Precoding Design With A Constraint On User Electromagnetic Radiation Exposure In Portable Devices

The number of mobile devices worldwide is growing at a rate of billions per year.Because of their integrated processing capabilities,motion sensors,communications,cameras and other functions,people are increasingly dependent on mobile phones.The communications of wireless devices relies on radio frequency waves as the transmission medium,and the large amount of exposed radio frequency waves bring electromagnetic radiation harm to the human body.How to reduce electromagnetic field radiation has become an increasingly concerning issue.Internationally,the SAR is used to measure the amount of radiation that the electromagnetic field causes to the human body.The traditional approach is to test the SAR value of a manufactured mobile terminal to meet the limits of the relevant organization,but the SAR constraints are not taken into account during the design phase.At the early stage of design,this research considered SAR and power as constraints,and at the same time reduced the near-field radiation to improve the far-field performance.This thesis addressed the issue that mobile devices did not take electromagnetic radiation constraints into account during the communications process,analyzes the impact of SAR constraints on uplink communications during the early design period,examines a code scheme under the constraints of power and electromagnetic radiation.Through analyzing the relevant material and data,exploring the SAR models,combines it with practical factors,we further investigate an adaptive high order SAR model.In order to understand the role of electromagnetic radiation constraints in uplink communications,incorporates the SAR constraint into the design process of mobile phone transmission.When the transmitter knows channel state,the beamformer is obtained to optimizes the transmission signal.Two kinds of beamforming optimization algorithms are then studied.Considering the power constraint and SAR constraint simultaneously,we explored a set of code words aimed at two transmitter two receiver MIMO systems,and compared them with the improved downlink transmission technology(such as Alamouti,Spatial Multiplexing,etc.).In order to achieve a greater coding gain,the Turbo code of 1/2 rate is further cascades.The simulation results show that SAR coding can ensure the high reliability and high speed of MIMO wireless communication transmission system s while reducing the potential damage of electromagnetic field radiation to the human body.Through the research in this thesis,we have preliminarily demonstrated that the reduction of near-field SAR is closely related to the improvement of far-field communication performance.It shows that considering the SAR constraint in the design stage has a significant effect on reducing the electromagnetic field to the human body.