Find Bandwith from Spectral Efficiency and Eb/N0 to give you a short intro of why I am asking here. My Uni is offering a TeleCom Lecture, I love the topic but all they teach is electronics, the exercise sheets are still TeleCom, we get no supporting material and after a few days of Google searching I have reached maximum confusion. Send help ;)

Ok here is the Deal:

We have a BPSK Modulated Signal with spectral efficiency of p = 0.7 bit/s/Hz.
We want to Transmit Rb = 2.048 Mbit/s
In addition, BER should be 10^-6 or Eb/N0 = 10.5 dB

Task: Find the Bandwith B.

I thought that Rb/p = B  will give me the desired result.
But here I never used Eb/N0. So I assume I am missing something.

What am I missing? Or is the simple relation I found already correct and Eb/N0 is just there to confuse me?
Your initial answer is correct -- the bandwidth depends only on the spectral efficiency and the symbol rate. $E_b/N_0$ is a figure of merit largely designed to be independent of the bandwidth.

Let me give you an example of where $E_b/N_0$ might come into play. Say you are required to provide $E_b/N_0 = 10$, and you know that your receiver is rated at $N_0 = 10 ^ {-12}$. Then, $E_b = 10 N_0 = 10^{-11}$. At a rate $R = 2 \times 10^6$, the received power is $(2 \times 10^6)(10^{-11} = 2 \times 10^{-5}$ watts, or $-47$ dB.

If you know the channel attenuation, then you can calculate the transmitted power. From there, you can calculate things like battery life. And so on...