Research On Electromagnetic Emission Aware Resource Allocation For Uplink OFDM Systems

With the proliferation of smart phones and the rich content of mobile Internet applications,the demand for mobile communications traffic has increased exponentially in recent years.While enjoying the convenient services provided by smart phones,people are also worried about the potential health effects due to exposure to electromagnetic radiation.The influence of mobile phone radiation on the human body is mainly manifested by thermal e ffects and non-thermal effects.The thermal effects may cause local warming of human tissues,which poses a potential hazard to human health.Therefore,how to reduce the radiation of mobile phones has become a growing concern of people.The amount of electromagnetic radiation of a mobile phone is directly related to the specific absorption rate,the transmission power of the mobile phone,and the transmission time.The specific absorption rate is currently the internationally accepted metric for electromagnetic radiation.However,since the specific absorption rate is easily affected by the mobile phone model and the user itself,the research on reducing the specific absorption rate is mostly from the perspective of mobile phone material and structural design.Most of the research on power is aimed at reducing power and improving energy efficiency,without considering the time dimension.In view of the above problems,in this thesis,the radiation reduction problem is solved by minimizing the transmission energy of mobile phones with the assumption that the user's specific absorption rate is fixed.Firstly,considering that data transmission generates more radiation than data reception,the uplink of OFDM wireless communication systems is used as the system model,and the mobile phone transmission energy is divided into two parts,including the pilot signaling energy and the data transmission energy.Then,according to the relationship between channel estimation and effective data transmission,two resource allocation algorithms are explored to solve the problem of transmission energy minimization,namely offline resource allocation algorithm and online resource allocation algorithm.Both of these algorithms are based on the assumption that the base station can accurately predict the uplink channel state information.The difference is that due to the effect of channel estimation model,the resource allocation in offline scheme is performed within the transmission window which contains T time slots,while online resource allocation is performed instantaneously on each time slot.In solving the resource allocation problem,appropriate subcarrier and power allocation algorithm are investigated for the two schemes respectively.The optimal solution is replaced by the suboptimal solut ion obtained by a multiple-step method,which achieves good performance at lower complexity.The simulation results show that compared with the traditional resource allocation algorithms based on spectrum/energy efficiency maximization,the two algorithms studied in this paper have great advantages in radiation reduction.The offline scheme performs better than the online scheme due to the design of transmission time window.However,when the target bit number is high,the online scheme will outperform the offline scheme.