Srikrishna Bhashyam

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This paper investigates subcarrier and power allocation in multiuser OFDM. The aim is to maximize the overall rate while achieving proportional fairness amongst users under a total power constraint. Achieving the optimal solution is computationally demanding thereby necessitating the use of suboptimal techniques. Existing sub-optimal techniques either use(More)
We propose a new subcarrier allocation algorithm for Orthogonal Frequency Division Multiple Access (OFDMA) that gives fair allocation of capacity to multiple users with different channel and traffic characteristics. This is achieved by utilizing buffer state information and measured traffic statistics in addition to channel state feedback. Multiuser(More)
Channel estimation techniques for code-division multiple access (CDMA) systems need to combat multiple access interference (MAI) effectively. Most existing estimation techniques are designed for CDMA systems with short repetitive spreading codes. However, current and next-generation wireless systems use long spreading codes whose periods are much larger(More)
Multiple antenna transmission and reception have been shown to significantly increase the achievable data rates of wireless systems. However, most of the existing analysis assumes perfect or no channel information at the receiver and transmitter. The performance gap between these extreme channel assumptions is large and most practical systems lie in(More)
The mobile wireless channel a ords inherent diversity to combat the e ects of fading. Existing code division multiple access (CDMA) systems, by virtue of spread-spectrum signaling and RAKE reception, exploit only part of the channel diversity via multipath combination. Moreover, their performance degrades under fast fading commonly encountered in mobile(More)
The performance of iterative decoding of low density parity check (LDPC) codes over binary erasure channels can be completely characterized by the study of stopping sets. Therefore, the burst erasure correction capability of a given LDPC code can be readily quantified by searching for stopping sets within consecutive bit nodes. In this work we study the(More)
In an Orthogonal Frequency Division Multiplexing (OFDM) downlink scenario, we propose joint subcarrier and power allocation for Channel-Aware Queue-Aware scheduling while allowing multiple users to share a single OFDM symbol. Our approach is to combine subcarrier and power allocation by optimizing a user’s power allocation immediately after the user has(More)
Antenna selection in Multiple-Input-Multipleoutput (MIMO) systems preserves diversity gain while significantly reducing hardware complexity. However, imperfect Channel State Information (CSI) affects performance. In this paper, we first analyze the performance of a MIMO system employing antenna selection at the transmitter and Maximal Ratio Combining (MRC)(More)
We investigate the effect of feedback delay on the outage probability of multiple-input single-output (MISO) fading channels. Channel state information at the transmitter (CSIT) is a delayed version of the channel state information available at the receiver (CSIR). We consider two cases of CSIR: (a) perfect CSIR and (b) CSI estimated at the receiver using(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)