U.S. Patent Nos. 6,477,151 and 6,633,536 are directed to synchronization between a mobile phone and base station and a mobile receive that can detect unexpected control messages (page 2).  The 151 patent recites receiving “a timing advance value once” (pages 5-6).  This limitation is not receiving one and only one per multi-frame as the claim and specification provide for a single TAI and TAV to both channels so operation is allowed when only receiving a TAV once (page 11).  The specification even teaches transmitting four times in a multi-frame (page 11).  Thus, there is infringement even though the accused device operates in multiple modes at all times so receive more than one TAV per multi-frame (pages 11-12).

The 536 patent recites “good state,” “bad state,” and “bit pattern” (pages 8-10).  A flag indicating that a frame may have errors is a third state (pages 26-27).  The phone treating the “may have” frame as if it has an error does not matter where the state is directed to the flagging of the frame (pages 26-27).  The state limitations requires one of two states flagging for error free or not error free, so flagging in a third state despite use of the third state as a bad state does not infringe (page 27).  For “bit pattern,” the accused uses a message format of 16-bit mode, 212-bit identifier, 16-bit mode, and 212-bit message (page 28).  During prosecution, the claim was distinguished from prior art with beginning and end of message indications with code words (page 29).  Since the identifier designates the message, there is no infringement (pages 29-30).  The fixed length of the message and the identifier location relative to the message also results in there not being a bit pattern (page 30).

Hindsight:  Absolute terms like “once” may be very limiting.  The context may help broaden such terms, but not using such terms may be better.  Embodiments in the specification exploring the bounds of the absolute term may help as well or may hurt.   Reciting only two states may be overly restrictive unless required for validity.  Requiring some frames to be bad state and other frames to be good state may be better by allowing for a third state.  Directing the claim language to treatment of frames may have helped, so drafting claims using different terms and/or approaches to the concept may help.  Remember, arguments in prosecution limit claims even where the term is broad.