Poonam Singh - Academia.edu (original) (raw)

Papers by Poonam Singh

Linear minimum mean square error (LMMSE) is the optimal channel estimator in the mean square erro... more Linear minimum mean square error (LMMSE) is the optimal channel estimator in the mean square error (MSE) perspective, however, it requires matrix inversion with cubic complexity. In this paper, by exploiting the circulant property of the channel frequency autocorrelation matrix RHH , an efficient LMMSE channel estimation method has been proposed for orthogonal frequency division multiplexing (OFDM) based on fast Fourier transformation (FFT) and circular convolution theorem. Finally, the computer simulation is carried out to compare the proposed LMMSE method with the classical LS and LMMSE methods in terms of performance measure and computational complexity. The simulation results show that the proposed LMMSE estimator achieves exactly same performance as conventional LMMSE estimator with much lower computational complexity.

TENCON 2017 - 2017 IEEE Region 10 Conference

In this paper, we consider a cooperative network, where base station (BS) and relay station (RS) ... more In this paper, we consider a cooperative network, where base station (BS) and relay station (RS) are enabled with a large number of antenna. For such network, the achievable rate and power efficiency is investigated. In uplink scenario, received signals across the RS and BS are detected with zero forcing (ZF) detector. We have also chosen ZF technique for precoder design, which is utilized across the RS in end-to-end signal transmission. When statistics of channel matrix and precoding matrix are known then SNR and achievable rate can be eaisly found by using random matrix theory. In such network, performance is also measured under different cooperation protocol. We have derived the tractable lower bound for the achievable rate which has also been numerically verified. Numerical results analyze the impact of a large number of RS and BS antenna for determining the achievable rate, where total transmit power remains constant. On the other side, the impact of a total number of RS and BS antenna on power efficiency has also been investigated where variation with total power to RS antennas is observed keeping BS antenna constant and vice versa.

2016 Twenty Second National Conference on Communication (NCC)

We consider the designing of a new set of uniquely decodable codes for uncoded synchronous overlo... more We consider the designing of a new set of uniquely decodable codes for uncoded synchronous overloaded CDMA system that exists for arbitrary values of spreading gain (code length). A fast and recursive method of construction is proposed where the orthogonal Hadamard matrix of least dimension (two), as the basis of construction regularizes a ternary pattern which is further leveraged to attain a rich simplicity in decoder design. The simplicity gained in designing of the proposed Comparison Aided Decoder (CAD) is prominent enough to neglect the marginal sacrifice in Bit Error Rate (BER) as compared to the optimum Maximum Likelihood Decoder (MLD) for noisy transmission. Despite its low complex nature, the detection retains it uniquely decodable (errorless) attribute in the absence of noise. Moreover, for large dimension of the proposed matrices, the loading capacity of the system as compared to the conventional CDMA gets a two fold enhancement.

2017 IEEE International Conference on Advanced Networks and Telecommunications Systems (ANTS)

This paper presents the performance analysis of the multiple antenna two-way amplify and-forward ... more This paper presents the performance analysis of the multiple antenna two-way amplify and-forward (AF) relay network in an interference-limited environment. Multiple antenna system is considered to overcome the fading effect. To avoid the high feedback overhead and fully exploit multiple antenna diversity, we employ transmit antenna selection (TAS) at the user node and analog network coding (ANC) at relaying node. We are assuming the presence of multiple co-channel interference (CCI) at the AF relay and noisy sources, an approximate closed-form expression for the overall outage probability (OOP) is derived. To gain more insight into system performance high SNR analysis is done and asymptotic expression for OOP is obtained. Furthermore, upper bound on ergodic capacity (EC) and approximate expression for symbol error probability(SEP) are derived. The tightness of our analysis is attested through Monte Carlo simulation and provides the insight into the impact of CCI under the general operating conditions and the key system parameters on overall system performance. Index Terms-Two-way relay systems, co-channel interferences, multi-antenna, AF relaying, overall outage probability, asymptotic analysis, symbol error probability, ergodic capacity.

