In a multi-user wideband millimeter wave (mmWave) communication system, the existing works optimize the hybrid precoder by assuming a priori subcarrier allocation. However, the beam squint effect in mmWave affects the...
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In a multi-user wideband millimeter wave (mmWave) communication system, the existing works optimize the hybrid precoder by assuming a priori subcarrier allocation. However, the beam squint effect in mmWave affects the gain over the subcarriers differently for different beam steer directions. Thus, the design of radio frequency (rf) precoder and subcarrier allocation are intertwined. Based on this observation, in this letter we propose a sub-array hybrid precoder design wherein we jointly estimate the rf precoder and subcarrier allocation and then design the baseband precoder. Our numerical results demonstrate the benefits of the proposed strategy compared to the existing approach wherein subcarrier allocation precedes the rf and baseband precoder design.
One of the approaches to support high data rates in beyond 5G cellular networks is the dense deployment of the small cell millimeter-wave (frequency range 2 (FR2)) (>24.5 GHz) base stations. However, this dense dep...
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One of the approaches to support high data rates in beyond 5G cellular networks is the dense deployment of the small cell millimeter-wave (frequency range 2 (FR2)) (>24.5 GHz) base stations. However, this dense deployment of base stations leads to high cost, because it requires fiber backhaul connection with the core network. One prominent solution is the integrated access and backhaul (IAB) network proposed in 3GPP Release 16, where some portion of wireless spectrum is used for backhaul to serve base stations instead of fiber, and the remaining portion of the spectrum is used for user equipment for communication. The partition of the spectrum into access and backhaul degrades the spectral efficiency of the IAB network. Thus, in this paper, we propose a full duplex (FD) enabled IAB network with large-scale array systems to enhance the spectral efficiency of the IAB network. In the FD IAB network, the IAB node is FD which transmits and receives at the same frequency/time resources. We consider a multi-cell multi-user IAB network with all the interferences due to FD transmission and evaluate the performance in terms of bit-error-rate and spectral efficiency. Moreover, an algorithm for choosing different users is proposed which is based on the cross-correlation of rf precoder weights. Further, identification of the optimal beam's index is also proposed which is based on the index of synchronization signal block and half-frame bit of physical broadcast channel payload of 5G NR. Finally, successive interference cancellation is proposed for self-interference mitigation in the digital domain.
Millimetre wave (mmWave) signal is promising for the challenge of bandwidth shortage and can motivate the research on large-scale antenna arrays. In this paper, the authors investigate the hybrid precoding design that...
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Millimetre wave (mmWave) signal is promising for the challenge of bandwidth shortage and can motivate the research on large-scale antenna arrays. In this paper, the authors investigate the hybrid precoding design that combines with a radio frequency (rf) precoder and a digital precoder for multi-user multiple-input single-output (MU-MISO) systems with large-scale antenna arrays. In practical large-scale antenna array systems, the small antenna spacing and the properties of a scattering environment can create a correlation between channel coefficients for separated receive units. Such correlation prejudices the performance of multi-user systems. This study proposes two approaches to reduce the channel correlation by the hybrid precoding structure. The first approach selects some vectors with the smallest influence with each other from all array response vectors to design an angular-based rf precoder. The second approach optimises the singular values characteristic of the virtual channel matrix before digital processing for the rf precoder. Then, the MU-MISO baseband precoding is implemented by reduced rf chains. Numerical results show that they have different performance depending on the environment. The first can achieve better performance when the channel correlation is not too high, while the second is more effective when the channel realisation is terribly ill-conditioned, especially for higher signal-noise ratio (SNR).
To achieve a far higher capacity in massive multi-input multi-output, the hybrid analog and digital precoding has been studied recently. In this paper, we consider the downlink single user communication system and pro...
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To achieve a far higher capacity in massive multi-input multi-output, the hybrid analog and digital precoding has been studied recently. In this paper, we consider the downlink single user communication system and propose an efficient matrix adaptive gradient descent algorithm to design the radio frequency precoder and combiner, and use the singular value decomposition method to obtain the digital precoder and combiner. Simulation results show that the proposed method can approach the performance of the conventional full digital precoding with a fast convergence rate.
The potential of millimetre wave frequencies band has motivated the study of large-scale antenna arrays to improve the spectrum efficiency of massive multiple-input multiple-output wireless communications systems. How...
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The potential of millimetre wave frequencies band has motivated the study of large-scale antenna arrays to improve the spectrum efficiency of massive multiple-input multiple-output wireless communications systems. However, conventional fully digital precoding schemes, which require one radio frequency (rf) chain for each antenna, are cost prohibitive and have high-power consumption. To address these hardware limitations, this study considers a hybrid precoding scheme that provides high performance in terms of spectrum efficiency. By deducing the derivative of the spectrum efficiency function with respect to the phase matrix variable of the rf precoder, an efficient rf precoding scheme based on the normalised matrix adaptive method (NMAM) is proposed. Numerical simulations show that the NMAM achieves excellent performance approaching that of fully digital precoding, with relatively low computational complexity.
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