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s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links
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ARTICLE IN PRESS Optik xxx (2014) xxx–xxx
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2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links Naresh Kumar National Institute of Technology, Hamirpur, H.P., India
a r t i c l e
i n f o
Article history: Received 5 July 2013 Accepted 2 January 2014 Available online xxx
a b s t r a c t HAP-to-satellite, one of the important applications of FSO/OWC technology, which will be deployed in space in the near future. In this paper, we have presented analysis of 2.50 Gbit/s OWC system using PPM modulation schemes and a distance of 2500 km was achieved at BER 10−6 in HAP to satellite links. © 2014 Elsevier GmbH. All rights reserved.
Keywords: Optical wireless communication (OWC) High altitude platforms (HAPs) Pulse position modulation (PPM)
1. Introduction Free-space optics (FSO) has the combined features of most dominated telecommunication technologies Wireless and Fiber Optics. Many of the aspects of FSO are related to fiber optics with an important difference of transmission medium which is free space rather than the glass of the fiber-optic cable. HAP-to-satellite link one of the important applications of FSO/OWC technology will be deployed for inter-satellite and deep-space communications because of its numerous advantages over radio-frequency (RF) technology such as extremely high bandwidth, license-free and interference immunity [1]. FSO has attracted considerable attention for a variety of applications like last mile connectivity, optical-fiber backup and enterprise connectivity. In a scenario, where optical satellite-to-ground links, the main problem is the blocking of the laser beam due to cloud coverage [2]. To find a remedy, current research concentrates on optical links from the satellite to high flying “platforms”, known as HAPs (high altitude platforms), which are situated well above the clouds [3]. HAP-to-satellite links are probably the ‘favourite’ for FSO in HAP scenarios. Unimpaired by atmospheric effects, the HAP-to-satellite link can harness the tremendous advantages of satellite communication, such as very long transmission ‘hops’, massive geographical coverage and immense remote sensing capabilities. Local data transmissions uploaded to the HAP can traverse the globe rapidly and reliably with the help of HAP-to-satellite, inter-satellite links and then be downloaded at their destination. Conversely, satellite-sensed
E-mail address: [email protected]
data can be downloaded locally to a ground station as needed using HAP infrastructure as a relay station [4,5]. The most reported modulation technique used for FSO is the digital pulse position modulation (DPPM) with direct-detection because of the lack of dispersion over the free space channel [6]. Pulse Position Modulation (PPM) schemes is the simplest and common modulation for the optical intensity channel and high power efficiency and high bandwidth efficiency. M-ary PPM achieved high Power efficiency at the expense of reduced bandwidth efficiency compared with other modulation schemes. Higher order modulation in PPM creates the higher peak power needed to overcome the weak average power [7]. Here considered M-ary pulse position modulation (Mary PPM) modulation schemes using an avalanche photodiode [8,9]. Here presented average bit error rate (BER) of M-ary pulse position modulation (PPM) under Gamma–Gamma fading channel [9]. Further improvement in inter-satellite transmission links using square root module is reported [10]. In this work, we have presented the analysis of FSO system using 2PPM modulation schemes in HAP to ground links with different parameters. The simulative setup description of PPM over FSO Communication System is reported in Section 2 followed by the simulation results discussion in Section 3. The conclusion drawn from our simulation results is presented in Section 4. 2. System description In our proposed PPM over OWC (Fig. 1), 2.5 Gbit/s RZ data is generated and then modulated into PPM coder using sequence generator with 2 bit per symbol. The 2.5 Gbit PPM data signal is processed in Laser driver & DML to producing the intermediate signal.
http://dx.doi.org/10.1016/j.ijleo.2014.01.047 0030-4026/© 2014 Elsevier GmbH. All rights reserved.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
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Fig. 1. (a) Simulation setup of OWC system using PPM modulation schemes in HAPto-satellite links. Where MTD is M-ary Threshold detector, LPF is low pass filter.
