A Novel Receiver Design of Nonorthogonal FDM Systems in Underwater Acoustics Communication

Abstract

While Orthogonal Frequency Division Multiplexing (OFDM) has been studied for a decade, the study of Non-Orthogonal Frequency Division Multiplexing (NOFDM) in underwater acoustics (UWA) communication has never been reported, to the best of our knowledge. Therefore, we investigate NOFDM technique for UWA communication considering the doubly-dispersive channel. The main feature of NOFDM is that it involves more closely packed subcarriers compared to OFDM, which results in higher spectral efficiency. However, this transmission suffers from severe Inter-Carrier-Interference (ICI). Since, we are considering doubly-dispersive channel, Inter-Symbol-Interference (ISI) is also encountered due to multipath propagation. Therefore, traditional receiver of NOFDM system in UWA channel, tends to have high computational complexity. Considering this problem, we design a receiver for NOFDM system, where Basis Expansion Model (BEM) is used along with Compressed Sensing (CS) channel estimation technique i.e., Orthogonal Matching Pursuit (OMP), which can effectively reduce the computational complexity. However, while implementing this technique in the real sea environment, the problem of long delay / Doppler spread is encountered due to guard intervals. Therefore, we propose the use of time domain equalizer, to mitigate the effect of long delay / Doppler spread. Simulation and experimental results based on Bit Error Rate (BER) demonstrate performance degradation due to severe interference in our proposed receiver. On the contrary, Mean Square Error (MSE) performance shows that our proposed receiver with OMP channel estimation outperforms OFDM receiver. Similarly, higher spectral efficiency gain is attained due to closely packed subcarriers.

Adaptive Channel Estimation for Underwater Acoustic OFDM System in Impulsive Noise Environment

“…Figure 5 Bit error rate (15) and c l = a l in (16). As can be seen, BER is decreased significantly through the ADSE algorithm when the SNR is higher, and the improvement is more obvious with the increase of Doppler scale.…”

“…A novel and computationally efficient channel estimation algorithm is proposed in [14]; the OMP algorithm is combined with the maximum a posteriori probability (MAP) technique to estimate the UWA channel gains. A greedy algorithm technique of the OMP implemented with the BEM is proposed in [15], where no prior information about channel statistics is required and the spectral leakage can be avoided. To make the expansion coefficients uncorrelated with the increasement of the OFDM frame length, time-varying complex-valued channel path gains are estimated using BEM based on the orthonormal discrete Legendre polynomials [16].…”

Sensor Selection for Hybrid AOA-TOA Localization with Correlated Measurement Noise in Underwater Wireless Sensor Networks

“…[1,2]. However, owing to the limitations are high power consumption, severe propagation delay, and so on [3][4][5][6]; it is not feasible to active all sensors to localize or track the unknown target in the underwater wireless sensor network (UWSN). Thus, the problems of sensor selection for target localization in UWSN have been considered; the goal is to make a compromise solution between the localization estimation accuracy and the best subset of activated sensors [7,8].…”

Underwater Acoustic Communication Receiver Using Deep Belief Network

“…A combination of these factors creates a complex challenge of modeling a sufficiently accurate channel model. To combat Doppler shifts, many Doppler scale estimation techniques have been proposed as seen in [14], [15].…”