A novel hybrid FSO / RF communication system with receive diversity

2019

IET Communications

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In this manuscript, two novel multi-hop relay-assisted hybrid Free Space Optical / Radio Frequency (FSO / RF) communication systems are presented and compared. In these structures, RF and FSO links, at each hop, are parallel and send data simultaneously. This is the first time that in a multihop hybrid FSO / RF structure, Detect and Forward protocol is used. In the first structure, at each hop, received signals with higher Signal to Noise Ratio (SNR) is selected. But in the second structure, at each hop, received FSO and RF signals are separately detected and forwarded and selection is done only at the last hop. Considering FSO link in Negative Exponential atmospheric turbulence and RF link in Rayleigh fading, for the first time, closedform expressions are derived for Outage Probability ( ) and Bit Error Rate ( ) of the proposed structures. MATLAB simulations are provided to verify derived expressions. The main motivation of this work is to answer this question that how much is the difference of selection at each hop and selection at the last hop. Results indicate that the structure with selection at each hop has better performance than the structure with selection at the last hop. At different target Outage Probability, selection at the last hop consumes about two times (~) more power than selection at each hop. Both structures are particularly suitable for long-range communications. However, selection at each hop, in the cost of more complexity, is recommended for applications which have problem with supplying the required power for communication.

Section: Introductionmentioning

confidence: 99%

Performance comparison of two novel relay‐assisted hybrid FSO/RF communication systems

2019

IET Communications

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“…4.1 Gamma-Gamma atmospheric turbulence with the effect of pointing error By substituting (12), (11), (20) and (24) into (25), Outage Probability of the proposed structure in Gamma-Gamma atmospheric turbulence with the effect of pointing error becomes as (26).…”

Section: Outage Probabilitymentioning

confidence: 99%

Performance evaluation of a novel relay‐assisted hybrid FSO/RF communication system with receive diversity

2019

IET Optoelectronics

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One of the main problems in mobile communication systems is the degradation of Radio Frequency (RF) connection when mobile user is far from base station. One way to solve this problem is to increase the transmitter power, but the mobile transmitter is not able to supply much power. Another way is to use a relay; among relay schemes, amplify and forward is better for long range communications. Amplify and forward relay is not affordable in terms of power consumption and performance, because it consumes a lot of power inefficiently and enhances the noise. Therefore, in other cases, except in the case of long range links, other relay protocols, such as decode and forward, as well as demodulate and forward, are preferable. In this paper, a novel multi-hop hybrid Free Space Optical (FSO) / RF link is presented; it is made up of two main parts. The first part establishes the connection between the mobile user and source base station, and the second part establishes the connection between the source and the destination base stations. In the first part, a mobile user wants to connect to the source base station via a long range link; therefore, a fixed gain amplify and forward relay with multiple receive antennas is used for communication establishment. In the second part, the source and the destination base stations are connected via a multi-hop hybrid parallel FSO / RF link with demodulate and forward relaying. Considering the FSO link in Gamma-Gamma atmospheric turbulence with the effect of pointing error in moderate to strong regime and the Negative Exponential atmospheric turbulence in saturate regime, and the RF link in Rayleigh fading, new closed form exact and asymptotic expressions are derived for the Outage Probability and Bit Error Rate of the proposed structure. Derived expressions are verified with MATLAB simulations. The results show that the performance of the proposed structure does not change with changing channel conditions; therefore, this structure is reliable and does not require more processing or power consumption in order to maintain system performance in poor channel conditions. Hence, the proposed structure is particularly suitable for mobile communications with limitations in power, processing and latency. The innovations and contributions of this paper, which are first introduced in the multi-hop hybrid FSO / RF hybrid structure, include the novelty of the proposed structure, the presentation of new exact and asymptotic mathematical solutions, the use of receive diversity, Bit Error Rate analysis, using amplify and forward as well as decode and forward protocols, taking into account a wide range of atmospheric turbulences with the effect of pointing error, using opportunistic selection and selection combining schemes.The atmospheric turbulence causes the random oscillation of the received signal intensity [5]. Many statistical models have been presented to investigate the effects of atmospheric turbulence including Log-Normal [6], Gamma-Gamma [7], K [8], M [9], and Negative Exponential [10]. Am...

“…Papers with Single-hop, have implemented parallel FSO/RF link [5][6][7][8], some of them used the idea of multi-user [4]. A new paper has investigated use of diversity in this area for the first time [21]. Dual hop papers mostly used series FSO and RF structure with RF at the first and FSO at the second hop [10][11][12][13][14][15][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Performance analysis of a novel hybrid FSO/RF communication system

2020

IET Optoelectronics

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In this paper, a novel dual-hop relay-assisted hybrid Free Space Optical / Radio Frequency (FSO / RF) communication system is presented. In this structure an access point connects users within the building to the Base Station via a hybrid parallel FSO / RF link, this link is proposed firstly. Parallel combination of FSO and RF links and use of an access point, will increase capacity, reliability and data rate of the system. It is the first time that the effect of number of users on the performance of a dualhop relay-assisted hybrid parallel FSO / RF system is investigated. FSO link is considered in Gamma-Gamma atmospheric turbulence with the effect of pointing error and RF link is considered in Rayleigh fading. For the first time, closed-form expressions are derived for Bit Error Rate (BER) and Outage Probability ( ) of the proposed system. Derived expressions are verified through MATLAB simulations. It is shown that the performance of the proposed system is almost independent of atmospheric turbulence intensity, thereby when atmospheric turbulence strengthens, low power consumption is required for maintenance of the system performance. Hence the proposed structure is particularly suitable for mobile communication systems in which a small mobile battery supplies transmitter power. Also the proposed system performance of the system is preferable even at low signal to noise ratio (SNR). Therefore, proposed structure significantly reduces power consumption while maintaining performance of the system.