The performance analysis of Alamouti space time block code (STBC) based orthogonal frequency divi... more The performance analysis of Alamouti space time block code (STBC) based orthogonal frequency division multiplexing (OFDM) is often analyzed on the assumption that the channel is constant over Alamouti code period (two consecutive OFDM symbol block). But when the channel is fast fading, this assumption does not hold good and causes co-channel interference (CCI). Hence, the simple Alamouti detection method is not sufficient to recover the original transmitted signal from the mixed transmitted signals at the receiver side. In this paper, we investigate several detection methods for cancelling the effect of CCI which includes SIC, ZF and DF. Finally, the performances of the above detection method are compared on the basis of symbol error rate (SER) for different mobile speed.

2017 9th International Conference on Communication Systems and Networks (COMSNETS), 2017

This paper presents the performance analysis of decode-and-forward (DF) relaying system in presen... more This paper presents the performance analysis of decode-and-forward (DF) relaying system in presence of both channel estimation error (CEE) and radio frequency impairments (RFI). First, the end-to-end signal-to-noise-plus-distortion-and-error ratio (SNDER) expression is derived, followed by an exact closed-form outage probability (OP) expression for Nakagami-m fading channel. As a special case, the OP analysis for Rayleigh fading channel is also provided. From the derived expressions, the relation amongst CEE and RFI is analyzed. For a complete study, the high SNR analysis of the derived equations is also carried out. The analytical results have been verified using the Monte Carlo simulations. Finally, intriguing results are presented with the help of plots shown in the numerical analysis.

In the last few years a lot of research has been carried out in the field of deliverance of infor... more In the last few years a lot of research has been carried out in the field of deliverance of information for improving its efficiency and reliability. However, the systematic analysis and verification of channel performance triggered wide interest of new researchers. The popular technique for transmission of signals over wireless channels was orthogonal frequency division multiplexing (OFDM). In the present investigation, multilayer perceptron (MLP) based algorithm called back propagation algorithm has been proposed in power line communication. The present method (back propagation algorithm) is a OFDM based model which exploited for the channel estimation. Simulations on a realistic indoor power-line system show that the results obtained from the channel estimation using present model are significantly improved when compared with competitive neural network. It is also noteworthy to mention that the computational complexity is decreased using the present algorithm. Keywords-Power Line...

2018 3rd International Conference for Convergence in Technology (I2CT), 2018

In this paper, we investigate the outage performance of a cooperative and cognitive radio system ... more In this paper, we investigate the outage performance of a cooperative and cognitive radio system where two secondary users (SUs) communicate through a relay via the two-way relaying. The coexistence of SUs with the primary users (PUs) in the same spectrum is possible by using underlay protocol, where the interference at the PU receiver is under a predefined threshold. Focusing on the cooperation process among the SU nodes and making use of the underlay cognitive approach, we derive the exact user outage probability(OP) in closed-form. Furthermore, the tight closed-form expression for the end to end OP is also derived, which is declared when any of a SU is in the outage. Our analysis employs transmit/receive beamforming at the SU nodes and analog network coding at relay node where opportunistic selection algorithm is deployed for selecting best relay in underlay scenario. Furthermore, we have derived the asymptotic performance and thus focus on the performance gain achieved by multi-...

Journal of Telecommunications and Information Technology, Mar 31, 2020

Most existing quasi-orthogonal space time block coding (QO-STBC) schemes have been developed rely... more Most existing quasi-orthogonal space time block coding (QO-STBC) schemes have been developed relying on the assumption that the channel is flat or remains static during the length of the code word symbol periods to achieve an optimal antenna diversity gain. However, in timeselective fading channels, this assumption does not hold and causes intertransmit-antenna-interferences (ITAI). Therefore, the simple pairwise maximum likelihood decoding scheme is not sufficient to recover original transmitted signals at the receiver side. To avoid the interferences, we have analyzed several signal detection schemes, namely zero forcing (ZF), two-step zero forcing (TS-ZF), minimum mean square error (MMSE), zero forcing-interference cancelation-decision feedback equalizer (ZF-IC-DFE) and minimum mean square error-interference cancelation-decision feedback equalizer (MMSE-IC-DFE). We have proposed two efficient iterative signal detection schemes, namely zero forcing-iterative interference cancelation-zero forcing-decision feedback equalization (ZF-IIC-ZF-DFE) and minimum mean square error-parallel interference cancelation-zero forcing-decision feedback equalization (MMSE-IIC-ZF-DFE). The simulation results show that these two proposed detection schemes significantly outperform all conventional methods for QOSTBC system over time selective channel.

