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In this paper, we study spatial half-duplex, where an antenna array is partitioned such that a subset of antennas is used for transmission, and others for reception in the same time and frequency. We use transmit-precoders to partition the antennas and design optimal precoders under two approaches. In one approach, precoder minimizes self-interference, for fixed downlink-rate. In another approach,...
We characterize upper bounds on the throughput capacity of a multi-tier millimeter wave (mmWave) network with diverse blockage probability, p(n), scaling scenarios. Communication links in the network are divided into three communication tiers sharing a single mmWave frequency. The bottom tier considers transmissions between n terminals and M (n) access points (APs). The top tier includes links between...
Massive MIMO-systems have received considerable attention in recent years as an enabler in future wireless communication systems. As the idea is based on having a large number of antennas at the base station it is important to have both a scalable and distributed realization of such a system to ease deployment. Most work so far have focused on the theoretical aspects although a few demonstrators have...
We study a three-node network with a full-duplex base-station communicating with one uplink and one downlink half-duplex node. In this network, both self-interference and inter-node interference are present. We use an antenna-theory-based channel model to study the spatial degrees of freedom of such network, and study if and how much does spatial isolation outperforms time-division (i.e. half-duplex)...
This work investigates the impact of imperfect statistical information in the uplink of massive MIMO systems. In particular, we first show why covariance information is needed and then propose two schemes for covariance matrix estimation. A lower bound on the spectral efficiency (SE) of any combining scheme is derived, under imperfect covariance knowledge, and a closed-form expression is computed...
We study an uplink multi secondary user (SU) cognitive radio system suffering statistical heterogeneity among SUs' channels. This heterogeneity may result in differentiated delay performances to these SUs and result in harmful interference to the PU. We first derive an explicit closed-form expression for the average delay in terms of an arbitrary power-control policy. Then, we propose a delay-optimal...
One of the basic aspects of Massive MIMO (MaMi) that is in the focus of current investigations is its potential of using low-cost and energy-efficient hardware. It is often claimed that MaMi will allow for using analog-to-digital converters (ADCs) with very low resolutions and that this will result in overall improvement of energy efficiency. In this contribution, we perform a parametric energy efficiency...
Conventional centralized data detection algorithms for massive multi-user multiple-input multiple-output (MU-MIMO) systems, such as minimum mean square error (MMSE) equalization, result in excessively high raw baseband data rates and computing complexity at the centralized processing unit. Hence, practical base-station (BS) designs for massive MU-MIMO that rely on state-of-the-art hardware processors...
In this work we design the precoders/combiners for a multiuser mmWave system considering a frequency selective channel model. We assume that the available channel information is imperfect, and only the estimates of the autocorrelation of the received signal, and the cross-correlation with the transmitted signal are available. Using this knowledge, the precoder and combiners are designed via an iterative...
In this paper, a downlink path-based precoding method for multiuser FDD massive MIMO systems is studied. Due to the huge feedback overhead of acquiring channel state information at the transmitter (CSI-T), FDD massive MIMO was usually considered impractical. In order to enhance the feasibility of such systems, a recent work proposed a precoding method without requiring CSI feedback by taking advantage...
Cell-Free Massive MIMO comprises a large number of distributed single-antenna access points (APs) serving a much smaller number of users. There is no partitioning into cells and each user is served by all APs. In this paper, the uplink performance of cell-free systems with minimum mean squared error (MMSE) and large scale fading decoding (LSFD) receivers is investigated. The main idea of LSFD receiver...
We consider a case where K closely located users communicate with a base station in the uplink of a wireless communication system. Each user has a certain number of assigned time-frequency slots at its disposal. At a small cost, which we in this paper consider as negliable, the users can communicate with each other and share their data. Thus, they can cooperate in the uplink in order to save transmit...
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