of the protocol but also to retransmissions resultant from quality of the channel. In a simplistic approach, channel efficiency can be equal to channel utilization assuming that acknowledge packets are zero-length and that the communications provider will not see any bandwidth relative to retransmissions or headers. Therefore, certain texts mark a difference between channel utilization and protocol efficiency.
In a point-to-point or point-to-multipoint communication link, where only one terminal is transmitting, the maximum throughput is often equivalent to or very near the physical data rate (the channel capacity
Channel capacity
In electrical engineering, computer science and information theory, channel capacity is the tightest upper bound on the amount of information that can be reliably transmitted over a communications channel...
), since the channel utilization can be almost 100% in such a network, except for a small inter-frame gap.
For example, in Ethernet the maximum frame size 1526 bytes (maximum 1500 byte payload + 8 byte preamble + 14 byte header + 4 Byte trailer). An additional minimum interframe gap corresponding to 12 byte is inserted after each frame. This corresponds to a maximum channel utilization of 1526/(1526+12)•100% = 99.22%, or a maximum channel use of 99.22 Mbit/s inclusive of Ethernet datalink layer protocol overhead in a 100 Mbit/s Ethernet connection. The maximum throughput or channel efficiency is then 1500/(1526+12) = 97.5 Mbit/s exclusive of Ethernet protocol overhead.
Factors affecting throughput
The throughput of a communication system will be limited by a huge number of factors. Some of these are described below:Analog limitations
The maximum achievable throughput (the channel capacity) is affected by the bandwidth in hertz and signal-to-noise ratio of the analog physical medium.Despite the conceptual simplicity of digital information, all electrical signals traveling over wires are analog. The analog limitations of wires or wireless systems inevitably provide an upper bound on the amount of information that can be sent. The dominant equation here is the Shannon-Hartley theorem, and analog limitations of this type can be understood as factors that affect either the analog bandwidth of a signal or as factors that affect the signal to noise ratio. It should be noted that the bandwidth of wired systems can be in fact surprisingly narrow, with the bandwidth of Ethernet wire limited to approximately 1 GHz, and PCB traces limited by a similar amount.
Digital systems refer to the 'knee frequency', the amount of time the digital voltage to rise from 10% of a nominal digital '0' to a nominal digital '1' or vice-verse. The knee frequency is related to the required bandwidth of a channel, and can be related to the 3 db bandwidth of a system by the equation :
Where Tr is the 10% to 90% rise time, and K is a constant of proportionality related to the pulse shape, equal to 0.35 for exponential rise, and 0.338 for Gaussian rise.
- RC losses: wires have an inherent resistance, and an inherent capacitanceCapacitanceIn electromagnetism and electronics, capacitance is the ability of a capacitor to store energy in an electric field. Capacitance is also a measure of the amount of electric potential energy stored for a given electric potential. A common form of energy storage device is a parallel-plate capacitor...
when measured with respect to ground. This leads to effects called parasitic capacitanceParasitic capacitanceIn electrical circuits, parasitic capacitance, stray capacitance or, when relevant, self-capacitance , is an unavoidable and usually unwanted capacitance that exists between the parts of an electronic component or circuit simply because of their proximity to each other...
, causing all wires and cables to act as RC lowpass filters. - Skin effectSkin effectSkin effect is the tendency of an alternating electric current to distribute itself within a conductor with the current density being largest near the surface of the conductor, decreasing at greater depths. In other words, the electric current flows mainly at the "skin" of the conductor, at an...
: As frequency increases, electric charges migrate to the edges of wires or cable. This reduces the effective cross sectional area available for carrying current, increasing resistance and reducing the signal to noise ratio. For AWGAWGAWG may refer to:In science and technology:* American wire gauge, a standardized sizing system for electrically conducting wire* Arbitrary waveform generator, a piece of electronic test equipment used to generate electrical waveforms...
24 wire (of the type commonly found in Cat 5e cable), the skin effect frequency becomes dominant over the inherent resistivity of the wire at 100 kHz. At 1 GHz the resistivity has increased to 0.1 ohms/inch. - Termination and ringing: For long wires (wires longer than 1/6 wavelengths can be considered long) must be modeled as transmission lines and take termination into account. Unless this is done, reflected signals will travel back and forth across the wire, positively or negatively interfering with the information-carrying signal.
- Wireless Channel EffectsRadio propagationRadio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
: For wireless systems, all of the effects associated with wireless transmission limit the SNR and bandwidth of the received signal, and therefore the maximum number of bits that can be sent.
