Patent ID: 7095856

Claim:
A method for a receiving device to maintain encryption synchronization in a multi-modulation TDM system whereby information is communicated in slots comprising a slot header and one or more data blocks, the data blocks each including a number of bits (N B ) and being eligible to be encoded at different respective modulation rates thereby creating a likelihood of different numbers of blocks in different slots, the method comprising: attempting, by the receiving device, to determine a number of blocks (B) in at least a first received slot; if the receiving device can not determine the number of blocks (B) in the first slot, determining a maximum number of blocks (B MAX ) that could be within the slot; and advancing an encryption state of the receiving device a number of bits (N B ×B MAX ); if the receiving device determines the number of blocks (B) in the first slot, advancing the encryption state of the receiving device B×N B bits, thereby corresponding to the number of bits in the first slot; and advancing the encryption state N B ×(B MAX −B) bits defining a shift of zero or more bits in addition to the number of bits in the first slot.