第三代行動通訊系統 (IMT-2000) 的主要目標是提供不同程度的服務品質保證。第三代行動通訊系統預期將可提供較大的系統容量和較高的傳輸速率，以支援無線網際網路服務和無線多媒體網路服務。因此，在第三代行動通訊系統中，碼 (code) 的分配和重新分配是相當重要的，因為我們可以藉此來提高碼的使用率。
在本篇論文中，於寬頻分碼多工存取系統 (W-CDMA) 下，針對 Universal Mobile Telecommunication System (UMTS) 所提出的四種服務品質類別，我們提出了一個新的分配碼的方法。在這個分配碼的方法中，我們使用了分群的機制來將整個系統資源分成兩群，在這樣的分群機制下來做分配碼和重新分配碼的動作。

經由模擬的結果，相較於其它比較的方法，我們所提出的方法可減少新進通話中斷的機率(new call blocking probability)以及增加系統的使用率。

The 3rd generation wideband CDMA (W-CDMA) systems support the relative higher and variable bit rate transmissions for applications with various quality-of-service (QoS) requirements. Code assignment and reassignment schemes in W-CDMA are essential, which aim to boost utilization of codes. In this thesis, a dynamic code assignment (DCA) scheme is proposed for traffics with various quality-of-service classes, i.e., conversational, streaming, interactive and background classes, introduced by Universal Mobile Telecommunication System (UMTS). For the proposed DCA scheme, the grouping mechanism statically partitions the entire code tree into two groups and each group serves traffics with various QoS requirements. Through the grouping mechanism, code assignments and reassignments are dynamically performed on new and released calls over each separated code group, respectively. The DCA for code assignments and reassignments are then investigated via the even-driven simulation. From the simulation results, the proposed DCA can reduce the new call blocking probability and thus improve the system utilization for W-CDMA.

[1] H. Holma and A. Toskala, WCDMA for UMTS. John Wiley & Sons, 2000.
[2] 3GPP TS 23.107, v3.3.0, QoS Concept and Architecture, June. 2000.
[3] 3GPP TR 25.922, v3.2.0, Radio Resource Management Strategies, June. 2000.
[4] T. Minn and K.-Y. Siu, “Dynamic Assignment of Orthogonal Variable-Spreading-Factor Codes in W-CDMA,” IEEE Journal on Selected Areas in Communications, vol. 18, pp. 1429-1440, Aug. 2000.
[5] R. Fantacci and S. Nannicini, “Multiple Access Protocol for Integration of Variable Bit Rate Multimedia Traffic in UMTS/IMT-2000 Based on Wideband CDMA,” IEEE Journal on Selected Areas in Communications, vol. 18, pp. 1441-1454, Aug. 2000.
[6] R. G. Cheng and P. Lin, “OVSF Code Channel Assignment for IMT-2000,” Proc. of IEEE Vehicular Technology Conference, vol. 3, pp. 2188-2192, 2000.
[7] F. Adachi, M. Sawahashi, and K. Okawa, “Tree-structure Generation of Orthogonal Spreading Codes with Different Lengths for Forward Link of DS-CDMA Mobile Radio,” Electronics Letters, vol. 33, pp. 27-28, Jan. 1997.
[8] E. Dahlman, B. Gudmundson, M. Nilsson, and J. Skold, “UMTS/IMT-2000 Based on Wideband CDMA,” IEEE Communication Magazine, vol. 36, pp. 70-80, Sept. 1998.
[9] F. Adach, M. Sawahashi, and H. Suda, “Wideband DS-CDMA for Next-Generation Mobile Communications Systems,” IEEE Communication Magazine, vol. 36, pp. 56-69, Sept. 1998.
[10] R. G. Cheng, “A code management mechanism for WCDMA mobile communication networks,” Proc. of International Workshop on Mobile Communications, pp. 348-353, Jun. 1999.