IC hardware considerations
Computational systems have finite processing power, and can drive finite current. Limited current drive capability can limit the effective signal to noise ratio for high capacitanceCapacitance
In electromagnetism and electronics, capacitance is the ability of a capacitor to store energy in an electric field. Capacitance is also a measure of the amount of electric potential energy stored for a given electric potential. A common form of energy storage device is a parallel-plate capacitor...
links.
Large data loads that require processing impose data processing requirements on hardware (such as routers). For example, a gateway router supporting a populated class B subnet, handling 10 x 100 Mbit/s Ethernet channels, must examine 16 bits of address to determine the destination port for each packet. This translates into 81913 packets per second (assuming maximum data payload per packet) with a table of 2^16 addresses this requires the router to be able to perform 5.368 billion lookup operations per second. In a worse case scenario, where the payloads of each Ethernet packet are reduced to 100 bytes, this number of operations per second jumps to 520 billion. This router would require a multi-teraflop processing core to be able to handle such a load.
- CSMA/CD and CSMA/CA "backoff" waiting time and frame retransmissions after detected collisions. This may occur in Ethernet bus networks and hub networks, as well as in wireless networks.
- Flow controlFlow controlIn data communications, flow control is the process of managing the pacing of data transmission between two nodes to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed with...
, for example in the Transmission Control ProtocolTransmission Control ProtocolThe Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
(TCP) protocol, affects the throughput if the bandwidth-delay productBandwidth-delay productIn data communications, bandwidth-delay product refers to the product of a data link's capacity and its end-to-end delay . The result, an amount of data measured in bits , is equivalent to the maximum amount of data on the network circuit at any given time, i.e. data that has been transmitted but...
is larger than the TCP window, i.e. the buffer size. In that case the sending computer must wait for acknowledgement of the data packets before it can send more packets. - TCP congestion avoidance controls the data rate. So called "slow start" occurs in the beginning of a file transfer, and after packet drops caused by router congestion or bit errors in for example wireless links.
Multi-user considerations
Ensuring that multiple users can harmoniously share a single communications link requires some kind of equitable sharing of the link. If a bottle neck communication link offering data rate R is shared by "N" active users (with at least one data packet in queue), every user typically achieves a throughput of approximately R/N, if fair queuing best-effort communication is assumed.- Packet lossPacket lossPacket loss occurs when one or more packets of data travelling across a computer network fail to reach their destination. Packet loss is distinguished as one of the three main error types encountered in digital communications; the other two being bit error and spurious packets caused due to noise.-...
due to Network congestionNetwork congestionIn data networking and queueing theory, network congestion occurs when a link or node is carrying so much data that its quality of service deteriorates. Typical effects include queueing delay, packet loss or the blocking of new connections...
. Packets may be dropped in switches and routers when the packet queues are full due to congestion. - Packet loss due to bit errors.
- Scheduling algorithms in routers and switches. If fair queuing is not provided, users that send large packets will get higher bandwidth. Some users may be prioritized in a weighted fair queuingWeighted fair queuingWeighted fair queuing is a data packet scheduling technique allowing different scheduling priorities to statistically multiplexed data flows.WFQ is a generalization of fair queuing . Both in WFQ and FQ, each data flow has a separate FIFO queue...
(WFQ) algorithm if differentiated or guaranteed quality of serviceQuality of serviceThe quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
(QoS) is provided. - In some communications systems, such as satellite networks, only a finite number of channels may be available to a given user at a given time. Channels are assigned either through preassignment or through Demand Assigned Multiple Access (DAMA). In these cases, throughput is quantized per channel, and unused capacity on partially utilized channels is lost..
Goodput and overhead
The maximum throughput is often an unreliable measurement of perceived bandwidth, for example the file transmission data rate in bits per seconds. As pointed out above, the achieved throughput is often lower than the maximum throughput. Also, the protocol overhead affects the perceived bandwidth.The throughput is not a well-defined metric when it comes to how to deal with protocol overhead. It is typically measured at a reference point below the network layer and above the physical layer.
The most simple definition is the number of bits per second that are physically delivered. A typical example where this definition is practiced is an Ethernet network. In this case the maximum throughput is the gross bitrate or raw bitrate.
However, in schemes that include forward error correction codes (channel coding), the redundant error code is normally excluded from the throughput. An example in modem
Modem
A modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
communication, where the throughput typically is measured in the interface between the Point-to-Point Protocol
Point-to-Point Protocol
In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes...
(PPP) and the circuit switched modem connection. In this case the maximum throughput is often called net bitrate or useful bitrate.
To determine the actual data rate of a network or connection, the "goodput
Goodput
In computer networks, goodput is the application level throughput, i.e. the number of useful information bits, delivered by the network to a certain destination, per unit of time. The amount of data considered excludes protocol overhead bits as well as retransmitted data packets...
