Truncating and oversampling OFDM signals in white Gaussian noise channels

Abstract

This work introduces a modified version of the orthogonal frequency division multiplexing (OFDM) signal by truncating OFDM symbols in the time domain. Sub-carriers are no longer orthogonally packed in the frequency domain as time samples are only partially transmitted, leading to improved spectral efficiency. In this work, mathematical expressions are derived for the newly proposed Truncated OFDM (TOFDM) signal, followed by interference analysis and performance comparisons. We also consider optimal and practical decoder architectures. Results from a Sphere Decoder-based decoder indicate that truncation length can significantly affect the error performance. With short truncation length, using a purpose designed detector, signals can be recovered even with truncated symbol transmission.

The First 15 Years of SEFDM: A Brief Survey

“…2014 [57] Block signal detection investigation Oct. 2014 [42] A soft detector using Turbo principle Nov. 2014 [20] Overview of SEFDM in 5G 2016 [18] 5G enabling technologies book chapter summarizes SEFDM 2016 [19] 5G signal processing book chapter summarizes SEFDM Jul. 2016 [17] Truncating OFDM signals to achieve high spectral efficiency Jul. 2016 [45] Comparison of Turbo decoder and Turbo equalizer for SEFDM Jul.…”

“…Recently a new waveform termed Truncated OFDM (TOFDM) was proposed, where the transmission rate is increased by truncating the OFDM symbols in time. This results in shorter transmission time compared to OFDM symbols [17].…”

Experimental SEFDM Pipelined Iterative Detection Architecture with Improved Throughput

“…Research into non-orthogonal modulation has increased rapidly over the last decade, with several candidate technologies proposed in the literature, with alternatives to SEFDM including faster-than-Nyquist (FTN) pulse shaping [10], and truncated-OFDM (TOFDM) [11], amongst others [12,13]. FTN is a time-domain technique that reduces the transmission period for each symbol, thus improving spectral efficiency.…”

Experimental implementation of real-time non-orthogonal multi-carrier systems in a realistic fading channel

“…Similarly, multi-stream faster-than-Nyquist (MFTN) systems have been suggested to improve the spectral efficiency beyond the Nyquist limit [2] [3]. Recently, a new waveform termed truncated OFDM (TOFDM) is proposed [4], where the transmission rate is increased without sacrificing bandwidth by partial time transmission of OFDM symbols, resulting in a shorter transmission time for OFDM symbols and frames to improve the data rate.…”