Based On Orthogonal Complementary Code Spread Spectrum Multi-carrier Cdma System Performance

The 3^rd generation mobile communication systems employ CDMA technology and use single codes as spreading codes. Due to the non-ideal correlation properties of the codes, the system capacity is reduced by multipath interference (MI) and multiple access interference (MAI). Orthogonal Complementary Code (OCC) possesses perfect cross-correltion and auto-correlation properties. Using OCC as spreading codes, MI and MAI can be theoretically eliminated.This paper analyzes the bit error rate (BER) of the multicarrier CDMA systems based on OCC spreading (MC-OCC-CDMA) in the correlated fading channels. The research results are of great reference value for the design of MC-OCC-CDMA system and the deployment of resource.The main contents of this work are listed as follows:The attributes of wireless channels are introduced and then several main fading models are enumerated. The expressions of calculating channel correlation are introduced, and on the basis of these expressions, a method, which can generate correlated Raleigh envelope, is presented.The definitions and properties of complementary code and complete complementary code are presented. The conception of OCC is interpreted. It is the superset of complete complementary code. The correlation property of OCC is also introduced. It is the theoretical basis of applying OCC into wireless communication systems.The BER of the MC-OCC-CDMA systems in the correlated fading channels is the primary focus of this work. Two parameters are proposed for measuring OCC's cross-correltion and auto-correlation properties under the correlated channels. Combining the correlation of OCCs with the correlation of sub-channels, these two parameters can be used to evaluate the multiple access interference-resist performance of the MC-OCC-CDMA systems under channel correlation condition. The deduction gives closed-form expression of system BER of MC-OCC-CDMA systems undergoing the correlated fading channels. The simulation results precisely match the numerical ones, which verifies the correctness of the derived formulae.The performance of MC-OCC-CDMA systems under different scenarios is also researched. MC-OCC-CDMA systems possess good anti-MAI ability, which is far better than the CDMA systems spread with single codes. The ability of MC-OCC-CDMA systems to eliminate MAI is enhanced with the increase of the correlation of sub-channels. The influences of OCC code parameters, correlation between sub-channels, frequency diversity and high order modulation on the performance of MC-OCC-CDMA systems are studied and several conclusions are derived. These conclusions are of great importance for MC-OCC-CDMA systems design and spectral resource schedule.Several existing problems in the research of MC-OCC-CDMA systems are pointed out and they outline the direction of future work.