Design of optimal FBMC subcarrier index modulation based on optimal prototype filter

Latest high speed 5G wireless communication networks require the utilization of bandwidth with minimal interference. FBMC has recently developed as suitable alternative of OFDM that gives better utilization of bandwidth by eliminating the need of cyclic prefix and it also support the minimum Out-of-Band energy. The performance of FBMC is depending upon the selection of coefficient for the prototype filter. This paper proposes a prototype filter design for Filter Bank Multicarrier (FBMC) system based on convex optimization to explore a superior quality of spectrum features without compromising the symbol reconstruction quality. The design process involves non-convex quadratically constrained quadratic programming (QCQP), which is transformed into the convex QCQP by solving 2nd order quadratic equation using YALMIP and MOSEK tools available in the MATLAB software. The proposed system aims to minimize the OoB energy emission, while providing a high quality symbol reconstruction and maintaining the fast spectrum decay. Frequency response of developed prototype filter is compared with Mirabbasi-Martin filter, Hermite filter and optimal finite duration pulse (OFDP). The prototype filter has achieved - 58.313 dB out-of-band energy and - 62.563 dB maximum side-lobe level. However, due to the accumulation of the interferences caused in the dispersive channels, a Sub-carrier Index Modulation (SIM) is incorporated in the FBMC. It is further devised by incorporating an Optimal Combination-Selection and an Optimal Combination-Mapping algorithm to enhance the performance of Signal to interference ratio (SIR) as well as Bit Error Probability (BEP). Optimal combination using gray code constellation is applied to reduce the BER. The obtained results have shown an improved performance over Bit error rate (BER) in relation with SIR i.e. 10(-6) BER against 18 dB SNR.