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Orthogonal Frequency Division Multiplexing (OFDM) can provide a flexible usage of the spectrum by controlling individual sub carriers. Sets of sub carriers can be zero-modulated to avoid interfering narrowband primary users, making OFDM a strong candidate for Cognitive Radio implementations. This paper presents the design and implementation of a non-contiguous OFDM physical layer (PHY) capable of...
The transmit adaptation is a key technique to realize the full potentials of orthogonal frequency-division multiplexing (OFDM) systems. In this paper, we first present a new channel state information (CSI) model in order to save the reverse channel spectrum. By using clustering and interpolation according to the correlation between subcarriers, the estimation of CSI is obtained at the transmitter...
In this paper, we study the energy-efficient distributed estimation problem for a wireless sensor network where a physical phenomena that produces correlated data is sensed by a set of spatially distributed sensor nodes and the resulting noisy observations are transmitted to a fusion center via noise- corrupted channels. We assume a Gaussian network model where (i) the data samples being sensed at...
Some communication applications, like multimedia, deliver data of different importance classes allowing unequal error protection (UEP) levels. In this paper, a multiple-input multiple-output (MIMO) system using orthogonal frequency division multiplexing (OFDM) is considered with a new UEP bit-loading algorithm based on the non-UEP algorithm by Chow, Cioffi, and Bingham. In the proposed bit-loading...
We characterize the total generalized squared correlation (TGSC) for a given signature sequence set used in uplink synchronous code division multiple access (S-CDMA) when channel state information is known perfectly at both transmitter and receiver. We give a definition of the TGSC based on the eigenvalues of Gram matrix associated to signature sequences set for multipath channels in the presence...
In this paper, we consider a new channel probing scheme for opportunistic scheduling in the uplink of orthogonal frequency division multiplexing (OFDM)-based wireless systems. To reduce signaling overhead for the probing, we consider a two-step channel probing process; called pre-probing and mainprobing. Good subchannels are first estimated through the pre-probing process using a probing signal transmitted...
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