Bandwidth-efficient OFDM transmission with iterative cyclic prefix reconstruction

Abstract

For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response, resulting in a loss of bandwidth efficiency. In this paper, we describe a new technique to restore the cyclicity of the received signal when the CP is not sufficient for OFDM systems. The proposed technique efficiently restores the cyclicity of the current received symbol by adding the weighted next received symbol to the current received symbol. Iterative CP reconstruction (CPR) procedure, based on the residual intersymbol interference cancellation (RISIC) algorithm, is analyzed and compared to the RISIC. In addition, we apply the CPR method to Alamouti space-time block coded (STBC) OFDM system. It is shown that in the STBC OFDM, tail cancellation as well as cyclic reconstruction of the CPR procedure should be repeated. The computational complexities of the RISIC, the proposed CPR, the RISIC with STBC, and the proposed CPR with STBC are analyzed and their performances are evaluated in multipath fading environments.We also propose an iterative channel estimation (CE) method for OFDM with insufficient CP. Further, we discuss the CE method for the STBC OFDM system with the CPR. It is shown that the CPR technique with the proposed CE method minimizes the loss of bandwidth efficiency due to the use of CP, without sacrificing the diversity gain of the STBC OFDM system. Index Terms: Channel estimation (CE), cyclic prefix (CP) reconstruction, intercarrier interference (ICI), interference cancellation, intersymbol interference (ISI), orthogonal frequency division multiplexing (OFDM), space-time block code (STBC).

Performance of Differential-Phase OFDM Systems over Selective Multipath Fading Channels

“…Accordingly, the received bit from the longest path will interfere with the previous τ max R sc =τ max R b /N bits. MC systems have proven to be more immune to ISI when compared to SC systems at the same transmission rate [5,6]. This is because MC systems have multi-subchannels, N, with relatively smaller bandwidth per subchannel.…”

Frequency domain signal processing for multi-carrier modulation systems

“…Therefore, the performance of CP OFDM cannot offer better BER performance than that of ZP OFDM with FDO technique. In [20] and [21], the CP reconstruction is employed to restore the cyclicity of the received symbol for multipath channel with large delay (i.e., larger than CP length). The received CP is removed and the virtual CP is reconstructed to remove the ISI after the transmitted symbols are estimated.…”