The average of a random process

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Discussion Overview

The discussion revolves around the average power of a continuous-time random process defined by a specific mathematical expression. Participants explore the definitions and implications of average power in the context of communication systems, particularly focusing on the relationship between expected values and instantaneous power.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant presents a random process v(t) and questions whether the average power can be expressed as E{|v(t)|^2}.
  • Another participant suggests that the interpretation of v(t) may depend on its physical meaning, questioning if it represents velocity.
  • A later reply clarifies that v(t) is the received signal in a communication system.
  • Another participant distinguishes between the expectation of a random variable and the average power of a deterministic signal, indicating that the average power is defined through a limit process that does not depend on time.
  • This participant implies that further work is needed to find the expected value of the average power.

Areas of Agreement / Disagreement

Participants express differing views on the definitions of average power and the necessary calculations to determine it, indicating that the discussion remains unresolved with multiple competing interpretations.

Contextual Notes

There are limitations regarding the assumptions about the physical interpretation of v(t) and the definitions of average power being discussed. The relationship between instantaneous power and expected values is also not fully resolved.

EngWiPy
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Hello all,

I have the following continuous-time random process:

v(t)=\sum_{k=0}^{K-1}\alpha_k(t)d_k+w(t)

where d_k are i.i.d. random variables with zero mean and variance 1, alpha_k(t) is given, and w(t) is additive white Gaussian process of zero-mean and variance N_0.

Can we say that the average power of v(t) is E{|v(t)|^2}?

Thanks
 
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That probably depends on what v is physically. Velocity?
 
Office_Shredder said:
That probably depends on what v is physically. Velocity?

Thanks for replying.

v(t) is the received signal in a communication system.
 
The word average can be used to refer to two things here. Expectation of a random variable is often referred to as average - what you have written down is the expected value of the instantaneous power of the signal. The average power of a (deterministic) signal is often defined as
\lim_{T \to \infty} \frac{1}{T} \int_{-T/2}^{T/2} |f(t)|^2 dt

This doesn't depend on t at all - if you want the expected value of this, then you need to do more work
 

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