Mostafa Sayed - Academia.edu (original) (raw)
Papers by Mostafa Sayed
Scientific Reports
We present here the FT-IR, DFT computation, XRD, optical, and photophysical characterization of a... more We present here the FT-IR, DFT computation, XRD, optical, and photophysical characterization of a heterocyclic compound with thienopyrimidine and pyran moieties. TD-DFT/DMOl3 and TD-DFT/CASTEP computations were used to study the geometry of isolated and dimer molecules and their optical behavior. The indirect (3.93 eV) and direct (3.29 eV) optical energy bandgaps, HOMO–LUMO energy gap (3.02 eV), and wavelength of maximum absorption (353 nm) were determined in the gas phase with M062X/6-31+G (d, p). A thin film of the studied molecule was studied using XRD, FT-IR, and UV–Vis spectroscopy. The average crystallite size was found as 74.95 nm. Also, the photoluminescence spectroscopy revealed that the compound exhibited different emission bands at the visible range with different intensities depending on the degree of molecular aggregation. For instance, solutions with different concentrations emitted blue, cyan, and green light. On the other hand, the solid-state material produced a dua...
ACS Omega, 2022
Schiff bases represent an essential class in organic chemistry with antitumor, antiviral, antifun... more Schiff bases represent an essential class in organic chemistry with antitumor, antiviral, antifungal, and antibacterial activities. The synthesis of Schiff bases requires the presence of an organic base as a catalyst such as piperidine. Base-free synthesis of organic compounds using a heterogeneous catalyst has recently attracted more interest due to the facile procedure, high yield, and reusability of the used catalyst. Herein, we present a comparative study to synthesize new Schiff bases containing indole moieties using piperidine as an organic base catalyst and Au@TiO 2 as a heterogeneous catalyst. In both methods, the products were isolated in high yields and fully characterized using different spectral analysis techniques. The catalyst was reusable four times, and the activity was slightly decreased. The presence of Au increases the number of acidic sites of TiO 2 , resulting in CO polarization. Yields of the prepared Schiff bases in the presence of Au@TiO 2 and piperidine were comparable. However, Au@TiO 2 is an easily separable and recyclable catalyst, which would facilitate the synthesis of organic compounds without applying any hazardous materials. Furthermore, the luminescence behavior of the synthesized Schiff bases exhibited spectral shape dependence on the substituent group. Interestingly, the compounds also displayed deep-blue fluorescence with Commission Internationale de l'Ećlairage (CIE) coordinates of y < 0.1. Thus, these materials may contribute to decreasing the energy consumption of the emitting devices.
Organic Communications, 2021
Heterocyclic compounds play an important role in our life due to their biological importance in t... more Heterocyclic compounds play an important role in our life due to their biological importance in the struggle of microorganisms. Herein, a series of novel hybrid compounds of thienopyrimidine with triazine and pyrimidine scaffolds were synthesized starting from difunctionalized compound 5-amino-4-phenyl-2-(p-tolylamino)thieno[2,3d]pyrimidine-6-carbonitrile (1). Moreover, the diazotization of compound 1 with sodium nitrite in an acidic medium gave the chloro-triazine compound 2 which was subjected to the nucleophilic substitution of chlorine atom with different nucleophiles delivered compounds 3a-5c. Furthermore, the reaction of compound 1 with carbon disulfide led to the formation of dithione derivative 6 which was alkylated with ethyl chloroacetate to give compound 7, on the other hand, the reaction of compound 1 with phenyl isothiocyanate produced 4-imino-3,9-diphenyl-7-(p-tolylamino)-3,4dihydropyrimido[4',5':4,5]thieno [2,3-d]pyrimidine-2(1H)-thione (8), while acylation of the amino group in compound 1 with acetic anhydride gave compound 9. All synthesized compounds were characterized by elemental and spectral analysis techniques (IR, 1 H NMR, 13 C NMR, Mass spectroscopy). Furthermore, the synthesized compounds were tested for their antimicrobial activity against different strains of bacteria and fungi, and the results obtained showed good to moderate activity with almost all the strains.