Wireless Communications and Mobile Computing

TENCON 2015 - 2015 IEEE Region 10 Conference, 2015

The Alamouti Space Time Block Code (STBC) based Orthogonal Frequency Division Multiplexing (OFDM)... more The Alamouti Space Time Block Code (STBC) based Orthogonal Frequency Division Multiplexing (OFDM) is very attractive in frequency selective channel as the channels remain constant over Alamouti code period (two consecutive OFDM symbol block). But when the channel is fast fading, this assumption does not hold good and causes co-channel interference (CCI). Hence, the simple Alamouti detection method is not sufficient to recover the original transmitted signal from the mixed transmitted signals at the receiver side. To cancel the effects of CCI, several detection techniques are addressed namely SIC, DMLD, DZFD, DF and ML. The ML method has the optimum performance but the computational complexity is very high. Therefore, we propose a suboptimal MDF detection which provides comparable performance to that of ML with very less computational complexity. Finally, the performances of the above detection methods are compared in terms of symbol error rate (SER) and computational complexity for STBC OFDM system over doubly selective channel.

2014 9th International Conference on Industrial and Information Systems (ICIIS), 2014

2013 IEEE Asia Pacific Conference on Postgraduate Research in Microelectronics and Electronics (PrimeAsia), 2013

In this paper, the channel estimation technique for space time block code (STBC) based multi-inpu... more In this paper, the channel estimation technique for space time block code (STBC) based multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) is investigated for multipath fading channel. The channel estimation is based on the comb-type pilot arrangement where the pilot subcarriers are placed at regular interval of each OFDM symbol block and are orthogonal between different transmitting antennas. Due to the advantages of orthogonal pilot subcarrier, the original transmitted signal is completely recovered from the mixed transmitted signal at the receiver side. The least square (LS) algorithm is adopted for estimation of channel at pilot subcarrier while the interpolation is done at data subcarrier. The performance of the developed channel estimation technique is compared with the traditional single-input singleoutput (SISO) OFDM system on the basis of symbol error rate (SER). The simulation results show that the STBC OFDM gives better performance than SISO OFDM and the SER decreases as the signal to noise ratio (SNR) and the number of receive antenna increases.

2014 Annual IEEE India Conference (INDICON), 2014

Alamouti coded Space Frequency Block Code (SFBC) based Orthogonal Frequency Division Multiplexing... more Alamouti coded Space Frequency Block Code (SFBC) based Orthogonal Frequency Division Multiplexing (OFDM) is very attractive due to its robustness against fast fading channel as the Channel Frequency Response (CFR) remain constant over Alamouti code period (two adjacent OFDM subcarrier). However, the channel is frequency selective as well as time selective. In frequency selective channel, the CFR are not constant for two adjacent OFDM subcarriers and hence leads to inter-symbol-interference (ISI) in SFBC-OFDM system. The inter-carrier-interference (ICI) also arises in OFDM system for time varying fast fading channel due to the loss of orthogonality among the subcarriers. Hence, both the ISI and ICI degrade the system performance for SFBC-OFDM system over time varying multipath fading channel. In this paper, we have proposed an iterative interference cancellation scheme which cancels the effect of ISI and ICI jointly. The proposed scheme cancels the interferences in two steps. In the first step, the Diagonalized Zero Forcing Detection (DZFD) method is used to suppress the effect of ISI. Then, in the second step, a simplified parallel interference cancellation (PIC) scheme coupled with decision statistics combining (DSC) is used to cancel the ICI effect and hence improves the system performance. The theory and simulation results verify that the proposed scheme achieves good performance in high time selective and high frequency selective channel environment for SFBC OFDM system.

