Multi-user MIMO

About: Multi-user MIMO is a research topic. Over the lifetime, 10265 publications have been published within this topic receiving 227206 citations. The topic is also known as: multi user mimo & MU-MIMO.

Massive MIMO with optimal power and training duration allocation

Abstract: We consider the uplink of multicell multiple-input-multiple-output systems, where the base stations (BSs), which are equipped with massive arrays, simultaneously serve several terminals in the same frequency band. We assume that the BS estimates the channel from uplink training and then uses the maximum ratio combining technique to detect the signals transmitted from all terminals in its own cell. We propose an optimal resource allocation scheme that jointly selects the training duration, the training signal power, and the data signal power in order to maximize the sum spectral efficiency for a given total energy budget spent in a coherence interval. Numerical results verify the benefits of the optimal resource allocation scheme. Furthermore, we show that more training signal power should be used at low signal-to-noise ratios (SNRs) and vice versa at high SNRs. Interestingly, for the entire SNR regime, the optimal training duration is equal to the number of terminals.

MIMO communications based on molecular diffusion

Abstract: Diffusion-based communication refers to the transfer of information using molecules as message carriers whose propagation is based on the law of molecular diffusion. Path loss can have a major impact on the link quality in molecular communication as the signal strength is shown inversely proportional to the cube of the communication distance. In this paper, various diversity techniques for Multi-Input Multi-Output (MIMO) transmissions based on molecular diffusion are proposed to improve the communication performance in nanonetworks in the presence of Multi-User Interference (MUI). Analogous to radio communication, the concept of diversity and Spatial Multiplexing (SM) can be successfully applied in molecular communication. To the best of our knowledge, our paper is the first which investigates the aspects of MIMO transmissions for molecular communication. Numerical results show that the proposed diversity techniques can successfully lower the error rate. Further performance improvement can be obtained by properly allocating molecules among the transmission nodes if the Channel State Information (CSI) is available at the transmitter end. To optimize the system throughput, a dynamic switching mechanism between the diversity mode and the Spatial Multiplexing (SM) mode can be employed.

Constant-Envelope Multi-User Precoding for Frequency-Selective Massive MIMO Systems

Abstract: We consider downlink precoding in a frequency-selective multi-user Massive MIMO system with highly efficient but non-linear power amplifiers at the base station (BS). A low-complexity precoding algorithm is proposed, which generates constant-envelope (CE) signals at each BS antenna. To achieve a desired per-user information rate, the extra total transmit power required under the per-antenna CE constraint when compared to the commonly used less stringent total average transmit power constraint, is small.

Two-way (true full-duplex) wireless

Abstract: Current wireless systems are one-way (similar to walkie-talkies), meaning that disjoint time or frequency segments are used to transmit and to receive. Realization of two-way wireless has challenged the research community for many years. This article1 establishes the theory and presents practical realization of two-way (true full-duplex) wireless. In contrast to the widely accepted beliefs, it is shown that two-way wireless is not only feasible, but is fairly simple, with virtually no degradation in signal-to-noise-ratio2. The innovation is in the antenna design and multiple levels for cancelling self-interference. Methods are developed to support Multiple-Input Multiple-Output (MIMO) two-way transmission, and asynchronous two-way links (useful in networking applications). The developed hardware uses off-the-shelf components, antennas have a simple structure, are omnidirectional (can be directional, if needed), do not suffer from bandwidth limitations, have a small size/spacing, and the increase in overall complexity is minimal. It is shown that two-way wireless can do more than doubling the rate. In particular: 1) Facilitates wireless networking. In particular, the ability to handle asynchronous users enables superimposing a half-duplex, low bit rate, low power, easy to detect network for control signaling superimposed (physical overlay, rather than logical) on top of the network of primary full-duplex data links. The superimposed links are separated from the primary full-duplex data links in the code domain, and use time multiplexing plus Carrier Sense Multiple Access (CSMA) among themselves. However, the conventional problems of CSMA are avoided as control links operate in parallel with primary full-duplex data links. The physical layer of control links is designed such that full-duplex data links can detect and cancel the interference caused by the superimposed control links. 2) Enhances security through desirable jamming. 3) Provides the ground to realize unconditional security (beyond computational or information theoretical security), using a simple method introduced in this article. 4) Facilitates multi-node distributed & collaborative signaling, including realization of Network Information Theoretic setups, and cognitive wireless. 5) Exploiting feedback, it improves point-to-point throughput, and enables ultra low power transmission. 6) Doubles the point-to-point throughput.

Baseband Receiver Design for Wireless MIMO-OFDM Communications

Abstract: The Second Edition of OFDM Baseband Receiver Design for Wirless Communications, this book expands on the earlier edition with enhanced coverage of MIMO techniques, additional baseband algorithms, and more IC design examples. The authors cover the full range of OFDM technology, from theories and algorithms to architectures and circuits.The book gives a concise yet comprehensive look at digital communication fundamentals before explaining signal processing algorithms in receivers. The authors give detailed treatment of hardware issues - from architecture to IC implementation.Links OFDM and MIMO theory with hardware implementationEnables the reader to transfer communication received concepts into hardware; design wireless receivers with acceptable implemntation loss; achieve low-power designsCovers the latest standards, such as DVB-T2, WiMax, LTE and LTE-AIncludes more baseband algorithms, like soft-decoding algorithms such as BCJR and SOVAExpanded treatment of channel models, detection algorithms and MIMO techniquesFeatures concrete design examples of WiMAX systems and cognitive radio apllications Companion website with lecture slides for instructorsBased on materials developed for a course in digital communication IC design, this book is ideal for graduate students and researchers in VLSI design, wireless communications, and communications signal processing. Practicing engineers working on algorithms or hardware for wireless communications devices will also find this to be a key reference.