2017 IEEE Intelligent Vehicles Symposium (IV), 2017
Narrowband power line communications (NB-PLC) and unlicensed wireless communications are the two ... more Narrowband power line communications (NB-PLC) and unlicensed wireless communications are the two leading communications technologies for the emerging two-way Vehicle-to-Grid (V2G) communications applications. In this paper, we exploit the media diversity provided by the availability of both the NB-PLC and wireless links to enhance the robustness against the interference and noise encountered on both links. In particular, we propose two efficient media diversity selection schemes to exploit the decoupled nature of the two communication links to reduce the bit error rate (BER) and increase the reliability of the V2G communication system. In addition, we derive closed-form expressions for the BER of our proposed media diversity selection schemes. Furthermore, we present simulation results that quantify the performance gains achieved by our proposed media diversity selection schemes compared to a single link (i.e. wireless-only or PLC-only) performance.
Current Chemistry Letters, 2022
Oxygen-containing heterocycles are largely distributed in natural and synthetic compounds. Coumar... more Oxygen-containing heterocycles are largely distributed in natural and synthetic compounds. Coumarins are among the most famous heterocycles which possess one oxygen atom in their rings. Coumarins are classified as multifunctional scaffold and are used as anti-oxidant reagents, anti-inflammatory, anti-microbial, anti-fungal, anti-HIV active, analgesic, anti-histaminic, insecticides, dyes, herbicides, sensitizers, perfumes, cosmetics and food additives. Due to their diverse applications in industrial and pharmaceutical fields, many chemists have given significant interest to these compounds. Herein, the review highlights various methods for the synthesis and interactions of coumarin moiety as one of the most efficient categories of heterocycles.
Polycyclic Aromatic Compounds, 2020
Nowadays heterocyclic compounds containing pyrimidine scaffold attract the interest of many organ... more Nowadays heterocyclic compounds containing pyrimidine scaffold attract the interest of many organic chemists due to their strong biological activity, so herein we present the synthesis of new polyc...
Current Chemistry Letters, 2021
Thiazolopyrimidnes are considered one of the most interesting classes in heterocyclic chemistry d... more Thiazolopyrimidnes are considered one of the most interesting classes in heterocyclic chemistry due to their pharmaceutical importance. Herein, we report the synthesis of some new heterocyclic compounds containing thiazolopyrimidine starting from compound (1) which was previously prepared in literature. The starting compound was allowed to react with different alkylating agents such as chloroacetone, chloroacetyl chloride, and phenacyl bromide to afford derivatives (2-4). Compound (5), benzylidene derivative, was obtained by the reaction of compound (2) with benzaldehyde while amino-dicarbonitrile compound (6) can be obtained by the reaction of compound (5) and malononitrile. Acetylation of amino group in compound (6) with chloroacetyl chloride led to formation of compound (7). Nucleophilic substitution of chlorine in compound (7) by aniline gave compound (8) which further subjected the Munich reaction to form compound (9). All new synthesized compounds were characterized using diff...
Optical Materials, 2020
Abstract Among several advantages of single-chromophore white-light-emitting dyes over mixed dyes... more Abstract Among several advantages of single-chromophore white-light-emitting dyes over mixed dyes are their phase stability and fabrication low-cost. Also, materials with aggregation-induced emission (AIE) have been employed as good bioprobes for DNA and for detecting some biomacromolecules sensitively and selectively. To be suitable for biological applications, the molecule should have AIE properties and be biocompatible. Indoles are electron-rich unsaturated compounds that display photophysical properties with potential applications such as fluorescent probes in addition to their widespread biological activities. Materials characterized with white-color emission, AIE activity, and biocompatibility are presented in this work. The thermal behavior and photophysical properties of some indole derivatives have been studied experimentally and theoretically using density functional theory. Besides their reported biological activities, the studied indole dyes show high thermal stabilities and AIE behavior. Some dyes gave white-color luminescence from a single chromophore, while others produced blue or green emissions. Theoretical and experimental results indicate that the different emission behavior of these dyes resulted from forming various kinds of aggregates with different intermolecular interactions.
