Hierarchical DCA in SDMA systems-variations and performance comparison

Due to the ever increasing number of subscribers of mobile communication services, an efficient usage of frequency bandwidth has become one of the most important tasks in the area of mobile communication systems. Both, dynamic channel allocation (DCA) and space division multiple access (SDMA) are promising candidate techniques to improve the spatial frequency reuse in multicellular mobile communication systems. DCA allows for an adaption of the channel-to-cell assignment pattern to current traffic demands. In SDMA systems two or more mobile stations (MS) can be assigned identical channels within the same cell if they are sufficiently separable by the base station antenna array in the up- and down-link directions. Since both SDMA and DCA are means to optimize the reuse of channels in the space domain, through their combination we can benefit from the merit of both approaches. An integrated channel allocation strategy, which combines SDMA and DCA in a way that is very efficient in terms of computational complexity and signalling overhead, is the Hierarchical SDMA DCA (HSDCA). This paper discusses several variations of HSDCA and compares their performance