# Basic questions to clarify (channel gain, taps, OFDM matlab sim)

1. ## Basic questions to clarify (channel gain, taps, OFDM matlab sim)

Hi everyone,

I'm doing a MATLAB simulation of OFDM, I'm following some steps to do that.

The first step:
You have a channel with independent zero mean complex Gaussian taps along with exponentially decaying power profile E{|hk|2|}=e-k/3 where k ∈ [0,21].

First of all, does this notation E{|hk|2|}=e-k/3 mean "The expected value of the channel gain hk is the variance "σ" e-k/3"? And is it "σ" or "σ2"?

And what are exactly the taps?

Anyway, I assumed that σ=e-k/3, so here is my matlab code for the first step:

Code:
```N=22;
k=0:21;
sigma=exp(-k/3);
h=(rand(N,1)+j*rand(N,1))*sigma;```

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2. ## re: Basic questions to clarify (channel gain, taps, OFDM matlab sim)

In frequency selective channels, there is intersymbol interference, and the received signal is written as

$3y_k=\sum_{m=0}^{K-1}h_mx_{k-m}+w_k$

Channel taps are the number of resolvable paths (Search for resolvable paths).

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