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In this paper, we propose novel user clustering schemes for downlink non-orthogonal multiple access (NOMA) system, where an N-antenna base station (BS) selects and serves 2N users from K single antenna user equipments (UEs) (K ≥ 2N and K is even). In particular, we propose a signal difference and alignment (SDA) framework to achieve fair and spectral efficient user clustering for NOMA with flexible...
In this paper, we propose a pair of low-complexity user selection schemes with zero-forcing precoding for multiuser massive multiple-input–multiple-output downlink systems, in which the base station is equipped with a large-scale antenna array. First, we derive approximations of the ergodic sum rates of the systems invoking the conventional random user selection (RUS) and the location-dependent user...
This paper introduces a Massive MIMO system for 5G New Radio (NR). Compared with LTE, which is initially designed for a single wide beam per cell, the system in the paper is natively designed for multiple narrow beams to fully utilize the benefits of Massive MIMO. Beside Massive MIMO, other 5G features, such as wide bandwidth and low latency, introduce additional challenges to hardware implantations...
Non-orthogonal multiple access (NOMA) is a promising technique for the fifth generation mobile communication system due to its high spectral efficiency (SE). Previous works focus on user scheduling or/and power allocation to achieve the maximization of sum rate. However, the energy efficiency (EE) has not been well studied for NOMA systems. In this paper, we aim to optimize user scheduling and power...
Non-orthogonal multiple access (NOMA) has been investigated recently as a candidate radio access technology for the fifth generation (5G) mobile communication due to its high spectral efficiency (SE). Green radio (GR) which focuses on energy efficiency (EE) is becoming an inevitable trend. In this paper, we study the tradeoff between EE and SE in downlink NOMA systems. The tradeoff problem is formulated...
In this paper, we investigate secure simultaneous wireless information and power transfer (SWIPT) in a two-tier downlink heterogeneous network (HetNet), wherein the ambient interference signals are exploited for both secure communications and wireless energy harvesting. We assume one macrocell base station (MBS) and several femtocell base stations (FBSs) simultaneously send information to their macrocell...
In this paper, we introduce an improved relative channel reciprocity calibration method in TDD massive multiple-input multiple-output (MIMO) systems. The improved calibration method divide the massive MIMO system into one Single-Input Single-Output (SISO) system and two Single-Input Multiple-Output (SIMO) systems instead of calibrating the massive MIMO directly. We select the channel with high channel...
Abstract-- We propose a low-complexity user selection scheme with zero-forcing precoding in multiuser MIMO downlink systems, where the base station (BS) is equipped with large-scale antenna arrays and the number of candidate-users is relatively small. The BS obtains the channel state information (CSI) of the user equipments (UEs) through the pilot-based minimum mean-square error channel estimation...
We propose a low-complexity transmission strategy in multi-user multiple-input multiple-output downlink systems. The adaptive strategy adjusts the precoding methods, denoted as the transmission mode, to improve the system sum rates while maintaining the number of simultaneously served users. Three linear precoding transmission modes are discussed, i.e., the block diagonalization zero-forcing, the...
In this paper we propose a downlink codebook-based opportunistic interference alignment (OIA) in a three-cell MIMO system. A codebook composed of multiple transmit vector sets is utilized to improve the multiuser selection diversity. The sum rate increases as the size of the codebook grows. In addition, during the user selection, effective channel gain and alignment metric are combined to generate...
In this paper, we propose two new opportunistic interference alignment (IA) schemes to mitigate interference in the K-cell uplink interference channel. Unlike the existing schemes that basically rely on the channel randomness to achieve asymptotical IA for all cells, the proposed schemes employ an active alignment approach to increase the possibility for perfect partial IA for one cell within the...
By introducing the leakage concept, the maximum signal-to-leakage-and-noise ratio (SLNR) scheme has been served as a candidate precoding scheme in the advanced long term evolution (LTE-Advanced) communication system. However, the original scheme allocates every user the same transmit power and takes the matched filter to decode the receive signals, which results in the limited bit error rate (BER)...
In this paper, we proposed an effective and unified transmit power allocation (TPA) scheme for the Singular Value Decomposition (SVD)-Assisted multi-user multiple-input multiple-output (MU-MIMO) downlink (DL) and uplink (UL) transmissions in the presence of imperfect channel state information (ICSI). The existing power allocation policies for the SVD-Assisted MU-MIMO system, such as equal power allocation...
In this paper, we investigate the Singular Value Decomposition (SVD)-Assisted multi-user multiple-input multiple-output (MU-MIMO) downlink transmission in the presence of imperfect channel state information (ICSI), and propose an effective transmit power allocation (TPA) scheme. The original equal power allocation (EPA) has been adopted in perfect CSI case. However, EPA doesn't exploit the CSI and...
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