Adaptive Code Assignment Algorithm for a Multi-User/Multi-Rate CDMA System

Qiyue YU  Fumiyuki ADACHI  Weixiao MENG  

IEICE TRANSACTIONS on Communications   Vol.E92-B   No.5   pp.1600-1607
Publication Date: 2009/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.1600
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Radio Access Techniques for 3G Evolution)
code assignment,  code tree,  cost function,  DCA,  CDMA,  

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Code division multiple access (CDMA) technique is used widely since it can flexibly support multi-rate multi-media services by changing the number of orthogonal spreading codes. In this paper, we present a new adaptive code assignment algorithm, which consists of three steps: reserved-space, improved-crowded-first-space, and multi-code combination to fully use the code space. Compared with the existing algorithms, the proposed algorithm can avoid the code blocking problem and lower its total blocking probability while keeping its computational complexity relatively low. Simulation results show that increasing the free space reduces the average total blocking probability while increasing the blocking probability of high rate users.