Research And Implementation Of Acquisition Of PN Code In EVDO Systems

CDMA 2000 1x EVDO, one of mainstream standards of 3G, is a telecom standard aiming at improving packet data transferring. An extra carrier is occupied to transfer packet data by EVDO. Some key technologies, including TDM (Time Division Multiplexing), AMC (Adaptive Modulation and Code), HARQ (Hybrid ARQ), high-level modulation, rate control, are adopted in EVDO systems, render the maximum rate of Forward to 2.4Mbps. Code acquisition is an important and radical problem in spread communication systems. A fast and efficient algorithm for code acquisition is quite valuable in both research and practice.In the first part of this thesis, evolution and some new techniques adoped by EVDO whice are different for CDMA 2000 and EVDO forward link physical layer structure are introduced.The second part focous on theory of code acquisition, and several code acquisition methods, such as method based on matched filter, method based on FFT (Fast Fourier Transformation), are introduced, and characters of methods above are discussed then. A simulation platform for code aquistion in EVDO systems is constructed in the third part. Two algorithms's performace in AWGN channel for code aquistion in EVDO systems, method based on FFT and method based on matchen filter, is described. And some factors, including threshold, combining length, frequency offset, are discussed how they affect performance of the two algorithms mentioned. The result of simulation shows that the perforamce of the method based on matched filter is excellent. Overall structure of PMF algrithm's implementation in FPGA is showed in the last part of thesis, and details of implementation are showed. And after a series of functional simulation, as well as the actual data measured in the real EVDO system, the hardware realizations of the algorithms are proved to be correct.