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Synchronized iPhones!
iOSDC 2018
@TachibanaKaoru
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About Me
@TachibanaKaoru
Freelance iOS Engineer
iOSDC Core Staff (Track A)
ϘϧμϦϯά͖
ࠓͷςʔϚɿཱྀΛ͠ͳ͕ΒࣄΛ͢Δ
όϦౡɺαϯτϦʔχౡɺόϯίΫɺϑΟϯϥϯυɺϊϧΣʔ
ͱ͖Ͳ͖φΨϊ 2018 ࢀՃத
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ࠓͷ
iOSσόΠεΛSyncͯ͠Γ͍ͨ͜ͱ
iOSσόΠεͷ࣌ࠁ߹Θͤ
σόΠεؒಉظ
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Sync ͯ͠Γ͍ͨ͜ͱ
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OK
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NG
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t
deviceA
deviceB
deviceC
deviceD
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Syncͱ
iOSͷϦϑϨογϡϨʔτʹ͋Θͤͯಉ͡ը໘Λදࣔ͢Δɻ
ؒͷදࣔ࣌ؒʹޡ͕ࠩ͋Δ߹ɺϦϑϨογϡϨʔτͷߋ৽ִؒҎ
Լɻ
͝ͱʹϦϑϨογϡϨʔτ͕ҟͳΔ߹ʹɺ࠷ૣ͍ʹ͋Θ
ͤΔɻ
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Syncͱ
iOSͰ࠷ૣ͍ϦϑϨογϡϨʔτ60fps
ϦϑϨογϡϨʔτͷߋ৽ִؒ1/60 = 16.66 msec
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ϦϑϨογϡϨʔτʹ͋Θͤͨඳը
CADisplayLinkΛ͑ɺϦϑϨογϡϨʔτʹ͋Θͤͯඳը͢Δ͜ͱ͕
Ͱ͖Δɻ
iOSͷϦϑϨογϡϨʔτجຊతʹ60͕ͩɺ༷ʑͳঢ়گʹΑͬͯม
Խ͢Δɻ
σόΠεͷछྨiOS versionɺforeground/backgroundͰಈ࡞͍ͯ͠Δϓ
ϩηεʹґଘɻ
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How to use CADisplayLink
let displaylink = CADisplayLink(target: self,
selector: #selector(drawSomething))
displaylink?.add(to: .current,
forMode: RunLoop.Mode.default)
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Ͳ͏ͬͨΒؒͷޡࠩΛ16.66 msec
ҎԼʹͰ͖Δʁ
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·ͣiPhoneͷγεςϜ࣌ؒΛ
͋ΘͤͯΈΔ
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ͯ͞ɻ͜͜ͰɺiPhoneͲ͏ͬͯ࣌
ؒΛ͋Θ͍ͤͯΔͷ͔Λ෮श͠·͢ɻ
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ձͷΈͳ͞Μʹ࣭Ͱ͢ɻ
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iOSσόΠεͲ͏ͬͯ࣌ࠁΛ͋Θ
͍ͤͯΔͷͰ͠ΐ͏ʁ
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iOSͷ࣌ࠁ͋Θͤ
ʢෳճՄʣ
1. ࣌ใ༻ͷిΛ͔͍ͭͬͯΔ
2. Πϯλʔωοτ্ͷ࣌ࠁαʔόʔʹΞΫηε͍ͯ͠Δ
3. GPS৴߸ʹؚ·Εͨ࣌ࠁΛར༻͍ͯ͠Δ
4. ܞଳిճઢ͔ΒऔಘͰ͖Δ࣌ࠁΛར༻͍ͯ͠Δ
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࣌ใ༻ͷిΛ
͔͍ͭͬͯΔ
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Πϯλʔωοτ্
ͷ࣌ࠁαʔόʔʹ
ΞΫηε͍ͯ͠Δ
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GPS৴߸ʹؚ·Εͨ
࣌ࠁΛར༻͍ͯ͠Δ
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ܞଳిճઢ͔
ΒऔಘͰ͖Δ࣌
ࠁΛར༻͍ͯ͠Δ