IEEE Access, 2018
The cyclostationary noise in low-voltage narrowband powerline communications (NB-PLC) severely de... more The cyclostationary noise in low-voltage narrowband powerline communications (NB-PLC) severely degrades the communication reliability. In this paper, we adopt single-input multi-output (SIMO) transmission to enhance the reliability of NB-PLC. Considering the SIMO receiver structure, we exploit the NB-PLC noise cyclostationarity and the high spatial correlations across multiple receive phases to design practical and efficient noise mitigation techniques. In particular, we propose two time-domain frequencyshift (FRESH) filtering-based cyclostationary signal recovery techniques with different performance and complexity levels. The proposed time-domain-based FRESH filtering techniques minimize the meansquared error in estimating the orthogonal frequency division multiplexing (OFDM) information signal in the time-domain. The FRESH filtering exploits the cyclic auto-correlation of both the NB-PLC noise and the OFDM information signal in addition to their cyclic cross-correlation across the receive phases. Moreover, we propose a frequency-domain-based cyclostationary noise mitigation technique that minimizes the meansquared error in estimating the OFDM information signal in the frequency-domain. The proposed frequencydomain-based technique exploits the cyclostationarity of the noise to estimate its power spectral density as well as the cross-correlation, per frequency subchannel, over multiple stationary noise temporal regions. Our proposed SIMO NB-PLC noise mitigation techniques are shown via simulation results conducted using noise field measurements to achieve considerable performance gains over single-input single-output techniques. In addition, we show that our proposed techniques achieve considerable performance gains over the conventional SIMO maximal-ratio-combiner designed assuming stationary noise.
IEEE Transactions on Wireless Communications, 2017
Narrowband powerline communications (NB-PLC) and unlicensed wireless communications are two leadi... more Narrowband powerline communications (NB-PLC) and unlicensed wireless communications are two leading communications technologies for the emerging Smart Grid applications. The channel and noise statistics experienced by powerline and wireless transmissions are independent and of a non-identical nature. In this paper, we exploit the diversity provided by the simultaneous transmission of the same information signal over powerline and wireless links to enhance the overall system reliability. In particular, we propose efficient techniques to combine the received signals of the NB-PLC and wireless links for both coherent and differential modulation schemes while considering the impulsive nature of the noise on both links. In addition, we derive closed-form expressions for the average biterror-rate of the proposed combining techniques. Furthermore, we present simulation results that quantify the performance gains achieved by our proposed receive diversity combining techniques compared to conventional combining techniques.
2014 IEEE Global Communications Conference, 2014
Narrowband power line communications (NB-PLC) and unlicensed wireless communications are consider... more Narrowband power line communications (NB-PLC) and unlicensed wireless communications are considered as the two leading two-way communications technologies for the emerging Smart Grid applications. In this paper, we propose exploiting the diversity provided by combining the received signals from the NB-PLC and wireless links, where both carry the same information, to provide robustness against the interference encountered on both links. First, we analyze the performance of each link separately in presence of impulsive noise and interference. Then, we study the performance when combining the output signals from both links and compare it to the performance of each link.
2013 Asilomar Conference on Signals, Systems and Computers, 2013
ABSTRACT In this work, we develop joint interference-aware random beam and spectrum selection sch... more ABSTRACT In this work, we develop joint interference-aware random beam and spectrum selection scheme that provide enhanced performance for the secondary network under the condition that the interference observed at the primary receiver is below a predetermined acceptable value. We consider a secondary link composed of a transmitter equipped with multiple antennas and a single-antenna receiver sharing the same spectrum with a set of primary links composed of a single-antenna transmitter and a single-antenna receiver. The proposed schemes jointly select a beam, among a set of power-optimized random beams, as well as the primary spectrum that maximizes the signal-to-interference-plus-noise ratio (SINR) of the secondary link while satisfying the primary interference constraint. In particular, we consider the case where the interference level is described by a q-bit description of its magnitude, whereby we propose a technique to find the optimal quantizer thresholds in a mean square error (MSE) sense.
2012 IEEE Globecom Workshops, 2012
ABSTRACT In spectrum sharing systems, a secondary user (SU) is allowed to share the spectrum with... more ABSTRACT In spectrum sharing systems, a secondary user (SU) is allowed to share the spectrum with a primary licensed user under the condition that the interference at the the primary user receiver (PU-Rx) is below a predetermined threshold. Joint primary spectrum and transmit antenna selection diversity schemes can be utilized as an efficient way to meet the quality of service (QoS) demands of the SUs while satisfying the interference constraint. In this paper, we consider a secondary link comprised of a secondary transmitter (SU-Tx) equipped with multiple antennas and a single-antenna secondary receiver (SU-Rx) sharing the same spectrum with a number of primary users (PUs) operating at distinct spectra. We present a performance analysis for two primary spectrum and transmit antenna switched selection schemes with different amount of feedback requirements. In particular, assuming Rayleigh fading and BPSK transmission, we derive approximate BER expressions for the presented schemes. For the sake of comparison, we also derive a closed-form BER expression for the optimal selection scheme that selects the best pair in terms of the SU-Rx signal-to-noise ratio (SNR) which has the disadvantage of high feedback requirements. Finally, our results are verified with numerical simulations.
