This paper analyzes performance and throughput of an adaptive bit allocation and variable rate algorithm depending on channel state information (CSI) and a transmit power in a multi-user OFDM transmission. The purpose of the presented multi-rate OFDM system using adaptive modulation is to increase bandwidth efficiency by controlling constellation size and to adapt proper service for each user a...

— Interference alignment allows multiple users to share the same frequency and time resource in a wireless communications system. At present, two performance bounds, in terms of degree of freedom, have been proposed. One is for infinite-dimension extension and the other is for MIMO systems. This paper provides an understanding of the MIMO bound by examining its proofs and shows that it does not...

Multiple-input multiple-output (MIMO) and orthogonal frequency division multiplexing (OFDM) stand as promising technologies to resolve bottlenecks in the traffic capacity of current and future high data rate wireless systems such as longterm evolution (LTE), Wi-Fi, and worldwide interoperability for microwave access (WiMAX). Recently, the expansion of MIMO systems to employ multiple users (mult...

This letter presents and analyzes orthogonal frequency-division multiplexing (OFDM)-based multi-carrier transmission for cell-free massive multi-input multi-output (CFmMIMO) over frequency-selective fading channels. Frequency-domain conjugate beamforming, pilot assignment, user-specific resource allocation are proposed. The CFmMIMO-OFDM system is scalable to serve a number of users flexible off...

the opportunity of a detailed link adaptation scheme. The combination of these transmission-and multiple access techniques in OFDM-FDMA is an ideal and very strong candidate for the downlink of future 4G mobile communication systems. This technical combination offers high cell capacities by exploiting the inherent multi user diversity effect of the system. To apply OFDM-FDMA in the uplink, the ...

In the MIMO-OFDM systems, the traditional methods of multi-user detection have some limitations in the rank-deficient scenarios, where the number of supported users exceeds the number of receiver antennas. The multiuser detection (MUD) based on the genetic simulated annealing algorithm (GSAA) is proposed for the rankdeficient problems in the multi-user MIMO-OFDM system. The simulation results s...

This article examines the performance of Wavelet based Multi-User MIMO OFDM (MUMIMO WOFDM) systems and a comparison is made with classical FFT based multiuser MIMO OFDM system. Wavelet analysis has some strong advantages over fourier analysis, as it allows a time-frequency domain operation, allowing optimal resolution and flexibility. Wavelets have been satisfactorily applied in almost all the ...

In this paper we propose a simple, yet flexible and efficient, channel estimator for the uplink in broadband Orthogonal Frequency Division Multiplexing (OFDM) systems. The processing is performed in the time-domain, by extracting the channel’s impulse response (CIR) for each user from a joint training signal. In this OFDM system, the pilot sequence we advocate, where all users share the same pi...