OFDM (signal whitening - phase noise generation) ? urgent!!!

[R110]

generation ofdm signal

Hi there
In OFDM transmitter (plz see the attachment file) there is a block with a function that creates a set of random phase vectors, which are used to whiten the transmitterd signal. each mapped data point is multipiled by a random phase to reduce peak to average power ratio of an OFDM data symbol.
the question is:
1. how this fuction can whiten the signal ?
2. how can we recover the signal after multipiling it by a random phase?
3. do you know any other usage for this function?

If you have a paper that explace the fuction of this block ( red part ) in detail. it would be appreciated if you let me know?

thanks in advance

 

[R110]

signal whiten peak

so does any body have a paper which has a good explanation for each bock in an OFDM based transmiiter??????????????
especially the "ENERGY DISPERSAL"

thanks