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Block Transmission Techniques
Published in Paulo Montezuma, Fabio Silva, Rui Dinis, Frequency-Domain Receiver Design for Doubly Selective Channels, 2017
Paulo Montezuma, Fabio Silva, Rui Dinis
The IB-DFE receiver can be implemented in two different ways, depending on whether the channel decoding output is outside or inside the feedback loop. In the first case the channel decoding is not performed in the feedback loop, and this receiver can be regarded as a low complexity turbo equalizer implemented in the frequency domain. Since this is not a true “turbo" scheme, we will call it “conventional IB-DFE." In the second case the IB-DFE can be regarded as a turbo equalizer implemented in the frequency domain and therefore we will denote it as “turbo IB-DFE." For uncoded scenarios it only makes sense to employ conventional IB-DFE schemes. However, it is important to point out that in coded scenarios we could still employ a “conventional IB-DFE" and perform the channel decoding procedure after all the iterations of the IB-DFE. However, since the gains associated with the iterations are very low at low-to-moderate SNR values, it is preferable to involve the channel decoder in the feedback loop, i.e., to use the “turbo IB-DFE."
Novel Detectors for Massive MU-MIMO Communications
Published in IETE Journal of Research, 2020
Ye-Shun Shen, Fang-Biau Ueng, Chin-Yang Kung
The single user MIMO (SU-MIMO) communication systems only consider the situation of a single mobile terminal in the same frequency band. But the MU-MIMO (multi-user multiple-input multiple-output) [11–13] can deploy multiple user terminals with the transmission resources of spatial distribution. The technology is named as spatial division multiple access (SDMA) technology which needs complex signal processing algorithm. Thus when large number of users accesses the same frequency band simultaneously [14], the MU-MMIMO can consider the overall capacity of communication network. The turbo multi-user detectors [15–16] based on the “turbo principle” for the MU-MMIMO communication systems are very important. The “turbo” multi-user detectors can achieve high performance. In this paper, the designed turbo receiver consists of a maximum a posteriori probability (MAP) equalizer and a soft input soft output (SISO) MAP decoder. Based on the soft estimation of the transmitted symbols at each iteration of the turbo receiver, the predicted channel is refined. The availability of accurate channel estimates at the BS receiver is crucial for achieving peak performance [5]. For the MU-MMIMO communications, it is necessary to design the turbo receiver with joint channel state estimator, multi-user detector, and turbo equalizer for MU-MMIMO SC-FDMA communication systems. In order to meet the practical requirements, the designed MU-MMIMO turbo detector must be with low complexity, low latency, and acceptable system performance. In this paper, we propose low-complexity turbo receiver with joint multi-user detector, channel estimator, and turbo equalizer for the MU-MMIMO SC-FDMA systems based on Neumann series expansion, successive over-relaxation (SOR), and symmetric successive over-relaxation (SSOR) principles. The organization of this paper is as follows. In Section 2, the system model is described. The proposed receiver with joint channel estimation, multi-user detection, and turbo equalization is described in Section 3. In Section 4, the low-complexity signal detectors and the corresponding computational complexity analyses are given. Finally, we give some simulation results and conclusions in Section 5 and Section 6, respectively.