maximum input level explaination for RF wireless

http://books.google.com.tw/books?id=26RfoKg2UxIC&pg=PA137&lpg=PA137&dq=maximum+input+level+RF+wireless&source=bl&ots=eIHpAVJ18X&sig=DiNePJ46g9gKeXkEbeA174M60Xw&hl=zh-TW&ei=TtbVTrL7BqXEmQXX9a1a&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDkQ6AEwAg#v=onepage&q=maximum%20input%20level%20RF%20wireless&f=false