Evolving LTE-Advanced to meet MTC requirements

Publications

A real-time platform for collaborative research on Visible Light Communication

Publication . Ribeiro, Carlos; Figueiredo, Mónica; Alves, Luis Nero

This paper reports the implementation and performance results of a real-time Visible Light Communication platform. The platform uses a high-level software abstraction architecture where the algorithms are developed and tested in MATLAB, using a modular architecture. With this modular approach it is very easy to add/remove blocks, making it amenable to collaboration with other groups with interest in this field, offering a real-time test bed to evaluate the performance of different modules, algorithms and optical front-ends, which is currently not available. The physical layer is based on DCO-OFDM and is implemented in a Xilinx Virtex-6 FPGA. We explore the optical front-end out-of-band bandwidth to transmit, showing the usefulness of adopting OFDM-based modulations schemes for VLC. Our system transmits at 2m over an indoor free space channel with 12MHz bandwidth, with more than 23dB gain difference, using QPSK, thus achieving 24Mbit/s with a BER smaller than the usual 3.8×10-3 limit.

2015-09Conference paper

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Optical digital to analog conversion performance analysis for indoor set-up conditions

Publication . Dobesch, Aleš; Alves, Luis Nero; Wilfert, Otakar; Ribeiro, Carlos Gaspar

In visible light communication (VLC) the optical digital to analog conversion (ODAC) approach was proposed as a suitable driving technique able to overcome light-emitting diode’s (LED) non-linear characteristic. This concept is analogous to an electrical digital-to-analog converter (EDAC). In other words, digital bits are binary weighted to represent an analog signal. The method supports elementary on–off based modulations able to exploit the essence of LED’s non-linear characteristic allowing simultaneous lighting and communication. In the ODAC concept the reconstruction error does not simply rely upon the converter bit depth as in case of EDAC. It rather depends on communication system set-up and geometrical relation between emitter and receiver as well. The paper describes simulation results presenting the ODAC’s error performance taking into account: the optical channel, the LED’s half power angle (HPA) and the receiver field of view (FOV). The set-up under consideration examines indoor conditions for a square room with 4 m length and 3 m height, operating with one dominant wavelength (blue) and having walls with a reflection coefficient of 0.8. The achieved results reveal that reconstruction error increases for higher data rates as a result of interference due to multipath propagation.

2017-10Journal article

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A software-defined radio FPGA implementation of OFDM-based PHY transceiver for 5G

Publication . Ribeiro, Carlos; Gameiro, Atílio

This paper introduces a software-defined radio implementation of an OFDM-based transceiver for the prototyping and testing of 5G physical layer algorithms. The implementation uses high level abstraction tools to develop and test the algorithms, significantly reducing the time and effort needed to test new features. The proposed architecture adopts interconnecting FIFOs between each functional block, reducing the critical paths and enabling complex designs to be implemented at higher clock rates. The proposed LTE-like transceiver is implemented using COTS FPGA and RF development boards. The real-time over-the-air demonstrator has an on-the-fly scalable bandwidth from 20 to 61.44 MHz, attaining close to 500 Mb/s when using 256-QAM modulation.

2017-02-15Journal article

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