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Symbol Error Probability of Incremental Relaying with Distributed/Centralized Relay Selection

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China Communications 2020年第11期17卷 141-155页

作者： Raed Alhamad Hatem Boujemaa Saudi Electronic University College of Computation and InformaticsRiyadh13316Saudi Arabia COSIM-SUPCOM Tunis2083 Tunisia

In this paper,we derive the Symbol Error Probability(SEP)of cooperative systems with incremental relaying and Distributed Relay Selection(DRS).The relays remain idle when the Signal to Noise Ratio(SNR)between the source and destination is larger than T.Otherwise,we activate a relay using DRS.Relay nodes transmit only if their SNR is larger than thresholdβ.If the SNRs of more than two relays is larger thanβ,there is a collision and the destination uses only the received signal from the source.If all relays have SNR less thanβ,no relay is chosen.Thresholdβis optimized to yield the lowest SEP at the destination.Our results are compared to centralized relay selection using opportunistic Amplify and Forward(OAF),Partial and Reactive Relay Selection(PRS and RRS).We compare our results to computer simulations for Rayleigh fading channels.

关键词： incremental relaying distributed relay selection centralized relay selection rayleigh fading channels

Enhanced spectrum sensing using a combination of energy detector,matched filter and cyclic prefix

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Digital Communications and Networks 2020年第4期6卷 534-541页

作者： Ghassan Alnwaimi Hatem Boujemaa King Abdulaziz University Saudi Arabia COSIM Lab SUPCOMTunisia

In this paper,we propose a sensing scheme based on energy detection,matched filter and cyclic prefix.Both Equal Gain Combining(EGC)and optimal combination of the aforementioned detectors are investigated in cooperative and non-cooperative spectrum sensing scenarios.In packet transmission systems such as OFDM(Orthogonal Frequency Division Multiple access)systems,the proposed scheme takes advantage of utilizing more samples than individual detectors,i.e.,cyclic prefix,training or pilot samples,and data payload samples.The proposed combine-sensing scheme offers higher detection probability and lower false alarm probability,as compared with the performance of individual detectors over the same frame duration.Simulation results are congruent with the theoretical curves and confirm the validity of our derivations.

关键词： Cooperative spectrum sensing Energy detector Matched filter Cyclic prefix CFAR CDR Cognitive radio networks False alarm probability Detection probability

Solar Energy Harvesting Using a Timer-Based Relay Selection

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Computers, Materials & Continua 2023年第1期74卷 2149-2159页

作者： Raed Alhamad Hatem Boujemaa Information Technology Department Saudi Electronic UniversityRiyadhSaudi Arabia UCAR-SUPCOM-COSIM Ariana2083Tunisia

In this paper,the throughput and delay of cooperative communications are derived when solar energy is used and relay node is selected using a timer.The source and relays harvest energy from sun using a photo voltaic system.The harvested power is used by the source to transmit data to the relays.Then,a selected relay amplifies the signal to the destination.Opportunistic,partial and reactive relay selection are used.The relay transmits when its timer elapses.The timer is set to a value proportional to the inverse of its Signal to Noise Ratio(SNR).Therefore,the relay with largest SNR will transmit first and its signal will be detected by the other relays that will remain idle to avoid collisions.Harvesting duration is optimized to maximize the throughput.Packet’s waiting time and total delay are also computed.We also derive the statistics of SNR when solar energy is used.The harvested power from sun is proportional to the sum of a deterministic radiation intensity and a random attenuation due to weather effects and clouds occlusion.The fixed radiation intensity depends on season,month and time t in hour.The throughput of cooperative communications with energy harvesting from sun was not yet studied.

关键词： Solar energy harvesting timer based relay selection relaying techniques throughput and delay analysis

NOMA with Adaptive Transmit Power Using Intelligent Reflecting Surfaces

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Computer Systems Science & Engineering 2023年第5期45卷 2059-2070页

作者： Raed Alhamad Hatem Boujemaa Information Technology Department Saudi Electronic UniversityRiaydhSaudi Arabia University of Carthage SUPCOM-COSIMAriana2083Tunisia

In this article,we use Intelligent Reflecting Surfaces(IRS)to improve the throughput of Non Orthogonal Multiple Access(NOMA)with Adaptive Transmit Power(ATP).The results are valid for Cognitive Radio Networks(CRN)where secondary source adapts its power to generate low interference at primary receiver.In all previous studies,IRS were implemented with fixed transmit power and previous results are not valid when the power of the secondary source is adaptive.In CRN,secondary nodes are allowed to transmit over the same band as primary users since they adapt their power to minimize the generated interference.Each NOMA user has a subset of dedicated reflectors.At any NOMA user,all IRS reflections have the same phase.CRN-NOMA using IRS offers 7,13,20 dB gain vs.CRN-NOMAwithout IRS for N=8,16,32 reflectors.We also evaluate the effects of primary interference.The results are valid for any number of NOMA users,Quadrature Amplitude Modulation(QAM)and Rayleigh channels.

关键词： IRS 6G CRN NOMA adaptive transmit power(ATP)