This Intermediate signal modulates directly the light of a DML of 36 mW operating at 1550 nm through a MZM. The light is then adapted to the optical wireless channel (OWC) propagation by collimators. The attenuation of the air is vacuum i.e. 0 dB/km. After propagation the signal is again collimated to an APD photodiode. The optical of sample spectra along the system is presented in Fig. 2. 3. Result and discussion The parameters used in this case are transmission range 2500 km, wavelength 1550 nm, data rate 2.50 Gbps, transmitter power 36 mW, transmitter aperture diameter 10 cm, receiver aperture diameter 20 cm, beam divergence 0.25 mrad, sigma add 1.9, attenuation 0 dB/km, pointing transmitter 1 urad (Fig. 3). It is observed that as we move higher receiver aperture diameter OSNR will be increases. The OSNR is improved in B2B by 81% and the reach greatly extended above the 2500 km. Further it is also
Fig. 2. Optical spectrums after the DML output.
observed that as we move higher receiver aperture diameter SNR will be increases. The SNR is improved in B2B by 93% and the reach greatly extended above the 2500 km. Fig. 4(a) depicts the measurement of OSNR versus range with different wavelengths. From Fig. 4(a), it has been observed that OSNR reduces from 68.8 to 64 dB in transmission range 1500–2500 km at wavelength 1550 nm. Alternatively; OSNR varies in the range of 73.6–69.2 dB in transmission range 1500–2500 km at wavelength 850 nm. Fig. 4(b) depicts the measurement of OSNR versus range with different transmission power. It has been shown that OSNR reduces from 66.4 to 62 dB in transmission range 1500–2500 km at transmission power 20 mW. Alternatively;
Fig. 3. The eye diagram of PPM over FSO system in (a) back to back is shown and; (b) the eye diagram of PPM over FSO system in 2500 km is show; (c) depict the evaluations of the OSNR versus receiver aperture diameter with B2B and 2500 km; (d) depict the evaluations of the SNR versus receiver aperture diameter with B2B and 2500 km.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
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Fig. 4. Optical PPM over FSO system (a) depict the evaluations of OSNR versus range with different wavelengths is shown and; (b) depict the evaluations of the OSNR versus range with different transmission power; (c) depict the evaluations of the OSNR versus transmitter pointing error angle with different receiver aperture diameter; (d) depict the evaluations of the OSNR versus RIN value with different transmission power.
OSNR varies in the range of 69.2–64.8 dB in transmission range 1500–2500 km at transmission power 40 mW. Further from Fig. 4(c) depicts the measurement of OSNR versus transmitter pointing error angle with different receiver aperture diameter. It has been also observed that OSNR reduced from 58.2 to 55 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 10 cm. Alternatively; OSNR reduces from 64.6 to 61.4 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 20 cm. Fig. 5(a) depicts the measurement of SNR versus range with different transmission power. It has been shown that SNR reduces
from 35 to 20 dB in transmission range 1500–2500 km at transmission power 20 mW. Alternatively; SNR varies in the range of 36–20 dB in transmission range 1500–2500 km at transmission power 40 mW. Further from Fig. 5(b) depicts the measurement of SNR versus transmitter pointing error angle with different receiver aperture diameter. It has been also observed that SNR reduced from 13 to 5 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 10 cm. Alternatively; SNR reduces from 25 to 21 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 20 cm. Fig. 5(c) depicts the measurement of SNR versus RIN value with different transmission power.
Fig. 5. Optical PPM over FSO system (a) depict the evaluations of the OSNR versus range with different transmission power is shown and; (b) depict the evaluations of the OSNR versus transmitter pointing error angle with different receiver aperture diameter; (c) depict the evaluations of the OSNR versus RIN value with different transmission power.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
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ARTICLE IN PRESS N. Kumar / Optik xxx (2014) xxx–xxx
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It has been shown that SNR reduces from 18 to 14 dB in RIN value −140 dB/Hz to −130 dB/Hz at transmission power 10 mW. Alternatively; SNR varies in the range of 28–26 dB in RIN value −140 dB/Hz to −130 dB/Hz at transmission power 36 mW. 4. Conclusion In this work, we have analyzed a 2.50 Gbit/s OWC system using PPM modulation schemes with various parameters (transmission range, transmission power, receiver aperture diameter and RIN value). From results it’s clear as we move to higher transmission wavelength, optical and electrical SNR with transmission range decreases. With the increase of receiver aperture, there is increase in optical & electrical SNR and with the increase of transmission range, optical & electrical SNR is decreasing. Also with the increase of transmission range, optical & electrical SNR is decreasing and with the increase of transmission power, optical & electrical SNR is also increasing. Hence 2.50 Gbit/s OWC system using PPM modulation schemes and a distance of 2500 km was achieved at BER10−6 in HAP to satellite links.
