Method and device for depuncturing data

DETAILED DESCRIPTION The present invention relates in general to a method and device for depuncturing data in the receiver circuitry of a digital communications system.
The method and device of the present invention provides a depuncturing circuit that is relatively simple, uses few logic components, is easily designed and implemented, and is easily modified to accommodate different puncture patterns and rates.
The depuncturing circuit and method of the present invention takes advantage of the observation that a given "bit" in a punctured data stream will never be more than a predetermined number of "bit-spaces" or clock cycles away from its original position in the pre-punctured data stream.
Thus, each bit in a punctured data stream is either in its pre-puncture position or "n" bits away from its pre-puncture position.
The punctured data stream is essentially a time line, and thus, depuncturing may be accomplished according to the present invention by sequentially selecting (according to the appropriate depuncture sequence) the current bit in the data stream, a delayed version of the current bit in the data stream, or a "puncture" signal which indicates that the bit position was punctured and therefore the logic level of that bit position is unknown.
The selection procedure may be implemented by using a multiplexer circuit to accept the different possible inputs, and a control circuit connected to the multiplexer circuit to sequentially select the inputs according to the appropriate depuncture sequence.
Accordingly, the depuncturing circuit of the present invention includes a multiplexer circuit that receives a punctured stream of data and a delayed version of the punctured stream of data.
The multiplexer circuit generates a multiplexer output which can be either a bit from the punctured stream of data, or a bit from the delayed version of the punctured stream of data.
A control circuit is coupled to the multiplexer circuit to select which multiplexer input appears on the multiplexer output