Research Of Physical Layer Security Based On Weighted Exponential Moving Average

Due to the broadcast nature of wireless channel,wireless communication is easily suffered from eavesdropping,tampering,node imitating and other illegal attacks.In the security field of wireless communication,traditional security schemes rely on the public key infrastructure and are likely subject to attack.Exploiting the characteristics of wireless channel can enhance the security of wireless communication.The secret key generation scheme based on physical layer by exploiting the characteristics of channel reciprocity,temporal variations and spatial variations,which is a cross-layer scheme that sufficiently utilize the resources of wireless channel.The secret key generation scheme based on physical layer involved with channel probing,channel quantization and key reconciliation.In this thesis,we propose a differential secret key generation scheme based on weighted exponential moving average method upon the analysis of previous works.In terms of channel quantization,the robustness and bit mismatch rate of current physical-layer-based schemes still need to be improved.Conventional two thresholds quantization is not stable when inserting or removing intermediate objects between legitimate users,then it causes enormous quantization errors.We adapt differential quantization processing the received signal strength in this paper,and the quantization thresholds are determined by mean value and variance.We proved that differential quantization can effectively resist the huge fluctuations of signals and a compared analysis will also be conducted to demonstrate that the differential quantization plays an important role in enhancing the stability of secret key generation scheme.To further decrease the bit mismatch rate,this paper combines the weighted exponential moving average method which is usually used in economics to process the received signal.Because of the small fluctuations caused by noise,huge quantization errors will appear,and it brings about the low consistency in key generation.Process the signals of legitimate users by weighted exponential moving average can effectively reduce the impact of small fluctuations,thus increasing consistency.The results of simulation proved that it can effectively decrease the bit mismatch rate using weighted exponential moving average.In this thesis,we also conduct performance analysis of the proposed secret key generation scheme based on weighted exponential moving average in terms of mean square error and the algorithm complexity.Mean square error analysis is to prove that though weighted exponential moving average algorithm process the received signals,it doesn’t change the original signals greatly which just describes the trend of received signals.Algorithm complexity analysis conducts from time complexity and space complexity.The analysis of time complexity via simulation platform,and theoretical analysis will conduct in space complexity.It proves that the algorithm have stable runtime and a good space complexity.