fso networks under turbulence - northumbria university 2013 research conference

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  • FSO networks: understanding route diversity under turbulence phenomena towards reliable

    FSO mesh networks design

    Joaquin Perez Soler

    Northumbria University 2013 Research Conference15th- 16th May 2013City Campus East

  • Northumbria Communications Research LabFaculty of Engineering and Environment

    Northumbria UniversityNewcastle upon Tyne, United Kingdom

    Northumbria University 2013 Research Conference15th- 16th May 2013City Campus East

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    FSO applications Sports events (F1) Campus, MAN networks

    (Cablefree, LightPointe ...)

    Security and defence communications (CASSIDIAN, EADS, ...)

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Air-to-Ground FSO

    Air-to-ground FSO quantum-key distribution communication (Nature Photonics 7, 382386 (2013))

    (Photos: DLR)Speed of 290 km/h

    at a distance of 20 km or 4 mrad/s

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Space-ground FSO

    Laser Communications Relay Demonstration LCRD

    High bandwidth geo-sync to ground optical link Downlink: 1.2 Gbps Uplink: 1.2 Gbps LCRD Payload Flight in 2016 or

    2017 on Loral Commercial Satellite

    Bidirectional low Earth orbit-to-ground optical link 2 Mb/s UL and 50 Mb/s DL

    M.W. Wright et al. , 26 September 2011, SPIE Newsroom.

    (Photos: NASA and SPIE)

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Intra-satellite Campus networks

    FSO link needs line of sight (LOS)

    Link Obstacles?? Buildings, fog,

    turbulence... No connection!

    A mesh topology as a solution??

    FSO networks

    (Photos: ESA)

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Node in a mesh topology: capture and disseminate

    its own data, serve as a relay for other Collaboration on routing

    Backup, flexibility, end-to-end quality of service assured, ...

    FSO and mesh topology Blocking link

    Node (transceiver) intelligence to find different route

    FSO mesh topology

    [1] J. Tapolcai, et al. Switching/merging node placement in survivable optical networks with SSP, Computer Communications, Volume 33, Issue 3, 26 February 2010, Pages 381-389, ISSN 0140-3664

    [1]

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Route diversity in FSO

    FSO link non-availability affected by: Turbulence Fog Blocking

    Test Diversity techniques Impact on route diversity?

    Diversity techniques as Maximal Ratio Combining (MRC), Equal Gain Combining (EGC) and Selection Combining (SelC) [2]

    [2] W. O. Popoola, Z. Ghassemlooy, J. I. H. Allen, E. Leitgeb, and S. Gao, "Free-space optical communication employing subcarrier modulation and spatial diversity in atmospheric turbulence channel," IET Optoelectron 2, 16-23 (2008).

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Turbulence in FSO Appears due to temperature gradient in the channel,

    movement of air particles and other eddies.

    Turbulence measurement in FSO Related with atmospheric scintillation and defining coefficient

    structure index Cn2

    From signal received (Rytov variance) Directly from scintillometers Indirectly from temperature variance

    (temperature gradient)

    22 1 22 62 2

    86 10nT TPC

    T R

    2 2 7/6 11/61.23 ,i n pC k L (Photo: Wikipedia)

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Measurements Outdoor FSO turbulence Cn2 [3]

    {}

    Indoor lab turbulence NCR Lab Proposal In-line 20 thermal sensors inside chamber monitoring temperature

    0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-0.06

    -0.04

    -0.02

    0

    0.02

    0.04

    0.06

    0.08

    normalized scintillation index [-]

    f

    i

    t

    e

    r

    r

    o

    r

    [

    -

    ]

    lognormal distribution fit errorgamma-gamma distribution fit error

    [3] J. Libich et al Influences of Turbulences in Near Vicinity of Buildings on Free-space Optical Links. IET Microwaves, Antennas & Propagation. 2011, vol. 9, no. 5, p. 1039-1044. ISSN 1751-8725.

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    FSO Diversity study Indoor chamber to replicate turbulence Inside - Route diversity paths affected by turbulence

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    FSO Diversity study Indoor chamber to replicate turbulence Inside - Route diversity paths affected by turbulence Measured different path configurations

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Measurements indep Route FSO links topology:

    Allow redundancy in case of failure of one FSO link, another path is used.

