I have seen two definitions for bandwidth: "For a transmission medium, the range of signal frequencies it may transmit" and "The maximum amount of data that can be transmitted in a network." So they are measured in hertz and and bits/second respectively. Could anyone clarify the definition for bandwidth in terms of computer networking?
Also, if it is the range of frequencies, how does this relate to transmission through a wire? Surely only one signal can traverse a wire at once so wouldn't the largest frequency be used all of the time. I can see why a large a bandwidth is good for wireless communication as the different frequencies differentiate between different communications.
Thanks.
13 Answers
Multiple frequencies can be used simultaneously for data, so the bits/second definition is more useful for digital, whereas for analog use, the first definition is better.
1These terms are used with different meanings in various technological domains.
In communications, which is the field most suited for computers, they both relate to the speed of the flow of data, with the difference that:
- Bandwidth usually refers to the total possible flow between two nodes, such as between two computers over all their unified connections, and
- Bitrate usually refers to the speed of one specific connection between source and sink, such as one Internet connection or while reading an audio file.
Bitrate can never exceed Bandwidth, but Bandwidth can be larger than one connection's bitrate.
For example, your Internet connection can have a maximal bandwidth, and you may have more than one process connecting over the Internet, each with its own bitrate.
So this works over two contsructs but all involved in the electromagentic spectrum.
Digital bandwidth in terms of data rates. This is commonly used to describe the maximum theoretical throughput of digital data or maximum allowed. For theoretical you are looking at in ideal circumstances with no loss of data. Though real world may differ. For maximum allowed is more like you purchasing internet access through your isp, the connection to your home may support 1Gbps but you only pay for 200Mbps. This is always measured in datasize per second.
For bandwidth in in terms of transportation medium, the most common you will see is radio frequencies like wifi. However can also be used on copper lines and fiber optical connections. This is the range of frequencies that can be used. Utilizing multiple frequencies together on a single medium is normally called mulitplexing. So if i have of range of 20-30 something hertz (ghz,mhz,khz etc) i can technically send a single bit on every frequency range that is possible for the transceiver to produce and the receiver to read within 20 to 30. So if both are able to create 100 subdivisions of frequency in that range you can send 100 bits per cycle. The Frequency it is sent on will denote the number of cycles that occur per second. For classic multiplexing capabilities on a physical medium you will often see an option to select the bandwidth or autonegotiate option, this is where one interface is slower than the other and allows the more advanced interface to downgrade its transmission so bits dont disappear into the void because the other interface can't recognise the frequency its being sent on.
