Conference Papers
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Item FPGA implementation of a BCH Codec for free space optical communication system(Institute of Electrical and Electronics Engineers Inc., 2014) Koila, S.; G.D., G.D.; Kulkarni, M.; Sripati, U.Future Free Space Optical (FSO) communication systems have the potential of communicating data at very high rates with very high levels of integrity over distances of up to a few kilometers (for terrestrial links). This technology has also been a candidate for setting up very high speed (∼3 Gbps) and highly reliable (BER ∼10-9) communication links between satellites in geo-synchronous orbits and ground stations. Since the free space optical medium can induce many forms of distortion (atmospheric turbulence effects, optical beam wander etc), the use of a channel code to detect and correct errors during the process of information transfer over the channel is essential. A correctly designed channel code can reduce the raw BER from unacceptable values to values that can be tolerated in many applications. In this paper, we have designed a Codec (encoder/decoder) pair for a (31, 16, 3) Bose, Ray-Chaudhuri, and Hocquenghem (BCH) code on the Nexys-4 FPGA platform. The performance of this BCH Codec has been tested over an indoor FSO channel and the improvement in terms of BER has been quantified. An improved syndrome computation circuit, parallel Chien search implementation and an improved method for calculating inverses in a finite field are the new features incorporated in this paper. We have been able to design and implement circuits which use these optimized approach and deliver real time encoding and decoding with an information transfer rate of 2 Mbps and can be extended upto a speed of 418Mbps. © 2014 IEEE.Item Performance of Spatial-Modulation and spatial-multiplexing systems over Weibull fading channel(Institute of Electrical and Electronics Engineers Inc., 2016) G.D., G.D.; Koila, S.; Neha, N.; Sripati, U.In this paper we have analyzed, quantified and compared the performance of variants of spatial modulation (SM) and spatial multiplexing (SMX) techniques over the GSM/3G frequency band. SMX systems use all the available transmit antennas for multiplexing the data symbols and hence achieve greater spectral efficiency. An SM system uses only one antenna at any given instant and achieves a reduction in the average energy consumption due to single RF chain activation. Some variants of (Spatial modulation (SM) namely Extended Spatial Modulation(EXSM), Enhanced Spatial Modulation (ESM) and Quadrature Spatial Modulation (QSM) use one or more antennas to provide a trade-off between spectral efficiency and energy efficiency. In battery operated devices, apart from increase in the spectral efficiency, energy efficiency also becomes a critical parameter of concern. This paper shows that EXSM provides superior BER performance in comparison to SMX systems. Thus, these schemes can be advantageously deployed in portable devices used in Mobile Wireless Communication Systems. In [9] it has been demonstrated that the Weibull distribution is a good fit to describe the multipath fading phenomenon in the GSM/3G band. In this paper, we have evaluated the performance of 2×2 and 2×4 SM, EXSM, ESM, SMX and QSM. We have also evaluated the performance of 3×3 SMX and EXSM systems. Our results indicate that a variant of SM specifically EXSM outperforms SMX systems by ∼4.7 dB in 2×2, 2×4 systems and ∼7 dB for 3×3 systems in a deep fading environment (Weibull with shape parameter=0.5). © 2015 IEEE.Item Performance of SM-NSTBC for Correlated HAP Fading Channels with Imperfect-CSI(Springer, 2020) Godkhindi Shrutkirthi, S.; G.D., G.D.; Shripathi Acharya, U.This paper analyzes the performance of Spatially Modulated Non-orthogonal Space Time Block Code (SM-NSTBC) scheme for a correlated high altitude platform (HAP) MIMO system in the presence of imperfect channel state information (Imp-CSI). The proposed SM-NSTBC employs cyclic codewords derived over Galois Field, which satisfies full rank property. The performance of SM-NSTBC is compared with traditional STBCs such as SM-OSTBC and STBC-SM schemes. It is observed through simulations that SM-NSTBC outperforms SM-OSTBC and STBC-SM schemes by a minimum of 2 dB in HAP correlated environments. Monte-Carlo simulations have been performed to validate the claims. © 2020, Springer Nature Singapore Pte Ltd.