2011 IEEE 73rd Vehicular Technology Conference (VTC Spring), 2011
In this paper, we study applying dual branch transmit switch-and-stay combining (SSC) technique f... more In this paper, we study applying dual branch transmit switch-and-stay combining (SSC) technique for underlay cognitive radio (UCR) networks. In UCR, the secondary user is allowed to share the spectrum with the primary (licensed) user under the condition that interference at the primary receiver is below a predetermined threshold. Assuming binary phaseshift keying (BPSK) modulation and Rayleigh fading channels, we develop a closed form expression for the average bit error rate (BER) of the secondary link as a function of the switching threshold. We then find a closed form expression for the optimal switching threshold in the sense of minimizing the average BER. For the sake of comparison we derive an expression for the average BER of the dual branch transmit selection combining (SC) technique. We finally investigate the effect of correlation between secondary and interference channels on the average BER and the associated optimal switching threshold.
2012 IEEE Vehicular Technology Conference (VTC Fall), 2012
ABSTRACT Spectrum sharing systems have been introduced to alleviate the problem of spectrum scarc... more ABSTRACT Spectrum sharing systems have been introduced to alleviate the problem of spectrum scarcity by allowing secondary unlicensed networks to share the spectrum with primary licensed networks under acceptable interference levels to the primary users. In this paper, we develop interference-aware random beam selection schemes that provide enhanced throughput for the secondary link under the condition that the interference observed at the primary link is within a predetermined acceptable value. For a secondary transmitter equipped with multiple antennas, our schemes select a random beam, among a set of power- optimized orthogonal random beams, that maximizes the capacity of the secondary link while satisfying the interference constraint at the primary receiver for different levels of feedback information describing the interference level at the primary receiver. For the proposed schemes, we develop a statistical analysis for the signal-to-noise and interference ratio (SINR) statistics as well as the capacity of the secondary link. Finally, we present numerical results that study the effect of system parameters including number of beams and the maximum transmission power on the capacity of the secondary link attained using the proposed schemes.
Scientific Reports
We present here the FT-IR, DFT computation, XRD, optical, and photophysical characterization of a... more We present here the FT-IR, DFT computation, XRD, optical, and photophysical characterization of a heterocyclic compound with thienopyrimidine and pyran moieties. TD-DFT/DMOl3 and TD-DFT/CASTEP computations were used to study the geometry of isolated and dimer molecules and their optical behavior. The indirect (3.93 eV) and direct (3.29 eV) optical energy bandgaps, HOMO–LUMO energy gap (3.02 eV), and wavelength of maximum absorption (353 nm) were determined in the gas phase with M062X/6-31+G (d, p). A thin film of the studied molecule was studied using XRD, FT-IR, and UV–Vis spectroscopy. The average crystallite size was found as 74.95 nm. Also, the photoluminescence spectroscopy revealed that the compound exhibited different emission bands at the visible range with different intensities depending on the degree of molecular aggregation. For instance, solutions with different concentrations emitted blue, cyan, and green light. On the other hand, the solid-state material produced a dua...
ACS Omega, 2022
Schiff bases represent an essential class in organic chemistry with antitumor, antiviral, antifun... more Schiff bases represent an essential class in organic chemistry with antitumor, antiviral, antifungal, and antibacterial activities. The synthesis of Schiff bases requires the presence of an organic base as a catalyst such as piperidine. Base-free synthesis of organic compounds using a heterogeneous catalyst has recently attracted more interest due to the facile procedure, high yield, and reusability of the used catalyst. Herein, we present a comparative study to synthesize new Schiff bases containing indole moieties using piperidine as an organic base catalyst and Au@TiO 2 as a heterogeneous catalyst. In both methods, the products were isolated in high yields and fully characterized using different spectral analysis techniques. The catalyst was reusable four times, and the activity was slightly decreased. The presence of Au increases the number of acidic sites of TiO 2 , resulting in CO polarization. Yields of the prepared Schiff bases in the presence of Au@TiO 2 and piperidine were comparable. However, Au@TiO 2 is an easily separable and recyclable catalyst, which would facilitate the synthesis of organic compounds without applying any hazardous materials. Furthermore, the luminescence behavior of the synthesized Schiff bases exhibited spectral shape dependence on the substituent group. Interestingly, the compounds also displayed deep-blue fluorescence with Commission Internationale de l'Ećlairage (CIE) coordinates of y < 0.1. Thus, these materials may contribute to decreasing the energy consumption of the emitting devices.
