Transmission Bandwidth and Sampling frequency In LTE standards, for a transmission bandwith of 2.5 MHz, the sampling frequency is 3.84 MHz. I was wondering with this choice, are we violating Nyquist theorem? 

I found the details in the following link (page 15)

http://www.freescale.com/files/wireless_comm/doc/white_paper/3GPPEVOLUTIONWP.pdf

I would have assumed that with a bandwith of 2.5 MHz, then the channel sampling frequency (signal input sampling frequency) should be at least 5 MHz?

Thanks.
Complex (I/Q) signal processing is used in this case. With a complex-valued signal sampled at a rate $B \text{ Hz}$, you can unambiguously represent a total bandwidth of $B \text{ Hz}$. 

What you're thinking of is the real-valued signal case, where a signal sampled at $B \text{ Hz}$ can unambiguously represent a total bandwidth of $\frac{B}{2} \text{ Hz}$. This is the most common statement of the Nyquist theorem, but it only holds for real-valued signals.

Note that the total number of "values" per second is the same, as each complex sample consists of a real and imaginary part. So, there's no "information gain" to be made by using complex sampling, it's just more convenient for many applications (including digital communications signal processing).