With the emergence of sixth-generation (6G) wireless services, low Earth orbit (LEO) satellite communications are increasingly recognized as a promising solution for providing extensive wireless coverage to terrestria...
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With the emergence of sixth-generation (6G) wireless services, low Earth orbit (LEO) satellite communications are increasingly recognized as a promising solution for providing extensive wireless coverage to terrestrial users. Subarray-based hybrid beamforming offers an efficient implementation method in millimeter wave (mmWave) communications;however, current approaches that use either non-overlapping or fully overlapping spectrum for subarrays may result in inefficient spectrum usage or severe inter-beam interference. In this paper, we investigate digital precoders for two partially spectral overlapping subarrays of LEO satellites using hybrid beamforming to enhance spectrum utilization while mitigating inter-beam interference. We propose and analyze an interference model for partially spectral overlapping subarrays, which theoretically characterizes the inter-beam interference effect resulting from partial spectrum overlapping in hybrid beamforming. Utilizing an approximated interference model to simplify the analysis, we derive a closed-form expression for a minimum mean square error (MMSE)-based digital precoder, constrained by total transmit power. Extensive computer simulations demonstrate the effectiveness of the proposed MMSE digital precoder in improving the bit error rate (BER), signal-to-interference-plus-noise ratio (SINR), sum rate, and spectrum utilization.
This work aims to provide an effective hybrid beam forming method with Dual-Deep-Network to overcome overhead for mm-wave massive MIMO systems. In this paper, a Dual-Deep-Network technique is described for the extract...
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This work aims to provide an effective hybrid beam forming method with Dual-Deep-Network to overcome overhead for mm-wave massive MIMO systems. In this paper, a Dual-Deep-Network technique is described for the extraction of statistical structures from a hybrid beam forming model based on mmWave logics, as well as training logic for the network map functions. The proposed approach of DDN is trained with proper data sequences used for communication and the training phase is conducted with the norms of numerous channel variants. With the nature of diverse channel states, a Dual-Deep-Network is required to manipulate the level of presence and abilities even after training as well. The performance level improvements are practically summarized in both the transmission and reception entities with the help of the proposed hybrid network architecture and the associated Dual Deep Network algorithm. Specifically, the BER versus SNR and spectral efficiency versus SNR are evaluated as well as the resulting accuracy levels are cross validated with numerous classical communication techniques. This paper shows the processing difficulties of the proposed approach and typically cross-validates with other beam forming logics. The computational cost and performance estimations are improved, and the metrics are clearly visualized on this paper based on improved beamforming procedures as well as the proposed approach of DDN based Multi-Resolution Code Book performance metrics are estimated clearly with proper mathematical model investigations. With 7Kbits/s/Hz and 1e-1, respectively, the key metrics of spectral efficiency and BER are enhanced.
Fully digital precoding has superior performance for millimeter wave (mmWave) multiple input and multiple output (MIMO) system. In fully digital precoding, each antenna is connected to one RF chain which results in hi...
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ISBN:
(纸本)9781665427722
Fully digital precoding has superior performance for millimeter wave (mmWave) multiple input and multiple output (MIMO) system. In fully digital precoding, each antenna is connected to one RF chain which results in high hardware complexity and high cost. Non-orthogonal multiple access (NOMA) is one of the promising techniques in future mobile communication. In this paper, we propose a fully digital mmWave massive MIMO system with a reduced hardware complexity and reduced energy consumption. The proposed system reduces the number of antennas and consequently the number of RF chains by applying a three stages antenna reduction algorithm. Moreover, a clustering algorithm is proposed in which users within same group are highly correlated, and users in different groups have low correlation with each other. The performance of the proposed system is evaluated in terms of energy efficiency and spectral efficiency. Numerical results show that the proposed system has superior performance in terms of energy efficiency at the expense of slight decrease in spectral efficiency.
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).
Hybrid precoding, combining the digital and analogue precoding, is a key enabler to reach a compromise between system performance and hardware complexity in millimetre wave (mmWave) massive multiple-input multiple-out...
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Hybrid precoding, combining the digital and analogue precoding, is a key enabler to reach a compromise between system performance and hardware complexity in millimetre wave (mmWave) massive multiple-input multiple-output (MIMO) systems. Most previous studies on hybrid precoding considered narrowband channels. However, mmWave systems are expected to operate on wideband channels with frequency selectivity. In this study, the authors focus on the hybrid precoding design in mmWave massive MIMO systems using orthogonal frequency division multiplexing (OFDM). By transforming the hybrid precoding problem into a series of sub-problems, they propose a low-complexity algorithm to design the digital precoder and analogue precoder alternately. In particular, a phase pursuit method is introduced to seek this solution of analogue precoding matrix with the constant amplitude constraint. Simulation results and complexity evaluations reveal that the proposed algorithm can obtain better performance and lower complexity than some existing solutions in mmWave OFDM systems.
Millimetre wave (mmWave) communication is a promising technique for fifth generation networks. Hybrid precoding is introduced to mmWave communication systems to provide a reasonable trade-off strategy between system p...
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Millimetre wave (mmWave) communication is a promising technique for fifth generation networks. Hybrid precoding is introduced to mmWave communication systems to provide a reasonable trade-off strategy between system performance and energy cost. The hybrid precoder with the partially-connected structure has relatively low hardware complexity and less energy consumption. In this study, the authors decompose the optimisation problem of analogue precoder into several subproblems, and introduce a heuristic method to find the solution. Then, they obtain the digital precoder according to the product of the channel matrix and analogue precoding matrix. Numerical simulations show that the proposed algorithm performs well in most cases. Considering the error of channel estimation or the finite resolution of phase shifters, the proposed algorithm is able to provide acceptable spectral efficiency as well.
