Abstract
This paper presents a multimode block-coded modulation method that enables both multimode transmission and coding gain. In multimode transmission, the property of data is changed for each mode, and the data are adaptively transmitted. In our method, all modes are constructed by separate multilevel block codes, wherein the number of levels, set partition, rate, and distance properties of each mode may differ from those of the other modes. Different modes may also have different signal constellations, that is, different modulation methods. The code length is the same for all modes, and the mode can be switched at each block boundary, if desired. This method uses one-way transmission where the transmitter has no feedback information from the receiver. In decoding, the maximum-likelihood decoding is carried out using the Viterbi (1967) algorithm. The decoding of all modes, including decoding of the mode index, can be accomplished using one trellis diagram. This paper describes the multimode encoding and decoding method, and analyzes the distance properties and upper bounds for inter- and intramodes. It is clarified at which distance the code should be increased to reduce the decoding mode error. Three design examples are presented for unequal error protection/equal error protection, variable rate, and hybrid additive white Gaussian noise/flat-fading codes.
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