Research And Realization Of PN Offset Optimization Algorithm In CDMA System

Now CDMA technology has been widely applied. The network scale increases gradually and the number of subscribers becomes more and more. So network engineers attach more and more importance to CDMA network optimization.Nowadays RPT Repeater is widely used in CDMA system and the large time delay often leads to the confusion of PN offset and finally mobile terminals'wrong identification, even handoff failures and a lot of dropped calls. The augment in amount of consumers and scale of CDMA networks inevitably results in widespread PN reuse, co-PN-offset interferences and adjacent PN-offset interferences. The major task of PN offset optimization is to avoid PN interferences. As a result, PN offset optimization with high criticality in CDMA networks has been paid closer attention to and become one of fundamental daily works.The contribution of this paper was to provide an elaborate description of a scheme for PN offset optimization after investigating and analyzing existing methods. The first current method only considers the PN minimum reuse distance and it is applied properly in some regions with sparse-distributed base stations. The second one pays attention to not only the reuse distance but also the number of cells sharing the same PN. Despite the improvement the second method as the first one takes so less elements into account and neglects some important ones, so it is also suitable to be applied in sparse-distributed regions merely. The third method innovatively considers the layer between two cells and using a simple formula calculates the score of every candidate PN. But it still neglects the PN minimum reuse distance and other significant elements and can not implemented automatically due to much artificial operation. While old methods don't present the same applicability when implemented in different regions, the scheme offered by the paper takes different steps based on dissimilar identity of cells in different regions. The PN optimization system calculates the layer of two cells by Delaunay triangulation algorithm instead of naked eyes. In regions with the dense-distributed base stations, the new method considers thoroughly appearance of one-way, two-way and adjacent PN-offset interferences and direction angle in order to diminish PN interference between two cells. This method also provides a formula to calculate the score of candidate PN, which include more important factors than the formula in the third method does. At last the score of PN is decided and the PN with highest score is the new PN for the original cell. Based on the data from two regions (the situations of base station density are somewhat distinct), after the four methods were implemented the separate results were compared and we could safely reach the conclusion that the new method can decrease the PN reuse situation in CDMA system more accurately and efficiently.In the latter part of this dissertation, other works related to CDMA optimization I have accomplished throughout my graduate research in lab is introduced, including the RSSI.data analysis, property analysis in CDMA system and improved neighbor cell updating system.