Keywords:-
Article Content:-
Abstract
Third generation UMTS wireless system is based on the WCDMA access technique. In this technique, all users share the same bandwidth simultaneously but with different codes. So in UMTS during communication, every new user will demand new OVSF codes. This behaviour effectively reduces the total number of available OVSF codes in each cell. Current OVSF codes in UMTS have a code blocking property that causes spectral efficiency loss up to 25%. To minimize the adverse effects of code blocking, several heuristic scheduling schemes were pro-posed in the literature. The synchronized time-multiplexed, nonblocking, i.e., NOVSF codes that are orthogonal to each other. No synchronized time-multiplexed, NOVSF code blocks the assignment of any other NOVSF code and, therefore, no code reassignment is needed.
References:-
References
IEEE J. Selected Areas in Comm., vol. 18, no. 8, pp. 1429-1440, Aug. 2010.
[2] Y.-C. Tesng, C.-M Chao, and S.-L.Wu, “Code Placement and Replacement Strategies for Wideband
CDMA OVSF Code Tree Management,” Proc. IEEE GLOBECOM Conf., vol. 1, pp. 562-566, 2001.
[3] Y.-C. Tesng, C.-M.Chao, and S.-L. Wu, “Code Placement and Replacement Strategies for Wideband
CDMA OVSF Code Tree Management,” IEEE Trans. Mobile Computing, vol. 1, no. 4, pp. 293- 302, Oct.-
Dec. 2011.
[4] 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 J. Selected Areas in Comm., vol. 18, no. 8,
pp. 1441-1454, Aug. 2000.
[5] W.-T. Chen, Y.-P.Wu, and H.-C. Hsiao, “A Novel Code Assignment Scheme for W-CDMA Systems,”
Proc. IEEE Vehicular Technology Conf., pp. 1182-1186, 2001.
[6] R. Assarut, M. Sawahashi, U. Yamamoto, Y. Onozato, and M. Masahiko, “Region Division Assignment
of Orthogonal Variable- Spreading-Factor Codes in W-CDMA,” Proc. IEEE Vehicular
Technology Conf., pp. 1884-1888, 2001.
[7] Y. Yang and T.-S.P. Yum, “Nonrearrangeable Compact Assignment of Orthogonal Variable Spreading
Factor Codes for Multi-Rate Traffic,” Proc. IEEE Vehicular Technology Conf., pp. 938-942,2001.
[8] A.N. Rouskas and D.N. Skoutas, “OVSF Codes Assignment and Reassignment at the Forward Link of
W-CDMA 3G Systems,” Proc. IEEE Ann. Int’l Symp. Personal Indoor and Mobile Radio Comm., pp. 2404-
2408, 2002.
[9] 3GPP, Technical Specification TS 25.922 V6.1.0, Radio Resource Management Strategies, Apr. 2004.
[10] R.-G. Cheng and P. Lin, “OVSF Code Assignment for IMT-2000,” Proc. IEEE Vehicular Technology
Conf., pp. 2188-2192, 2000.
[11] F. Shueh, Z.-E.O. Liu, and W.-S.E. Chen, “A Fair, Efficient, and Exchangeable Channelization Code
Assignment Scheme for IMT-2000,” Proc. IEEE Int’l Conf. Personal Wireless Comm., pp. 429-433,2000.
[12] H. C¸ am, “Nonblocking OVSF Codes and Enhancing Network Capacity for 3G Wireless and Beyond
Systems,” Computer Comm.,vol. 26, no. 17, pp. 1907-1917, Nov. 2003.