Carrier Interferometry Coded Single Carrier FDMA (CI/SC-FDMA) for Next Generation Underwater Acoustic Communication

Abstract

Underwater acoustic (UWA) communication suffers from large propagation delays, limited bandwidth, frequency dependent attenuation and severe multipath fading. Low power consumption, acceptable bit error rate and minimal complexity are three critical factors for UWA sensor network design. Orthogonal frequency division multiple access (OFDMA) is an attractive option because of its robustness against frequency selective underwater channel. But, OFDMA suffers from high peak-to-average power ratio (PAPR) and high sensitivity to frequency offsets. Single carrier FDMA (SC-FDMA) has not been well investigated over UWA channel in literature. Two variants of SC-FDMA namely interleaved FDMA (IFDMA) and localized FDMA (LFDMA) are considered here. Firstly, through simulation it has been observed that IFDMA performs significantly better than OFDMA, in terms of SER and PAPR. However, IFDMA outperforms LFDMA in terms of PAPR, but SER performance of IFDMA is poor as compared to that of LFDMA. In case of power limited uplink UWA communication, IFDMA serves as a feasible solution. But for downlink, where lower SER is an important performance parameter, LFDMA is an efficient multiple access scheme. The use of carrier interferometry (CI) codes with SC-FDMA further enhances the SER and PAPR performance over highly frequency selective UWA transmission. We have also evaluated the effect of multi-user diversity for CI/SC-FDMA over 5-tap frequency selective UWA channel by applying scheduling algorithm. The algorithm selects the sensor mote with best channel condition for transmission.