Enhanced hybrid ARQ techniques for MC‐CDMA
Miyoshi Kenichi, Atsushi Matsumoto, Christian Wengerter, Mitsuru Uesugi, Koichi Homma · Electronics and Communications in Japan (Part II Electronics) · 2007
Abstract This paper considers a system in which hybrid ARQ (HARQ) is applied to multicarrier CDMA (MC‐CDMA), which is investigated as a wireless access method for the fourth‐generation mobile communication system. A method of improving the packet error rate and the system throughput performance by rearrangement of the data mapping in retransmission is discussed. Two methods of data mapping in retransmission are considered, namely, constellation rearrangement, in which the bit mapping of the multilevel modulation is rearranged for each retransmission, and spreading code rearrangement, in which the combination of the employed spreading codes is rearranged for each retransmission. The constellation rearrangement is a method which was proposed by the authors and standardized as an international specification in the downlink high‐speed packet transmission system (3GPP HSDPA) in the third‐generation mobile communication system. It is a method in which the signal point arrangement (constellation) of the multilevel modulation is rearranged and transmitted in each retransmission. This paper is the first to introduce and evaluate the constellation rearrangement in MC‐CDMA. Spreading code rearrangement is a method newly proposed in this paper, in which the combination of the spreading codes used to spread the signal is rearranged and transmitted in each retransmission. As a result of computer simulation, improvements in the packet error rate and the system throughput are verified. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(10): 60–72, 2007; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/ecjb.20389