Turbo-Coded MC-CDMA Communication Link over Strong Turbulence Fading Limited FSO Channel with Receiver Space Diversity

Hassan, Md. Zoheb; Bhuiyan, Tanveer Ahmed; Tanzil, S. M. Shahrear; Majumder, S. P.

doi:10.5402/2011/701670

Cited by 5 publications

(1 citation statement)

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“…The ACO-OFDM based FSO system introduced by this article in the following sections belongs to the RF over FSO territory. Popular RF over FSO topics also include the sub-carrier multiplexed free space optics (SIM-FSO), 6-8 code division multiplexing access (CDMA) over FSO,10,11 etc. Different from the broadcasting nature of RF, the typical FSO waves travel only through the LOS path, i.e., a pointto-point assumption had been widely adpoted.…”

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Non-line-of-sight ultraviolet communication based on DHT ACO-OFDM

Gao

Chen

2012

SPIE Proceedings

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Free space optical (FSO) communication has attracted tremendous research interest in the recent year. Most existing works focus only on the line-of-sight (LOS) transmission by infrared (IR) or visible light lasers/LEDs, while this article suggested a framework of non-line-of-sight (NLOS) FSO, motivated by our recent experimental results on the successful transmission of NLOS ultraviolet (UV) beams for up to kilometers, which is comparable to the typical distance a LOS FSO transmission. The NLOS provides an alternate path when the LOS path is shadowed or is highly attenuated. In order to mitigate the multipath dispersion of the NLOS FSO, a baseband orthogonal frequency division multiplexing (OFDM) modulation scheme was proposed, based on Discrete Hartley Transform (DHT) and asymmetric clipping to guarantee the positive-realness of the transmitted optical intensity. The proposed system could reduce the hardware complexity of transmitter and receiver. Minimum mean square error (MMSE) precoder was applied before the DHT to remove the crosstalk between subcarriers, i.e. the frequency domain orthogonality of OFDM was preserved. Performance of the BPSK modulated communication system was given under lognormal atmospheric turbulence for demonstration of the feasibility of the proposed method.In this era of gigabits, optical communication is gradually becoming a necessary part of urban life. High speed communications among towns and cities have been achieved thanks to the employment of optical fiber as backbone. It is often costly or even impossible to connect the backbone and client premises by optical fiber, known as a "last mile" problem. This problem urges the emergence of FSO communications to bridge the gap. Latest laboratory and space experiments have demonstrated it as a ready-to-deploy, cost-effective, license-free, and high-bandwidth access measure 1, 2 . Compare to the radio frequency (RF) systems, the optical wave systems also outperform for much smaller antennas that takes up less volumn and power. 3 Similarities and differences coexist between the RF and FSO terminologies so that ideas for FSO can be borrowed from the more widely-studies RF but cautiously. Multiple-input-multiple-output (MIMO) schemes which take advantage of diversity has been shown as an efficient technique to mitigate the atmospheric turbulence for FSO. 4 Multihop FSO may serve as one of another means for combating the strong turbulence with help of relays that are able to amplify the attenuate signals. 5 Transmission of RF signals over FSO link also draw considerable attention. The ACO-OFDM based FSO system introduced by this article in the following sections belongs to the RF over FSO territory. Popular RF over FSO topics also include the sub-carrier multiplexed free space optics (SIM-FSO), 6-8 code division multiplexing access (CDMA) over FSO,10,11 etc. Different from the broadcasting nature of RF, the typical FSO waves travel only through the LOS path, i.e., a pointto-point assumption had been widely adpoted. Therefore, the FSO channels...

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confidence: 99%