Balachander Narasimhan

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Effective Inter-carrier Interference (ICI) mitigation for MIMO-OFDM requires accurate channel estimation which is very challenging due to the large number and fast time-varying nature of the channel parameters to be estimated using scattered pilots. We present a novel SFBC-OFDM scheme for doublyselective channels and a reduced-complexity channel estimation(More)
Direct conversion orthogonal frequency division multiplexing (OFDM) systems suffer from transmit and receive analog processing impairments such as in-phase/quadrature (I/Q) imbalance causing inter-carrier interference (ICI) among sub-carriers. Another source of performance-limiting ICI in OFDM systems is Doppler spread due to mobility. However, the nature(More)
Direct-conversion multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) transceivers enjoy high data rates and reliability at practical implementation complexity. However, analog front-end impairments such as I/Q imbalance and high mobility requirements of nextgeneration broadband wireless standards result in(More)
Direct-conversion Orthogonal Frequency Division Multiplexing (OFDM) systems suffer from transmit and receive analog processing impairments such as In-phase/ Quadrature (I/Q) imbalance causing Inter-Carrier Interference (ICI) between the sub-carriers. Another source of performance-limiting ICI, but with a different nature, in OFDM systems is Doppler spread(More)
I/Q imbalance and high mobility in OFDM systems result in performance-limiting intercarrier interference (ICI). However, the nature of ICI due to each of them is quite different. Unlike previous works which considered these two impairments separately, we develop a unified mathematical framework to characterize and mitigate ICI when both impairments are(More)
In this sequel to [1], the joint Tx/Rx I/Q imbalance model of mobile SC-FDE transceivers is extended to include the effect of residual carrier frequency offset. Furthermore, the equivalent channel model for multiple-antenna spatially-multiplexed SC-FDE transceivers in the presence of I/Q imbalance and mobility is derived and an effective digital baseband(More)
Effective inter-carrier interference (ICI) mitigation for MIMO-OFDM requires accurate channel estimation which is very challenging due to the large number and fast time-varying nature of the channel parameters to be estimated using scattered pilots. We present a novel SFBC-OFDM scheme for doubly-selective channels and a reduced complexity channel estimation(More)
Single-carrier frequency-division multiple-access (SC-FDMA) has been adopted in the uplink of the LTE standard due to its lower peak-to-average-power ratio (PAPR) compared to orthogonal frequency-division multiple access (OFDMA). Recent activities in the LTE-advanced (LTE-A) standardization have focused on effective uplink transmit diversity schemes with(More)
Previous work [1] on I/Q imbalance in SC-FDE transceivers investigates the effect of receiver I/Q imbalance but does not consider Doppler effects due to mobility. SCFDE in doubly-selective channels is studied in [2] and [3] but without considering I/Q imbalance. In this paper, we derive an equivalent channel model for SC-FDE in the presence of both joint(More)
In-phase and Quadrature-phase (I/Q) imbalance is a major performance-limiting impairment for directconversion Orthogonal Frequency Division Multiplexing (OFDM) transceivers. I/Q imbalance degrades the Signal-to-Noise-Ratio in an OFDM system by causing Inter-Channel-Interference (ICI) between image subcarriers. Doppler spread due to mobility also causes ICI(More)