Performance analysis of hybrid SAC-OCDMA-OFDM model over free space optical communication
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Performance analysis of hybrid SAC‑OCDMA‑OFDM model over free space optical communication Urmila Bhanja1 · Chinmayee Panda1 Received: 22 November 2018 / Accepted: 14 August 2020 © China Computer Federation (CCF) 2020
Abstract Recently, free space optical (FSO) communication network has gained popularity because of its unlicensed spectrum, high data rate, low power consumption and ease of installation. Spectral amplitude coded optical code division multiple access (SAC-OCDMA) technique has become significant because of enhanced network capacity, privacy, and simultaneous use of multiple asynchronous users. However, the climatic turbulence causes signal fluctuations and degrades the quality of the received signal. Therefore, to improve the quality of the received signal in this work, SAC-OCDMA technique is integrated with orthogonal frequency division multiplexing (OFDM) technique and performance of such hybrid model is investigated. Two SAC-OCDMA codes are proposed in this work referred as triangular matrix-zero cross correlation (TM-ZCC) and pulse shifting substitution-zero cross correlation (PSS-ZCC) codes. The hybrid model uses the novel one dimensional (1D) SAC-OCDMA codes with two different types of receivers such as modified AND (M-AND), and single photodiode detection (SPD) receivers over Gamma-Gamma fading channel to evaluate the bit error rate (BER) performance of the proposed hybrid model. It is observed from the simulation results that the hybrid SAC-OCDMA-OFDM model with SPD detection receiver performs better in terms of bit error rate (BER) than that of M-AND detection receiver. Furthermore, it is also observed from the simulation results that the hybrid model based on the proposed TM-ZCC code performs better than the proposed PSS-ZCC code in terms of BER and higher FSO distance coverage. The performance of the proposed model is estimated for 20 and 30 active users simultaneously at various data rates. The TM-ZCC and PSS-ZCC codes are generated using MATLAB platform and the proposed hybrid SAC-OCDMA-OFDM model is validated using optisystem version 15 over the Gamma-Gamma fading channel. Keywords SAC-OCDMA · Bit error rate · PSS-ZCC · TM-ZCC · OFDM · Gamma-Gamma channel model · FSO
1 Introduction The free space optical communication system (FSO) is increasingly gaining popularity as an alternative technology for optical fiber networks, especially in areas where the deployment of optical fiber is not feasible (Bekkali et al. 2010). FSO is an optical communication technology that utilizes line of sight (LOS) communication (Esmail et al. 2016a; Srinivasan and Sridharan 2010). Rain and fog are the main attenuation factor that deteriorates the performance * Urmila Bhanja [email protected]; [email protected] Chinmayee Panda [email protected] 1
Department of ETC, Indira Gandhi Institute of Technology Sarang, Dhenkanal, India
of FSO (Esmail et al. 2016b; Achour 2002). In addition to climatic conditions, atmospheric turbulence conditions also show challenges for FSO. R
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