Abstract
A method for channel estimation in wideband massive Multiple-Input Multiple-Output systems using hybrid digital analog architectures is developed. The proposed method is useful for Frequency-Division Duplex at either sub-6 GHz or millimeter wave frequency bands and takes into account the beam squint effect caused by the large bandwidth of the signals. To circumvent the estimation of large channel vectors, the posed algorithm relies on the slow time variation of the channel spatial covariance matrix, thus allowing for the utilization of very short training sequences. This is possibledue to the exploitation of the channel structure. After identifying the channel covariance matrix, the channel is estimated on the basis of the recovered information. To that end, we propose a novel method that relies on estimating the tap delays and the gains as sociated with each path. As a consequence, the proposed channel estimator achieves low computational complexity and significantly reduces the training overhead. Moreover, our numerical simulations show better performance results compared to the minimum mean-squared error solution.
Highlights
Massive Multiple-Input Multiple-Output (MIMO) and millimeter wave technologies are promising candidates to satisfy the demands of future wideband wireless communication systems.A common feature of these technologies is the deployment of antenna arrays with a large number of elements while keeping the size of the antenna aperture small
Hybrid architectures with an analog preprocessing network operating in the Radio Frequency (RF) domain have been proposed to reduce the number of complete RF chains [2]
We show numerically that the number of channel paths can be estimated without significant performance losses and negligible computational cost
Summary
A common feature of these technologies is the deployment of antenna arrays with a large number of elements while keeping the size of the antenna aperture small This way, advantages such as large beamforming gains necessary to compensate the propagation losses at mmWave frequencies, or the ability to support many spatially multiplexed streams, are efficiently achieved [1,2]. Deploying massive antenna arrays raises concerns in terms of hardware cost and power consumption, especially at mmWave frequencies. To alleviate these requirements, hybrid architectures with an analog preprocessing network operating in the Radio Frequency (RF) domain have been proposed to reduce the number of complete RF chains [2]. Results obtained for fully digital scenarios are not applicable to the hybrid case in general, and new precoding or combining solutions are needed
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