![]() I fear that all of these are possibilities and, consequently, my recommendation is the following: when precision is important-for example, if your boss says “the system must have a bandwidth of one hundred megabits per second or you’re fired”-ask for clarification. So, what exactly is the bandwidth of a digital communication system? Is it the maximum rate at which individual bits can be transferred? Is it the maximum rate at which data can be transferred, where “data” refers only to the payload of a packet? Does it account for the rate of bit or packet errors that typically occur for a given set of operating conditions, meaning that it is the rate at which data can be successfully transferred? In this context, “bandwidth” is simply the rate at which your computer is successfully sending and receiving data, and this rate fluctuates because it is influenced by overall network conditions. Is the frequency response of your networking hardware really that variable? Does your modem randomly vary the frequency of its communication signals? Does the speed capability of your connection constantly change? I think not. The results of these tests will not be identical from one day to the next or even from one measurement cycle to the next. For example, there are websites that will measure the “bandwidth” of your Internet connection. Nowadays, if someone hands you a document and tells you to peruse it, you really have no idea what you’re supposed to do.Ī similar difficulty arises when we separate the concept of bandwidth from its etymological reality. The traditional meaning of the word “peruse” is “to read carefully or thoroughly.” For some reason, people started using it to mean “read quickly, take a look at”-perhaps because the word sounds more relaxed, like “cruise” or “snooze.” This meaning became so common that it was included in some dictionaries, despite the fact that it is the opposite of the original meaning. Given the actual definition of bandwidth-i.e., the width of a band of frequencies-why is this term used to describe concepts like data transfer rates? The answer is related to how language evolves. Computing bandwidth (including memory bandwidth)Ĭommunication Bandwidth: Bandwidth as a Measure of Data Transfer. ![]() You may hear the term bandwidth in any of these following contexts: This type of bandwidth seems to be more or less equivalent to “throughput,” i.e., the maximum rate at which a system can produce or process data it is typically expressed in bits per second rather than hertz. It’s not surprising, then, that the word “bandwidth” is now used in a way that places emphasis on data transfer rather than frequency response or spectral characteristics. Otherwise, the carrier’s capacity (in terms of speed) for data transfer would be lower than that of the original signal. The carrier signal (blue, showing frequency modulation) must have more bandwidth than the baseband signal (red). ![]() Thus, more bandwidth corresponds to a higher maximum rate of data transfer. If a signal has more bandwidth-in this case meaning that it includes or is compatible with higher frequencies-it can change more rapidly. To transfer data, a signal must change in some way and the rate at which these changes occur influences the rate at which information can be transferred. The concept of bandwidth is closely linked to the ability of a system to transmit information. Nowadays, though, many electrical engineers devote a large portion of their labors to digital systems and, consequently, we must confront additional meanings and details associated with the term “bandwidth.” Bandwidth as Throughput My previous article on the definition of bandwidth explored the complexities of this term in the context of amplifiers, filters, and RF systems. This article discusses how to interpret and specify bandwidth in systems that involve data transmission and digital processing.
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