    Route diversity improves availability of the network.

    Case under study: Same network end, different paths Independent paths, how to calculate turbulence effect? Needed to compare with correlated paths

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Measurements indep Route

    14

    10-2 10-1 100 10110-3

    10-2

    10-1

    100

    R2 from FSO [-]

    R2

    f

    r

    o

    m

    s

    e

    n

    s

    o

    r

    s

    [

    -

    ]

    10-2 100 10210-14

    10-12

    10-10

    10-8

    C

    n2

    [

    m

    -

    2

    /

    3

    ]

    CT2 [K2 m-2/3]

    (b)(a)

    (a) Rytov variances derived from received optical signal and from thermal sensors measurements(symbols, red circles - channel 1, blue crosses - channel 2)

    (b) Cn2 theoretical relations (black dotted lines) derived from measured thermal distributions (channel1 red and channel 2 blue lines) and Cn2 derived from measured of optical power on CT2 measured bythe sensor line (symbols; red circles - channel 1, blue crosses channel 2)

    Good agreement

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Measurements correl Route FSO network redundancy Case under study :

    two links terminating at the same point passing the common volume with similar turbulence characteristic one optical links is along the distant part influenced by non-

    correlated turbulent flow

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Measurements correl Route Diversity gain defined as the difference between

    attenuation of single link and minimum attenuation in case of joint diversity links.

    Two isolated channels, enhancement if we can change to the unaffected channel = Diversity technique Selection Combining (SelC)

    0 0.2 0.4 0.6 0.8 0.9

    0

    2

    4

    6

    8

    Qch1/Qch2 [-]

    D

    i

    v

    e

    r

    s

    i

    t

    y

    g

    a

    i

    n

    [

    d

    B

    ]

    isolated channelspartially correlated turbulences

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Measurements correl RouteCase of increased turbulence level from low towards moderate in Ch2:

    route diversity scheme is efficient of both channels experience different turbulences along their links compare to the case when both links pass through a common turbulent channel.

    17

    100 101 102-1

    0

    1

    2

    3

    4

    5

    6

    channels Cn2 ratio [-]

    D

    i

    v

    e

    r

    s

    i

    t

    y

    g

    a

    i

    n

    [

    d

    B

    ]

    isolated channelspartially corelated turbulences

    channel 1weakchannel 2mid tostrongturbulences

    bothchannels

    weakturbulences

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Conclusion Valuable information

    Physical parameters diversity scheme ROUTING Influence on FSO networks design

    Maximum number of hops between nodes Prediction of routes From physical to network layer

    Next steps More route diversity cases Implement the turbulence measurement in to network

    routing algorithms Simulate FSO mesh networks behaviour

  • NorthumbriaUniversity2013ResearchConference 15th/16thMay2013

    Conclusion Route diversity measured under several deployments Joint journal publications with European Institutions (Fresnel

    Institute Marseille, CTU Prague) [5, 6] This will allow us to transfer knowledge on other institutions :

    E.g. CTU developed an indoor FSO chamber

    19

    [5] S. Zvanovec, J. Perez, Z. Ghassemlooy, S. Rajbhandari, J. Libich,"Route diversity analyses for free-space optical wireless links withinturbulent scenarios," Opt. Express, vol. 21 (6), pp. 7641-7650,2013.

    [6] J. Perez, S. Zvanovec, Z. Ghassemlooy, W. O. Popoola,"Experimental characterization and mitigation of turbulence inducedsignal fades within an ad hoc FSO network(Link)," Opt. Express, vol22 (3), pp. 3208-3218, 2014.

  • OCRG and NCRLab teams @ Northumbria University Prof Zabih Ghassemlooy

    Czech Technical University, Prague Dr Stanislav Zvanovec

    EU COST action IC1101 and IC0802

    ACKNOWLEDGEMENTS

  • NCRLab WeeklyResearchMeeting 01December2014

  • Thank you

    www.linkedin.com/in/joaquinperezsoler/enhttp://joaquinperezsoler.blogs.upv.es