The Pilot Pattern Design For Sparse Channel Estimation In OFDM System

Recent advances in compressed sensing(CS)for pilot-assisted channel estimation have been widely investigated,and many sparse recovery algorithms have been applied.Compared with the traditional channel estimation method,the channel estimation technique based on CS can using the sampling rate which is far lower than the Nyquist sampling rate to reconstruct the sparse signal with effectively.Among them,the common sparse channel reconstruction algorithm mainly includes: Orthogonal matching pursuit(OMP),Compressive sampling matching pursuit(CoSaMP)and so on.Besides,some convex optimization algorithm such as Sparse reconstruction by separable approximation(SpaRSA)and YALL1 algorithm can also be used as a reconstruction algorithm to recover the sparse channel.Just like the traditional channel estimation technology,people always do some research focused on the improvement and innovation of channel estimation algorithm,but often ignore the other factors which can influence the channel estimation performance such as the structural design of the pilot patterns.In fact,many researches has shown that different pilot pattern plays a very important role on the performance of sparse channel estimation.Therefore,in this paper,the problem of pilot pattern design was considered.We are going to figure out the relationship between pilot pattern and channel estimation and ensure the whole system have better performance of channel estimation.In this paper,we are summing up the existing algorithms on the basis of the traditional pilot pattern design algorithm firstly.Then,we do some changes to the traditional algorithms in order to reduce the complexity and improve the convergence rate of the previous algorithm.Moreover,an adaptive pilot pattern design algorithm combines with the CIR estimation in real-time was considered.Compared with the traditional methods,the characteristics of the proposed adaptive algorithm is that when the great changes have taken place in the wireless channel environment,the pilot pattern will be redesigned following the previous steps until it is convergent again,which ensure the pilot pattern be always suit for the specific wireless channel.The contribution of this article summarized as follows:1.In this paper,we summary the existing pilot structure design standard,and give algorithm implementation according to different standards respectively.Based on the analysis and comparison of the performance with different standards,it shows that the details about the various standards.2.In this paper,we have made some improvement based on the traditional MIP standard by combining with genetic algorithm to searching for the optimal pilot patterns.Compared with the traditional algorithm,this new method can reduce the complexity of the algorithm and improve the stability and convergence of the algorithm with efficiency.3.In addition,we also made some improvement for MIP standard itself and proposed an improved deterministic pilot pattern design standard.Compared with the traditional MIP standard,this new standard ful y considers the other factors in the process of sparse signal recovery,it will ensure the estimation performance more stable and more accurate.4.In this paper,the problem of pilot pattern design combined with the CIR estimation in real-time was considered,and an adaptive algorithm has been proposed.Compared with the traditional methods such as MIP-OMP,the proposed adaptive algorithm considers the pilot pattern design combing with the actual channel characteristics,and select the suitable pilot pattern upon the specific environment.Moreover,the characteristics of the proposed adaptive algorithm is that when the great changes have taken place in the wireless channel environment,the pilot pattern will be redesigned following the previous step until it is convergent again,which ensure the pilot pattern be always suit for the specific wireless channel.5.In order to reduce the complexity of adaptive algorithm in practical application,this paper consider to improve the adaptive algorithm combine with the MIP standard.By taking the pretreatment on the pilot pattern,this improved adaptive algorithm will decrease the iteration times and time which algorithm required for convergence,and it will also reduce the computation complexity of the whole system.