SFDMA-spatial focus division multiple access

The concept of spatial focus division multiple access (SFDMA) is presented. SFDMA intends to increase capacity by exploiting diversity as well as reducing interference. Adaptive antennas are employed to focus the power of more than one base station simultaneously towards the mobile station's position. Signals focused towards the mobile station are divided by code division multiple access. The availability of space diversity facilitates the mitigation of Rayleigh fading as well as of log-normal fading caused by shadowing. As signals come from various base stations they can be exploited by navigational processing in order to obtain a position estimation as an alternative to ranging signals of global navigation satellite systems.