Differences between Throughput and Bandwidth Explained

This tutorial explains the differences between the throughput and bandwidth in detail. Learn what the throughput and bandwidth are and how they differ from each other.

Both throughput and bandwidth describe transmission speeds. Bandwidth describes the information-carrying capacity of a medium, while throughput describes the actual use of that capacity.

To understand the basic difference between throughput and bandwidth, think about a highway. If 24 cars can go through on a highway in a second, then the bandwidth of that highway is 24 cars per second.

But, in practice, this never happens. Cars can’t be driven in bumper-to-bumper mode. The actual number of cars that can go through depends on several conditions such as weather, road condition, and lights. If under given conditions only 20 cars can go through in a second, then the throughput of that highway is 20 cars per second.

The following image shows this example.

throughput and bandwidth

Let’s take one more example.

File size: 46 megabits

Ethernet overhead (the total of extra information which each data packet contains such as header and trailer): 10 megabits.

The total amount of data to be transferred: 56 megabits (46 megabits + 10 megabits)

Bandwidth (Maximum data transfer speed): 56 Mbps

Amount of data lost due to errors and acknowledgments: 28 Mbps

Throughput: 56 Mbps - 28 Mbps = 28 Mbps

The time it takes to transfer the entire file: 56 megabits/28 Mbps = 2 seconds

Throughput always remains lower than the bandwidth. Because of this, provides usually advertises connection speed in up to form such as; up to 100 Mbps, up to 1 Gbps, etc.

Next time, when you subscribe for a new Internet connection, subscribe for a connection that offers a higher bandwidth than your requirement. For example, if you require 1Gbps bandwidth, subscribe for a connection that offers a bandwidth rate of 1.25 Gbps or higher.

Measuring throughput and bandwidth

Computer networks use two types of signals; analog and digital for data transmission. The throughput and bandwidth of digital signals are measured in the bit rate. A bit rate is the number of bits transmitted per second, such as 1000 bits per second or 1Kbps.

The following table lists the common bits rate of digital signals used in computer networks.

Bits Rate Description
1bps 1 bit per second
1Kbps 1000 bits per second
1Mbps 1,000,000 bits per second
1Gbps 1,000,000,000 bits per second
1Tbps 1,000,000,000,000 bits per second

The throughput and bandwidth of analog signals are measured in the baud rate. A baud rate is the number of symbols transmitted per second. A symbol is a voltage, frequency, pulse, or phase change in the analog transmission.

Calculating bandwidth of analog signals

The bandwidth of analog signals is computed by subtracting the lower frequency from the higher one. For example, if a cable can carry frequencies from 300 Hz to 3300 Hz, then the bandwidth of that cable is 3000 Hz (3300 - 300).

Let’s take one more example, a human can hear a signal of frequency range 300 to 3000. So the bandwidth of a human voice is 2700 Hz (3000 - 300).

Frequency range Used by
535 kHz to 1605 kHz AM Radio stations
88 to 108 MHz FM Radio stations
108 to 174 MHz VHF Cable stations
174 to 216 MHz VHF television stations
216 to 470 MHz UHF Cable stations
470 to 890 MHz UHF television stations
230MHz to 3 THz Radar

A higher frequency represents a larger bandwidth. A larger bandwidth provides faster transmission.

Common factors that affect bandwidth and throughput

Transmitting device
A transmitting device converts data into signals and load signals on the medium. A slow transmitting device can lower the throughput rate. For example, suppose, a cable of 100Mbps bandwidth is connected with a NIC that can transmit data at the rate of 10Mbps. In this case, even the bandwidth of the cable is 100Mbbps, the bandwidth of transmission will be 10 Mbps and the actual data transmission rate (throughput) will be even less.

Distance
Signals lose strength as they travel on a medium. Because of this, the throughput of a medium decreases as the distance increases. Amplifiers (for analog signals) and repeaters (for digital signals) are used to increase signals’ strength.

Environment
When signals travel through a medium, their environment affects them. For example, EMI (electro-magnetic-interface) fields and cross-talk affect digital signals, noise and attenuation affect analog signals, and weather and obstacles affect radio waves.

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