Research And Implement Of Cell Search Algorithm In LTE System

As the mainstream technology standard of 4G and 5G mobile communication system, LTE and its further technology has been widely researched and commercial applied with its advantage in the peak transmission rate and spectral efficiency. In the LTE system, mobile devices must firstly perform a cell search process before making a call or data transmission, through the process mobile devices get the cell numbers they are in, and establish time synchronization and frequency synchronization. This paper focuses on the cell search algorithm in LTE system and its hardware implementation.In the LTE system, the cell search is completed by three steps, firstly, get half frame timing position and sector number by PSS detection; secondly, get cyclic prefix length by CP type detection. In the end, get cell group number by SSS detection, and then determine cell number. Frequency offset estimation and correction can be completed during this three steps.For PSS detection, conventional half-frame timing position detection algorithms are divided into two types(Cross-correlation type and structure type), and the algorithms of this two types are researched and analyzed in detail. What's more, time-domain and frequency-domain sector number detection algorithm in PSS detection are compared and analyzed. For CP type detection, conventional contrast algorithm and threshold algorithm are studied in detail. On the PSS detection and CP type detection algorithms are studied, an improved PSS detection and CP type detection algorithm is proposed, in the proposed algorithm, half-frame timing position and CP type can be detected at the same time, it eliminates the need for a separate CP type detection module and reduces the cell search time. By using frequency domain sector detection algorithm, the proposed algorithm can save storage space, and detect sector number with Integer frequency offset can be estimated at the same time. For SSS detection, several conventional SSS detection algorithms are studied, Combined with simulation results it verifies that the direct cross-correlation SSS detection algorithm has a good advantage in performance in low frequency offset channel environment.Given the good performance of the direct cross-correlation SSS detection algorithm and the proposed PSS detection and CP type detection algorithm, This paper designs a new cell scheme, in this scheme, half-frame timing position, cyclic prefix length, the sector number and the frequency offset information are got by using the proposed PSS detection and CP type detection algorithm. The frequency offset of SSS time domain signal is corrected to make the performance advantages of direct cross-correlation SSS detection algorithm better played. The hardware implementation of this cell search scheme is proposed in this paper, and the detection mechanism in the half frame time position detection module is improved. A real-time detection mechanism based on dynamic threshold is used.Software and hardware simulation results show that: the proposed PSS detection and CP type detection algorithm has a strong anti-frequency offset ability in half-frame timing position detection, and the performance of its CP type detection is good and stable. The new cell search scheme designed in this paper has excellent detection performance in Gaussian environment and ETU environment.