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When I read papers about channels, I usually see something Quasi-static Channel,

Does "Quasi-static Channel" mean "time-variant channel" or "time-invariant channel"?

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closed as unclear what you're asking by Marcus Müller, lennon310, Stanley Pawlukiewicz, jojek Aug 21 '18 at 9:03

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ Hello Marcus, First, thank you for your downvoting !! .. Yes I understand what you mean but I need the answer to be in general. If I cited such reference the answer will be according to that citation. What I need is a general description. Exactly as below answers. Thank you for your understanding. please, cancel your downvoting. $\endgroup$ – New_student Aug 19 '18 at 16:15
  • $\begingroup$ sorry, that's dumb. "we need the answer to be in general". Great, so if I answer "quasi-static is when you have a bear dancing in front of your antenna", it's right, too? Because I wrote a paper where "quasi-static" means exactly that. $\endgroup$ – Marcus Müller Aug 19 '18 at 16:27
  • $\begingroup$ I.e. the answers you've gotten aren't "in general". They are just a specific understanding of the term, in a context that their authors don't mention. In that sense, they aren't correct at all. $\endgroup$ – Marcus Müller Aug 19 '18 at 16:28
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    $\begingroup$ I think that the motivation behind the question may have originated from the definition of the term itself. In general, anything "quasi" is "not exactly". Another example would be "quasi real-time" systems. So, "quasi static" is time-variant with the rate (of change) being relatively slow. But how much and by how much depends on the application. "Quasi" originates in Latin, like "et al, i.e., a priori, de facto, in vivo" and others. From this point of view, the question would be off topic but... $\endgroup$ – A_A Aug 19 '18 at 16:55
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    $\begingroup$ I am sorry, I voted to close the question too quickly from the review panel, without noticing that it had already receive an accepted answer. In any case, I have found this a very useful and helpful community. $\endgroup$ – A_A Aug 19 '18 at 17:07
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Quasi-static is almost-static. In other words, for a block (or window) period of time, you could assume that your channel is static. Below, i attach a figure that depicts this scenario. As you can see the channel could be assumed static for around 100 ms.

enter image description here

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  • $\begingroup$ Thank you so much .. got it. It means the channel is time invariant during block period but it might be time variant otherwise. we can say it's a special case of time-variant channel. $\endgroup$ – New_student Aug 19 '18 at 16:17
  • $\begingroup$ Yeah its as if you got piecewise static functions. $\endgroup$ – Ahmad Bazzi Aug 19 '18 at 16:19
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Quasi-static channels can be said as "block-wise" time (in)variant. For example, your channel has no variations over time (not in delay domain) for some time-period, e.g., 1 ms, but the channel may change after 1 ms.

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  • $\begingroup$ Thank you so much .. got it. It means the channel is time invariant during block-wise but it might be time variant otherwise. $\endgroup$ – New_student Aug 19 '18 at 16:16

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