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This paper analyzes the performance of random vector quantization (RVQ) for limited feedback nullforming in multi-input multi-output (MIMO) communication systems with and without receiver coordination. A single-stream scenario is considered in which one or more primary receivers request nulls by providing limited feedback to the transmitter. Without receiver coordination, each primary receiver informs...
In this paper, we present a method which jointly performs robust channel estimation and signal detection over rank-deficient MIMO links. This technique achieves an excellent estimation of the channel matrix by using all detected symbols within a data frame. Symbol detection is achieved by means of a sphere decoding algorithm. The proposed scheme is equivalent to having the training preamble occupy...
Power Line Communications (PLCs) enable new and highly convenient networking functions in the framework of Smart-Grids and use an already built-in network. A Multiple Input Multiple Output (MIMO) architecture can strongly improve the PLC performances and links' reliability. In this contribution the effect of self-interference generated by relay nodes has been considered and the MIMO potentials for...
Multiple Input Multiple Output (MIMO) methods significantly improve the coverage of Power Line Communications (PLC) compared to Single Input Single Output (SISO) systems. This paper describes the implementation and results of the first real-time MIMO PLC feasibility study. Our system setup includes two PCs, each containing two FPGAs. It enables the comparison of SISO versus MIMO PLC transmissions...
In this paper we consider two alternate packet structures for estimating the multi-input multi-output (MIMO) powerline channel and their impact on achievable application throughputs. In the first packet structure, an orthogonal pair of OFDM symbols is used to estimate the channel. When compared to single-input single-output (SISO) transmissions that use one OFDM symbol to estimate the channel, there...
In this paper a statistical description of in-home MIMO power line channels is derived, based on channel measurements in the 0 to 100 MHz range. In particular, it is shown that the power delay profile has a statistical distribution that could be well described by Weibull and Gaussian distributions. It is also confirmed that the channel attenuation has a linear behavior as a function of the frequency...
The MIMO system convincingly promises a better bit rate in comparison with a SISO system. The system gets even efficient when OFDM is implemented with MIMO to obtain better data rates even in hostile channel environment. Research establishes OFDM as a potential candidate for use in MIMO systems for the reasons like inherent FFT, waveform adaptation, advanced antenna techniques, multiple access, interoperability,...
Estimation of Multi Input Multi Output (MIMO) channels can be performed by Artificial Neural Network (ANN)s such as Multi Layer Perceptron (MLP)s. However, the cost of training overload in case of time varying MIMO channels is the main bottleneck of such ANN architectures for which a viable alterative, namely, the Recursive Recurrent Network (RNN) is explored. Although for tightly coupled real and...
In this work multistage MIMO equalization and source separation method is adapted to operate as a successive interference cancellation (SIC) scheme to improve the quality of received signal in a high interference environment. In a 3-stage setup, after capturing the signal of interest (SOI), interference is estimated and cancelled at second stage. After cancellation of the interference, the last stage...
In this paper, we propose an efficient link adaptation scheme for the 3GPP Long Term Evolution Advanced (LTEA) uplink with turbo successive interference cancelation (Turbo-SIC) receiver and imperfect channel estimation. Link adaptation for non-linear MIMO receivers such as Turbo SIC is not straightforward because the soft-outputs of such receiver cannot be simply modeled using a scalar Gaussian channel...
Channel reciprocity is regarded as one of the most important advantages of TDD systems. However, the RF front-ends contribute to the channel experienced, and their TX/RX mismatches might cause reciprocity error, and thus degrade system throughput. Therefore, channel reciprocity calibration is a crucial issue. Among the existing calibration methods, Over-the-air (OTA) calibration is a promising approach...
In this paper, we investigate the joint effects of high-power amplifier (HPA) nonlinearity, in-phase/quadrature-phase (I/Q) imbalance and crosstalk, on the performance of multiple-input multiple-output (MIMO) transmit beamforming (TB) systems, and propose a compensation method for the three impairments together. The performance of the MIMO TB system equipped with the proposed compensation scheme is...
In downlink Multiuser Multiple-Input Multiple-Output (MU-MIMO) systems, the zero-forcing (ZF) transmission is a simple and effective technique for separating users and data streams of each user at the transmitter side, but its performance depends greatly on the accuracy of the available channel state information (CSI) at the transmitter. Due to the existence of the CSI delay and channel estimation...
The MIMO system convincingly promises a better bit rate in comparison with a SISO system. The system gets even efficient when OFDM is amalgamated with MIMO to obtain better data rates even in hostile channel environment. Research establishes OFDM as a potential candidate for use in MIMO systems for the reasons like inherent FFT, waveform adaptation, advanced antenna techniques, multiple access, interoperability,...
Although maximum a posteriori probability (MAP) channel estimator has an optimal performance for MIMO-OFDM systems, its high complexity could be in the order of O(K3), where K is the number of subcarriers. So, in this paper, we introduce an H-infinity estimator which has good performance, but with much less complexity. Next, lots of matrices inversions and multiplications are reduced by the iterative...
When the receiver of a multiple-input multiple-output (MIMO) channel does not know the channel state, but only a linear estimate thereof, the rates achieved with (suboptimal) Gaussian codebooks become difficult to compute. However, one can resort to upper and lower bounds known from literature. Extending the ideas of earlier works on the resource allocation (time and energy) between pilot and data...
In this paper, we present a WiMAX baseband SoC implemented in 90nm and capable of high-speed transmission at 300km/h. This SoC is integrated in a USB device that also includes an RF transceiver for MIMO WiMAX transmission. The baseband transmitter generates a WiMAX waveform according to the IEEE 802.16e Rev2 specification. In this time-division duplex WiMAX system, the uplink subframe is composed...
Hardware platforms and testbeds are an essential tool to evaluate, in realistic scenarios, the performance of wireless communications systems. In this work we present a multiuser Multiple-Input Multiple-Output (MIMO) testbed made up of 6 nodes, each one with 4 antennas, which allows us to evaluate Interference Alignment (IA) techniques in indoor scenarios. We specifically study the performance of...
In this paper we focus on finding a suitable Link Adaptation (LA) algorithm which is implemented as Channel Quality Indicator (CQI) selection technique in the 3GPP Long Term Evolution (LTE) system. The potential of Link Adaptation in the LTE system is not fully exploited. Therefore in our study, we compare the performances from different LA algorithms in the LTE system. The presented LA algorithms...
Significant throughput gains can be achieved in a multi-user MIMO (MU-MIMO) wireless system by exploiting the combination of multi-user scheduling and multi-user diversity. Open-loop MU-MIMO (OL-MU-MIMO) is a codebook based precoding technique where precoders are fixed a priori at the base station (BS) in a known fashion and the user needs to feedback which precoding vector is to be chosen referred...
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