[2] COST 297, HAPCOS – High altitude platforms for communications and other services [online], 2007, February, Available at: www.hapcos.org [3] G.M. Djuknic, J. Freidenfelds, Y. Okunev, Establishing wireless communications services via high-altitude aeronautical platforms: a concept whose time has come? IEEE Commun. Mag. (1997) 128–135. [4] A.K. Majumdar, J.C. Ricklin, Free-Space Laser Communications, Principles and Advantages, Springer Science LLC, 233 Spring Street, New York, NY 10013, USA, 2008. [5] D. Grace, M. Mohorcic, Broadband Communication via High Altitude Platforms, John Wiley & Sons Ltd., UK, 2010. [6] S. Sheikh Muhammad, T. Javornik, I. Jelovcan, Z. Ghassemlooy, E. Leitgeb, Comparison of hard-decision and soft decision channel coded M-ary PPM performance over free space optical links, Eur. Trans. Telecomm. 20 (2008) 746–757. [7] J. Singh, V.K. Jain, Performance analysis of BPPM and M-ary PPM optical communication systems in atmospheric turbulence, IETE Tech. Rev. 25 (4) (2008) 146–153. [8] H. Kaushal, V.K. Jain, S. Kar, Effect of atmospheric turbulence on acquisition time of ground to deep space optical communication system, Int. J. Electron. Circ. Syst. 3 (4) (2009) 183–187. [9] Y. Xiang, L. Zengji, Y. Peng, S. Tao, BER performance analysis for M-ary PPM over gamma–gamma atmospheric turbulence channels, wireless communications networking and mobile computing (WiCOM), in: 6th International Conference on Xidian University, Xi’an, China, 23–25 September, 2010, pp. 1–4. [10] V. Sharma, N. Kumar, Improved analysis of 2.5 Gbps-inter-satellite link (ISL) in inter-satellite optical wireless communication (IsOWC) system, Opt. Commun. 286 (2013) 99–102.
References [1] N.A. Mohammed, R.A. Mohammed, H.A. Moustafa, Improved performance of M-ary PPM in different free-space optical channels due to Reed Solomon code using APD, Int. J. Sci. Eng. Res. 2 (4) (2011) 1–4.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
ARTICLE IN PRESS Optik xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.de/ijleo
2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links Naresh Kumar National Institute of Technology, Hamirpur, H.P., India
a r t i c l e
i n f o
Article history: Received 5 July 2013 Accepted 2 January 2014 Available online xxx
a b s t r a c t HAP-to-satellite, one of the important applications of FSO/OWC technology, which will be deployed in space in the near future. In this paper, we have presented analysis of 2.50 Gbit/s OWC system using PPM modulation schemes and a distance of 2500 km was achieved at BER 10−6 in HAP to satellite links. © 2014 Elsevier GmbH. All rights reserved.
Keywords: Optical wireless communication (OWC) High altitude platforms (HAPs) Pulse position modulation (PPM)
1. Introduction Free-space optics (FSO) has the combined features of most dominated telecommunication technologies Wireless and Fiber Optics. Many of the aspects of FSO are related to fiber optics with an important difference of transmission medium which is free space rather than the glass of the fiber-optic cable. HAP-to-satellite link one of the important applications of FSO/OWC technology will be deployed for inter-satellite and deep-space communications because of its numerous advantages over radio-frequency (RF) technology such as extremely high bandwidth, license-free and interference immunity [1]. FSO has attracted considerable attention for a variety of applications like last mile connectivity, optical-fiber backup and enterprise connectivity. In a scenario, where optical satellite-to-ground links, the main problem is the blocking of the laser beam due to cloud coverage [2]. To find a remedy, current research concentrates on optical links from the satellite to high flying “platforms”, known as HAPs (high altitude platforms), which are situated well above the clouds [3]. HAP-to-satellite links are probably the ‘favourite’ for FSO in HAP scenarios. Unimpaired by atmospheric effects, the HAP-to-satellite link can harness the tremendous advantages of satellite communication, such as very long transmission ‘hops’, massive geographical coverage and immense remote sensing capabilities. Local data transmissions uploaded to the HAP can traverse the globe rapidly and reliably with the help of HAP-to-satellite, inter-satellite links and then be downloaded at their destination. Conversely, satellite-sensed
E-mail address: [email protected]
data can be downloaded locally to a ground station as needed using HAP infrastructure as a relay station [4,5]. The most reported modulation technique used for FSO is the digital pulse position modulation (DPPM) with direct-detection because of the lack of dispersion over the free space channel [6]. Pulse Position Modulation (PPM) schemes is the simplest and common modulation for the optical intensity channel and high power efficiency and high bandwidth efficiency. M-ary PPM achieved high Power efficiency at the expense of reduced bandwidth efficiency compared with other modulation schemes. Higher order modulation in PPM creates the higher peak power needed to overcome the weak average power [7]. Here considered M-ary pulse position modulation (Mary PPM) modulation schemes using an avalanche photodiode [8,9]. Here presented average bit error rate (BER) of M-ary pulse position modulation (PPM) under Gamma–Gamma fading channel [9]. Further improvement in inter-satellite transmission links using square root module is reported [10]. In this work, we have presented the analysis of FSO system using 2PPM modulation schemes in HAP to ground links with different parameters. The simulative setup description of PPM over FSO Communication System is reported in Section 2 followed by the simulation results discussion in Section 3. The conclusion drawn from our simulation results is presented in Section 4. 2. System description In our proposed PPM over OWC (Fig. 1), 2.5 Gbit/s RZ data is generated and then modulated into PPM coder using sequence generator with 2 bit per symbol. The 2.5 Gbit PPM data signal is processed in Laser driver & DML to producing the intermediate signal.
