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The paper considers the issue of activating inactive terminals by control signaling in the downlink in a massive MIMO system. There are two basic difficulties with this. First, the lack of CSI at the transmitter. Second, the short coherence interval, which limits the number of orthogonal pilots in the case of many antennas. The proposed scheme deals with these issues by repeating the transmission...
Mobile data traffic is predicted to grow exponentially in the future. To address the challenge and consider the form factor limitation at the base station, 3D millimeter wave massive MIMO has been introduced as an enabling technology for 5G systems. In 3D millimeter wave massive MIMO systems, due to the large number of antennas and limited number of clusters, a base station will mainly rely on the...
We propose a novel channel estimation method for suppression of interference during uplink training in massive MIMO systems. The method makes use of the received uplink data to improve upon the estimation of solely training based estimators. It is based on the maximum a-posteriori criterion and outperforms state-of-the-art methods in terms of estimation accuracy and robustness. We further propose...
The Interfering Broadcast Channel (IBC) applies to the downlink of cellular and heterogenous networks, which are limited by multi-user (MU) interference. The interference alignment (IA) concept has shown that interference does not need to be inevitable. In particular spatial IA in MIMO IBC allows for low latency. However, IA requires perfect and typically global Channel State Information at the Transmitter(s)...
Massive multi-user multiple-input multiple-output (MU-MIMO) systems are cellular networks where the base stations (BSs) are equipped with hundreds of antennas, N, and communicate with tens of mobile stations (MSs), K, such that, N » K » 1. Contrary to most prior works, in this paper, we consider the uplink of a single-cell massive MIMO system operating in sparse channels with limited scattering. This...
We present a simple algorithm to compute the factors of a Unimodular-Upper (UU) polynomial matrix decomposition. The algorithm relies on the classical LU factorization and the inverse of the unimodular factor is also provided. Such decomposition is useful for spatial multiplexing in MIMO channel transmission system since it enables to reduce the MIMO channel matrix into independent SISO channels by...
The problem of joint zero-forcing (ZF) beamforming (BF) together with optimal power allocation (PA) and antenna selection (AS) for throughput maximization is considered in this paper for multi-user multiple input single output (MU-MISO) systems. We introduce a new formulation for the joint ZF and PA problem by adapting the algebraic subspace approach which finds a proper set for the optimization variable...
The multiple-input and multiple-output (MIMO) channel model is very useful for the presentation of a wide range of wireless communication systems. This paper addresses the joint design of a precoder and a receiver for a point-to-point MIMO channel model in a scenario in which perfect channel state information (CSI) is available at both ends. We develop a novel framework for the dual transmission-reception...
For MIMO systems with binary or QPSK signalling, soft demodulation techniques based on semidefinite relaxation (SDR) offer a desirable balance between performance and computational cost. In this paper we expand on an extension of that approach to systems with higher-order QAM signalling. In particular, we develop a customized dual-scaling algorithm to solve the semidefinite program that constitutes...
We consider the problem of two-dimensional (2D) transmit beamforming design for phased-MIMO Radar with a limited number of transmit power amplifiers. Subarray partitioning is used in MIMO radar where individual subarrays operate in a phased-array mode leading to a reduction in the number of power amplifiers required. However, the use of subarray partitioning results in poor transmit beampattern characteristics...
In this paper we develop an algorithm for computing the optimal transmission parameters, which include the transmission covariance, the time-shares and the user-orderings that minimize a particular class of objectives defined over the capacity region of Gaussian multiple antenna multiple access channels. This class includes objectives that are twice-differentiable, non-increasing and convex in the...
This work discusses efficient techniques for detection in large-dimension multi-user multiple-input multiple-output (MIMO) systems that are highly overdetermined. We exemplify the application of conjugate gradient methods in the setup of our interest and compare its performance with respect to methods based on the Neumann series expansion. We also bring to light some important insights on the performance...
In this paper, a simple user-scheduling-and-beamforming method is proposed for massive multi-user multiple-input multiple-output (MU-MIMO) downlink adopting two-stage beamforming. The key ideas of the proposed scheduling-and-beamforming method are to divide users into several candidate subsets according to the level of alignment of user channels to the dominant directions of the channel covariance...
We consider a cellular network in which the base stations (BSs) are supported by a large amount of very low-complexity relays that are spread over the entire area, like a carpet. This carpet of relays enables massive antenna arrays and sophisticated multi-user MIMO transmission at the BSs, as they see only the static relays as the nodes they communicate with. On the other hand, the communication via...
This paper compares two distinct downlink multicell interference mitigation techniques for wireless cellular networks: large-scale (LS) multiple-input multiple-output (MIMO) and network MIMO. The considered cellular network operates in a time-division duplex (TDD) fashion and includes non-overlapping cooperating clusters, where each cluster comprises B base-stations (BSs), each equipped with multiple...
In wireless networks, the availability of multiple transmitting antennas can be exploited in several ways. One way is to reduce the interference to unintended receivers by placing beamforming nulls in those directions, as is done in zero-forcing beamforming. Another is to boost the received signal strength at the desired receiver using “matched” transmit beamforming. This work studies a partial zero-forcing...
Through orders-of-magnitude larger bandwidths and small wavelengths that enable high-dimensional multiple-input multiple-output (MIMO) operation, millimeter-wave (mm-wave) systems operating from 30–300 GHz provide a unique opportunity for meeting the exploding capacity demands on wireless networks. Previously, the performance of multiuser MIMO (MU-MIMO) precoders that exploit the concept of beamspace...
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