A widely adopted standard for wireless communication is the 3rd Generation Partnership Project (3GPP) standard. The 3GPP standard has had many revisions, including an evolution into the Long-Term Evolution (LTE) standards. The LTE standards also continue to evolve, such that there are multiple releases, one of which is the LTE standards Release 12 (e.g., Rel-12).
The LTE standard includes a specification of a rate matching block or module, both at the physical layer at the transmitter of the base station (e.g., an evolved NodeB or eNB) and at the physical layer at the transmitter of the user equipment (UE). Rate matching is performed over code blocks after turbo encoding. An LTE turbo encoder provides three output streams of the same length for each input stream, the first stream being the original input stream called a systematic stream, and the remaining two streams are interleaved versions of the input stream called parity 1 and parity 2 streams. These three streams are the input of the rate matching block.
At the rate matching block each of the three bit streams may be arranged into a matrix, C, having 32 columns by R rows. If the number of bits, D, at each of the three bit streams is not divisible by 32, each stream may be prepended with null bits so that each will contain full double words, e.g., a double word contains 32 bits and after prepending the number of bits in each of the three bit streams is a divisible by 32. The data may then undergo a series of operations which modify the order of the bits: permutation, transposition, bit shuffling and bit selection. Bit selection may include pointing to a starting point of a combined bit stream (e.g., a data stream that includes all three data streams) and removing the null bits. The starting point is typically not at the beginning of the combined bit stream. The combined bit stream, starting at the starting point and without the null bits, may then be forwarded to the next block at the transmitter.
Known systems mark the null bits when they are inserted, before the permutation, and remove them in the bit selection sub-block, after all bit ordering operations are done. However, marking costs in more memory accesses and longer processing time required for the series of operations performed at the rate matching block. One marking method includes using a full byte to represent a single bit of data. Another bit in this byte indicates if the bit is a null bit. Clearly, this method is very inefficient in terms of memory usage and processing time.