The Low-Power Adaptive Pseudonoise Code Acquisition System for Direct-Sequence Spread-Spectrum Communications
|關鍵字:||低功率;偽雜訊碼;直接序列展頻通訊;通訊;可適性系統;low-power;pseudonoise code;direct-sequence spread-spectrum;communication;adaptive system|
The thesis discusses some advanced approaches to improve the direct-sequence spread-spectrum communication systems, especially on the pseudonoise ( PN ) code design and the PN code acquisition system. Three different approaches to improve performance of PN code acquisition systems are proposed for the use of spread-spectrum wireless applications in this thesis. The power consumption, bandwidth occupation, system complexity, and average acquisition time are comprehensively analyzed when discussing the performance of PN code acquisition systems. System simulation with ADS for fading channels and silicon verification had all been explored for analysis and theoretic proven. Introduction of this thesis in disclosed in Chapter 1. In Chapter 2, the author gives a brief introduction to the spread-spectrum communication systems. The definition of the spread-spectrum communication is given at first and then followed by the components, application, and implementation issues of the direct-sequence spread-spectrum communication systems. The receiver structure of the direct-sequence spread-spectrum communication systems is briefly introduced in Chapter 3. The PN code acquisition system of the direct-sequence spread-spectrum communication system is introduced in this chapter. The system performance issues of the PN code acquisition architecture are discussed in this chapter. The average acquisition time, channel bandwidth, system complexity, and power consumption are considered. The three different approaches to improve the system performance of the PN code acquisition system are also briefly introduced in this chapter. The author proposes an efficient searching algorithm in Chapter 4 to design the efficient PN code applied in the direct-sequence spread-spectrum communication system. The orthogonal degree and toggle rate of the PN code are verified for system performance, bandwidth occupation, and power consumption. The proposed power-saving pseudonoise ( PSPN ) code have the properties with low-power, bandwidth-efficiency, and better system performance when compared to the conventional PN codes. Theoretic analysis of PSPN code is applied at first and then followed by system simulation by ADS. The power consumption is verified by silicon measurement. The author proposes the optimized threshold decision ( OTD ) algorithm in Chapter 5. This algorithm is proposed to design the optimized PN code acquisition system. The optimized PN code acquisition system is defined as the PN code acquisition system with maximal probability of detection and constant probability of false alarm or with minimal probability of false alarm and constant probability of detection. By analysis and simulation, the proposed algorithm is proved to be efficient and convergent guaranteed. A novel low-power, adaptive PN code acquisition architecture is proposed in Chapter 6. The proposed PN code acquisition architecture dynamically updates the sampling rate and decision threshold values according to the estimated channel noise level. The adaptation scheme is implemented by look-up table in power management module, where the values in the look-up table is pre-calculated by the proposed adaptive sampling rate and threshold control ( ASTC ) algorithm. The PN code acquisition architecture is designed to meet the system specifications of minimal probability of detection and maximal probability of false alarm. Combined with the OTD algorithm proposed in Chapter 5, the proposed adaptive sampling rate and threshold control ( ASTC ) algorithm achieves the optimized sampling rate and threshold values for PN code acquisition system. The proposed PN code acquisition system outperforms the conventional PN code acquisition system at power consumption by 60% to 70% and meets the system requirements. Some conclusions and future works are discussed in Chapter 7.