2014 Annual IEEE India Conference (INDICON), 2014

From the last decade much more emphasis were drawn to develop robust Cognitive Radio Networks (CR... more From the last decade much more emphasis were drawn to develop robust Cognitive Radio Networks (CRNs). For robust CRNs, Spectrum Sensing is one of the most important issue for its better existence in licensed spectrum. Spectrum sensing is used for finding unoccupied frequency bands, called white space or spectrum holes. However, spectrum sensing performance in practice is often compromised with multipath fading, shadowing and receiver uncertainty issues due to low signal to noise ratio (SNR). In this paper, we propose a robust double threshold feature detector (DTFD) that detect even very low SNR primary user. Here we have used DTFD in cooperative spectrum sensing scenario in cognitive radio networks (CRNs) on a additive white Gaussian noise (AWGN) channel. Here individual detectors employ double threshold method in feature based detection of Orthogonal Frequency Division Multiplexing (OFDM) signal, and sends their results to fusion center (FC) where final decision takes place. Detection is done by using popular autocorrelation property of cyclic prefix (CP) in OFDM signal. From proposed technique, our objective is to achieve a better sensing performance under very low SNR, such that the primary networks and the CRNs can coexist in better way. Simulation results are done under theoretical perspective which illustrate that the proposed sensing technique can reliably detect OFDM signals at SNR as low as-20 dB.

2009 First UK-India International Workshop on Cognitive Wireless Systems (UKIWCWS), 2009

This paper presents a novel multiple access scheme for uplink of future mobile communications usi... more This paper presents a novel multiple access scheme for uplink of future mobile communications using Multi-Symbol Encapsulated Orthogonal Frequency Division Multiplexing (MSE-OFDM). MSE-OFDM is a bandwidth efficient OFDM scheme, where a number of OFDM symbols are grouped together as a frame and protected by one single cyclic prefix (CP). This reduces the extent of redundancy caused by the CP and increases the bandwidth efficiency of the system. In the proposed scheme, a number of OFDM symbols from one user are grouped and one cyclic prefix is used for a group of symbols. Thus, we can get better spectral efficiency as compared to conventional OFDMA. The FFT size is also reduced, which improves the robustness to synchronization errors and reduces the PAPR.

International Conference on Communication and Electronics System Design, 2013

In this paper, we present a quantitative comparison of two agile modulation techniques employed b... more In this paper, we present a quantitative comparison of two agile modulation techniques employed by cognitive radio transceivers operating in a dynamic spectrum access (DSA) network. One of the modulation techniques is single carrier frequency division multiple access (SC-FDMA). The other modulation technique under study is a variant of multicarrier code division multiple access (MC-CDMA). Although several studies comparing conventional OFDM and MC-CDMA has been conducted in literature to justify robust error performance of MC-CDMA, a quantitative performance evaluation of these schemes has not been performed when employed in a DSA network. In this paper we show that their performances can be significantly different from the conventional setup. Analytical expressions for the error probability of an SC-FDMA transceiver have been derived and compared with computer simulation results. The results show that the error robustness of SC-FDMA is relatively better then MC-CDMA in underlay communication.

2013 IEEE International Conference on Electronics, Computing and Communication Technologies, 2013

2013 IEEE CONFERENCE ON INFORMATION AND COMMUNICATION TECHNOLOGIES, 2013

This paper presents a basic useful technique for carrier frequency offset (CFO) estimation in ort... more This paper presents a basic useful technique for carrier frequency offset (CFO) estimation in orthogonal frequency division multiplexing (OFDM) over frequency selective fading channel. The performance of OFDM system is very sensitive to CFO, which introduces inter-carrier interference (ICI). In cyclic prefix (CP) based estimation, the CFO can be found from the phase angle of the product of CP and corresponding rear part of the OFDM symbol. In CFO estimation using training symbol, the CFO estimation range can be increased by reducing the distance between two blocks of samples for correlation. This was made possible by using training symbol that are repetitive with shorter period. An analytic expression in form of mean square error(MSE) of frequency offset synchronization is reported, and simulation results verify theoretical analysis.

