Research On SNR Estimation Based On Adaptive MIMO-WPDM System

The main problem of future wireless communication is how to use the limited spectrum resources to achieve the maximum transmission rate.In order to overcome this problem,we need to take some advanced technology.WPDM system which Combined with MIMO technology(hereinafter referred to as MIMO-WPDM system),not only has realized the high speed of data transmission with variable bandwidth,but also has significantly increased channel capacity and spectral efficiency.It's one of the effective technical measures to solve the main problem of future wireless communication.MIMO-WPDM system with adaptive transmission technology,whose transmission mode can be adjusted adaptively according to the channel condition,so as to realize more reliable and effective communication.However,the signal to noise ratio(SNR)parameter need to be used in related technology of adaptive transmission,and these parameters need to be estimated in the actual communication system.Obviously,it is very important to effectively estimate the SNR of the adaptive MIMO-WPDM system.Several typical SNR estimation algorithms which were applicable to AWGN channels and wireless fading channels were introduced to the problem about SNR estimation of multi-carrier system in this paper.Simulation results showed that these algorithms could effectively estimate SNR in the respective channel environment,but when the channel environment couldn't meet the requirements of those algorithms,the estimation performance would be seriously deteriorated.Next,According to the tight supporting nature of subcarrier of WPDM system,the part outside the supporting interval of the received signal was selected.And its energy was solved,which was taken as the average noise energy of the corresponding subcarrier.And the SNR of each subcarrier was estimated.And the SNR mean value of system could be obtained finally.In the time and frequency selective fading channels,simulation results showed when the endpoint of the supporting interval was accurately detected and noise interval was reasonably selected,the proposed algorithm could more accurately estimate the value of SNR.Meanwhile,it had high precision and wide estimation range,and the estimation performance was less affected by channel fading.In addition,for the SNR estimation problem about MIMO system,a SNR estimation algorithm based on QR decomposition was introduced.But its performance depended on the results of channel estimation.Then the SNR estimationalgorithm based on subspace in SIMO system was expanded,which has been extended to the MIMO-WPDM system.By solving statistical average of the characteristic value of noise subspace,the estimated value of noise power could be obtained,and then SNR of the received signal on each channel antenna has been estimated.Simulation results showed that the algorithm had stable estimation performance and lower estimation error in wireless fading channels,and estimation error of system with larger size of antenna was smaller.