" measurement definition may be used. For example in file transmission, the "goodput" corresponds to the file size (in bits) divided by the file transmission time.
The "goodput
Goodput
In computer networks, goodput is the application level throughput, i.e. the number of useful information bits, delivered by the network to a certain destination, per unit of time. The amount of data considered excludes protocol overhead bits as well as retransmitted data packets...
" is the amount of useful information that is delivered per second to the application layer
Application layer
The Internet protocol suite and the Open Systems Interconnection model of computer networking each specify a group of protocols and methods identified by the name application layer....
protocol. Dropped packets or packet retransmissions as well as protocol overhead are excluded. Because of that, the "goodput" is lower than the throughput. Technical factors that affect the difference are presented in the "goodput
Goodput
In computer networks, goodput is the application level throughput, i.e. the number of useful information bits, delivered by the network to a certain destination, per unit of time. The amount of data considered excludes protocol overhead bits as well as retransmitted data packets...
" article.
Integrated Circuits
Often, a block in a data flow diagramData flow diagram
A data flow diagram is a graphical representation of the "flow" of data through an information system, modelling its process aspects. Often they are a preliminary step used to create an overview of the system which can later be elaborated...
has a single input and a single output, and operate on discrete packets of information. Examples of such blocks are FFT modules or binary multiplier
Binary multiplier
A binary multiplier is an electronic circuit used in digital electronics, such as a computer, to multiply two binary numbers. It is built using binary adders....
s. Because the units of throughput are the reciprocal of the unit for propagation delay
Propagation delay
Propagation delay is a technical term that can have a different meaning depending on the context. It can relate to networking, electronics or physics...
, which is 'seconds per message' or 'seconds per output', throughput can be used to relate a computational device performing a dedicated function such as an ASIC
ASIC
ASIC may refer to:* Application-specific integrated circuit, an integrated circuit developed for a particular use, as opposed to a customised general-purpose device.* ASIC programming language, a dialect of BASIC...
or embedded processor to a communications channel, simplifying system analysis.
Wireless and cellular networks
In wireless networkWireless network
Wireless network refers to any type of computer network that is not connected by cables of any kind. It is a method by which homes, telecommunications networks and enterprise installations avoid the costly process of introducing cables into a building, or as a connection between various equipment...
s or cellular systems, the system spectral efficiency in bit/s/Hz/area unit, bit/s/Hz/site or bit/s/Hz/cell, is the maximum system throughput (aggregate throughput) divided by the analog bandwidth and some measure of the system coverage area.
Over analog channels
Throughput over analog channels is defined entirely by the modulation scheme, the signal to noise ratio, and the available bandwidth. Since throughput is normally defined in terms of quantified digital data, the term 'throughput' is not normally used; the term 'bandwidth' is more often used instead.Common Misconceptions
Many people find it difficult to distinguish between throughput and latencyLatency
Latency or latent may refer to:*Latency period , the time between exposure to a pathogen, chemical or radiation, and when symptoms first become apparent...
, having an expectation that low latency must imply high throughput, and high latency must imply low throughput.
See also
- GoodputGoodputIn computer networks, goodput is the application level throughput, i.e. the number of useful information bits, delivered by the network to a certain destination, per unit of time. The amount of data considered excludes protocol overhead bits as well as retransmitted data packets...
- Greedy sourceGreedy sourceA greedy source is a traffic generator that generates data at the maximum rate possible and at the earliest opportunity possible. Each source always has data to transmit, and is never in idle state due to congestion avoidance or other local host traffic shaping...
- Measuring network throughputMeasuring network throughputThroughput of a network can be measured using various tools available on different platforms. This page explains the theory behind what these tools set out to measure and the issues regarding these measurements.-Reasons for measuring throughput in networks:...
- Network traffic measurementNetwork traffic measurementIn computer networks, network traffic measurement is the process of measuring the amount and type of traffic on a particular network. This is especially important with regard to effective bandwidth management.- Tools :...
- Link and system spectral efficiencySpectral efficiencySpectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system...
- Traffic generation model
- IperfIperfIperf is a commonly used network testing tool that can create TCP and UDP data streams and measure the throughput of a network that is carrying them. Iperf is a modern tool for network performance measurement written in C++....
- TtcpTtcpTTCP may refer to:*ttcp, a computer utility program for measuring network throughput*The Technical Cooperation Program, an international organisation concerned with cooperation on defence science and technology matters...
- bwpingBwpingbwping is a tool to measure bandwidth and response times between two hosts using Internet Control Message Protocol echo request/echo reply mechanism. It does not require any special software on the remote host...