Linear minimum mean square error (LMMSE) is the optimal channel estimator in the mean square erro... more Linear minimum mean square error (LMMSE) is the optimal channel estimator in the mean square error (MSE) perspective, however, it requires matrix inversion with cubic complexity. In this paper, by exploiting the circulant property of the channel frequency autocorrelation matrix RHH , an efficient LMMSE channel estimation method has been proposed for orthogonal frequency division multiplexing (OFDM) based on fast Fourier transformation (FFT) and circular convolution theorem. Finally, the computer simulation is carried out to compare the proposed LMMSE method with the classical LS and LMMSE methods in terms of performance measure and computational complexity. The simulation results show that the proposed LMMSE estimator achieves exactly same performance as conventional LMMSE estimator with much lower computational complexity.

TENCON 2017 - 2017 IEEE Region 10 Conference

In this paper, we consider a cooperative network, where base station (BS) and relay station (RS) ... more In this paper, we consider a cooperative network, where base station (BS) and relay station (RS) are enabled with a large number of antenna. For such network, the achievable rate and power efficiency is investigated. In uplink scenario, received signals across the RS and BS are detected with zero forcing (ZF) detector. We have also chosen ZF technique for precoder design, which is utilized across the RS in end-to-end signal transmission. When statistics of channel matrix and precoding matrix are known then SNR and achievable rate can be eaisly found by using random matrix theory. In such network, performance is also measured under different cooperation protocol. We have derived the tractable lower bound for the achievable rate which has also been numerically verified. Numerical results analyze the impact of a large number of RS and BS antenna for determining the achievable rate, where total transmit power remains constant. On the other side, the impact of a total number of RS and BS antenna on power efficiency has also been investigated where variation with total power to RS antennas is observed keeping BS antenna constant and vice versa.

2016 Twenty Second National Conference on Communication (NCC)

We consider the designing of a new set of uniquely decodable codes for uncoded synchronous overlo... more We consider the designing of a new set of uniquely decodable codes for uncoded synchronous overloaded CDMA system that exists for arbitrary values of spreading gain (code length). A fast and recursive method of construction is proposed where the orthogonal Hadamard matrix of least dimension (two), as the basis of construction regularizes a ternary pattern which is further leveraged to attain a rich simplicity in decoder design. The simplicity gained in designing of the proposed Comparison Aided Decoder (CAD) is prominent enough to neglect the marginal sacrifice in Bit Error Rate (BER) as compared to the optimum Maximum Likelihood Decoder (MLD) for noisy transmission. Despite its low complex nature, the detection retains it uniquely decodable (errorless) attribute in the absence of noise. Moreover, for large dimension of the proposed matrices, the loading capacity of the system as compared to the conventional CDMA gets a two fold enhancement.

2017 IEEE International Conference on Advanced Networks and Telecommunications Systems (ANTS)

This paper presents the performance analysis of the multiple antenna two-way amplify and-forward ... more This paper presents the performance analysis of the multiple antenna two-way amplify and-forward (AF) relay network in an interference-limited environment. Multiple antenna system is considered to overcome the fading effect. To avoid the high feedback overhead and fully exploit multiple antenna diversity, we employ transmit antenna selection (TAS) at the user node and analog network coding (ANC) at relaying node. We are assuming the presence of multiple co-channel interference (CCI) at the AF relay and noisy sources, an approximate closed-form expression for the overall outage probability (OOP) is derived. To gain more insight into system performance high SNR analysis is done and asymptotic expression for OOP is obtained. Furthermore, upper bound on ergodic capacity (EC) and approximate expression for symbol error probability(SEP) are derived. The tightness of our analysis is attested through Monte Carlo simulation and provides the insight into the impact of CCI under the general operating conditions and the key system parameters on overall system performance. Index Terms-Two-way relay systems, co-channel interferences, multi-antenna, AF relaying, overall outage probability, asymptotic analysis, symbol error probability, ergodic capacity.

