Rahul Makkar

Bio: Rahul Makkar is an academic researcher from LNM Institute of Information Technology. The author has contributed to research in topics: Computer science & Telecommunications link. The author has an hindex of 1, co-authored 8 publications receiving 4 citations.

Performance analysis of non‐orthogonal multiple access assisted cooperative maritime communication system over two‐wave with diffuse power fading

Abstract: Non‐orthogonal multiple access (NOMA) and millimeter‐wave (mmWave) communication are two promising technologies to fulfill the high throughput and reliable communication requirements. Maritime communication systems use a generalized fading at near‐sea‐surface channels (for seashore to ship/boat/fishing fleet communication) to provide reliable communication due to atmospheric turbulence. Experimental research on generalized two‐wave diffuse power (TWDP) fading reveal the footprints of mmWave. This article proposes novel exact and asymptotic closed‐form expressions of average symbol error probability (ASEP) of NOMA users for cooperative maritime communication systems over TWDP fading with the different modulations. The end‐to‐end closed‐form expressions are derived in terms of Appell's and Lauricella's hypergeometric functions. Also, the ASEP is shown using the power allocation factor for different modulation schemes. The proposed system provides better transmission reliability using generalized TWDP fading. Further, the outage probability of the system described above is analyzed using the distance, path loss exponent, transmission rate, and Rician factor as performance metrics for both the NOMA users. Effects of fading outage parameters on the system performance are studied. The end‐to‐end exact numerical results have been verified with the Monte‐Carlo simulations that validate with asymptotic results at a high SNR regime.

Performance of Downlink SISO NR System using MMSE-IRC Receiver

Abstract: In this work, we investigated the performance of single input single output (SISO) downlink channel considering 5G new radio (NR). A number of parameters such as different modulation schemes, channel coding with varying code rates, scalable numerology μ and 3GPP channel models have been considered for evaluation. In addition, the minimum mean square error-interference rejection combining (MMSE-IRC) technique for interference mitigation and bit error rate (BER) performance is analyzed and presented. We also compared the sum-rate performance of LTE and 5G NR. It is observed that MMSE-IRC receiver successfully mitigates the interferences compared to only MMSE based receiver. Simulation results also show performance improvement over various parameters like sum-rate, interference mitigation and BER compared to prior technologies i.e. 4G-LTE, WiMAX, etc.

Performance of M-QAM Scheme over TWDP Fading for Multiple Receive Antennas System

Abstract: In this paper, we analyze a M-ary quadrature amplitude modulation (M-QAM) scheme over twowave with diffuse power (TWDP) fading environment for multiple receive antennas based system. We consider a Selective decode-and-forward (DF) relayed system with multiple receive antennas at the relay and the destination node. Utilizing the moment generating function of TWDP fading distribution, we derive the closed form expression for the exact average symbol error rate (ASER) for MQAM scheme. Moreover, in order to get the better insight of the system, we also perform the asymptotic analysis for the considered system. Simulation results are presented for different scenarios and it is observed that analytical results show excellent agreement with the simulation results.

Low Complexity Based QR-LRL OSIC Detector for Downlink NOMA-MIMO Systems

Abstract: Power domain NOMA SISO system achieve more capacity compared to OMA system for a given power. To enhance the overall system capacity, NOMA-MIMO based downlink system with superposition coding (SC) coding is considered in this work. With the incorporation of MIMO, the detector subject to interuser as well as interantenna interference. Conventionally, after receiving the signal from the base station (BS), each user eliminates the interantenna interference using zero-forcing (ZF) based linear detector. This paper proposes low-complexity based QR-LRL detector to overcome jointly the interuser interference and interantenna interference. The performance of the proposed detector under BER and capacity metrics compared with ZFSIC and ML detectors. Simulation results show that the proposed receiver guarantees near ML performance with lower complexity for NOMA-MIMO downlink systems. It presents the sumrate improvement for various MIMO configurations with different modulation orders. It also provides optimal power allocation factor $(\alpha)$ to experience the same BER at both the near user (NU) and the far user (FU) using ZF and QR-LRL detector.

Dual-mode index modulation based OFDM system over NOMA networks

Abstract: Non-orthogonal multiple access (NOMA) scheme is strongly recommended due to its ability to serve multiple users sharing the same frequency and time resources for next-generation radio access networks. Index modulation (IM) over the orthogonal frequency division multiplexing (OFDM) system creates a new dimension for data transmission in terms of subcarrier indices selection bits to enhance the spectral efficiency (SE) through selection diversity gain. By combining IM and conventional OFDM with NOMA, multiple users reap the aforesaid benefits with the variation of power allocation factors and subcarrier indices pattern. Inspired by OFDM-IM NOMA, a dual-mode OFDM-IM technique with NOMA (DM-OFDM-IM NOMA) users is proposed in this paper. The proposed method increases the SE using indices selection bits and data transmission through all the OFDM subcarriers employing different constellation sets. The error performance of the proposed method is evaluated using the maximum-likelihood (ML) and log-likelihood ratio (LLR) detection techniques. The simulation results for the proposed method validates the improvement in SE compared to conventional method over different modulation order. Also, the computational complexity is presented for proposed and existing OFDM-IM NOMA technique using both ML and LLR detectors.

