On the practical implementation of VFDM-based opportunistic systems: issues and challengesReport as inadecuate




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1 Chaire Radio Flexible - Chaire Radio Flexible Alcatel-Lucent-Supélec 2 DEI - Department of Information Engineering Padova 3 CITI - CITI Centre of Innovation in Telecommunications and Integration of services 4 Electrics-Electronics Engineering Department - Fatih University 5 VNU University of Engineering and Technology 6 Chaire Radio Flexible Alcatel-Lucent-Supélec Chaire Radio Flexible - Chaire Radio Flexible Alcatel-Lucent-Supélec 7 Electrics-Electronics Engineering Department - Fatih University

Abstract : Vandermonde-subspace frequency division multiplexing VFDM is a physical layer technique for cognitive two-tiered networks, allowing for the coexistence of an orthogonal frequency division multiplexing OFDM legacy system and a cognitive secondary system in a time division duplex mode. It consists of a linear null-space precoder used by the secondary transmitter to effectively cancel the interference towards one or more primary receivers, while guaranteeing a non-negligible rate to a served secondary receiver. In this work, we propose an implementation of an experimental test-bed using the new SDR4All platform developed at the Alcatel-Lucent Chair on Flexible Radio SUPELEC to take a step towards a proof of concept of a VFDM-based system. We focus on the secondary link, where an opportunistic transmitter-receiver pair communicates over moderately frequency selective channels, characterized by very short root mean square r.m.s. delay spreads and non uniform power delay profiles PDP. The obtained results show the practical feasibility of a VFDM transmission over a secondary link. However, a significant bit error rate BER loss with respect to the previously shown achievable theoretical performance is evident. A thorough analysis of the structure of the VFDM precoder is carried out and the impact of the channel characteristics on the performance of the opportunistic system is discussed. Numerical findings demonstrate that the potential BER drop can be addressed by designing a suitable flexible receiver able to deal with the effect induced by non uniform PDP and short r.m.s. delay spread channels.





Author: Marco Maso - Leonardo S. Cardoso - Ejder Bastug - Nguyen Linh-Trung - Mérouane Debbah - Ozgur Ozdemir -

Source: https://hal.archives-ouvertes.fr/



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