Done. Its frequency response function (the channel's reaction to signals of different frequencies) might be something like this: The bandwidth of a channel depends on the physical properties of the channel, so a copper wire will have a different bandwidth from a wireless channel and from an optical fiber. What actually matters is the ratio of the channel bandwidth to the signal bandwidth. Now the "Bandwidth" is the region around the carrier that contains the "information". Signals with a wider bandwidth will be distorted when passing through, possibly making them unintelligible. Bandwidth and frequency both are the measuring terms of networking. Couldn't we have a data scheme that just relies on the presence of voltage being a 1 and the absence being a 0. When you change from one state (0) to another (1), you generate energy at various frequencies (spectra). Since the exact bandwidth of a binary signal depends on several factors, its useful to look at the theoretical upper bound for any data signal over a given channel. If we were to perform a Fourier analysis on it, we would discover that increasing the data rate (by making the bits shorter and closer to each other), increases the signal's bandwidth. Further the Shannon–Hartley theorem states how much "data" can be transmitted using a given bandwidth (because of noise). The definition of bandwidth is frequency range and it seems to be correct to say that higher bandwidth guarantees higher data rate. Furthermore, PSK will be constructed if signal is delayed. S/N is the signal-to-noise ratio (SNR) or the carrier-to-noise ratio (If QAM did not need more bandwidth, QAM could be used in small bandwidth and it would mean that bandwidth has nothing to do with data rate). (Theoretically it can run from 0 to infinity, but then the center frequency is no longer 100KHz.) Why do I have more bandwidth if I use more frequencies? Here's the relationship bandwidth and frequency: Higher bandwidth, higher frequency. For this reason, bandwidth is often quoted relative to the frequency of operation which gives a better indication of the structure and sophistication needed for the circuit or device under consideration. What you're asking is far more relevant to telecommunications, electrical engineering, or even computer science than network engineering in all but the strictest, most literal sense. Less repeating of what? Generally speaking, you can modulate using combinations of: Are there many frequencies available on the wire? The definition of frequency is: the number of occurrences of a repeating event per unit time. Also for example on a DSL line, for Frequency Division Multiplexing, because multiple users will be allocated less frequency, there will be less bandwidth per user on a given link / wire. Because as far as I know, mode bandwidth on the wire = more bit rate / second. Why is 20KHz better? That means that our signal has a bandwidth of 1Mhz. With this definition, it is clear that the bandwidth cannot be larger than the highest transmit frequency. The higher the frequency, the more bandwidth is available. Channel numbers do not denote power “levels”, so channel 11 is not “better” than channel 1 simply because it is ten digits higher. The Shannon Capacity is one theoretical way to see this relation, as it provides the maximum number of bits transmitted for a given system bandwidth in the presence of noise. Bandwidth refers to the amount of data you can transfer in a unit of time, as well as the range of frequencies used to transmit the data. You're good, move on, there's far more to learn. Bandwidth and frequency are two concepts that are common for science and engineering majors around the world. What is the relationship between the bandwith on a wire and the frequency? I am very confused about one particular thing: Suppose I want to send a data on the wire something like this: 01010101, where it will look some thing like this as a Signal: Well the data to be sent must be represented by a signal, and the signal in this situation is the "change in the voltage" on the link / wire (assume we are using cables, not wireless link). You're done, move on to Layer 2. Worse, if there are many harmonics, they can add to greatly increase the noise level. Why do I have more bandwidth if I use more frequencies? One reason that an FM system might space 0 and 1 symbols 1.5KHz apart is because there are limits to how well, how quickly, and how economically the modem can measure the frequency changes on the wire. The increased speed is achieved partly by using higher-frequency radio waves than previous cellular networks. In the earlier time of wireless communication, it was measured that the required bandwidth of this was narrower, and necessary to decrease noise as well as interference. In this case, all you need is an upgraded internet package as your internet usage needs might have increased. I am trying to learn networking (currently Link - Physical Layer); this is self-study. Mike offered an excellent answer but not exactly to what you were asking. I'd be quite surprised if most CCIE's could answer this question to the degree Mike Pennington did... and wouldn't be surprised at all if they didn't know enough to ask the original question with as much depth as you did! So if 1.5 KHz is enough for this, why would I use more bandwidth? data bandwidth) within the signal. In particular, if you want to, at some remote location, separate the "signal" from the "carrier", then it's useful to not have the "carrier" in the same frequency … A larger pipe can carry a larger volume of water, and hence more water can be delivered between two points with larger pipe. @MikePennington I'm well aware of that. measured in watts (or volts squared). a modulated signal, often denoted C, i.e. Higher frequency -> higher bandwidth throughput. https://networkengineering.stackexchange.com/questions/6014/what-is-the-relationship-between-the-bandwith-on-a-wire-and-the-frequency/6043#6043, Also, on the receiving end, you have the NyquistâShannon sampling theorem that limits what can be detected, https://networkengineering.stackexchange.com/questions/6014/what-is-the-relationship-between-the-bandwith-on-a-wire-and-the-frequency/10554#10554, On the one hand, it may be true that this isn't directly useful information day to day managing a wired network. 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