Krishnamurthy Giridhar

Learn More
Spatial smoothing is a widely used preprocessing scheme for direction-of-arrival (DOA) estimation of more than one source from a single snapshot, although the effective array aperture gets reduced by this process. In this paper we propose a preprocessing scheme applicable for DOA estimation algorithms that exploit the shift invariance property of the array(More)
We describe an algorithm for sparse channel estimation applicable to orthogonal frequency division multiplexing systems. The proposed algorithm uses a least squares (LS) technique for channel estimation and a generalized Akaike information criterion to estimate the channel length and tap positions. This effectively reduces the signal space of the LS(More)
We consider the uplink channel estimation of a multipath wireless channel used for orthogonal frequency division multiple access (OFDMA) transmission, where the uplink uses a pseudo-random ldquotilerdquo allocation pattern. A tile is made of small number of physically adjacent data subcarriers along with a few embedded pilot subcarriers and an uplink(More)
We look at the performance of turbo coded OFDM systems in the presence of narrowband interference (NBI) and co-channel interference (CCI). In systems employing standards such as the IEEE 802.16d/e, CCI behaves like NBI with the number of affected subcarriers ranging from 10% to 30%. Hence we treat symbol detection in such systems as detection in(More)
Closed-loop (feedback) rate-one channel orthogonalized space-time block codes (CO-STBCs) for 3 and 4 transmit antennas using a single (real) phase feedback are proposed. These codes with ideal feedback achieve full diversity and result in maximum likelihood (ML) decoding with only linear processing at the receiver. In this paper, we study the impact on the(More)
We treat decision-directed channel tracking (DDCT) in mobile orthogonal frequency-division multiplexing (OFDM) systems as an outlier contaminated Gaussian regression problem, where the source of outliers are the incorrect symbol decisions. Existing decision-directed estimators such as the expectation-maximization (EM)-based estimators and the 2-D-MMSE(More)
Single Snapshot R-D Unitary Tensor-ESPRIT Using an Augmentation of the Tensor Order (SS-U-TE-ATO) is a subspace-based parameter estimation technique for R-dimensional (R-D) undamped harmonics using a single snapshot of data. In SS-U-TE-ATO the measurement data is packed into a measurement tensor to which spatial smoothing is applied. We propose the(More)
This paper proposes a joint channel-estimation method for the desired and interfering channels for cell edge users in reuse-1 orthogonal frequency-division multiplexing (OFDM) cellular systems. The following assumptions are made in proposing the algorithm: 1) The desired and interferer’s channel multipath delays do not overlap; 2) the same pilot sequence is(More)
Closed-loop, rate-one, channel orthogonalized space-time block codes (CO-STBCs) for three and four transmit antennas using a single (real) phase feedback term have been proposed . These codes achieve full diversity and result in maximum likelihood (ML) decoding with only linear processing at the receiver similar to OSTBCs. In this paper, we propose a(More)