François Delaveau

Second-order optimal array receivers for synchronization of BPSK, MSK, and GMSK signals corrupted by noncircular interferences

The synchronization and/or time acquisition problem in the presence of interferences has been strongly studied these last two decades, mainly to mitigate the multiple access interferences from other users in DS/CDMA systems. Among the available receivers, only some scarce receivers may also be used in other contexts such as F/TDMA systems. However, these receivers assume implicitly or explicitly circular (or proper) interferences and become suboptimal for noncircular (or improper) interferences. Such interferences are characteristic in particular of radio communication networks using either rectilinear (or monodimensional) modulations such as BPSK modulation or modulation becoming quasirectilinear after a preprocessing such as MSK, GMSK, or OQAM modulations. For this reason, the purpose of this paper is to introduce and to analyze the performance of second-optimal array receivers for synchronization and/or time acquisition of BPSK, MSK, and GMSK signals corrupted by noncircular interferences. For given performances and in the presence of rectilinear signal and interferences, the proposed receiver allows a reduction of the number of sensors by a factor at least equal to two.

Tag signals for early authentication and Secret Key Generation in wireless public networks

In this paper, a new protocol is proposed for securing both authentication and communication in wireless public networks. It relies on the combination of two techniques presented in the article: Tag Signal (TS) and Secret Key Generation (SKG). First, tag signals are used to securely exchange identification information, perform Channel Frequency Response (CFR) and provide a controlled radio advantage to legitimate users. Then secret keys are generated using authenticated CFR to protect communication. In addition to the presentation of the techniques, measured CFR and SKG performance are also provided for real WiFi communications.