The performance analysis of Alamouti space time block code (STBC) based orthogonal frequency divi... more The performance analysis of Alamouti space time block code (STBC) based orthogonal frequency division multiplexing (OFDM) is often analyzed on the assumption that the channel is constant over Alamouti code period (two consecutive OFDM symbol block). But when the channel is fast fading, this assumption does not hold good and causes co-channel interference (CCI). Hence, the simple Alamouti detection method is not sufficient to recover the original transmitted signal from the mixed transmitted signals at the receiver side. In this paper, we investigate several detection methods for cancelling the effect of CCI which includes SIC, ZF and DF. Finally, the performances of the above detection method are compared on the basis of symbol error rate (SER) for different mobile speed.

2017 9th International Conference on Communication Systems and Networks (COMSNETS), 2017

This paper presents the performance analysis of decode-and-forward (DF) relaying system in presen... more This paper presents the performance analysis of decode-and-forward (DF) relaying system in presence of both channel estimation error (CEE) and radio frequency impairments (RFI). First, the end-to-end signal-to-noise-plus-distortion-and-error ratio (SNDER) expression is derived, followed by an exact closed-form outage probability (OP) expression for Nakagami-m fading channel. As a special case, the OP analysis for Rayleigh fading channel is also provided. From the derived expressions, the relation amongst CEE and RFI is analyzed. For a complete study, the high SNR analysis of the derived equations is also carried out. The analytical results have been verified using the Monte Carlo simulations. Finally, intriguing results are presented with the help of plots shown in the numerical analysis.

In the last few years a lot of research has been carried out in the field of deliverance of infor... more In the last few years a lot of research has been carried out in the field of deliverance of information for improving its efficiency and reliability. However, the systematic analysis and verification of channel performance triggered wide interest of new researchers. The popular technique for transmission of signals over wireless channels was orthogonal frequency division multiplexing (OFDM). In the present investigation, multilayer perceptron (MLP) based algorithm called back propagation algorithm has been proposed in power line communication. The present method (back propagation algorithm) is a OFDM based model which exploited for the channel estimation. Simulations on a realistic indoor power-line system show that the results obtained from the channel estimation using present model are significantly improved when compared with competitive neural network. It is also noteworthy to mention that the computational complexity is decreased using the present algorithm. Keywords-Power Line...

2018 3rd International Conference for Convergence in Technology (I2CT), 2018

In this paper, we investigate the outage performance of a cooperative and cognitive radio system ... more In this paper, we investigate the outage performance of a cooperative and cognitive radio system where two secondary users (SUs) communicate through a relay via the two-way relaying. The coexistence of SUs with the primary users (PUs) in the same spectrum is possible by using underlay protocol, where the interference at the PU receiver is under a predefined threshold. Focusing on the cooperation process among the SU nodes and making use of the underlay cognitive approach, we derive the exact user outage probability(OP) in closed-form. Furthermore, the tight closed-form expression for the end to end OP is also derived, which is declared when any of a SU is in the outage. Our analysis employs transmit/receive beamforming at the SU nodes and analog network coding at relay node where opportunistic selection algorithm is deployed for selecting best relay in underlay scenario. Furthermore, we have derived the asymptotic performance and thus focus on the performance gain achieved by multi-...

Journal of Telecommunications and Information Technology, Mar 31, 2020

Most existing quasi-orthogonal space time block coding (QO-STBC) schemes have been developed rely... more Most existing quasi-orthogonal space time block coding (QO-STBC) schemes have been developed relying on the assumption that the channel is flat or remains static during the length of the code word symbol periods to achieve an optimal antenna diversity gain. However, in timeselective fading channels, this assumption does not hold and causes intertransmit-antenna-interferences (ITAI). Therefore, the simple pairwise maximum likelihood decoding scheme is not sufficient to recover original transmitted signals at the receiver side. To avoid the interferences, we have analyzed several signal detection schemes, namely zero forcing (ZF), two-step zero forcing (TS-ZF), minimum mean square error (MMSE), zero forcing-interference cancelation-decision feedback equalizer (ZF-IC-DFE) and minimum mean square error-interference cancelation-decision feedback equalizer (MMSE-IC-DFE). We have proposed two efficient iterative signal detection schemes, namely zero forcing-iterative interference cancelation-zero forcing-decision feedback equalization (ZF-IIC-ZF-DFE) and minimum mean square error-parallel interference cancelation-zero forcing-decision feedback equalization (MMSE-IIC-ZF-DFE). The simulation results show that these two proposed detection schemes significantly outperform all conventional methods for QOSTBC system over time selective channel.

