In This thesis, some efficient PN offset planning strategies are proposed for the PN offset planning problems in multi-layer synchronous CDMA network encompassing both macrocells and fiber-optic microcells. Recently, fiber-optic microcellular systems have been recognized as economical means for increasing capacity of mobile communications. When a fiber-optic microcellular system is applied to a synchronous CDMA system special caution is required in planning PN offsets identifying conventional base-stations(macro cells) and micro base station(fiber-optic microcells) because of the transmission delay between a MSBTS and each micro base station.
Proposed methods divide the total PN offset planning problem into two independent PN offset planning problems, PN offset planning problem for macrocells and PN offset planning problem for fiber-optic microcells, by dividing available PN offsets into two groups- one for macrocells and the other for microcells - and guard intervals between them.
To solve the PN offset planning problem for the macrocells, conventional PN offset planning strategy is used and to solve the PN offset planning problem for the fiber-optic microcells, new PN offset planning methods are proposed.
First, we introduce three different PN offset planning methods for fiber-optic microcells based on cluster reuse. ToFoD method simply incorporates the fiber-optic delay with the conventional method for the macrocells. I-ToFoD method tries to improve ToFoD method by assigning PN offsets with advanced phases to micro base stations having shorter fiber-optic delay. In Pseudo-GPS method, fiber-optic delay is pre-compensated at MSBTS. These methods based on PN offset reusing by cluster can give optimal solution for the uniform ideal hexagonal cell network, but they cannot be used for the fiber-optic microcell network composed of small microcells whose radii are less than a few hundred meters.
Second, we present a graph coloring based PN offset planning method. This method dose not guarantees the optimal solution but this gives a sub-optimal solution for the large variety of fiber-optic micro cell networks. This proposed method can be effectively used especially for the island cell featured fiber-optic microcell network.
