Research On Spectrum Sharing And Energy Allocation In Cognitive Radio Network

In recent years,with the rapid development of wireless communication industry,the shortage of spectrum resources is becoming increasingly prominent.Meanwhile,with the diversity,intelligent and wide-oriented development of communication terminals,the power consumption of personal mobile devices is becoming increasingly severe.How to improve the spectral efficiency of the communication system,while reducing the energy consumption,is more and more important.Spectrum sharing and energy harvesting are promising techniques to improve the bandwidth and energy efficiencies to meet the ever-growing demand of wireless data transmissions.The main work in this paper can be demonstrated as follows:Firstly,this paper proposes an efficient relay-based spectrum sharing protocol in the cognitive radio network,where the secondary user(SU)can implicitly harvest the radio frequency(RF)energy from the primary user(PU)transmissions.Using the harvested energy,the SU can assist the PU transmission to exchange for the opportunity of spectrum access.Both the Alamouti coding and the superposition coding techniques are adopted by the transmitters to facilitate the primary data relaying and the secondary data transmission simultaneously.The joint decoding and the interference cancelation techniques are adopted by the receivers to retrieve the desired signals.The more power allocated for the primary data relaying,the higher throughput can be achieved for the PU,while the less throughput is available for the SU with less energy remained.The optimal power allocation is numerically determined by maximizing the SU throughput while guaranteeing the PU throughput.Numerical results show that protocol can greatly improve the system throughput and the impacts of various system settings are revealed for the network deployment.Secondly,this paper studies cooperative spectrum sharing in cognitive radio networks with wireless energy harvesting(EH),where all the primary and secondary users are overlaid on the 2-D plane.this paper propose an algorithm to optimally allocate the bandwidth and time resources.Each primary user(PU)should harvest energy from the wireless signal sent by its access point(AP),whereas all the APs and the secondary users have stable power supply.To improve EH efficiency,an EH zone is applied around each PU,where the secondary transmitter(ST)with the shortest distance toward the PU is selected to transfer the wireless energy.Using the harvested energy,the PU can transmit its data over the reverse link to the AP,but the data transmission is more likely to fail due to the weak transmission power and the severe path loss.In this case,a cooperative region is applied between each PU and its corresponding AP,where a suitable ST with the best channel quality toward the AP is selected to forward the primary data.The performance requirement of the primary system can be easily satisfied with ST cooperation,and thus,a fraction of bandwidth can be released to the secondary-data transmission.By analyzing system performance this paper uses the stochastic geometry theory to facilitate both the EH and data transmission.The optimization problem is formulated to maximize the area throughput of the secondary system under the performance constraint of the primary system.Performance results are presented to validate theoretical analysis and show the impacts of various system settings.