Section: New Results

Flexible Radio Node

Participants : Florin Hutu, Tanguy Risset, Jacques Verdier, Guillaume Villemaud, Cédric Levy-Bencheton.

This section summarizes the early results obtained from the research axis flexible radio nodes.

In [41] , [75] , a candidate architecture for LTE-Advanced receiver is proposed. Based on the combination of MIMO techniques and flexible spectrum access, LTE-Advanced terminals will require the increasing of the analog front-end complexity. To reduce the complexity of the analog front-end, an innovative architecture based on the merge between the double IQ and the code multiplexing structures is proposed. Simulation and measurement results show that, in a Gaussian case, the bit error rate is similar when using the proposed architecture and the state of the art front-end stack-up structure. A complexity evaluation study reveals significantly reduced power consumption of the proposed single front-end architecture.

The current generation of mobile terminals can communicate on multiple modes using several antennas. However, their energy consumption remains a critical parameter. In [58] , [74] , we explore the combination of multiple communication modes and MIMO as a possible way to reduce the energy consumption of both the terminals and the network. We propose a realistic energy model for the PHY layer of a MIMO and multi-mode terminal, taking into account the MAC layer behaviour. We show that the combination of MIMO and multi-mode provides a solution to reduce global energy consumption.

Software means programmable. Hence software defined radio means that the radio should now be programmable. We know what computer programming means, and we agree, up to a certain level, on how it should be done. But do we know what programming a radio means? Several questions are still open: what will an SDR platform look like in ten years? Will there exist software radio code? What will be the technical challenges and commercial issues behind this code? Programming is more precise than configuring or tuning, it implies a much greater level of freedom for the programmer. But it also means much cheaper implementations in many cases and in particular a re-use of the same hardware for different protocols (i.e. with different programs). This is, to our point of view [76] , the main difficulty of software radio programming: reconfiguration and in particular dynamic reconfiguration. Dynamic (i.e. very fast) reconfiguration is now mandatory because some protocols, 3GPP-LTE (Third Generation Partnership Program Long Term Evolution) for instance, propose channel adapting for each frame, requiring a setting of the channel estimation parameter in a few milliseconds.