Wireless Communications and Mobile Computing

TENCON 2015 - 2015 IEEE Region 10 Conference, 2015

The Alamouti Space Time Block Code (STBC) based Orthogonal Frequency Division Multiplexing (OFDM)... more The Alamouti Space Time Block Code (STBC) based Orthogonal Frequency Division Multiplexing (OFDM) is very attractive in frequency selective channel as the channels remain constant over Alamouti code period (two consecutive OFDM symbol block). But when the channel is fast fading, this assumption does not hold good and causes co-channel interference (CCI). Hence, the simple Alamouti detection method is not sufficient to recover the original transmitted signal from the mixed transmitted signals at the receiver side. To cancel the effects of CCI, several detection techniques are addressed namely SIC, DMLD, DZFD, DF and ML. The ML method has the optimum performance but the computational complexity is very high. Therefore, we propose a suboptimal MDF detection which provides comparable performance to that of ML with very less computational complexity. Finally, the performances of the above detection methods are compared in terms of symbol error rate (SER) and computational complexity for STBC OFDM system over doubly selective channel.

2014 9th International Conference on Industrial and Information Systems (ICIIS), 2014

2013 IEEE Asia Pacific Conference on Postgraduate Research in Microelectronics and Electronics (PrimeAsia), 2013

In this paper, the channel estimation technique for space time block code (STBC) based multi-inpu... more In this paper, the channel estimation technique for space time block code (STBC) based multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) is investigated for multipath fading channel. The channel estimation is based on the comb-type pilot arrangement where the pilot subcarriers are placed at regular interval of each OFDM symbol block and are orthogonal between different transmitting antennas. Due to the advantages of orthogonal pilot subcarrier, the original transmitted signal is completely recovered from the mixed transmitted signal at the receiver side. The least square (LS) algorithm is adopted for estimation of channel at pilot subcarrier while the interpolation is done at data subcarrier. The performance of the developed channel estimation technique is compared with the traditional single-input singleoutput (SISO) OFDM system on the basis of symbol error rate (SER). The simulation results show that the STBC OFDM gives better performance than SISO OFDM and the SER decreases as the signal to noise ratio (SNR) and the number of receive antenna increases.

2014 Annual IEEE India Conference (INDICON), 2014

Alamouti coded Space Frequency Block Code (SFBC) based Orthogonal Frequency Division Multiplexing... more Alamouti coded Space Frequency Block Code (SFBC) based Orthogonal Frequency Division Multiplexing (OFDM) is very attractive due to its robustness against fast fading channel as the Channel Frequency Response (CFR) remain constant over Alamouti code period (two adjacent OFDM subcarrier). However, the channel is frequency selective as well as time selective. In frequency selective channel, the CFR are not constant for two adjacent OFDM subcarriers and hence leads to inter-symbol-interference (ISI) in SFBC-OFDM system. The inter-carrier-interference (ICI) also arises in OFDM system for time varying fast fading channel due to the loss of orthogonality among the subcarriers. Hence, both the ISI and ICI degrade the system performance for SFBC-OFDM system over time varying multipath fading channel. In this paper, we have proposed an iterative interference cancellation scheme which cancels the effect of ISI and ICI jointly. The proposed scheme cancels the interferences in two steps. In the first step, the Diagonalized Zero Forcing Detection (DZFD) method is used to suppress the effect of ISI. Then, in the second step, a simplified parallel interference cancellation (PIC) scheme coupled with decision statistics combining (DSC) is used to cancel the ICI effect and hence improves the system performance. The theory and simulation results verify that the proposed scheme achieves good performance in high time selective and high frequency selective channel environment for SFBC OFDM system.

