Research On PN Code Acquisition Algorithm In Cdma2000 Systems

PN (Pseudo Noise) code has good correlation and pseudo-randomness, which plays an important role in the third generation mobile communication system. cdma2000 system uses the short code (Short PN code) to achieve synchronization, long code (Long PN code) to achieve privacy. Short code and Long code acquisition is a very important issue in three ways. (1)The received signal exists carrier frequency offset and synchronization, the conventional algorithm can not effectively acquisition under large frequency offset , low signal to noise ratio to receive signals; (2) Non-cooperation and low SNR conditions lead to long-code is unknown, acquisition success probability is not high;(3)Current algorithm depend on constant data at special occasions, long code cannot acquainted from the business data. Therefore, the short code and long code acquisition is studied in this paper.After analysis of PN code in the cdma2000 system, then designed a PN Code Acquisition scheme to recover the data under the Non-cooperation conditions. Main contents including:1. Design and Implementation of Sequential PN code acquisition scheme. The scheme is based on the received signal demodulation process and divided into three phases: In initialization phase, acquisition the short code to achieve synchronization; in the channel establishment phase, acquisition long code, the information correctly recovered; if channel establishment phase can not acquisition long code, need to continue to acquisition business communication stage. The scheme has improved signal reception and information recover reliability to improve the overall receiver performance.2. Proposed joint time-frequency domain correction of the short code coherent acquisition algorithm. The algorithm is based on the Cyclostationarity of short code, on the frequency offset and non-synchronized joint correction code, so that the correction signal and local codes with similar coherence, and finally acquisitioned by correlation detection achieved. Simulation results show that, the algorithm can adapt to non-synchronous received signal distortion and improve the low SNR conditions, the large dynamic synchronization of the received signal probability.3. Proposed mask recover algorithm based on register state differential, obtain the key parameters of the long code (Mask Code) in low SNR. First, analyze the system signaling, the channel establishment phase from the fixed format data to be captured to obtain a long code; and then, using the feature of different time with a common long code mask, according to the state register and output the formation of a long relationship between the three codes by dimension reduction, exhaustive, and is estimated to recover the mask; Finally, the solution has been to re-create a long code mask to achieve a long code acquisition, improve the acquisition probability.4. Proposed long code acquisition algorithm based on decoupling. First, in the full analysis of the voice coding and convolution coding method, the characteristics of repeat, interleave rule of long code generating and the physical layer data, established the equations; in the end, the equations is worked out, the solution based on the decoupling of business data and long code, realized the separation of long code and business data.