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Capacity-coverage tradeoff balancing is a classical but critical problem for practical wireless multi- cell network optimization. Increasing the average capacity is often at the expense of decreasing the cell coverage and vice versa. It becomes more complex in massive multiple-input/multiple-output (MIMO) networks to balance the above two performance indicators since capacity is much highly improved...
By calculating the effective max-min SINR (signal- to-interference-plus-noise ratio) and the corresponding power controls explicitly, and selectively dropping a small number of mobiles based on a simple and effective algorithm, we demonstrate that for both downlink and uplink, employing maximum-ratio or zero-forcing linear pre-coding and de-coding, Massive MIMO with max- min power control performs...
In this paper, we analyze the performance of the fractional pilot reuse (FPR) scheme with pilot contamination mitigation in massive multiple-input multiple-output (MIMO) system. In FPR, users are classified into the cell- center and the cell-edge ones according to their signal-to- interference-plus-noise ratios (SINRs) at the receiver side. Then, the cell- edge users with low SINRs in different cells...
This paper proposes a novel uplink power control scheme in a single cell for massive MIMO (Multiple-Input-Multiple-Output). The proposed algorithm exploits the spatial degrees of freedom provided by massive MIMO to achieve the highest signal to interference-plus-noise ratio (SINR) for each user by considering the mutual spatial correlation arising from other users. It also minimizes the required uplink...
In distributed massive multi-input multi-output (DM-MIMO) system, the number of users simultaneously served is greatly restricted if the pilots allocated for users are orthogonal. In this paper, a dynamic pilot reuse strategy within a single cell DM-MIMO system is proposed in order to reduce pilot overhead. The reuse in this strategy is applied so that maximum average sum-rate is satisfied within...
Massive Multiple-input Multiple-output (MIMO) adaption is one of the primary evolving objectives for the next generation high speed train (HST) communication system. In this paper, we consider how to design an efficient low-complexity location-aware beamforming for the multi-user (MU) massive MIMO system in HST scenario. We first put forward a lowcomplexity beamforming based on location information,...
A massive multiple-input, multiple-output (mMIMO) downlink is considered with fixed wideband beams known as Grid of Beams (GoBs). The radio channel of a typical urban macro scenario will be shown to be sparse, and in combination with a linear maximum ratio combining beamforming method is used at the user equipment. Simulation results for urban macro cells show that reasonable spectral efficiencies...
This paper describes our activities related to massive multiple-input multiple-output (MIMO) for use in 5G mobile communication networks. To achieve capacity enhancement and low power consumption for 5G wireless access systems, massive MIMO has drawn attention as one of the key technologies. Our research focuses on the utilization of massive MIMO in the low super-high-frequency (SHF) band, which is...
This work deals with beamforming for the MIMO Interfering Broadcast Channel (IBC), i.e. the Multi-Input MultiOutput (MIMO) Multi-User Multi-Cell downlink (DL). The novel beamformers are here optimized for the Expected Weighted Sum Rate (EWSR) for the case of Partial Channel State Information at the Transmitters (CSIT). Gaussian (Posterior) partial CSIT can optimally combine channel estimate and channel...
The degrees-of-freedom (DoF) of the multi-antenna three-way channel (3WC) with an intermittent node is studied. Special attention is given to the impact of adaptation when the intermittent node has the largest number of antennas. A non-adaptive transmission scheme based on interference alignment, zero-forcing, and erasure-channel treatment is proposed, and its corresponding DoF region is derived....
This paper presents an application-specific instruction-set processor (ASIP) for multiuser multiple-input multiple-output (MU-MIMO) broadcast precoding. The ASIP is designed for a base station (BS) with four antennas to perform user scheduling and precoding. Transport triggered architecture (TTA) is used as the processor template and high level language is used to program the ASIP. Several special...
Traffic aware precoder/decoder design in multi-cell multi-user multiple-input multiple-output systems is considered with the objective of weighted queue minimization, where the original non-convex optimization problem is solved via successive convex approximation. Centralized pilot reuse algorithms for mitigating the pilot contamination are investigated to reflect the traffic aware optimization objective...
In this paper, we investigate the problem of pilot optimization, resource allocation, and user association in a massive MIMO heterogeneous network (HetNet) with wireless backhaul (WB) and linear processing. The objective is to maximize the sum downlink rate of all users, subject to constraints on data rate of WB and fairness-aware constraints. Such a problem is formulated as an integer programming...
Despite the promising benefits of the cloud-radio access network (C-RAN), the fronthaul (FH) imposes stringent requirements in terms of data rate, latency, jitter and synchronisation. In the classical C-RAN, the FH capacity scales linearly with the number of the transmitting antennas, which has posed severe demands on the FH capacity, especially due to emerging 5G technologies such as massive MIMO...
With the progress of wireless communication technology, networks become more and more interference limited. One core aspect for guaranteeing required signal qualities in interference limited networks is power control. A simple, yet powerful power control algorithm (PCA) is Yates' iterative standard PCA, which is well known and can be applied to various physical layer technologies. However, for some...
Pilot contamination limits the potential benefits of massive multiple input multiple output (MIMO) systems. To mitigate pilot contamination, in this paper, an efficient channel estimation approach is proposed for massive MIMO systems, using sparse Bayesian learning (SBL) namely coupled hierarchical Gaussian framework where the sparsity of each coefficient is controlled by its own hyperparameter and...
Nonlinear power amplifiers distort the transmitted signal and out-of-band (OOB) radiation becomes a source of interference for users operating in adjacent channels. This paper studies the effect of Massive Multiple Input Multiple Output (MIMO) system on the OOB interference. Massive MIMO relies on channel based precoding which ensures the signal is added constructively at the receiver user equipment...
Wi-Fi is the dominant wireless indoor broadband solution and thus key for meeting the exponential traffic growth. The recent IEEE 802.11ac amendment enables PHY data rates exceeding 1 Gbps. However, it is not clear how this increased per-link performance, achieved especially via wider channels, translates to network-level performance. The latter is crucial for understanding the true potential of emerging...
Multi-User Multiple Input Multiple Output (MU-MIMO) enables a multi-antenna access point (AP) to serve multiple users simultaneously, and has been adopted as the IEEE 802.11ac standard. While several PHY-MAC designs have recently been proposed to improve the throughput performance of a MU-MIMO WLAN, they, however, usually assume that all the concurrent streams are of roughly equal length. In reality,...
Large-scale MU-MIMO is a promising technology to scale network capacity and the capacity gain grows linearly with the numbers of antennas and users in theory. However, its practical deployment faces three critical challenges in the state-of-the-art WLANs: i) the demand of a large number of expensive RF chains; ii) the linear growth of feedback overheads with the number of antennas; iii) the lack of...
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