| dc.description.abstract | Cognitive radio (CR) has been proposed as a technology to improve the spectrum efficiency
by giving an opportunistic access of the licensed-user spectra to unlicensed users.
We consider an overlay CR consisting of a primary macro-cell and cognitive small cells of
cooperative secondary base stations (SBS). We suggest studying a CR where an orthogonal
frequency division multiplexing is used for both the primary users (PU) and the secondary
users (SU). In order to cancel the interferences, a precoding is required at the SBS. Therefore,
we first derive the interferences expression due to SU at the PU receiver. Then, zero
forcing beamforming (ZFBF) is considered to cancel the interferences. However, applying
ZFBF depends on the channels between the SBS and the PU. A channel estimation is hence
necessary. For this purpose, we propose to approximate the channel by an autoregressive
process (AR) and to consider the channel estimation issue by using a training sequence.
The received signals, also called the observations, are considered to be disturbed by an
additive white measurement noise. In that case, the AR parameters and the channel can be
jointly estimated from the received noisy signal by using a recursive approach. Nevertheless,
the corresponding state space representation of the system is non-linear. Then, we
propose to carry out a complementary study by compare non-linear Kalman filter based
approaches. | en_US |