Organic Communications, 2021
Heterocyclic compounds play an important role in our life due to their biological importance in t... more Heterocyclic compounds play an important role in our life due to their biological importance in the struggle of microorganisms. Herein, a series of novel hybrid compounds of thienopyrimidine with triazine and pyrimidine scaffolds were synthesized starting from difunctionalized compound 5-amino-4-phenyl-2-(p-tolylamino)thieno[2,3d]pyrimidine-6-carbonitrile (1). Moreover, the diazotization of compound 1 with sodium nitrite in an acidic medium gave the chloro-triazine compound 2 which was subjected to the nucleophilic substitution of chlorine atom with different nucleophiles delivered compounds 3a-5c. Furthermore, the reaction of compound 1 with carbon disulfide led to the formation of dithione derivative 6 which was alkylated with ethyl chloroacetate to give compound 7, on the other hand, the reaction of compound 1 with phenyl isothiocyanate produced 4-imino-3,9-diphenyl-7-(p-tolylamino)-3,4dihydropyrimido[4',5':4,5]thieno [2,3-d]pyrimidine-2(1H)-thione (8), while acylation of the amino group in compound 1 with acetic anhydride gave compound 9. All synthesized compounds were characterized by elemental and spectral analysis techniques (IR, 1 H NMR, 13 C NMR, Mass spectroscopy). Furthermore, the synthesized compounds were tested for their antimicrobial activity against different strains of bacteria and fungi, and the results obtained showed good to moderate activity with almost all the strains.
2017 IEEE Intelligent Vehicles Symposium (IV), 2017
Narrowband power line communications (NB-PLC) and unlicensed wireless communications are the two ... more Narrowband power line communications (NB-PLC) and unlicensed wireless communications are the two leading communications technologies for the emerging two-way Vehicle-to-Grid (V2G) communications applications. In this paper, we exploit the media diversity provided by the availability of both the NB-PLC and wireless links to enhance the robustness against the interference and noise encountered on both links. In particular, we propose two efficient media diversity selection schemes to exploit the decoupled nature of the two communication links to reduce the bit error rate (BER) and increase the reliability of the V2G communication system. In addition, we derive closed-form expressions for the BER of our proposed media diversity selection schemes. Furthermore, we present simulation results that quantify the performance gains achieved by our proposed media diversity selection schemes compared to a single link (i.e. wireless-only or PLC-only) performance.
Current Chemistry Letters, 2022
Oxygen-containing heterocycles are largely distributed in natural and synthetic compounds. Coumar... more Oxygen-containing heterocycles are largely distributed in natural and synthetic compounds. Coumarins are among the most famous heterocycles which possess one oxygen atom in their rings. Coumarins are classified as multifunctional scaffold and are used as anti-oxidant reagents, anti-inflammatory, anti-microbial, anti-fungal, anti-HIV active, analgesic, anti-histaminic, insecticides, dyes, herbicides, sensitizers, perfumes, cosmetics and food additives. Due to their diverse applications in industrial and pharmaceutical fields, many chemists have given significant interest to these compounds. Herein, the review highlights various methods for the synthesis and interactions of coumarin moiety as one of the most efficient categories of heterocycles.
Polycyclic Aromatic Compounds, 2020
Nowadays heterocyclic compounds containing pyrimidine scaffold attract the interest of many organ... more Nowadays heterocyclic compounds containing pyrimidine scaffold attract the interest of many organic chemists due to their strong biological activity, so herein we present the synthesis of new polyc...
Current Chemistry Letters, 2021
Thiazolopyrimidnes are considered one of the most interesting classes in heterocyclic chemistry d... more Thiazolopyrimidnes are considered one of the most interesting classes in heterocyclic chemistry due to their pharmaceutical importance. Herein, we report the synthesis of some new heterocyclic compounds containing thiazolopyrimidine starting from compound (1) which was previously prepared in literature. The starting compound was allowed to react with different alkylating agents such as chloroacetone, chloroacetyl chloride, and phenacyl bromide to afford derivatives (2-4). Compound (5), benzylidene derivative, was obtained by the reaction of compound (2) with benzaldehyde while amino-dicarbonitrile compound (6) can be obtained by the reaction of compound (5) and malononitrile. Acetylation of amino group in compound (6) with chloroacetyl chloride led to formation of compound (7). Nucleophilic substitution of chlorine in compound (7) by aniline gave compound (8) which further subjected the Munich reaction to form compound (9). All new synthesized compounds were characterized using diff...
