Combining super‐orthogonal space‐frequency trellis coding, constellation shaping by shell mapping, and OFDM for high data rate broadband mobile communications

Abstract

In this paper, we seamlessly combine three transmission techniques to design an improved performance broadband mobile communication system with two transmit antennas. In so doing, we took inspiration from the V.34 data modem toolbox designed for public switched telephone network. We modified the constellation shaping by shell mapping algorithm to apply it only to the orthogonal frequency division multiplexing (OFDM) frame sent by the first antenna, in such a way that the peak‐to‐average power ratio (PAPR) is also reduced for the second antenna. We use a 24‐point quadrature amplitude modulation (QAM) signal constellation on each subcarrier, while the reference system employs 16 QAM for the same data rate. The 24 QAM constellation is partitioned into four subsets and six rings of four two‐dimensional points each. Two adjacent OFDM frequencies form with the symbols transmitted on them the entries of a 2 × 2 matrix similar to Alamouti's scheme. Two rings corresponding to adjacent OFDM frequencies form a super‐ring. The constellation shaping algorithm is applied to shells made up of super‐rings instead of rings as usual. Super‐orthogonal space‐frequency trellis coding is used on pairs of subcarriers. The proposed system was simulated using two channel models, and the performance was evaluated against the uncoded OFDM reference system. It has both reduced PAPR, and better bit error rate and frame error rate performances. Copyright © 2014 John Wiley & Sons, Ltd.