Two-Step Analog-Digital Multiuser Equalizer for Hybrid Precoded mmWave Communications

Magueta, Roberto; Castanheira, Daniel; Silva, Adão; Dinis, Rui; Gameiro, Atílio

doi:10.1109/glocomw.2018.8644213

Cited by 2 publications

(12 citation statements)

References 15 publications

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“…Due to the complexity of the optimization problem, we propose an approach to sequentially compute the analog phase shifters for each RF chain, i.e., we first compute the analog coefficients for RF chain 1, then 2, and so on. The computational complexity of the proposed fully iterative analog-digital is higher than the two-step approaches [29][30][31], but its performance is clearly better. Moreover, the simulation results show that the proposed scheme achieves a performance close to the fully digital equalizer.…”

Section: Contributionsmentioning

confidence: 94%

“…The major novelty of this work is the design of a fully iterative hybrid multi-user equalizer, where both analog and digital parts of equalizer are computed iteratively, allowing better performance than the two-step approaches, with fixed analog part, proposed by the authors in [29][30][31]. Both the analog and digital parts are derived by minimizing the sum of the mean square error, which can be shown to be equivalent to minimizing the weighted difference between the hybrid and the fully digital equalizers.…”

Section: Contributionsmentioning

confidence: 99%

“…Since the aim is to design a multi-user equalizer, in this paper, we consider the pure analog precoders discussed in [29,31], which are briefly discussed here. In the first case, presented in [31], we consider that the UT has no access to CSI, which simplifies the overall design, and in the second case, designed in [29], we consider an analog precoder based on the knowledge of partial CSI at the transmitter, i.e., only the average AoD is assumed to be known at the transmitters.…”

Section: Transmitter Designmentioning

confidence: 99%

“…This approach was then extended to the partially connected case, and a novel technique that dynamically constructs the hybrid subarrays knowing the long-term channel characteristics was proposed. Recently, solutions for wideband mmWave multi-user downlink massive MIMO-OFDM systems were proposed in [26], and for uplink in [27][28][29][30][31]. Hybrid precoders for downlink OFDM wideband mMIMO systems, aimed at minimizing the total transmit power of the base station, subject to both the coverage constraint of signaling and data rate requirements of users were proposed in [26].…”

Section: Introductionmentioning

confidence: 99%

“…Also for sub-connected architecture, but using a dynamic subarray antennas, it was designed in [29], a two-step hybrid equalizer, where in the first step, the antennas are dynamically mapped to the RF chains and then, in the second step, an iterative digital equalizer is designed. In [30,31], it was also applied the two-step approach, both for full-connected architectures, using in [30] the constant envelope OFDM (CE-OFDM) modulation technique, and in [31], SC-FDMA.…”

Section: Introductionmentioning

confidence: 99%

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Iterative Analog–Digital Multi-User Equalizer for Wideband Millimeter Wave Massive MIMO Systems

Magueta

Castanheira

Pedrosa

et al. 2020

Sensors

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Most of the previous work on hybrid transmit and receive beamforming focused on narrowband channels. Because the millimeter wave channels are expected to be wideband, it is crucial to propose efficient solutions for frequency-selective channels. In this regard, this paper proposes an iterative analog–digital multi-user equalizer scheme for the uplink of wideband millimeter-wave massive multiple-input-multiple-output (MIMO) systems. By iterative equalizer we mean that both analog and digital parts are updated using as input the estimates obtained at the previous iteration. The proposed iterative analog–digital multi-user equalizer is designed by minimizing the sum of the mean square error of the data estimates over the subcarriers. We assume that the analog part is fixed for all subcarriers while the digital part is computed on a per subcarrier basis. Due to the complexity of the resulting optimization problem, a sequential approach is proposed to compute the analog phase shifters values for each radio frequency (RF) chain. We also derive an accurate, semi-analytical approach for obtaining the bit error rate (BER) of the proposed hybrid system. The proposed solution is compared with other hybrid equalizer schemes, recently designed for wideband millimeter-wave (mmWave) massive MIMO systems. The simulation results show that the performance of the developed analog–digital multi-user equalizer is close to full-digital counterpart and outperforms the previous hybrid approach.

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Section: Contributionsmentioning

confidence: 94%

Section: Contributionsmentioning

confidence: 99%

Section: Transmitter Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Iterative Analog–Digital Multi-User Equalizer for Wideband Millimeter Wave Massive MIMO Systems

Magueta

Castanheira

Pedrosa

et al. 2020

Sensors

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Hybrid Multi-User Equalizer for Massive MIMO Millimeter-Wave Dynamic Subconnected Architecture

et al. 2019

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This paper proposes a hybrid multiuser equalizer for the uplink of broadband millimeterwave massive multiple input/multiple output (MIMO) systems with dynamic subarray antennas. Hybrid subconnected architectures are more suitable for practical applications since the number of required phase shifters is lower than in fully connected architectures. We consider a set of only analog precoded users transmitting to a base station and sharing the same radio resources. At the receiver end, the hybrid multiuser equalizer is designed by minimizing the sum of the mean square error (MSE) of all subcarriers, considering a two-step approach. In the first step, the digital part is iteratively computed as a function of the analog part. It is considered that the digital equalizers are computed on a per subcarrier basis, while the analog equalizer is constant over the subcarriers and the digital iterations due to hardware constraints. In the second step, the analog equalizer with dynamic antenna mapping is derived to connect the best set of antennas to each radio frequency (RF) chain. For each subset of antennas, one antenna and a quantized phase shifter are selected at a time, taking into account all previously selected antennas. The results show that the proposed hybrid dynamic two-step equalizer achieves a performance close to the fully connected counterpart, although it is less complex in terms of hardware and signal processing requirements. INDEX TERMS Multiuser equalizer, hybrid dynamic architecture, massive multiple input/multiple output (MIMO), millimeter-wave communications.

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Two-Step Analog-Digital Multiuser Equalizer for Hybrid Precoded mmWave Communications

Cited by 2 publications

References 15 publications

Iterative Analog–Digital Multi-User Equalizer for Wideband Millimeter Wave Massive MIMO Systems

Iterative Analog–Digital Multi-User Equalizer for Wideband Millimeter Wave Massive MIMO Systems

Hybrid Multi-User Equalizer for Massive MIMO Millimeter-Wave Dynamic Subconnected Architecture

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