Spatial CDMA - A distributed multiple antenna access method for broadband wireless communication

We propose a new technique called Spatial CDMA, with capacity growing linearly as the number of receiving antennas for multiple antenna elements (MAE). Since spatially separated users each uses a different set of paths to reach a receiver, we can imagine that the multipath "impairment" actually could be used to our advantage to improve capacity and reduce transmission errors. In effect, each user has a multipath transmission signature that helps to distinguish its information transmission. This transmission signature becomes more complex when we have multiple receivers at the base station, and multiple transmitters at the user. We analyze and explore new techniques to learn and match the spatial CDMA code of each user. These techniques are based on a technique discovered for optical CDMA called Pattern Code Modulation (PACM). PACM uses a pattern of pulses for each user as a CDMA signature. For Spatial CDMA, the PACM code of each user is further enhanced by the multipaths between the user and the receiver array at the base station. To analyze Spatial CDMA, we model the multiple access interference as a filtered Poisson shot noise process, and use a convolution formula and transform domain methods to study the probability of false detection of a spatial CDMA pattern. We use this probability of false detection to evaluate the capacity of Spatial CDMA. We show that Spatial CDMA could be used for reliable, adaptive, and high capacity wireless multiple access communications, enabling high quality video and data transmission over local and wide area networks.