# Coded-GFDM for Reliable Communication in Underwater Acoustic Channels
## 2 Literature Review  
While GFDM for underwater acoustic communication has recently gotten attention, there exists very little related work. In this section, we go through some of the recent state of the art. [PERSON] et al. [16] have proposed a golden coded GFDM system for 5G radio frequency (RF) communication. Space time block code based golden codes have been employed to achieve diversity gains in a MIMO configuration. A higher capacity and improved bit-error-rates are obtained outperforming an uncoded GFDM system and OFDM. In [8], when evaluating the performance of an uncoded GFDM system for a shallow underwater acoustic channel, it has been observed that while having higher spectral efficiency and flexibility, GFDM outperforms OFDM in SER. It still has a slightly higher complexity compared to a traditional OFDM system. Woods Hole Oceanographic Institution (WHOI) Micro-Modem [17] uses BCH (64,10), BCH (128,8), and Hamming (14,9) coding schemes for reliable acoustic communication underwater.  
[PERSON] et al. [18] proposed an improved filter structure to enhance equalization and used both convolutional and low-density parity-check (LDPC) encoding schemes. [PERSON] et al. [19] evaluated the performance of various forward error correction codes. The encoders are implemented using an FPGA and it is observed that LDPC has the smallest area while RS encoder has the largest. We employed BCH codes for peak-to-average power (PAPR) reduction in OFDM for UACs [20]. It was concluded that other than BER improvements, the PAPR of an OFDM system is significantly reduced when ciphered BCH codes are utilized. [PERSON] et al. [15] have assessed the forward error correction capabilities of convolutional codes of code rate \(1/2\) in the presence of multipathin underwater acoustic channels. The authors suggest the proposed convolutional codes for OFDM in multipath channel without equalizers in a slow-moving scenario. Authors in [21] have proposed a BCH encoded OFDM system for underwater acoustic communication. Channel information was not available. They have employed BCH (15,11) and BCH (15,7) with interleaving. BCH encoded system outperformed an uncoded OFDM system and the encoded system that didn't use interleaving.  
[PERSON] et al. [22] have investigated several coding schemes and waveforms for ultra-reliable and low-latency applications in the RF domain while considering both doubly-selective as well as frequency selective channels. It is observed that turbo codes outperform all other coding schemes investigated. [PERSON] and [PERSON] [23,24] have proposed a GFDM modulated underwater acoustic transmission system. They used the Rayleigh distribution based multipath channel model along with ambient noise. They employed root raised cosine (RRC) filter for pulse shaping. For known channel state information, the results were compared against OFDM and filter bank multicarrier (FBMC) systems. [PERSON] et al. [12] proposed a pre-coded GFDM for high data rate RF transmission. A variety of transforms were used for different operations and a reduction in implementation complexity was achieved. None of the works mentioned above have done a thorough evaluation of the well-known and well-established block codes i.e., BCH and Reed-Solomon, and the convolutional codes with GFDM. This paper tries to fill this gap.