2014 Annual IEEE India Conference (INDICON), 2014

From the last decade much more emphasis were drawn to develop robust Cognitive Radio Networks (CR... more From the last decade much more emphasis were drawn to develop robust Cognitive Radio Networks (CRNs). For robust CRNs, Spectrum Sensing is one of the most important issue for its better existence in licensed spectrum. Spectrum sensing is used for finding unoccupied frequency bands, called white space or spectrum holes. However, spectrum sensing performance in practice is often compromised with multipath fading, shadowing and receiver uncertainty issues due to low signal to noise ratio (SNR). In this paper, we propose a robust double threshold feature detector (DTFD) that detect even very low SNR primary user. Here we have used DTFD in cooperative spectrum sensing scenario in cognitive radio networks (CRNs) on a additive white Gaussian noise (AWGN) channel. Here individual detectors employ double threshold method in feature based detection of Orthogonal Frequency Division Multiplexing (OFDM) signal, and sends their results to fusion center (FC) where final decision takes place. Detection is done by using popular autocorrelation property of cyclic prefix (CP) in OFDM signal. From proposed technique, our objective is to achieve a better sensing performance under very low SNR, such that the primary networks and the CRNs can coexist in better way. Simulation results are done under theoretical perspective which illustrate that the proposed sensing technique can reliably detect OFDM signals at SNR as low as-20 dB.

2009 First UK-India International Workshop on Cognitive Wireless Systems (UKIWCWS), 2009

This paper presents a novel multiple access scheme for uplink of future mobile communications usi... more This paper presents a novel multiple access scheme for uplink of future mobile communications using Multi-Symbol Encapsulated Orthogonal Frequency Division Multiplexing (MSE-OFDM). MSE-OFDM is a bandwidth efficient OFDM scheme, where a number of OFDM symbols are grouped together as a frame and protected by one single cyclic prefix (CP). This reduces the extent of redundancy caused by the CP and increases the bandwidth efficiency of the system. In the proposed scheme, a number of OFDM symbols from one user are grouped and one cyclic prefix is used for a group of symbols. Thus, we can get better spectral efficiency as compared to conventional OFDMA. The FFT size is also reduced, which improves the robustness to synchronization errors and reduces the PAPR.

International Conference on Communication and Electronics System Design, 2013

In this paper, we present a quantitative comparison of two agile modulation techniques employed b... more In this paper, we present a quantitative comparison of two agile modulation techniques employed by cognitive radio transceivers operating in a dynamic spectrum access (DSA) network. One of the modulation techniques is single carrier frequency division multiple access (SC-FDMA). The other modulation technique under study is a variant of multicarrier code division multiple access (MC-CDMA). Although several studies comparing conventional OFDM and MC-CDMA has been conducted in literature to justify robust error performance of MC-CDMA, a quantitative performance evaluation of these schemes has not been performed when employed in a DSA network. In this paper we show that their performances can be significantly different from the conventional setup. Analytical expressions for the error probability of an SC-FDMA transceiver have been derived and compared with computer simulation results. The results show that the error robustness of SC-FDMA is relatively better then MC-CDMA in underlay communication.

2013 IEEE International Conference on Electronics, Computing and Communication Technologies, 2013

2013 IEEE CONFERENCE ON INFORMATION AND COMMUNICATION TECHNOLOGIES, 2013

This paper presents a basic useful technique for carrier frequency offset (CFO) estimation in ort... more This paper presents a basic useful technique for carrier frequency offset (CFO) estimation in orthogonal frequency division multiplexing (OFDM) over frequency selective fading channel. The performance of OFDM system is very sensitive to CFO, which introduces inter-carrier interference (ICI). In cyclic prefix (CP) based estimation, the CFO can be found from the phase angle of the product of CP and corresponding rear part of the OFDM symbol. In CFO estimation using training symbol, the CFO estimation range can be increased by reducing the distance between two blocks of samples for correlation. This was made possible by using training symbol that are repetitive with shorter period. An analytic expression in form of mean square error(MSE) of frequency offset synchronization is reported, and simulation results verify theoretical analysis.