Üçüncü nesil WCDMA sistemlerinde dinamik kod tahsisi
Dynamic code assignment in third generation WCDMA systems
- Tez No: 135936
- Danışmanlar: YRD. DOÇ. DR. ADNAN KAVAK
- Tez Türü: Yüksek Lisans
- Konular: Bilgisayar Mühendisliği Bilimleri-Bilgisayar ve Kontrol, Elektrik ve Elektronik Mühendisliği, Computer Engineering and Computer Science and Control, Electrical and Electronics Engineering
- Anahtar Kelimeler: Dinamik kod tahsisi, Sabit kod tahsisi, OVSF, WCDMA, UMTS
- Yıl: 2003
- Dil: Türkçe
- Üniversite: Kocaeli Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Elektronik-Bilgisayar Eğitimi Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 97
Özet
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Özet (Çeviri)
ABSTRACT Keyword: Dynamic Code Assigment, Fixed Code Assigment, OVSF, WCDMA, UMTS, AB-DKT Recently Second Generation (2G) systems have become insufficient to meet to explosive demands for mobile communications services. In order to meet these demands, Third Generation (3G) systems UMTS/IMT-2000, which provide date rates up to 2 Mbps have been developed by ETSI. In this standard, WCDMA (Wideband Code Division Multiple Access) technique has been selected for UTRA FDD mode operation. The third-generation systems are supposed to have better quality and coverage, be more power and bandwidth efficient, and be deployed in diverse environments. In the 2G CDMA systems, each user is assigned a single Orthogonal Constant Spreading Factor (OCSF), and therefore fixed number users can be supported. Since 3G systems aim to support more users with higher data rates, fixed code assignment method used in conventional 2G systems are inefficient to meet these requirements. Therefore, it is essential to develop new dynamic OVSF (Orthogonal Variable Spreading Factor) code assignment for 3G systems. In this study, dynamic OVSF code assignment methods which aims to increase capacity (number of users) in WCDMA systems are investigated and a dynamic OVSF code assignment algorithm so called Root-Code Divided Dynamic Code Assignment (RC-DCA) is proposed. The main idea in the proposed algorithm is to divide the code-tree into two sub-trees from the root code and transfer the codes from lower cost part to the higher cost part. Cost function is calculated from the code-pattern of each sub-tree, which is the composite of occupied codes and their rates. The proposed RC-DCA method is compared with another dynamic code assignment (Minn-Siu DCA- MS-DCA) and fixed code assignment (FCA) methods. In terms of blocking probability and spectral efficiency the RC-DCA method outperforms FCA method and has approximately the same performance as MS-DCA method. The disadvantage of RC-DCA is that it has longer execution time for the code assignment as compared to the above two algorithms. The reason for this is that the proposed algorithm has larger number of continuously reassigned codes than MS-DCA does. However, the execution times of the two algorithms are expected to converge as the rates of requesting calls increase.
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