http://dx.doi.org/10.1016/j.ijleo.2014.01.047 0030-4026/© 2014 Elsevier GmbH. All rights reserved.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
G Model IJLEO-54320; No. of Pages 4
ARTICLE IN PRESS N. Kumar / Optik xxx (2014) xxx–xxx
2
Fig. 1. (a) Simulation setup of OWC system using PPM modulation schemes in HAPto-satellite links. Where MTD is M-ary Threshold detector, LPF is low pass filter.
This Intermediate signal modulates directly the light of a DML of 36 mW operating at 1550 nm through a MZM. The light is then adapted to the optical wireless channel (OWC) propagation by collimators. The attenuation of the air is vacuum i.e. 0 dB/km. After propagation the signal is again collimated to an APD photodiode. The optical of sample spectra along the system is presented in Fig. 2. 3. Result and discussion The parameters used in this case are transmission range 2500 km, wavelength 1550 nm, data rate 2.50 Gbps, transmitter power 36 mW, transmitter aperture diameter 10 cm, receiver aperture diameter 20 cm, beam divergence 0.25 mrad, sigma add 1.9, attenuation 0 dB/km, pointing transmitter 1 urad (Fig. 3). It is observed that as we move higher receiver aperture diameter OSNR will be increases. The OSNR is improved in B2B by 81% and the reach greatly extended above the 2500 km. Further it is also
Fig. 2. Optical spectrums after the DML output.
observed that as we move higher receiver aperture diameter SNR will be increases. The SNR is improved in B2B by 93% and the reach greatly extended above the 2500 km. Fig. 4(a) depicts the measurement of OSNR versus range with different wavelengths. From Fig. 4(a), it has been observed that OSNR reduces from 68.8 to 64 dB in transmission range 1500–2500 km at wavelength 1550 nm. Alternatively; OSNR varies in the range of 73.6–69.2 dB in transmission range 1500–2500 km at wavelength 850 nm. Fig. 4(b) depicts the measurement of OSNR versus range with different transmission power. It has been shown that OSNR reduces from 66.4 to 62 dB in transmission range 1500–2500 km at transmission power 20 mW. Alternatively;
Fig. 3. The eye diagram of PPM over FSO system in (a) back to back is shown and; (b) the eye diagram of PPM over FSO system in 2500 km is show; (c) depict the evaluations of the OSNR versus receiver aperture diameter with B2B and 2500 km; (d) depict the evaluations of the SNR versus receiver aperture diameter with B2B and 2500 km.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
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ARTICLE IN PRESS N. Kumar / Optik xxx (2014) xxx–xxx
3
Fig. 4. Optical PPM over FSO system (a) depict the evaluations of OSNR versus range with different wavelengths is shown and; (b) depict the evaluations of the OSNR versus range with different transmission power; (c) depict the evaluations of the OSNR versus transmitter pointing error angle with different receiver aperture diameter; (d) depict the evaluations of the OSNR versus RIN value with different transmission power.