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iOSͷ࣌ࠁ͋Θͤ
ʢෳճՄʣ
1. ࣌ใ༻ͷిΛ͔͍ͭͬͯΔ
2. Πϯλʔωοτ্ͷ࣌ࠁαʔόʔʹΞΫηε͍ͯ͠Δ
3. GPS৴߸ʹؚ·Εͨ࣌ࠁΛར༻͍ͯ͠Δ
4. ܞଳిճઢ͔ΒऔಘͰ͖Δ࣌ࠁΛར༻͍ͯ͠Δ
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iOSͷ࣌ࠁ͋Θͤ
1. ࣌ใ༻ͷిΛ͔͍ͭͬͯΔ
2. Πϯλʔωοτ্ͷ࣌ࠁαʔόʔʹΞΫηε͍ͯ͠Δ
3. GPS৴߸ʹؚ·Εͨ࣌ࠁΛར༻͍ͯ͠Δ
4. ܞଳిճઢ͔ΒऔಘͰ͖Δ࣌ࠁΛར༻͍ͯ͠Δ
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iOSͷ࣌ࠁ͋Θͤ
1. ࣌ใ༻ͷి ඪ४ి
2. Πϯλʔωοτ্ͷ࣌ࠁαʔόʔʹΞΫηε NTP
3. GPS৴߸ʹؚ·Εͨ࣌ࠁ GPS
4. ܞଳిճઢ͔ΒऔಘͰ͖Δ࣌ࠁ NITZ
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iOSͷ࣌ࠁ͋Θͤ
NITZ GPS NTP
iPhone ○ ○ ○
iPad (with Mobile) ○ ○ ○
iPad (without Mobile) × ○ ○
iPod touch × × ○
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iOSͷ࣌ࠁ͋Θͤ
ͲͷͰͲͷํࣜΛ༏ઌ͍ͯ͠Δ͔ެද͞Ε͍ͯͳ͍ɻ
ड৴࣌ͷਫ਼ʹΑͬͯ࠾༻ɾෆ࠾༻Λม͍͑ͯΔՄೳੑ͋Δɻ
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ඪ४ి
ใ௨৴ݚڀػߏʢNICTʣͰӡ༻͍ͯ͠Δ࣌ใ༻ͷి
͍ΘΏΔి࣌ܭͰΘΕ͍ͯΔΈ
ຊࠃ͚
࣌ࠁUTCͰૹ৴͞ΕΔ
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NTP
Network্ͷ NTPαʔόʔʢ࣌ࠁαʔόʔʣʹଓͯ࣌͠ࠁΛઃఆ͢Δɻ
UTC͕৴͞ΕΔ
Mac OSͰɺσϑΥϧτNTP time.asia.apple.com ʢมߋՄʣ
iosͰɺσϑΥϧτNTPมߋෆՄ
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GPS
ΞϝϦΧ͕ཧ͢ΔӴΛͬͨଌҐγεςϜ
ੈքதͰ༻Մೳ
GPS time͕ૹ৴͞ΕΔ
࣌ࠁਫ਼ඇৗʹߴ͍͕ɺਖ਼͘͠ܭࢉ͢ΔͨΊʹGPSӴ4ͭͷ৴߸Λ
ड৴͢Δඞཁ͕͋Δ
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NITZ
Network Identity and Time Zone
௨৴ΩϟϦΞ͔Β৴͞ΕΔ࣌ࠁ
ରԠͨ͠ΩϟϦΞͰͷΈ༻Մೳ
ਫ਼ͦΕͧΕͷࣄۀऀʹΑΔ
UTCϕʔεͷLocal TimeɺTime Zone͕ૹ৴͞ΕΔ
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࣌ࠁ߹Θͤͷํ๏
औಘํ๏ Time
ඪ४ి ి UTC
NTP Πϯλʔωοτճઢ UTC
GPS ి GPS Time
NITZ ܞଳిճઢ
Local Time
(on UTC)
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…What is UTC/GPS Time?
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JST, UTC, TAI
http://www.nict.go.jp/JST/JST5.html
JST 13:02:45
UTC 04:02:45
TAI 04:03:22
9:00:00
0:00:37
TimeZone
???
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What is TAI?
TAI : Temps Atomique International ʢϑϥϯεޠʣɺࠃࡍݪࢠ࣌
Le TAI est une échelle de temps-coordonnée définie dans un repère de référence
géocentrique avec comme unité d'échelle la seconde du SI telle qu'elle est réalisée sur
le géoïde en rotation
༁ɿTAI , ճస͢ΔδΦΠυ্Ͱ࣮ݱ͞ΕΔ SI ͷඵΛΓͷ୯Ґͱͨ͠, ৺࠲ඪܥͰఆٛ͞ΕΔ࠲ඪ࣌ͷ
ΓͰ͋Δ
― CCDS ͷ໌ɺBIPM Com. Cons. Déf. Seconde, 1980, 9, S 15 ٴͼ Metrologia, 1981, 17, 70
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What is TAI?
