Investigation of intra-cellular toroidal sectorisation in a DS-CDMA cellular system

The splitting of bandwidth resources in a cellular system incurs wastage of this premium limited commodity, but is necessary in order to manage the multiplexing and frequency reuse in the system. In FDMA and TDMA systems this normally involves the use of guard bands and with direct sequence code division multiple access (DS-CDMA) systems it may result from dividing the overall frequency allocation into smaller spread spectrum bandwidths. Splitting the resources in a DS-CDMA system reduces the overall system capacity and its flexibility to handle a variety of data rates, but enables a higher degree of spectrum utilisation as users within the system can now be managed more efficiently rather than all generating noise contributions in the same part of the spectrum. The paper investigates the optimum allocation and usage of the spectrum in a DS-CDMA cellular environment. This is gauged by the number of users per cell and the overall spectrum efficiency. The paper proposes the use of in-cell toroidal frequency sectorisation to increase the capacity of a DS-CDMA system and therefore the frequency reuse factor, when combined with power control, to determine the coverage radius of the mobile transmitter