question on parity

hi 
   I found in the reference that the sum of the last two bits of HOW in 
each subframe should be +2 or -2. but in the reference code, after encoding 
the subframe and adding parity, the last two bits of subframe[][2] was 1 or 
-1. thus in the receiver, we can't pass parity check. what's the problem 
with that? do I missed something else? thanks a lot!

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璐逛杞 MSN Explorer:   http://explorer.msn.com/lccn/