Tested modifications for 23.04 Ms/s 100 PRB transmission/reception (Downlink)....

Tested modifications for 23.04 Ms/s 100 PRB transmission/reception (Downlink).  This will reduce I/Q acquisition times for 20 MHz channels.  new option in dlsim (-E) for testing 1536-point DFT instead of 2048 for this lower sampling rate. Added normalization to idft1536.  Should also be added to dft1536 later.