Design and Analysis of Time-Based Code Allocation Schemes in W-CDMA Systems
IEEE Transactions on Mobile Computing
Efficient integration OVSF code management strategies in UMTS
Computer Communications
Vacant Code Searching and Selection of Optimum Code Assignment Scheme in WCDMA Wireless Networks
NGMAST '09 Proceedings of the 2009 Third International Conference on Next Generation Mobile Applications, Services and Technologies
Call elapsed time and reduction in code blocking for WCDMA networks
SoftCOM'09 Proceedings of the 17th international conference on Software, Telecommunications and Computer Networks
Reducing internal and external fragmentations of OVSF codes in WCDMA systems with multiple codes
IEEE Transactions on Wireless Communications
Downlink Throughput Maximization in CDMA Wireless Networks
IEEE Transactions on Wireless Communications
Fast dynamic code assignment in next generation wireless access networks
Computer Communications
Dynamic assignment of orthogonal variable-spreading-factor codes in W-CDMA
IEEE Journal on Selected Areas in Communications
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In this paper, a top down code search scheme is proposed that identify an optimum OVSF code for assignment at the base station of CDMA wireless networks. An optimum vacant code is the one whose usage produces least code blocking compared to other eligible codes. This scheme provides least code blocking compared to existing schemes without reassignments. In addition, the codes searched during locating the optimum code are significantly less than other existing schemes. The call establishment delay which is a significant factor for real time applications is directly proportional to the number of searches and should be low. The design is explained for single code, and extended to multi code assignment to improve code blocking. The multi code assignment is done using four ways. The first and second multi code schemes uses minimum and maximum rakes for a fixed rate system. The third scheme called scattered multi code scheme divide the incoming call into rate fractions equal to number of rakes available in the system, and each rate fraction is handled in a similar way in which the new call is handled in single code scheme. The rate fractions may be scattered or grouped in the code tree. The fourth multi code scheme, namely grouped multi code scheme allocates codes to all the fractions as close as possible. This maximizes future higher rate vacant codes availability by leaving a complete sub tree vacant when call using multi code ends.