Shahid Bashir¹, Imran Khan², Fahd N. Al-Wesabi³, Nadhem Nemri³, Ammar Zahary⁴, Quang Ngoc Nguyen^5,*

CMC-Computers, Materials & Continua, Vol.68, No.3, pp. 3029-3044, 2021, DOI:10.32604/cmc.2021.017015

Abstract The device-to-device (D2D) networking technology is extended to the conventional cellular network to boost the communication efficiency of the entire network, forming a heterogeneous 5G and beyond (B5G) communication network. D2D communication in a cellular cell will boost the efficiency of the spectrum, increase the ability of the device, and reduce the communication burden of base stations through the sharing of approved cell resources, causing serious interference as well. The device-to-device (D2D) networking technology is extended to the conventional cellular network to boost the communication efficiency of the entire network, forming a heterogeneous 5G communication network. D2D communication in a… More >

Latif Jan¹, Mohammad Haseeb Zafar¹, Abdul Waheed², Mahdi Zareei³, Faisal Alanazi^4,*

CMC-Computers, Materials & Continua, Vol.68, No.3, pp. 3133-3145, 2021, DOI:10.32604/cmc.2021.014857

Abstract Spatial diversity plays a significant role in wireless communication systems, including the Fourth Generation (4G) and Fifth Generation (5G) systems, and it is expected to be a fundamental part of the future wireless communication systems as well. The Multiple-Input Multiple-Output (MIMO) technology, which is included in the IEEE 802.16j standard, still holds the most crucial position in the 4G spectrum as it promises to improve the throughput, capacity, spectral, and energy efficiency of wireless communication systems in the 2020s. This makes MIMO a viable technology for delay constrained medical and health care facilities. This paper presents an approximate closed-form expression… More >

Seulgi Lee¹, Ji-Sung Jung¹, Young-Hwan You², Hyoung-Kyu Song^1,*

CMC-Computers, Materials & Continua, Vol.68, No.2, pp. 2205-2219, 2021, DOI:10.32604/cmc.2021.017008

Abstract This paper proposes an improved hybrid beamforming system based on multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system. The proposed beamforming system improves energy efficiency compared to the conventional hybrid beamforming system. Both sub-connected and full-connected structure are considered to apply the proposed algorithm. In the conventional hybrid beamforming, the usage of radio frequency (RF) chains and phase shifter (PS) gives high power and hardware complexity. In this paper, the phase over sampling (POS) with switches (SW) is used in hybrid beamforming system to improve the energy efficiency. The POS-SW structure samples the value of analog beamformer to make lower… More >

Park Chan-Yeob, Hyun-Ro Jae, Jun-Yong Jang, Song Hyoung-Kyu^*

CMC-Computers, Materials & Continua, Vol.68, No.1, pp. 137-148, 2021, DOI:10.32604/cmc.2021.016108

Abstract Linear precoding methods such as zero-forcing (ZF) are near optimal for downlink massive multi-user multiple input multiple output (MIMO) systems due to their asymptotic channel property. However, as the number of users increases, the computational complexity of obtaining the inverse matrix of the gram matrix increases. For solving the computational complexity problem, this paper proposes an improved Jacobi (JC)-based precoder to improve error performance of the conventional JC in the downlink massive MIMO systems. The conventional JC was studied for solving the high computational complexity of the ZF algorithm and was able to achieve parallel implementation. However, the conventional JC… More >

Ji-Sung Jung¹, Won-Seok Lee¹, Yeong-Rong Lee¹, Jaeho Kim², Hyoung-Kyu Song^1,*

CMC-Computers, Materials & Continua, Vol.67, No.3, pp. 3057-3070, 2021, DOI:10.32604/cmc.2021.015673

