Abstract
Multi-beam massive multiple-input–multiple-output (MIMO) configurations that utilize high-power beam selection in the analog parts and blind algorithms such as the constant modulus algorithm (CMA), which do not require channel state information (CSI), in the digital parts, have been proposed in the literature to improve the transmission rates and efficiency. In this paper, we evaluate the transmission performance in the downlink, with simple control at the base station (BS) and user terminal (UTs), for massive MIMO transmissions. Through computer simulations, it is shown that the analog multi-beam selection at the BS and the application of CMA at the UT with two antennas can effectively realize transmissions with high-order modulation schemes. In addition, the weight update switching by the CMA is proposed in order to obtain fast and stable performance with a realistic data size.
Highlights
The multiuser multiple-input–multiple-output (MU-MIMO) systems have been incorporated into the Long Term Evolution (LTE)-Advanced and IEEE 802.11ac standards [1]
We focus on evaluating the ideal performance at the user terminals (UTs) by securing a sufficient number of symbols and iterations so that the weight of the constant modulus algorithm (CMA) converges ideally even when using
Assuming that the CMA operates in an actual system, we focus on evaluating the performance for realistic data sizes, because, it is not possible to secure the large number of symbols required for controlling the weights
Summary
The multiuser multiple-input–multiple-output (MU-MIMO) systems have been incorporated into the Long Term Evolution (LTE)-Advanced and IEEE 802.11ac standards [1]. In conventional analog–digital hybrid massive MIMO configurations [15,16], a beam scanning is required for user tracking in each sub-array, and overheads are incurred in determining the analog weight values. Unlike conventional analog–digital hybrid massive MIMO configurations, analog multi-beams are created and several beams with large received powers are selected in the analog part without the overhead for the beamforming [14]. We propose a transmission beamforming method that uses multi-beam massive. It is necessary to consider the control of the analog part and the digital part in the downlink respectively, because the proposed configuration employs the analog–digital hybrid method, unlike conventional digital beamforming (DBF). The performances with realistic data sizes are presented to verify the effectiveness of the proposed method
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