Bit Error Probability of MQAM in the Presence of Phase Noise

Abstract: In Gray coded rectangular and square quadrature amplitude modulation (QAM), for each bit, the bit decision boundaries are distributed only along one dimension. Consequently, the exact calculation of bit error probability (BEP) of rectangular and square QAM in the additive white Gaussian noise (AWGN) channel results in simple one-dimensional (1-D) error/Q-functions. This is while the symbol decision boundaries involve two dimensions. This paper presents exact and general expressions for the BEP of Gray coded M -ary rectangular and square QAM in the presence of phase noise in the AWGN as well as flat-fading channels. In doing so, we first derive exact expressions for the BEP of MQAM in the presence of a fixed phase error. The expression will be a weighted sum of 1-D complementary error functions for the AWGN channel. For the flat-fading channels, these formulas consist of only single integrals or simple functions. We then integrate the formulas across noise distribution, to derive the average BEP expression of Gray coded MQAM in the presence of random phase error. Moreover, we provide an exact expression for the bit error floor (BEF) of MQAM in the presence of phase noise in the AWGN and fading channels. The exact expressions include numerous terms for higher order MQAM. Considering the most dominant terms of the exact expressions, we also propose simpler expressions. Simulation results validate the accuracy of the proposed exact expressions for arbitrary levels of input SNR. Moreover, the results show very good performance for the approximate expressions.

Performance analysis of non‐orthogonal multiple access assisted cooperative maritime communication system over two‐wave with diffuse power fading

Abstract: Non‐orthogonal multiple access (NOMA) and millimeter‐wave (mmWave) communication are two promising technologies to fulfill the high throughput and reliable communication requirements. Maritime communication systems use a generalized fading at near‐sea‐surface channels (for seashore to ship/boat/fishing fleet communication) to provide reliable communication due to atmospheric turbulence. Experimental research on generalized two‐wave diffuse power (TWDP) fading reveal the footprints of mmWave. This article proposes novel exact and asymptotic closed‐form expressions of average symbol error probability (ASEP) of NOMA users for cooperative maritime communication systems over TWDP fading with the different modulations. The end‐to‐end closed‐form expressions are derived in terms of Appell's and Lauricella's hypergeometric functions. Also, the ASEP is shown using the power allocation factor for different modulation schemes. The proposed system provides better transmission reliability using generalized TWDP fading. Further, the outage probability of the system described above is analyzed using the distance, path loss exponent, transmission rate, and Rician factor as performance metrics for both the NOMA users. Effects of fading outage parameters on the system performance are studied. The end‐to‐end exact numerical results have been verified with the Monte‐Carlo simulations that validate with asymptotic results at a high SNR regime.

Spectrally efficient M‐ary QAM based multi‐antenna cooperative system over TWDP fading channel

Abstract: To cater the ever‐increasing demand of wireless high‐speed data access and mobile users, one of the potential enablers toward the sustainable improved network capacity is the network densi...

Performance analysis of least reliable symbol based ordered successive interference cancelation detection method for uplink NOMA

Abstract: Nonorthogonal multiple access (NOMA) is one of the key techniques to improve the spectral efficiency required for fifth‐generation (5G) mobile networks. A severe interuser interference is encountered during the detection process in the uplink NOMA scenario, leading to the imperfect successive interference cancelation (SIC), thereby resulting in extreme SIC error propagation. In this work, we propose a novel least‐reliable symbol‐based ordered‐successive interference cancelation (LRS‐OSIC) detection method for uplink NOMA to mitigate the severe effects of SIC error propagation. The bit error rate (BER) performance is presented for different phase‐shift keying (PSK) modulation schemes to better understand the proposed LRS‐OSIC algorithm. Further, detailed comparative analysis with the existing detection techniques for uplink NOMA is illustrated in terms of error rate and computation complexity. The obtained results prove that the proposed LRS‐OSIC detection method for uplink NOMA outperforms other existing techniques and closely matches the best achievable error performance as accomplished by the maximum likelihood (ML) decoder. Moreover, the simulation results are extended for three user scenarios to validate the benefits of the proposed LRS‐OSIC algorithm for more than two user scenarios.

An embedded pilot power based channel estimation and low-complexity feedback equalization scheme for OTFS system

Abstract: Orthogonal Time Frequency Space modulation (OTFS) has evolved as an astounding modulation technique for high-speed communication in a doubly dispersive channel. In any wireless communication system, channel estimation and equalization are essential at the receiver to recover the transmitted data. To accomplish this for the emerging OTFS based systems, a modified embedded pilot-based channel estimation technique and low complexity feedback equalization algorithm for integer Doppler shifts in the delay-Doppler domain are proposed in this paper. Our channel estimation scheme exploits embedded-pilot arrangement, and the symbol equalization relies on the Interference calculation and its mitigation iteratively. To achieve this we contemplate a prudent arrangement of symbols in the OTFS frame in such a way that the Guard symbols prevent the interference between data symbols and the pilot symbol at the receiver. Two distinct lumps of received data of the same OTFS frame will be engaged in channel estimation and data detection. An analytical expression of the theoretical Cramer Rao Lower Bound (CRLB) is derived and plotted for the proposed channel estimation scheme. The attained simulation results for Bit-Error-Rate (BER) under the proposed scheme show a significant error rate improvement over the Minimum Mean Squared Error (MMSE) equalization algorithm. Further, a lower computational complexity is also achieved in comparison with modified MMSE detection and MP detection algorithms.