Abstract
To further enhance frequency-asynchronous distributed Alamouti-coded (FADAC) orthogonal frequency division multiplexing (OFDM), we propose a new scheme which combines the partial maximum likelihood detection (PMLD) to the residual intercarrier interference cancellation (RIC). In order to decrease the performance gap from intercarrier interference- (ICI-) free level after single time iteration of the RIC, the final stage of the proposed scheme performs the PMLD limited to the symbols of less-reliable decision variables. We show that with the practically acceptable candidate symbol set size, a single iteration for RIC is enough to achieve the ICI-free performance. Moreover, the proposed scheme substantially expands the allowable ranges of the three undesirable terms, i.e., the timing and frequency offsets between the transmit antennas and the multipath delay spreads.
Highlights
Distributed antenna systems (DASs) have been one of the hottest topics in 5G wireless communication systems [1,2,3]
E subcarrier spacing is set to 15 kHz which is taken from long-term evolution (LTE) standard [18]. e subblock size nc which varies according to delay spread is taken from the results in [7]
We use the compact labels to each scheme in the legend: “(1)” for frequency-asynchronous distributed Alamouti-coded (FADAC) orthogonal frequency division multiplexing (OFDM) as it only uses the stage (1) in Figure 4, “(1) + (2)” for FADAC OFDM with SIC as it corresponds to the stages (1) and (2) in Figure 4, and “(1) + (2) + (3)” for the proposed scheme
Summary
Distributed antenna systems (DASs) have been one of the hottest topics in 5G wireless communication systems [1,2,3]. In [9,10,11], typical structures of interference cancellation algorithms for the conventional Alamouticoded OFDM with the distributed antennas have been proposed. As the conventional Alamouti-coded OFDM has no ICI self-cancellation property for frequency asynchronous distributed antennas, considerable number of cancellation iterations has to be performed until the performance converges because the accuracy of the initial detection symbol is low. In [13], Kim et al have combined a typical decision-directed iterative ICI cancellation scheme to frequency-asynchronous distributed Alamouti-coded OFDM (FADAC OFDM) shown to outperform the other existing approaches [7]. In order to decrease the performance difference from ICI-free performance after single-time iteration of ICI cancellation, the final stage of the proposed scheme performs the partial maximum likelihood detection (PMLD) limited to the symbols of low-reliability decision variables (DVs). By performing Alamouti decoding on R(b,Ak) and R(b,Bk), the estimated symbol xl is detected
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