Limited-Search Chase Decoding Algorithm for LDPC Coded Underwater Acoustic Multiuser Channels

In this paper, we propose a low-complexity soft-input/soft-output (SISO) Chase multiuser detector that has a polynomial computational complexity in terms of the number of the least reliable bit positions for low-density parity-check (LDPC) coded code-division multiple-access (CDMA) systems, which is a potentially competitive technology for underwater acoustic networks (UWAN). Simulation results over highly correlated channels show that the proposed detector can afford searching over a larger number of the least reliable bit positions and achieve better bit-error-rate (BER) performance as compared with the Chase-II detector at much lower complexity.

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NOVEL LOW-COMPLEXITY ANT COLONY BASED MULTIUSER DETECTOR FOR DIRECT SEQUENCE CODE DIVISION MULTIPLE ACCESS

International Journal of Computational Intelligence and Applications ◽

10.1142/s146902680500157x ◽

2005 ◽

Vol 05 (02) ◽

pp. 201-214 ◽

Cited By ~ 1

Author(s):

SAMER L. HIJAZI ◽

BALASUBRAMANIAM NATARAJAN

Keyword(s):

Code Division Multiple Access ◽

Multiple Access ◽

Low Complexity ◽

Foraging Strategy ◽

Ant Colony ◽

Direct Sequence ◽

Multiuser Detector ◽

Sequence Code ◽

Cooperative Foraging ◽

Code Division Multiple

In this paper, we present a novel multiuser detection (MUD) technique based on ant colony optimisation (ACO), for synchronous direct sequence code division multiple access systems. ACO algorithms are based on the cooperative foraging strategy of real ants. While an optimal MUD design using an exhaustive search method is prohibitively complex, we show that the ACO-based MUD converges to the optimal bit-error-rate performance in relatively few iterations providing 95% savings in computational complexity. This reduction in complexity is retained even when considering users with unequal received powers.

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Robust MVDR Estimation via Polynomial Rooting for MC-CDMA Carrier Frequency Offset

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.2687 ◽

2013 ◽

Vol 284-287 ◽

pp. 2687-2693

Author(s):

Ing Jiunn Su ◽

Chiao Chan Huang

Keyword(s):

Carrier Frequency ◽

Code Division Multiple Access ◽

Multiple Access ◽

Carrier Frequency Offset ◽

Low Complexity ◽

Frequency Offset ◽

High Accuracy ◽

Cdma Systems ◽

Code Division Multiple ◽

Polynomial Rooting

In this letter, we present a blind carrier frequency offset (CFO) estimator by exploiting the polynomial rooting technique for multicarrier-code division multiple access (MC-CDMA) systems. Relative high accuracy and low-complexity to the CFO estimation can be achieved by rooting a polynomial. Simulation results are provided for illustrating the effectiveness of the proposed blind polynomial rooting estimator.

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A fractional Fourier transform–based channel estimation algorithm in single-carrier direct sequence code division multiple access underwater acoustic communication system

International Journal of Distributed Sensor Networks ◽

10.1177/1550147719826001 ◽

2019 ◽

Vol 15 (1) ◽

pp. 155014771982600 ◽

Cited By ~ 1

Author(s):

Lin Zhou ◽

Qingsheng Zhao ◽

Shukai Chi ◽

Yanlong Li ◽

Lanjun Liu ◽

...

Keyword(s):

Fourier Transform ◽

Communication System ◽

Code Division Multiple Access ◽

Multiple Access ◽

Fractional Fourier Transform ◽

Direct Sequence ◽

Underwater Acoustic ◽

Single Carrier ◽

Sequence Code ◽

Code Division Multiple

Due to the complexity and variability of the underwater acoustic channel, the communication signal is affected by multi-path, time delay, and Doppler frequency shift. Based on the advantageous characteristics of fractional Fourier transform on chirp signal processing, a fractional Fourier transform–based algorithm using combined linear frequency–modulated signal is proposed, which can estimate parameters of underwater acoustic channel and has a better performance than the existing methods. To distinguish multi-user in underwater acoustic communication system, a single-carrier direct sequence code division multiple access communication system combined with the fractional Fourier transform–based algorithm is proposed. Thus, a preliminary study on underwater multi-target identification is carried out. The simulation and experimental results show that the fractional Fourier transform–based algorithm is simple and effective, and the energy can be focused at the “best” fractional order, which can directly determine the multi-path number and complete the channel estimation. The proposed single-carrier direct sequence code division multiple access communication system has good performance on bit error rate when we use corresponding spreading code to distinguish multi-user.

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