Single Carrier Transmission With Frequency Domain Equalization Research Articles

Robust Transceiver Design for SC-FDE Multi-hop Full-Duplex Decode-and-Forward Relaying Systems

In this paper, we consider the robust transceiver design for a multi-hop full-duplex decode-and-forward (DF) relay system employing single-carrier transmission with frequency-domain equalization (SC-FDE). We take into account the effect of imperfect channel state information (CSI) where the CSI errors are modeled as Gaussian random variables with known statistics. The design of the precoding at the transmitter and the equalization at the receiver is formulated as an optimization problem with the objective to minimize two relevant performance metrics, namely, the sum mean-square error (MSE) and the maximum MSE across the different hops, subject to separate transmit power constraints for the nodes. We show that the equalization filters can be optimized individually at the receiving nodes and take the form of robust Wiener filters. However, due to the loopback/backward interference, the transmit signals in the different hops are coupled and the transmit precoding problem leads to a nonconvex power allocation problem in the frequency domain. To find the optimal power allocation, we first employ a sequential geometric programming (sGP) approach, which uses the condensation technique to transform the objective function into a posynomial and then solves a sequence of standard GP problems. The sGP approach requires global channel knowledge at a central node and the involved subproblems admit only numerical solutions. To gain further insight into the structure of the problem, we also consider an alternating optimization (AO) approach for power allocation where convex programming problems and difference of convex programming problems are solved in an alternating manner. The resulting AO algorithm admits closed-form solutions in each iteration step and requires less signaling overhead compared to the centralized sGP scheme. Numerical results for the MSEs and achievable rates of the proposed robust schemes are provided, showing that the proposed sGP and AO algorithms yield significant performance gains compared to conventional half-duplex relay systems and nonrobust full-duplex designs.

Low-Complexity Iterative Frequency Domain Decision Feedback Equalization

Single-carrier transmission with frequency-domain equalization (SC-FDE) offers a viable design alternative to the classic orthogonal frequency-division multiplexing (OFDM) technique. However, SC-FDE using a linear equalizer may suffer from serious performance deterioration for transmission over severely frequency-selective fading channels. An effective method of solving this problem is to introduce nonlinear decision feedback equalization (DFE) to SC-FDE. In this paper, a low-complexity iterative DFE operating in the frequency domain of single-carrier systems is proposed. Based on the minimum-mean-square-error (MMSE) criterion, a simplified parameter estimation method is introduced to calculate the coefficients of the feedforward and feedback filters, which significantly reduces the implementation complexity of the equalizer. Simulation results show that the performance of the proposed simplified design is similar to the traditional iterative block DFE under various multipath fading channels, but it imposes a much lower complexity than the latter.

Experimental Demonstration of 120-Gb/s PDM CO-SCFDE Transmission Over 317-km SSMF

Single-carrier transmission with frequency-domain equalization (SCFDE) is promising for a 100-Gb/s or even higher optical fiber transmission system by combining the advantages of lower peak-to-average power ratio and less computation complexity. In this letter, we present the first polarization-division-multiplexed coherent optical SCFDE transmission experiment. By utilizing three optical carriers, we demonstrate a 120-Gb/s coherent optical system over 317-km standard single-mode fiber without inline chromatic dispersion compensation.

Periodic Spectrum Transmission for Single-Carrier Transmission Frequency-Domain Equalization

This paper proposes a frequency diversity scheme using only even-numbered samples for single-carrier transmission with frequency-domain equalization (SC-FDE). In the proposed scheme, a periodical frequency spectrum generated by using only even-numbered samples in the time domain provides the frequency redundancy, which is utilized for frequency diversity. Moreover, in order to avoid the data rate reduction due to the decrease in the samples within one block, the high-level modulation is applied to each sample and the transmitting power of each sample can be doubled for the equivalent power transmission instead. Computer simulation results show that the proposed scheme provides a steeper BER curve than the typical SC-FDE over frequency selective fading channels, while the typical SC-FDE is more favorable than the proposed scheme over flat fading channels. Moreover, the proposed scheme still retains its characteristic even when channel estimation and channel coding are additionally taken into account.

Cyclic prefixed single carrier transmission in ultra-wideband communications

This letter proposes cyclic prefixed single carrier transmission with frequency domain equalization (SC-FDE) as an alternative physical layer solution for UWB communications. The performance of SC-FDE over IEEE 802.15.3a UWB channel models is analyzed, simulated and compared with that of impulse based single carrier UWB (SC-UWB) and multicarrier UWB employing orthogonal frequency division multiplexing (OFDM-UWB). The impact of channel coding on the performance of OFDM and SC-FDE in UWB is also studied. Our results demonstrate performance advantage of the SC-FDE scheme, especially when implementation issues such as low complexity and low power consumption for UWB are taken into consideration. The performance of SC-FDE with diversity combining using oversampling is also investigated

A review of cyclically extended single carrier transmission with frequency domain equalization for broadband wireless transmission

In this paper we investigate the concept of cyclically extended single carrier transmission with frequency domain equalization (SC/FDE). We present a detailed mathematical derivation of fast Fourier transform (FFT) based optimum linear receivers, and we describe the signal processing steps of an efficient FDE implementation structure. With a specific system design, where the parameters have been adapted to the IEEE 802.11a and Hiperlan/2 orthogonal frequency division multiplexing (OFDM) based wireless local area network (WLAN) standards in the 5 GHz band, we demonstrate that SC/FDE is a powerful candidate for high speed wireless future applications. Copyright © 2003 AEI.