A Study of OVSF Code Assignment 游智為、黃鈴玲
E-mail: [email protected]
ABSTRACT
In the mobile communication technologies of the 3rd Generation Partner-ship Project (3GPP)，there is a wideband digital
technology named WCDMA (Wideband Code Division Multiple Access)．This technology includes the identity between the cell site and the customer premise equipment and data channelize．In the technology of data channelize，Orthogonal Variable Spreading Factor (OVSF) code can distinguish the different data tunnels and promise the orthogonality for different customer tunnels or the same customer but different business tunnels．Furthermore，this technology allows users apply the same frequency to translate information and undisturbed by each other．Therefore，upon providing the flexible application of the data trans-mitted speed
，OVSF code has a great contribution of supplying the multime-dia service．However，due to its distinctive feature of orthogonlity
，there is a limitation of the code allocation．It should concern both intelligence and good integration mechanism to achieve OVSF tree’s highest system utilization．At present，the method of the OVSF coding has the following main directions for progression
．The one is to reduce the probability of Code Blocking．The other is to lower the system resource expense generated by the reassignment．Finally is to decrease the delay time of request，in other words，it is to decline the operation algorithm time of the whole allocation process．The thesis is to make use of the schedule mechanism and integrates the methods mentioned above to develop a new allocation mechanism．
Keywords : WCDMA ; OVSF
Table of Contents
第一章 緒論...3 第二章 相關文獻及理論基礎...6 2.1 OVSF編碼樹...6 2.2 單碼與多碼 系統...7 第三章 OVSF碼的配置與重配置機制...10 3.1 配置機制(Assignment Schemes)...10 3.2 重配
置(Reassignment Scheme)機制..13 第四章 OVSF配置等候排程機制法...16 第五章 模擬結...22 第六章 結 論...30 參考文獻...31
REFERENCES
[1] 3GPP Technical Specification TS 25.213 V4.2.0 (Release 4) Spreading and Modulation (FDD), Dec. 2001.
[2] R. Assarut, K. Kawanishi, R. Deshpande, U. Yamamoto, and Y. Onozato, “Performance Evaluation of Orthogonal Variable Spreading Factor code Assignment Schemes in W-CDMA,” IEEE International Conference on Communications, vol. 5, pp. 3050- 3054, 2002.
[3] R. Assarut, U. Yamamoto, and Y. Onozato, “Region Division Assignment of Orthogonal Variable Spreading Factor Codes in W-CDMA,”
The 54th IEEE Vehicular Technology Conference, vol. 3, pp. 1884-1888, 2001.
[4] C.-M. Chao, Y.-C. Tseng, and L.-C. Wang, “Reducing Internal and External Fragmentations of OVSF Codes in WCDMA Sys-tems with Multiple Codes,” IEEE Wireless Communications and Networking Conference, Vol. 1, pp. 693-698, 2003.
[5] W.-T. Chen, Y.-P. Wu, and H.-C. Hsiao, “A Novel Code As-signment Scheme for W- CDMA Systems,” The 54th IEEE Ve-hicular Technology Society Conference, vol. 2, pp. 1182-1186, 2001 [6] R.-G. Cheng and P. Lin, “OVSF code channel assignment for IMT-2000,”
The 51st IEEE Vehicular Technology Conference, vol. 3, pp. 2188-2192, 2000.
[7] M. Dell’Amico and M. L. Merani, “Efficient Algorithms for the Assignment of OVSF Codes in Wideband CDMA,” IEEE In-ternational Conference on Communications, vol.5, pp. 3055-3060, 2002.
[8] C. E. Fossa and N. J. Davis, “A Dynamic Code Assignment Algorithm for Quality of Service in 3G Wireless Networks,” IEEE Wireless Communications and Networking Conference, vol. 1, pp. 1-6, 2002.
[9] T. Minn and K.-Y. Siu, “Dynamic Assignment of Orthogonal Variable Spreading Factor code of W-CDMA,” IEEE Journal on Select Areas in Communications, pp. 1429-1440, 2000.
[10] A. N. Rouskas and D. N. Saoutas, “OVSF Codes Assignment and Reassignment at the Forward Link of W-CDMA 3G Sys-tems,” The 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Vol. 5, pp. 2404-2408, 2002.
[11] F. Shueh and W.-S. E. Chen, “Code assignment for IMT-2000 on forward radio link,” The 53rd IEEE Vehicular Technology Society Conference, vol. 2, pp. 906-910, 2001.
[12] Y.-C. Tseng and C.-M. Chao, “Code Placement and Replace-ment Strategies for Wideband CDMA OVSF Code Tree Man-agement,”
IEEE Transactions on Mobile Computing, vol. 1, no. 4, pp. 293- 302, 2002.