Abstract Massive multiple input multiple output (MIMO) has become essential for the increase of capacity as the millimeter-wave (mmWave) communication is considered. Also, hybrid beamforming systems have been studied since full-digital beamforming is impractical due to high cost and power consumption of the radio frequency (RF) chains. This paper proposes a hybrid beamforming scheme to improve the spectral efficiency for multi-user MIMO (MU-MIMO) systems. In a frequency selective fading environment, hybrid beamforming schemes suffer from performance degradation since the analog precoder performs the same precoding for all subcarriers. To mitigate performance degradation, this paper uses the average channel covariance matrix for… More >

Adeeb Salh¹, Lukman Audah^1,*, Qazwan Abdullah¹, Nor Shahida M. Shah², Shipun A. Hamzah¹, Shahilah Nordin³, Nabil Farah²

CMC-Computers, Materials & Continua, Vol.67, No.3, pp. 3189-3214, 2021, DOI:10.32604/cmc.2021.014746

Abstract Energy efficiency (EE) is a critical design when taking into account circuit power consumption (CPC) in fifth-generation cellular networks. These problems arise because of the increasing number of antennas in massive multiple-input multiple-output (MIMO) systems, attributable to inter-cell interference for channel state information. Apart from that, a higher number of radio frequency (RF) chains at the base station and active users consume more power due to the processing activities in digital-to-analogue converters and power amplifiers. Therefore, antenna selection, user selection, optimal transmission power, and pilot reuse power are important aspects in improving energy efficiency in massive MIMO systems. This work… More >

Jun-Yong Jang¹, Won-Seok Lee¹, Jae-Hyun Ro¹, Young-Hawn You², Hyoung-Kyu Song^1,*

CMC-Computers, Materials & Continua, Vol.67, No.2, pp. 1729-1745, 2021, DOI:10.32604/cmc.2021.015424

Abstract In this paper, a novel precoding scheme based on the Gauss-Seidel (GS) method is proposed for downlink massive multiple-input multiple-output (MIMO) systems. The GS method iteratively approximates the matrix inversion and reduces the overall complexity of the precoding process. In addition, the GS method shows a fast convergence rate to the Zero-forcing (ZF) method that requires an exact invertible matrix. However, to satisfy demanded error performance and converge to the error performance of the ZF method in the practical condition such as spatially correlated channels, more iterations are necessary for the GS method and increase the overall complexity. For efficient… More >

Shahid Bashir¹, Mohammed H. Alsharif², Imran Khan³, Mahmoud A. Albreem⁴, Aduwati Sali⁵, Borhanuddin Mohd Ali⁵, Wonjong Noh^6,*

CMC-Computers, Materials & Continua, Vol.66, No.1, pp. 263-274, 2021, DOI:10.32604/cmc.2020.012404

Abstract With the development of wireless mobile communication technology, the demand for wireless communication rate and frequency increases year by year. Existing wireless mobile communication frequency tends to be saturated, which demands for new solutions. Terahertz (THz) communication has great potential for the future mobile communications (Beyond 5G), and is also an important technique for the high data rate transmission in spatial information network. THz communication has great application prospects in military-civilian integration and coordinated development. In China, important breakthroughs have been achieved for the key techniques of THz high data rate communications, which is practically keeping up with the most… More >

Sangmi Moon¹, Hyeonsung Kim¹, Seng-Phil Hong², Mingoo Kang³, Intae Hwang^1,*

CMC-Computers, Materials & Continua, Vol.66, No.1, pp. 59-70, 2021, DOI:10.32604/cmc.2020.013132

Abstract Millimeter-wave communications are suitable for application to massive multiple-input multiple-output systems in order to satisfy the ever-growing data traffic demands of the next-generation wireless communication. However, their practical deployment is hindered by the high cost of complex hardware, such as radio frequency (RF) chains. To this end, operation in the beamspace domain, through beam selection, is a viable solution. Generally, the conventional beam selection schemes focus on the feedback and exhaustive search techniques. In addition, since the same beam in the beamspace may be assigned to a different user, conventional beam selection schemes suffer serious multi-user interference. In addition, some… More >