Error Performance Analysis to Increase Capacity of A Cellular System Using SDMA

Abstract: One of the biggest drawbacks of the wireless environment is the limited bandwidth. However, the users sharing this limited bandwidth have been increasing considerably.Space Division Multiple Access (SDMA) is a new technology by which the capacity of existing mobile communication systems can economically be increased. This paper has been presented how the capacity can be enhanced by using SDMA with smart antennas in mobile communications system. Based on Adaptive Antenna Array (AAA) technology the spatial dimension of the existing system is exploited by means of forming independent radio beams in each of the original channels. This paper analyses the comparison of average Bit Error Rate (BER) of SDMA and CDMA technique and the different ways in which SDMA can be introduced to increase the capacity of a cellular system. The probability of error is found for a standard omni directional base station antenna, and another set of curves is found for flat top beam having a directivity of 5.1dB. It is assumed that k separate flat top beams can be formed by base station and pointed each of the k users within the cell of interest. Noticing that for an average probability of error greater than 0.1 in a propagation path loss environment of n=4, the flat top beam will support 200 users, whereas the omni-directional antenna will support only 50 users. This increase the number of user is roughly equal to the directivity offered by the flat top beam system, and illustrates the promise SDMA offers for improving capacity in wireless system. Here multipath fading is not considered.