Vdlm2 standard modification proposition reporting channel occupancy to ground stations
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VDLM2 standard modification proposition: Reporting channel occupancy to ground stations. AEEC Datalink Sys. Sub committee (MIAMI July 2012) Patrick Delhaise Laurent Meyer. Agenda. Context recall the needs What has been performed so far Averaging versus statistical frequencies

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VDLM2 standard modification proposition: Reporting channel occupancy to ground stations

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Vdlm2 standard modification proposition reporting channel occupancy to ground stations

VDLM2 standard modification proposition:Reporting channel occupancy to ground stations

AEEC Datalink Sys. Sub committee (MIAMI July 2012)

Patrick Delhaise

Laurent Meyer

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Agenda

Agenda

  • Context recall

    • the needs

    • What has been performed so far

  • Averaging versus statistical frequencies

    • What is interesting to measure ?

  • Which frames are to be used to convey channel utilization ?

    • XID, RR, others ?

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Include channel occupancy in downlinks the needs

Include channel occupancy in downlinks: the needs

  • Some local frequency pollution perceived by in flight aircraft

    • Voice break thru

    • Channel saturation

    • Any kind of interferences

  • Can happen in any traffic scheme (light, heavy)

  • No easy ways to detect it on ground.

    • EUROCONTROL undertook a monitoring activity with the CCRM but results are geographically limited

  • Need by ACSPs to balance their aircraft between several frequencies.

    • Decisions are taken without knowing the aircraft point of view regarding saturation.

The idea: provide a way to exchange locally perceived channel utilization.

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Include channel occupancy in downlinks

Include channel occupancy in downlinks

  • Characterization of recurrent channel interference

    • Characterized by a significant amount of 100 % of channel utilization in a short period of time

  • Characterization of a channel coming close to saturation

    • According to flight tests, a lot of non consecutive peaks observed.

  • Averaging non appropriate.

  • Preferring a statistical distribution

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Include channel occupancy in downlinks proposal

Include channel occupancy in downlinks : proposal

  • Aircraft to send periodically statistical distribution of lastly received CU from its VDR.

    • On 4 bits: number of CU = 100% received during the 15 last seconds

    • On 4 bits : number of CU > 50 % and < 100% received during the 15 last seconds.

  • Much more reliable than averaging

  • But how to convey such an information to the ground ?

    • XIDs ?

    • INFO ?

    • RR ?

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Include channel occupancy in downlinks receive ready

Include channel occupancy in downlinks (receive ready)

  • Constraints

    • Frequency of reporting shall be sufficient to have a precise view on traffic load.

    • But it shall not induce overhead in heavy traffic situation.

  • Solution: Receive ready

    • Present in a variable proportion in all AVLC link.

      • On heavy load, it gets piggy backed through the INFO frame sending. Thus natural regulation.

      • Due to T2 timer (max delay between acks : 500 ms) even in heavy load there is about 20% of RRs exchanged.

      • When window closes an RR P=1 is sent.

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Proportion of rrs in a typical day seen by moon

Proportion of RRs in a typical day seen by MOON.

RR Average 25 %

Account for 5% of bytes exchanged

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Include channel occupancy in downlinks our proposition

Include channel occupancy in downlinks (Our proposition)

  • In downlinked received ready

    • Add an extra byte with the following format

      • On 4 bits(MSBs): number of CU = 100% received during the 15 last seconds

      • On 4 bits(LSBs) : number of CU > 50 % and < 100% received during the 15 last seconds.

  • In uplinked receive ready

    • Why not doing the same ? (optional, to be discussed)

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Questions

Questions ?

  • Patrick DELHAISE

    • [email protected]

  • Laurent MEYER

    • [email protected]

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