Optical Materials, 2020
Abstract Among several advantages of single-chromophore white-light-emitting dyes over mixed dyes... more Abstract Among several advantages of single-chromophore white-light-emitting dyes over mixed dyes are their phase stability and fabrication low-cost. Also, materials with aggregation-induced emission (AIE) have been employed as good bioprobes for DNA and for detecting some biomacromolecules sensitively and selectively. To be suitable for biological applications, the molecule should have AIE properties and be biocompatible. Indoles are electron-rich unsaturated compounds that display photophysical properties with potential applications such as fluorescent probes in addition to their widespread biological activities. Materials characterized with white-color emission, AIE activity, and biocompatibility are presented in this work. The thermal behavior and photophysical properties of some indole derivatives have been studied experimentally and theoretically using density functional theory. Besides their reported biological activities, the studied indole dyes show high thermal stabilities and AIE behavior. Some dyes gave white-color luminescence from a single chromophore, while others produced blue or green emissions. Theoretical and experimental results indicate that the different emission behavior of these dyes resulted from forming various kinds of aggregates with different intermolecular interactions.
IEEE Access, 2018
The cyclostationary noise in low-voltage narrowband powerline communications (NB-PLC) severely de... more The cyclostationary noise in low-voltage narrowband powerline communications (NB-PLC) severely degrades the communication reliability. In this paper, we adopt single-input multi-output (SIMO) transmission to enhance the reliability of NB-PLC. Considering the SIMO receiver structure, we exploit the NB-PLC noise cyclostationarity and the high spatial correlations across multiple receive phases to design practical and efficient noise mitigation techniques. In particular, we propose two time-domain frequencyshift (FRESH) filtering-based cyclostationary signal recovery techniques with different performance and complexity levels. The proposed time-domain-based FRESH filtering techniques minimize the meansquared error in estimating the orthogonal frequency division multiplexing (OFDM) information signal in the time-domain. The FRESH filtering exploits the cyclic auto-correlation of both the NB-PLC noise and the OFDM information signal in addition to their cyclic cross-correlation across the receive phases. Moreover, we propose a frequency-domain-based cyclostationary noise mitigation technique that minimizes the meansquared error in estimating the OFDM information signal in the frequency-domain. The proposed frequencydomain-based technique exploits the cyclostationarity of the noise to estimate its power spectral density as well as the cross-correlation, per frequency subchannel, over multiple stationary noise temporal regions. Our proposed SIMO NB-PLC noise mitigation techniques are shown via simulation results conducted using noise field measurements to achieve considerable performance gains over single-input single-output techniques. In addition, we show that our proposed techniques achieve considerable performance gains over the conventional SIMO maximal-ratio-combiner designed assuming stationary noise.
IEEE Transactions on Wireless Communications, 2017
Narrowband powerline communications (NB-PLC) and unlicensed wireless communications are two leadi... more Narrowband powerline communications (NB-PLC) and unlicensed wireless communications are two leading communications technologies for the emerging Smart Grid applications. The channel and noise statistics experienced by powerline and wireless transmissions are independent and of a non-identical nature. In this paper, we exploit the diversity provided by the simultaneous transmission of the same information signal over powerline and wireless links to enhance the overall system reliability. In particular, we propose efficient techniques to combine the received signals of the NB-PLC and wireless links for both coherent and differential modulation schemes while considering the impulsive nature of the noise on both links. In addition, we derive closed-form expressions for the average biterror-rate of the proposed combining techniques. Furthermore, we present simulation results that quantify the performance gains achieved by our proposed receive diversity combining techniques compared to conventional combining techniques.
2014 IEEE Global Communications Conference, 2014
Narrowband power line communications (NB-PLC) and unlicensed wireless communications are consider... more Narrowband power line communications (NB-PLC) and unlicensed wireless communications are considered as the two leading two-way communications technologies for the emerging Smart Grid applications. In this paper, we propose exploiting the diversity provided by combining the received signals from the NB-PLC and wireless links, where both carry the same information, to provide robustness against the interference encountered on both links. First, we analyze the performance of each link separately in presence of impulsive noise and interference. Then, we study the performance when combining the output signals from both links and compare it to the performance of each link.
