Conference Proceeding

# Convolutional Code Spread Multicarrier System with Complementary Sequences

Sch. of Aerosp., Tsinghua Univ., Beijing
06/2008; DOI:10.1109/ICC.2008.390 In proceeding of: Communications, 2008. ICC '08. IEEE International Conference on
Source: IEEE Xplore

ABSTRACT A novel convolutional code spread scheme for multi- carrier system with high diversity gain is proposed in this paper. This scheme, named by convolutional code spread multicarrier (CCSM), convolutionally spreads the data symbols onto several consecutive subcarriers with complementary sequences. Compared with the traditional OFDM and OFDM-CDM systems, CCSM enjoys high BER performance with equivalent spectrum efficiency in multipath Rayleigh fading channels. Moreover, the special structure of convolutional spreader in CCSM makes the system suitable for high order modulation, which undoubtedly endows the CCSM with the attractable capability of high transmission capacity.

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ABSTRACT: In this paper, orthogonal frequency-division multiplexing-code-division multiplexing (OFDM-CDM) is presented and investigated as alternative to conventional OFDM for high rate data transmission. An additional multipath diversity gain can be obtained with OFDM-CDM by spreading each data symbol in frequency and time. The optimum reliability information for the Viterbi (1979) decoder is derived for OFDM-CDM systems, and the tradeoff between spreading and channel coding in OFDM systems is presented. By using efficient interference cancellation or joint detection techniques, it can be shown that OFDM-CDM outperforms conventional OFDM with respect to bit error rate (BER) performance and bandwidth efficiency.
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ABSTRACT: A new multiplexing scheme with high diversity gain for multicarrier systems, which is called multicarrier convolutional multiplexing (MCCM), is proposed. In this scheme the data symbols are spread onto several subcarriers by a convolutional spreader. Compared to the conventional OFDM (orthogonal frequency division multiplexing) system, the MCCM system using well designed spreading codes can achieve diversity with order equal to the length of the codes in frequency selective fading channels. A simple free distance searching algorithm is utilized to search the codes with the optimized performance. The best codes of length four are presented and their performance is evaluated by numerical simulations.
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• ##### Article: Complementary sets of sequences
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ABSTRACT: A set of equally long finite sequences, the elements of which are either + 1 or - 1, is said to be a complementary set of sequences if the sum of autocorrelation functions of the sequences in that set is zero except for a zero-shift term. A complementary set of sequences is said to be a mate of another set if the sum of the cross-correlation functions of the corresponding sequences in these two sets is zero everywhere. Complementary sets of sequences are said to be mutually orthogonal complementary sets if any two of them are mates to each other. In this paper we discuss the properties of such complementary sets of sequences. Algorithms for synthesizing new sets from a given set are given. Recursive formulas for constructing mutually orthogonal complementary sets are presented. It is shown that matrices consisting of mutually orthogonal complementary sets of sequences can be used as operators so as to per form transformations and inverse transformations on a one- or two-dimensional array of real time or spatial functions. The similarity between such new transformations and the Hadamard transformation suggests applications of such new transformations to signal processing and image coding.
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