Millimetre wave (mmWave) multiple-input multiple-output (MIMO) systems have been proposed to enable Gbps communication for next-generation cellular systems and local area networks. To compensate for the severe propaga...
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Millimetre wave (mmWave) multiple-input multiple-output (MIMO) systems have been proposed to enable Gbps communication for next-generation cellular systems and local area networks. To compensate for the severe propagation loss of the mmWave channel, a cost-effective hybrid precoding architecture, combining a digital precoder and an analogue precoder, is widely used in mmWave MIMO systems. In this study, two hybrid precoding algorithms based on particle swarm optimisation (PSO) algorithm will be proposed for two different hybrid precoding structures, i.e. the fully connected and partially connected structures. First, the authors use the phase of the analogue precoding variable to replace the corresponding variable with the constraints of the unit norm to solve the non-convex constraints skillfully. Then they design analogue precoding by using PSO algorithm and compute the digital precoding based on the least squares solution. Finally, the proposed algorithms are compared with the existing advanced algorithms. Simulation results demonstrate that the proposed algorithms can approach the optimal performance under the corresponding structure.
In this study, the authors consider multi-user millimetre wave (mmWave) multiple-input multiple-output (MIMO) downlink communications for multi-carrier scenarios, e.g. orthogonal frequency-division multiplexing (OFDM)...
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In this study, the authors consider multi-user millimetre wave (mmWave) multiple-input multiple-output (MIMO) downlink communications for multi-carrier scenarios, e.g. orthogonal frequency-division multiplexing (OFDM) a common analogue precoder and combiner for the transmitter and receiver to maximise spectral efficiency is the main challenge for multi-carrier MIMO systems, they propose two methods to solve this problem. The first method designs the analogue precoder and combiner based on the channel average of all subcarriers, which helps reduce computational complexity. Moreover, the channels of all subcarriers can be viewed as a third-order tensor, and the second method is based on tensor unfolding, which makes full use of the channel information of all subcarriers. When the common analogue precoder and combiner are fixed, they consider designing a digital precoder to maximise the signal-to-leakage-plus-noise ratio of each user in every subcarrier, which leads to closed-form solutions compared with the block diagonal method. Simulation results demonstrate that the performance of the proposed methods is close to that of the fully digital precoding method, and increasing the number of RF transceiver chains helps improve the performance of the proposed methods.
Millimeter wave MIMO systems provide orders of magnitude in data rates due to larger bandwidth than conventional MIMO systems. On the other hand, they experience severe free-space pathloss as carrier frequency ten-fol...
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ISBN:
(纸本)9781538663585
Millimeter wave MIMO systems provide orders of magnitude in data rates due to larger bandwidth than conventional MIMO systems. On the other hand, they experience severe free-space pathloss as carrier frequency ten-fold increases. The resulting small wavelength helps to overcome pathloss with beamforming gain using massive antennas, known as precoding. In mmWave MIMO system, hybrid beamforming combines analog beamforming with digital precoding to reduce the energy consumption and complexity. Hybrid beamforming uses a smaller number of RF chains, which have large power consumption, than the number of antennas. In order to design analog and digital precoder, a large number of calculations such as the SVD of channel is required. In this paper, we propose low complexity hybrid precoding algorithm using beam steering, which utilizes array response vectors of the channel. We first propose the method of selection the analog beamforming matrix without any SVD or inversion of matrices. Then, we find the digital precoding matrix which performs a maximum of the total sum rate with fixed analog beamforming matrix. Since our proposed algorithm applies a set of array response vectors that are used to form the channel, there is no need for complicated operations as SVD like traditional precoding algorithms. Simulation results show that proposed algorithm can reduce the computational complexity while achieving about 93% the same performance in achievable rate compared to typical hybrid precoding in mmWave MIMO systems.
Millimeter wave MIMO systems provide orders of magnitude in data rates due to larger bandwidth than conventional MIMO systems. On the other hand, they experience severe free-space pathloss as carrier frequency ten-fol...
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ISBN:
(纸本)9781538663592;9781538663585
Millimeter wave MIMO systems provide orders of magnitude in data rates due to larger bandwidth than conventional MIMO systems. On the other hand, they experience severe free-space pathloss as carrier frequency ten-fold increases. The resulting small wavelength helps to overcome pathloss with beamforming gain using massive antennas, known as precoding. In mmWave MIMO system, hybrid beamforming combines analog beamforming with digital precoding to reduce the energy consumption and complexity. Hybrid beamforming uses a smaller number of RF chains, which have large power consumption, than the number of antennas. In order to design analog and digital precoder, a large number of calculations such as the SVD of channel is required. In this paper, we propose low complexity hybrid precoding algorithm using beam steering, which utilizes array response vectors of the channel. We first propose the method of selection the analog beamforming matrix without any SVD or inversion of matrices. Then, we find the digital precoding matrix which performs a maximum of the total sum rate with fixed analog beamforming matrix. Since our proposed algorithm applies a set of array response vectors that are used to form the channel, there is no need for complicated operations as SVD like traditional precoding algorithms. Simulation results show that proposed algorithm can reduce the computational complexity while achieving about 93% the same performance in achievable rate compared to typical hybrid precoding in mmWave MIMO systems.
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