Research On Techniques And Systems Of Cognitive Radio Energy Harvesting And Relaying Transmission

Cognitive radio(CR),as a technology that can effectively utilize spectrum resources,has become a research hot spot of wireless communication.In CR,the secondary user(SU)can share the licensed spectrum of the primary user(PU)in the premise of without affecting the communication quality of PU.The interference from SU to PU must satisfying the interference power limitation.Then the transmission power of the SU will be limited,and its performance can not be guaranteed.Therefore,relaying technology is combined with CR to construct cognitive relay system(CRS)or cognitive relay network(CRN).The relay technology has the advantages of expanding the coverage of the networks,covering some shadows,saving energy consumption and so on,which could significantly improve the performance of SU.In addition,many wireless communication terminals need to be powered by batteries,there may be problems such as its cost could be too high or it may be inconvenient to replace the batteries.So that obtaining energy by energy harvesting(EH)technology from radio-frequency signals has attracted much attention.This dissertation researches on CRS,relay systems based on EH and CRS based on EH.From the aspects of some problems such as system performance analysis,node or antenna selection and power allocation,and mainly focus on investigating outage probability(OP),throughput,diversity property as well as symbol error rate(SER),which could be probably resulted from imperfection of channel state information(CSI)or hardware impairment.The main work and contributions of the dissertation are as follows:1)The outage performance of a cognitive amplify-and-forward(AF)relay system with a best relay selection strategy(BRS)is researched.About the OP of SU under the condition of imperfect CSI estimations of the links from the SU to the PU,closed-form expressions for the upper and lower bounds of the OP and the asymptotic expressions of the OP in the condition of high signal-to-noise ratio(SNR)are derived through a geometrical analysis method which features slight integral region adjustment.Further,the general expressions of the geometrical analysis method are studied,and the general exact and asymptotic expressions for the OP are derived.Some simulation results corroborate the theoretical analysis.The simulation results show that the OP is influenced by the number of relays as well as the imperfect CSI,and it show that the effectiveness of the geometrical analysis method is better than the conventional one as a benchmark.It also reveals that the closer the adjusted integral region is to the original integral region,the better the geometrical analysis method.Moreover,the asymptotic analysis results based on the high SNR regime reveals that they appear to be very tight with the theoretical analytical lower bound and that the diversity order of the system is equal to the number of relays and independent of the imperfection of CSI.2)We has proposed a wireless powered DF relay system scheme,and studied several performance metrics.In particular,the system is based on time switching(TS)protocol for relay transmission,the energy-constrained relay harvesting energy from the transmitted signals of a power beacon(PB),the CSI of the transmission channel between any two nodes are imperfect.Closed-form expressions of the exact OP are derived firstly,and then the asymptotic expressions of the OP are derived,and the throughput as well as the SER are deduced based on the expressions of the OP.Furthermore,both transmission power of the source and the PB are optimized through the throughput maximization.Finally,some Monte Carlo simulation are conducted to corroborate the theoretical analysis,and reveal the impact of the transmission power of the source and PB as well as the imperfection of CSI on the system performance.Then we considered a wireless powered DF multi-relay system,and analysed the relationship between the multi-relay and the signal-relay system.The closed-form expressions of the exact OP and asymptotic expressions of OP for the multi-relay system are obtained through the closed-form expressions of the OP for the signal-relay system.The OP of the multi-relay system is compared with the signal-relay system.Finally,the correctness of the theoretical analysis is verified by some simulation results.3)We have proposed a CRS scheme based on EH.Specifically,the required energy of source and relay are harvested by the signals transmitted from a PB,the best antenna of the multiantenna source is selected to forward the information to destination through the relay.Here we play the emphases on the outage performance with hardware impairments,closed-form expressions of the OP and the throughput are derived,and the correctness of the theoretical analysis is verified by some Monte Carlo simulation results.Moreover,a CRS scheme based on EH,which has a direct link between the signal-antenna source and the destination is considered,the performance of the system is investigated.4)We have proposed a cognitive radio non-orthogonal multiple access(CR-NOMA)relay system based on EH.The required energy of source and relay are harvested by the signals transmitted from a PB.The source transmit the superimposed signals to the destination across the relay,the relay and the destination separate the signal utilizing the successive interference cancellation(SIC).Given the multiple PU's receivers and the hardware impairment,the closed-form expressions of the OP is derived.Finally,the correctness of the analysis is verified by simulation results.