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Joint channel identification in punctured hybrid ARQ retransmissions

The channel estimation of a bandwidth efficient automatic repeat request (ARQ) system in which retransmissions are symbol or bit-wise punctured is presented in this paper. Unlike simple ARQ in which an erroneous packet is retransmitted, many hybrid ARQ systems aim to conserve bandwidth by only retransmitting a punctured or recoded data packet. In this paper, we formulate a joint subspace based blind channel estimation algorithm for a punctured hybrid ARQ network. We show that this new method can improve the identifiability conditions for channel estimation as well as the overall system performance.