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We propose an efficient time-domain channel estimation method for polarization interleaving orthogonal frequency division multiplexing passive optical network (OFDM-PON) with direct detection. Compared with the frequency-domain least square channel estimator (FLSE) and intra-symbol frequency-domain averaging (ISFA), the time-domain channel estimator (TD-CE) with overhead reduction demonstrates better...
We propose a MIMO ultraviolet (UV) communication system which can increase the data rate effectively. The bit error rate (BER) performance of a 2×2 MIMO scheme is measured and analyzed by offline experiments.
A multiuser multi-input multi-output (MU-MIMO) downlink system with block diagonalization-based precoding is presented with a study of the impact of limited bandwidth resource for the feedback-links on the sum capacity. The channel estimation is acquired at each user via downlink training, and the linear quantized form of estimated channels is fed back to the base station (BS) via noisy, finite-rate...
Estimation of carrier frequency offset (CFO) is a challenging task in practical systems specifically in the uplink of multiuser systems where multiple CFOs are present in the received signal. Massive MIMO as a multiuser technique has recently attracted a great deal of attention among researchers. However, to the best of our knowledge, there is no study looking into the joint estimation of CFOs and...
Aiming at the requirement of Doppler and channel estimation which applied to underwater mobile communication with orthogonal frequency division multiplexing (OFDM) technology, a PN sequence based method for Doppler and channel estimation is proposed, an underwater acoustic OFDM communication system structure is given and a block data frame based on PN sequence is designed. For the Doppler estimation...
Pre-equalization and adaptive diversity schemes are available for channel compensation. Such techniques require channel prediction because a channel changes in time. Previously, we reported a channel prediction technique to increase the accuracy by focusing on polarization state and combine multiple polarization components estimated in the nearest past signal set. However, when the polarization state...
Workload is the amount of cognitive effort executed by a certain subject. Several attempts have been done in order to measure workload level. However, there exists a difficulty in analyzing workload: the problem of individuality, or variability among different individuals and how they respond to similar tasks. In order to have a more objective measure of workload level, the authors employed a more...
We investigate the performance of a hybrid, opportunistic/underlay Licensed Shared Access (LSA) system, in the presence of Spectrum Sensing (SS) and Channel Estimation (CE) uncertainties, and derive a simple closed form expression for the system's Bit Error Rate (BER). Based on the derived expression, we introduce an optimization problem for optimally selecting the time allocated to the SS and CE...
In this paper, we consider the problem of pilot based data transmission in massive multiple-input multiple-output (MIMO) systems where each receiver antenna is equipped with a low-precision analog-to-digital converter (ADC). Under the quantized MIMO setting, we derive a tight approximation of the uplink spectral efficiency considering a maximal ratio combining receiver. Capitalizing on the derived...
This paper addresses the training signal design for the channel estimation in two-way multiple-input-and-multiple-output (MIMO) relay systems, where the channels are correlated. We first derive the backward channel estimator with the optimal training signal sent by the relay node. Given the estimated backward channels and the probabilistic knowledge of the estimation error, we mainly focus on the...
In this paper, we consider the beamforming training (BFT) technique, which is performed prior to the downlink (DL) data transmission in a time-division duplexing multi-user massive multiple-input multiple-output system. The BFT provides the estimates of effective channel state information (CSI) to all users rather than the statistic CSI in the case without the BFT, such that a more reliable DL data...
To meet the goal of ten-fold increase in spectral efficiency, multiuser multiple-input-multiple-output (MU-MIMO) techniques capable of achieving high spatial multiplexing gains are expected to be an essential component of fifth-generation (5G) radio access systems. This increase in multiplexing gain, made possible by equipping base stations with a large number of antennas, entails a proportional increase...
This paper addresses the design of MSE-optimal preambles for multicarrier channel estimation under a maximum likelihood or minimum mean squared error criterion. The derived optimality condition gives insight on how to allocate the pilots that compose the preamble. While many papers show that equispaced and equipowered allocation is optimal, the generalized condition demonstrates that there exist many...
This paper considers the transmit power balancing trade-off between the pilot and data signals in a two-hop full-duplex decode-and-forward relay link when the feedforward data channels are Rayleigh-fading and the residual feedback self-interference channel follows Rician-fading. The study concentrates on time-multiplexed orthogonal pilot sequences since simultaneously transmitted orthogonal pilots...
Orthogonal Frequency Division Multiplexing (OFDM) is widely used in the wireless local area network (WLAN) standards like IEEE 802.11a/n/ac. OFDM has high spectral efficiency, enabling the high data rates required for video streaming and sharing of large files. However, the impact of analog front-end non-idealities in an OFDM system limits its performance. One such non-ideality is IQ imbalance. At...
Exploiting the full benefits of massive multiple input multiple output (MIMO) technology can be directly affected by the efficiency of the channel state information (CSI) estimation. This paper focuses on frequency division duplexing (FDD) channel estimation and feedback. To the sparsity of the frequency selective massive MIMO channels, a two-step multiple approximate message passing algorithm is...
This paper considers a massive multi-user MIMO downlink time-division duplex system where a large number of antennas at the base station serves single-antenna users in the same time-frequency resource. In the downlink channel, we assume that users obtain an efficient information on the channel state, with the aid of pilot sequences transmitted by BS, to decode the data signals. It is assumed that...
Abstract-Due to the huge unlicensed spectrum, millimeter wave (MMW) communication are gaining much attention for 5G cellular systems. To combat the severe path loss encountered, MMW communication often resorts to multiple-input multipleoutput (MIMO) beamforming. The capacity-optimal transmit and receive beamforming vectors are determined by the singular value decomposition (SVD) of channel matrix...
As a promising technique to meet the drastically growing demand for both high throughput and uniform coverage in the fifth generation (5G) wireless networks, massive multiple-input multiple-output (MIMO) systems have attracted significant attention in recent years. However, in massive MIMO systems, as the density of mobile users (MUs) increases, conventional uplink training methods will incur prohibitively...
This paper investigates optimal resource allocation scheme for a typical uplink single-cell massive MIMO system over spatially correlated fading channels. To reduce the pilot contamination effect, we first propose the orthogonal user grouping strategy to partition the terminals into serval groups and assume the users in the same group reuse an identical orthogonal pilot sequence. Employing this strategy,...
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