Dynamic code assignment for OVSF code system

The OVSF-CDMA system must allocate user codes to support a new call, when it supports variable user data rates. Accordingly, the user code would be easily blocked without an efficient code reassignment algorithm. This paper presents a right first dynamic code assignment (RFDCA) algorithm, which aims at always keeping the OVSF codes tree in an optimal right first (RF) state on the basis of the number-topology count (Nt). This algorithm realizes a quick assignment of the OVSF codes to the new callers so that the reassignment of OVSF code could be minimized when new calls arrive, further improving the spectral efficiency of the systems. In this paper, we have analyzed the algorithm by adopting Markov process and have practiced the simulation experiment. The theoretical analysis and the simulation experiment acquire the same results, proving the effectiveness of the algorithm. More importantly, the result of the simulation experiment indicates the number of reassigned codes (NRC) is far fewer than that of other algorithms when new calls arrive