An orthogonal frequency divided group code for CP-CDMA system: Comb spectrum code

The motivation is to develop better CDMA codes for reducing the hardware complexity of the conventional CP-CDMA. This technology combines the frequency orthogonality of OFDM to CDMA code design for grouping the codes and allows a significant reduction for the calculations in channel equalization. The proposed method is referred to as OFDG code, which divides the codes of M chips in length into N groups, which are orthogonal one another in frequency domain. Each of the groups contains K codes which are mutually orthogonal in time domain. The design principle is introduced and a solution, called CS code, is obtained by the use of two operations to the conventional orthogonal code set; (1) an operation of cyclic repetition and (2) an operation of angle rotation. In comparison with the CP-CDMA, the points taken to channel equalization of CP-CS CDMA can be reduced by a factor of 1/N. The simulation results confirm the effectiveness of this approach.