In this paper, a delay diversity orthogonal frequency-division multiplexing (DD OFDM) transmission scheme in amplify-and-forward (AF) full-duplex relay systems is investigated. One direct source-to-destination link, o...
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In this paper, a delay diversity orthogonal frequency-division multiplexing (DD OFDM) transmission scheme in amplify-and-forward (AF) full-duplex relay systems is investigated. One direct source-to-destination link, one relay forwarding link, and residual self-interference are considered in the system. The necessary cyclic prefix length is investigated and a suitable AF relay protocol in the full-duplex relay OFDM system is proposed. This paper demonstrates that the AF relay link and the direct source-to-destination link can be combined to provide spatial diversity. The key is that the DD OFDM scheme is used to transform the spatial diversity into increased channel frequency diversity that is further exploited by using the bit-interleaved coding. The bit error rate performance of the proposed system is verified by simulation results.
Link adaptation is recognized as a powerful technique for enhancing spectral efficiency over wireless channels. While its theoretical aspects are well understood, it is not clear yet how to practically deal with limit...
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ISBN:
(纸本)9781479944828
Link adaptation is recognized as a powerful technique for enhancing spectral efficiency over wireless channels. While its theoretical aspects are well understood, it is not clear yet how to practically deal with limited feedback. In this paper, we study a frequency-selective link adaptation scheme for orthogonal frequency division multiplexing (OFDM). The modulation order is adjusted per resource block (smallest time-frequency unit assigned to a user), while a joint coding rate is used for all variable-length codewords, comprising resource blocks with different modulations. In order to meet the required coding rate, adaptive puncturing is applied after a fixed-rate Turbo encoder. Link adaptation is guided by an effective signal-to-noise ratio (SNR), which is calculated over several subcarriers by a mapping function. 3GPP LTE compliant link-layer simulations were performed for optimizing the SNR interface so that the spectral efficiency is maximized under a codeword error rate constraint and tradeoffs between feedback savings and spectral efficiency losses were elaborated. The result is a thoroughly tested link-layer abstraction for 3GPP LTE including adaptive modulation and bit-interleaved coding that can be also used for system-level simulations towards future mobile radio systems.
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