Research On Blind Rate Detection Scheme For Multi-Rate CDMA System

Multi-rate CDMA technology can support more flexible and higher rate data transmission than single-rate CDMA technology. Therefore, this technology has been exploited wider and wider in the design of mobile communication systems. The rate information of received signal sequences should be acquired before decoded. In uncooperative situation, the blind rate detection (BRD) technologies are exploited to obtain rate information. There are two main problems ex-isting in the BRD technologies. First of all, it need too much system resources and detection time to detect the rate information for long rate set (LRS) or ultra long rate set (ULRS) CDMA system. Then, the detection success ratio is small when signal-to-noise ratio (SNR) is low, and decreases sharply with SNR declining.To solve the BRD problems for LRS CDMA system, this dissertation proposes a new symbol repetition factor estimate BRD (SBRD) model and a new algorithm. To work out the BRD prob-lems for ULRS CDMA system, this dissertation proposes a search space optimization scheme and a new algorithm for the first stage of the scheme. This dissertation has researched the fol-lowing main contents:1) Auto-correlation matrix decision based SBRD (AMD-SBRD) model is proposed. The tra-ditional SBRD algorithms ignore the difference among the received symbols, which results in low capacity against declining SNR. Therefore, the AMD-SBRD model utilizes auto-correlation information of every symbol's amplitude to estimate the symbol repetition factor. This model has low complexity, and high successful decision ratio. When some symbols'amplitude change seriously, the performance of AMD-SBRD model will fluctuate widely. Therefore, modified AMD-SBRD (MAMD-SBRD) model is proposed. MAMD-SBRD model picks out the bad points and judges the whole tendency of the auto-correlation matrix to estimate the symbol repe-tition factor. This model has a good stability performance, and can realize BRD under the condi-tions of low SNR for multi-rate CDMA signal sequences.2) Multiple rate features extracting based BRD (MRFE-BRD) algorithm is proposed. This algorithm utilizes five rate features to optimize the performance of MAMD-SBRD model. The symbol interleaving feature can decrease the model time delay. The relationship between symbol repetition and sequence repetition has been given, which increase the scope of application for this model. The coding rate feature can be used to recognize different rate modes with the same repetition feature. The rate change feature can reduce the model detection scope. And other sig-naling features can also improve the model performance at different degree. The simulation re-sults show that this algorithm can raise the decision success ratio effectively, and bring down the detection delay largely.3) Search space progressive optimization based BRD (SSPO-BRD) scheme is designed. All the SBRD technologies are not suitable to ULRS systems. Therefore, SSPO-SBRD scheme di-vides the ULRS into several level subsets, and utilizes coarse detection and precise detection to recognize these subsets. This scheme can reduce the scope of rate set step by step, and detect the exact rate value finally. Signal constellation features extraction based modulation modes classification (SCFE-MMC) algorithm is utilized. SCFE-MMC can implement the coarse detec-tion for SSPO-BRS scheme. This algorithm considers the modulation modes as the dividing cri-terion, and utilizes the fuzzy clustering and constellation matching means to classify the modula-tion modes. The simulation results show that this algorithm can recognize the modulation modes such as MPSK and 16-QAM, which can determine the first level rate subset.4) EV-DO Rev.A system BRD modular is designed. To test the performance of BRD module, a system testing model is set up by Simulink. And two BRD modules are designed for the for-ward traffic link and the reverse traffic link. The modules utilizes many means such as multiple slots data extraction, packets transmission end decision, rate scope table query, different algo-rithms invoking and status divide. And the dissertation also gives the modular structure chart for these two modules, which can guide the engineering practice. The testing results show that this design can satisfy the system requirements well.