Joint channel estimation and detection of partial ARQ in OFDM

A new algorithm in the spirit of cross-layer design is presented. Partial Automatic Repeat Request (PARQ) is one of the oldest forms of cross-layer design. The idea behind PARQ is to only retransmit a partial sequence back to the receiver and hopefully by using intelligent signal processing and joint channel estimation and symbol detection, the receiver can fully recover the data despite only receiving a piece of the sequence. Joint symbol detection is investigated using a novel OFDM based system while joint channel estimation is performed using a modified subspace algorithm called punctured subspace algorithm or PSSM. It is shown that the joint estimation of two T-spaced channels can be uniquely identified without the coprime condition using only second order statistics (SOS). The algorithms for joint channel estimation and symbol detection are novel because both exploit the fact that the sequences are of unequal lengths. The complexity of both algorithms are manageable and the overall system performance is quite promising.