Bit error probability analysis of MIMO multicarrier spread spectrum for different channels and modulations

Multiple access techniques are used in next generation wireless communication systems to allow many users to share the available spectrum efficiently. In this paper we investigate performance of a Multi Carrier Spread Spectrum system (MC-SS). The Principle of MC-SS system is to spread a data sequence by a given spreading sequence in frequency domain and allow it to modulate N subcarriers instead of one carrier. The idea is to combine such scheme with Orthogonal Frequency Division Multiplexing (OFDM) for efficient use of spectrum. Since OFDM makes use of overlapping subcarriers in frequency domain. The system consists of combination of Multiple Inputs and Multiple Outputs (MIMO) communication with Orthogonal Frequency Division multiplexing modulation scheme to provide significant increase in a system data rate, bandwidth efficiency and Quality of service (QOS). One of the important advantages of receiver structure is spatial diversity obtained by Maximum Ratio Combiner (MRC). In order to recover original information, Maximum Ratio Combiner do the phase corrected weighted addition of signals transmitted through each branch. The BER analysis is conducted for the system under different channel conditions and with different number of subcarriers. It is observed that for higher values of subcarriers and diversity, system performance in terms of BER is improved. The result shows that BER is proportional to the size M of the mapping technique used in the system.