Extended DFE Detection Scheme in MIMO-OFDM System

Low-Complexity QRD-M with Path Eliminations in MIMO-OFDM Systems

“…In Figure 7, the complexities for the adaptive QRD-M in [10] and LR-aided QRD-M in [12] are also shown for comparison. The average number of metric operations for the conventional QRD-M is shown with M = 1,4,8,16, and all results are not changed with respect to the signal-to-noise ratio (SNR) because the number of survival paths at all layers is M. However, the average number of metric operations of the proposed QRD-M is lower than the conventional QRD-M (M = 4), and is approximated to the conventional QRD-M (M = 1) with respect to increased SNR because the difference of ASEDs between necessary survival paths and unnecessary survival paths is large. Additionally, the average number of metric operations of the proposed QRD-M is lower than the adaptive QRD-M and LR-aided QRD-M due to more path eliminations by adaptively calculated threshold at each layer.…”

“…In addition, the modified tree structure QRD-M eliminates unnecessary paths only from the top layer to the In Figures 10 and 11, the number of complex multiplications for the conventional and the proposed QRD-M using 16-QAM and 64-QAM modulation is shown with respect to the number of transmit antennas, respectively. For comparison, the number of complex multiplications for the E-DFE, which has poor error performance compared to proposed QRD-M in [16], is also shown. In this simulation, it is assumed that the multiplication of two complex numbers requires four real multiplications.…”

“…For comparison, the number of complex multiplications for the E-DFE, which has poor error performance compared to proposed QRD-M in [16], is also shown. In this simulation, it is assumed that the multiplication of two complex numbers requires four real multiplications.…”

“…The complexity for the proposed QRD-M is lower than several QRD-M algorithms in [6][7][8][9][10][11][12] because the proposed QRD-M eliminates many unnecessary survival paths due to adaptively calculated thresholds at all layers considering the used modulation scheme. For further comparisons, the complexity for the E-DFE in [16] which has poor error performance is also compared with the proposed QRD-M. The complexity for the E-DFE is higher than the proposed QRD-M at 10 dB SNR for 16-QAM and 20 dB for 64-QAM.…”

“…Table 2 represents the number of complex multiplications for the conventional and the proposed QRD-M. For simple representation, it is assumed that the number of transmit antennas is the same as receive antennas. The number of complex multiplications 12N 3 t + 4N 2 t is always required for calculating the inverse channel matrix, QR decomposition of the channel and multiplying Q H with Y. Additionally, the number of complex multiplications for the extended decision feedback equalizer (E-DFE) is represented where CLLL N t is the number of complex multiplications for complex Lenstra-Lenstra-Lovász (CLLL) algorithm in a N t × N t system [16]. The aim of the inverse channel matrix calculation is to decide the detection order at the receiver so as to minimize the error propagation.…”