OSNR varies in the range of 69.2–64.8 dB in transmission range 1500–2500 km at transmission power 40 mW. Further from Fig. 4(c) depicts the measurement of OSNR versus transmitter pointing error angle with different receiver aperture diameter. It has been also observed that OSNR reduced from 58.2 to 55 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 10 cm. Alternatively; OSNR reduces from 64.6 to 61.4 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 20 cm. Fig. 5(a) depicts the measurement of SNR versus range with different transmission power. It has been shown that SNR reduces
from 35 to 20 dB in transmission range 1500–2500 km at transmission power 20 mW. Alternatively; SNR varies in the range of 36–20 dB in transmission range 1500–2500 km at transmission power 40 mW. Further from Fig. 5(b) depicts the measurement of SNR versus transmitter pointing error angle with different receiver aperture diameter. It has been also observed that SNR reduced from 13 to 5 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 10 cm. Alternatively; SNR reduces from 25 to 21 dB in the in transmitter pointing error angle 1–4 urad at receiver aperture diameter 20 cm. Fig. 5(c) depicts the measurement of SNR versus RIN value with different transmission power.
Fig. 5. Optical PPM over FSO system (a) depict the evaluations of the OSNR versus range with different transmission power is shown and; (b) depict the evaluations of the OSNR versus transmitter pointing error angle with different receiver aperture diameter; (c) depict the evaluations of the OSNR versus RIN value with different transmission power.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047
G Model IJLEO-54320; No. of Pages 4
ARTICLE IN PRESS N. Kumar / Optik xxx (2014) xxx–xxx
4
It has been shown that SNR reduces from 18 to 14 dB in RIN value −140 dB/Hz to −130 dB/Hz at transmission power 10 mW. Alternatively; SNR varies in the range of 28–26 dB in RIN value −140 dB/Hz to −130 dB/Hz at transmission power 36 mW. 4. Conclusion In this work, we have analyzed a 2.50 Gbit/s OWC system using PPM modulation schemes with various parameters (transmission range, transmission power, receiver aperture diameter and RIN value). From results it’s clear as we move to higher transmission wavelength, optical and electrical SNR with transmission range decreases. With the increase of receiver aperture, there is increase in optical & electrical SNR and with the increase of transmission range, optical & electrical SNR is decreasing. Also with the increase of transmission range, optical & electrical SNR is decreasing and with the increase of transmission power, optical & electrical SNR is also increasing. Hence 2.50 Gbit/s OWC system using PPM modulation schemes and a distance of 2500 km was achieved at BER10−6 in HAP to satellite links.
[2] COST 297, HAPCOS – High altitude platforms for communications and other services [online], 2007, February, Available at: www.hapcos.org [3] G.M. Djuknic, J. Freidenfelds, Y. Okunev, Establishing wireless communications services via high-altitude aeronautical platforms: a concept whose time has come? IEEE Commun. Mag. (1997) 128–135. [4] A.K. Majumdar, J.C. Ricklin, Free-Space Laser Communications, Principles and Advantages, Springer Science LLC, 233 Spring Street, New York, NY 10013, USA, 2008. [5] D. Grace, M. Mohorcic, Broadband Communication via High Altitude Platforms, John Wiley & Sons Ltd., UK, 2010. [6] S. Sheikh Muhammad, T. Javornik, I. Jelovcan, Z. Ghassemlooy, E. Leitgeb, Comparison of hard-decision and soft decision channel coded M-ary PPM performance over free space optical links, Eur. Trans. Telecomm. 20 (2008) 746–757. [7] J. Singh, V.K. Jain, Performance analysis of BPPM and M-ary PPM optical communication systems in atmospheric turbulence, IETE Tech. Rev. 25 (4) (2008) 146–153. [8] H. Kaushal, V.K. Jain, S. Kar, Effect of atmospheric turbulence on acquisition time of ground to deep space optical communication system, Int. J. Electron. Circ. Syst. 3 (4) (2009) 183–187. [9] Y. Xiang, L. Zengji, Y. Peng, S. Tao, BER performance analysis for M-ary PPM over gamma–gamma atmospheric turbulence channels, wireless communications networking and mobile computing (WiCOM), in: 6th International Conference on Xidian University, Xi’an, China, 23–25 September, 2010, pp. 1–4. [10] V. Sharma, N. Kumar, Improved analysis of 2.5 Gbps-inter-satellite link (ISL) in inter-satellite optical wireless communication (IsOWC) system, Opt. Commun. 286 (2013) 99–102.
References [1] N.A. Mohammed, R.A. Mohammed, H.A. Moustafa, Improved performance of M-ary PPM in different free-space optical channels due to Reed Solomon code using APD, Int. J. Sci. Eng. Res. 2 (4) (2011) 1–4.
Please cite this article in press as: N. Kumar, 2.50 Gbit/s optical wireless communication system using PPM modulation schemes in HAP-to-satellite links, Optik - Int. J. Light Electron Opt. (2014), http://dx.doi.org/10.1016/j.ijleo.2014.01.047