Abstract
Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) proves to be a better choice for high speed underwater acoustic (UWA) communication as it increases the data rate and solves the bandwidth limitation issue; however, at the same time, it increases the design challenges and complexity of the receivers. Inter-Symbol Interference (ISI) and Inter-Carrier Interference (ICI) are introduced in the received signal by the extended multipath and Doppler shifts along with different types of noises due to the noisy acoustic channel. Here we propose two iterative receivers: one is ICI unaware iterative MIMO-OFDM receiver, which uses a novel cost function threshold based soft information decision feedback method. The second one is ICI aware progressive iterative MIMO-OFDM receiver, which adapts and increases the progressions according to the level of ICI present in the received signal, while fully utilizing the soft information from the previous iterations, therefore reducing the complexity. Orthogonal Matching pursuit (OMP) channel estimation, low density parity check (LDPC) decoding and minimum mean square error (MMSE) equalization schemes are exploited by both the receivers. The proposed receivers are analyzed and compared with the standard Alamouti MIMO receiver as a reference and also compared with the non-iterative, basic turbo iterative and non-progressive iterative MIMO receivers. Simulations and experimental results prove the efficiency and effectiveness of the proposed receivers.
Highlights
Underwater acoustics (UWA) communication has attracted huge attention during the last two decades because of the extension of its applications to different domains
Unaware iterative receiver and we discuss the results of the Inter-Carrier Interference (ICI) aware progressive iterative receiver for MIMO Orthogonal Frequency Division Multiplexing (OFDM) communication
In order to verify the effectiveness of the proposed MIMO-OFDM ICI-aware progressive receiver, this sectionResults tests the system experimentally by adding Doppler to the experimental setup
Summary
Underwater acoustics (UWA) communication has attracted huge attention during the last two decades because of the extension of its applications to different domains. Alternate ways need to be found in order to improve the efficiency of UWA communication, as the speed of sound is constant inside water and cannot be increased. Orthogonal Frequency Division Multiplexing (OFDM) is considered to be a low-complexity and highly efficient modulation scheme, which overcomes the problem of ISI to a large extent. MIMO was introduced recently in UWA communication to efficiently use the acoustic bandwidth and increase the system capacity by exploiting the spatial diversity. The combination of MIMO and OFDM is a tempting low-complexity solution for bandwidth-efficient communications over frequency selective and bandwidth limited UWA channels [8,9,10,11,12]. In this paper we propose a low-complexity, novel progressive iterative MIMO-OFDM receiver for the UWA communication system, which outperforms all the previous designs in terms of complexity and performance.
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