本文針對第三代行動通訊系統W-CDMA中，應用固定式波束及適應性波束兩種類型的智慧型天線於基地台上，探討使用巨觀分集(macro-diversity)和微觀分集(micro-diversity)方法對於系統效能的改善。當智慧型天線部署在基地台上，用戶在兩鄰近波束的重疊區域中時，我們利用巨觀分集來補償其天線增益的損失。其次，由於智慧型天線所形成的輻射波束(beam)較窄，因此本文使用微觀分集來收集從用戶來的多重路徑訊號，並提出一種收集多重路徑的方法來實現微觀分集，並透過模擬來評估其效益。我們發現，在細胞內使用巨觀分集，對於主波束寬度為12度，在臨界值為-1dB的時候，每個用戶傳送的功率平均可以減少30%。而在細胞間使用巨觀分集，當臨界值為+3dB時，則可以減少30%的發射功率。而不論是在細胞內或細胞間，使用巨觀分集都可以改善訊號位元能量對干擾功率密度的比。我們又發現其減少的量和主波束的寬度成反比。由此可知巨觀分集可以大大的減少用戶發射的功率，延長電池使用的時間。與全方向搜尋相比，我們所提出的多重路徑收集的方法，至少可以減少70%的搜尋數目。對於四個可解析的路徑，使用微觀分集後，可使位元能量對干擾的功率密度比增加3dB，而其標準差至少可以減低1dB。一般來說，巨觀分集和微觀分集確實可以增強智慧型天線應用在CDMA系統上的效能。

The macro- and micro-diversity schemes for the W-CDMA base stations deployed with smart antennae are investigated and their performances in terms of the improvement in the received bit energy to interference PSD ratio are evaluated, where both the adaptive and fixed beam schemes are considered for smart antenna systems. The macro-diversity scheme is employed to compensate the decrease of antenna gain when mobiles are located in the overlapping areas between two adjacent beams, while the micro-diversity is employed to collect the multi-path signals. A multi-path collecting algorithm is proposed to perform micro-diversity, and associate simulations are performed to evaluate its’ performance. We find that, for intra-cell macro-diversity, the average reduction of transmitted power is 30% for a beamwidth of 120 and a macro-diversity threshold of -1dB; while it is 8% for inter- cell macro-diversity for a threshold of +3dB. Consequently, the interference generated by mobiles is reduced and the bit-energy-to-interference PSD ratio is improved. In the micro-diversity, the proposed algorithm can provide at least 70% reduction in the number of search. For four resolvable paths, there is improvement on the received bit energy to interference PSD ratio in terms of a 3 dB increase in the mean value and a at least 1 dB decrease in the standard deviation. In general, both macro- and micro-diversity are indeed can be used to enhance the performance of CDMA systems deployed with smart antennae.

封面內頁
簽名頁
授權書………………………………………………………………………iii
中文摘要……………………………………………………………………iv
Abstract………………………………………………………………………v
誌謝…………………………………………………………………………vi
Table of Contents………………………………………………………vii
List of Figures……………………………………………………………ix
List of Tables……………………………………………………………xi
Chapter 1 Introduction……………………………………………………1
Chapter 2 CDMA and Smart Antenna for Cellular Radio……………5
2.1 The Cellular Concept………………………………………………5
2.2 Mobile Radio Channel………………………………………………7
2.2.1 Path Loss………………………………………………………9
2.2.2 Shadowing effect……………………………………………10
2.2.3 Multi-path fading…………………………………………10
2.3 Spread Spectrum techniques and CDMA System………………12
2.4 Smart antennas……………………………………………………17
Chapter 3 Macro Diversity schemes for W-CDMA systems
employing smart antennas…………………………………23
3.1 System model………………………………………………………23
3.2 Intra-cell Macro-dviersity……………………………………27
3.2.1 Transmitted power reduction ……………………………28
3.2.2 Improvement in Eb/I0………………………………………31
3.3 Inter-cell Micro-diversity……………………………………35
3.3.1 Transmitted power reduction……………………………35
3.3.2 Improvement in Eb/I0………………………………………38
Chapter 4 Micro-diversity schemes for W-CDMA systems
employing smart antenna……………………………………40
4.1 Multi-path collection for adaptive beam schemes………40
4.2 Multi-path collection for fixed beam schemes……………42
4.3 Performance of micro-diversity………………………………44
4.4 Simulations and results………………………………………45
4.5 Summary……………………………………………………………46
Chapter 5 Conclusions……………………………………………………50
Reference……………………………………………………………………52

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