Subject: what affects communication during space travel?

what are the difficulties associated with effective and reliable communications 
between satellites and earth caused by
a)distance
b)van allen radiation belts
c)sunspot activity
It is for a year12 Physics assessment that i'm having trouble finding info on.  
It includes the statement: Compare the use of microwaves and radiowave 
technology as effective communication strategies for space travel.  then to 
include a description of what i just asked you in the comments.
thank you for your time.

Re: what affects communication during space travel?