2013 Asilomar Conference on Signals, Systems and Computers, 2013
ABSTRACT In this work, we develop joint interference-aware random beam and spectrum selection sch... more ABSTRACT In this work, we develop joint interference-aware random beam and spectrum selection scheme that provide enhanced performance for the secondary network under the condition that the interference observed at the primary receiver is below a predetermined acceptable value. We consider a secondary link composed of a transmitter equipped with multiple antennas and a single-antenna receiver sharing the same spectrum with a set of primary links composed of a single-antenna transmitter and a single-antenna receiver. The proposed schemes jointly select a beam, among a set of power-optimized random beams, as well as the primary spectrum that maximizes the signal-to-interference-plus-noise ratio (SINR) of the secondary link while satisfying the primary interference constraint. In particular, we consider the case where the interference level is described by a q-bit description of its magnitude, whereby we propose a technique to find the optimal quantizer thresholds in a mean square error (MSE) sense.
2012 IEEE Globecom Workshops, 2012
ABSTRACT In spectrum sharing systems, a secondary user (SU) is allowed to share the spectrum with... more ABSTRACT In spectrum sharing systems, a secondary user (SU) is allowed to share the spectrum with a primary licensed user under the condition that the interference at the the primary user receiver (PU-Rx) is below a predetermined threshold. Joint primary spectrum and transmit antenna selection diversity schemes can be utilized as an efficient way to meet the quality of service (QoS) demands of the SUs while satisfying the interference constraint. In this paper, we consider a secondary link comprised of a secondary transmitter (SU-Tx) equipped with multiple antennas and a single-antenna secondary receiver (SU-Rx) sharing the same spectrum with a number of primary users (PUs) operating at distinct spectra. We present a performance analysis for two primary spectrum and transmit antenna switched selection schemes with different amount of feedback requirements. In particular, assuming Rayleigh fading and BPSK transmission, we derive approximate BER expressions for the presented schemes. For the sake of comparison, we also derive a closed-form BER expression for the optimal selection scheme that selects the best pair in terms of the SU-Rx signal-to-noise ratio (SNR) which has the disadvantage of high feedback requirements. Finally, our results are verified with numerical simulations.
2011 IEEE 73rd Vehicular Technology Conference (VTC Spring), 2011
In this paper, we study applying dual branch transmit switch-and-stay combining (SSC) technique f... more In this paper, we study applying dual branch transmit switch-and-stay combining (SSC) technique for underlay cognitive radio (UCR) networks. In UCR, the secondary user is allowed to share the spectrum with the primary (licensed) user under the condition that interference at the primary receiver is below a predetermined threshold. Assuming binary phaseshift keying (BPSK) modulation and Rayleigh fading channels, we develop a closed form expression for the average bit error rate (BER) of the secondary link as a function of the switching threshold. We then find a closed form expression for the optimal switching threshold in the sense of minimizing the average BER. For the sake of comparison we derive an expression for the average BER of the dual branch transmit selection combining (SC) technique. We finally investigate the effect of correlation between secondary and interference channels on the average BER and the associated optimal switching threshold.
2012 IEEE Vehicular Technology Conference (VTC Fall), 2012
ABSTRACT Spectrum sharing systems have been introduced to alleviate the problem of spectrum scarc... more ABSTRACT Spectrum sharing systems have been introduced to alleviate the problem of spectrum scarcity by allowing secondary unlicensed networks to share the spectrum with primary licensed networks under acceptable interference levels to the primary users. In this paper, we develop interference-aware random beam selection schemes that provide enhanced throughput for the secondary link under the condition that the interference observed at the primary link is within a predetermined acceptable value. For a secondary transmitter equipped with multiple antennas, our schemes select a random beam, among a set of power- optimized orthogonal random beams, that maximizes the capacity of the secondary link while satisfying the interference constraint at the primary receiver for different levels of feedback information describing the interference level at the primary receiver. For the proposed schemes, we develop a statistical analysis for the signal-to-noise and interference ratio (SINR) statistics as well as the capacity of the secondary link. Finally, we present numerical results that study the effect of system parameters including number of beams and the maximum transmission power on the capacity of the secondary link attained using the proposed schemes.