How does asymptotic approximation follow in this scenario?

  • Context: Graduate 
  • Thread starter Thread starter EngWiPy
  • Start date Start date
  • Tags Tags
    Approximation
Click For Summary

Discussion Overview

The discussion revolves around the asymptotic behavior of a double sum involving random variables as one parameter, M, approaches infinity. Participants explore the implications of this behavior in the context of probability theory, specifically referencing the law of large numbers.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the meaning of the symbols used in the equation, particularly the terms h_i(l) and E.
  • Another participant identifies E as the expectation and h as random variables, suggesting that the asymptotic behavior follows from the law of large numbers.
  • Several participants discuss the nature of the asymptotic expression, debating whether it approaches a ratio of 1 or a difference of 0 as M approaches infinity.
  • One participant expresses uncertainty about the interpretation of the asymptotic behavior, asking for clarification on the implications of dividing by M or subtracting M.
  • A later reply confirms that the limit of the double sum divided by M approaches 1, referencing the law of large numbers as a foundational theorem in probability theory.
  • Another participant notes a caveat regarding the independence of the random variables h_i for different indices i.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of the asymptotic behavior, with multiple competing views regarding the implications of the limit as M approaches infinity.

Contextual Notes

There are unresolved questions about the definitions and properties of the random variables involved, as well as the assumptions regarding their independence.

EngWiPy
Messages
1,361
Reaction score
61
Hello,

I am reading a paper, and the author claimed that in asymptotic sense as M goes to infinite:

[tex]\sum_{i=1}^M\sum_{l=0}^L|h_i(l)|^2=M[/tex]

where:

[tex]\sum_{l=0}^L\mathbb{E}\left\{|h_i(l)|^2\right\}=1[/tex].

How is that asymptotic follows?

Thanks in advance
 
Physics news on Phys.org
There are undefined symbols. What kind of things are hi(l)? What is the meaning of E?
 
mathman said:
There are undefined symbols. What kind of things are hi(l)? What is the meaning of E?

E is the expectation, and h are random variables.

I got it, it is just by using the law of large numbers.

Thanks
 
In the equation cited, what is asymptotic? Ratio -> 1 (true) or difference -> 0 (false)?
 
mathman said:
In the equation cited, what is asymptotic? Ratio -> 1 (true) or difference -> 0 (false)?

as M goes to infinite.
 
S_David said:
as M goes to infinite.

I know you mean as M -> ∞, but my question is what is supposed to happening as M -> ∞, expression divided by M -> 1 (true) or expression minus M -> 0 (false)?
 
mathman said:
I know you mean as M -> ∞, but my question is what is supposed to happening as M -> ∞, expression divided by M -> 1 (true) or expression minus M -> 0 (false)?

I am sorry, I did not understand you quiet well. Can you say it in different way, please?
 
I have the feeling that he is dividing by M.
 
chiro said:
I have the feeling that he is dividing by M.

If he is dividing by the M the result would be 1 not M.
 
  • #10
S_David said:
I am sorry, I did not understand you quiet well. Can you say it in different way, please?
Let ∑(M) be the double sum you are talking about. There are two ways of expressing the limit as M -> ∞, {∑(M)}/M -> 1 (true) or ∑(M) - M -> 0 (false).
 
  • #11
mathman said:
Let ∑(M) be the double sum you are talking about. There are two ways of expressing the limit as M -> ∞, {∑(M)}/M -> 1 (true) or ∑(M) - M -> 0 (false).

[tex]\lim_{M\xrightarrow{}\infty}\frac{1}{M}\sum_{i=1}^M\sum_{l=0}^L|h(l)|^2=1[/tex]
 
  • #12
S_David said:
[tex]\lim_{M\xrightarrow{}\infty}\frac{1}{M}\sum_{i=1}^M\sum_{l=0}^L|h(l)|^2=1[/tex]
True. The author is making use of one of the fundamental theorems of probability theory - the law of large numbers.
 
  • #13
mathman said:
True. The author is making use of one of the fundamental theorems of probability theory - the law of large numbers.

Yes, right. Thanks
 
  • #14
S_David said:
Yes, right. Thanks

There is one caveat: hi independent of hj for i ≠ j.
 

Similar threads

  • · Replies 9 ·
Replies
9
Views
3K
Replies
1
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 16 ·
Replies
16
Views
3K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 0 ·
Replies
0
Views
2K