TAI ɺճస͢ΔδΦΠυ্Ͱ࣮ݱ͞ΕΔ SI ͷඵΛΓͷ୯Ґͱ͠
ͨɺ৺࠲ඪܥͰఆٛ͞ΕΔ࠲ඪ࣌ͷΓͰ͋Δɻ
δΦΠυͱɺٿͷฏۉւਫ໘ʹۃΊͯྑ͘Ұக͢ΔδΦϙςϯ
γϟϧ໘Λݴ͏ɻʢWikipediaͷδΦΠυͷ߲ΑΓʣ
·͋ɺʮ͍͍ͩͨւਫ໘্ʯͱͱΒ͍͑ͯͩ͘͞ɻ
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ͳͥʮδΦΠυʯ্ͳͷ͔
Ұൠ૬ରੑཧͷӨڹͰɺॏྗͷڧ͞
ʹΑͬͯɺ࣌ؒͷྲྀΕ͕ӨڹΛ͏͚Δ͔
ΒͰ͢ɻ
ඪߴ͕ߴ͘ͳΕͳΔ΄Ͳɺॏྗऑ͘
ͳΓɺ࣌ؒૣ͘ਐΈ·͢ɻ
Slow
Fast
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What is TAI?
TAI ɺճస͢ΔδΦΠυ্Ͱ࣮ݱ͞ΕΔ SI ͷඵΛΓͷ୯Ґͱ͠
ͨɺ৺࠲ඪܥͰఆٛ͞ΕΔ࠲ඪ࣌ͷΓͰ͋Δɻ
SIͷඵͱɺʮηγϜ133ݪࢠͷجఈঢ়ଶͷ2ͭͷඍࡉߏ४ҐʢF
= 4, M = 0 ͓Αͼ F = 3, M = 0ʣؒͷભҠʹରԠ͢Δ์ࣹͷपظͷ 9
192 631 770 ഒͷܧଓ࣌ؒɻʯʢ1967੍ఆʣ
1967ΑΓલɺ̍ͷ͞Λ 86400 Ͱׂͨ͠ͷͰͨ͠ɻ
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What is TAI?
TAIͱɺఱମͷಈ͖ʢٿଠཅͳͲʣͷಈ͖Λجૅʹͨ͠Θ͚Ͱͳ
͘ɺʮද໘Ͱଌఆ͍ͯ͠ΔʢηγϜʣݪࢠ࣌ܭΛجຊʹͨ࣌͠ࠁܥʯ
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What is UTC?
UTC : Coordinated Universal Timeɺ ڠఆੈք࣌
ࠃࡍݪࢠ࣌ (TAI) ʹ༝དྷ͢Δݪࢠ࣌ܥͷ࣌ࠁͰɺUT1ੈք࣌ʹಉௐ͢ΔΑ
͏ʹௐ͞Εͨج४࣌ࠁΛࢦ͢ɻ
1972͔ΒΘΕ͍ͯΔɻ
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What is UTC?
ࠃࡍݪࢠ࣌ (TAI) ʹ༝དྷ͢Δݪࢠ࣌ܥͷ࣌ࠁͰɺUT1ੈք࣌ʹಉௐ͢ΔΑ
͏ʹௐ͞Εͨج४࣌ࠁΛࢦ͢ɻ
UTCͱTAIͷඵͷ͞ಉ͡ɻ
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What is UTC?
ࠃࡍݪࢠ࣌ (TAI) ʹ༝དྷ͢Δݪࢠ࣌ܥͷ࣌ࠁͰɺUT1ੈք࣌ʹಉௐ͢ΔΑ
͏ʹௐ͞Εͨج४࣌ࠁΛࢦ͢ɻ
UT1ఱମͷಈ͖͔Βܭࢉͨ࣌͠ࠁܥ
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What is UTC?
ݫີͳ࣌ࠁଌఆ͕Ͱ͖ΔΑ͏ʹͳͬͯ͘Δͱɺ̍ͷ͞ɺ̍ͷ͞
͕ݫີʹҰఆͰͳ͍͜ͱ͕Θ͔͖ͬͯ·ͨ͠ɻ
͜͜ͰΘ͔Γ͘͢ɺ̍ͷ͕͞13 SIඵͷͱɺ16 SIඵͷ͕͋Δ
߹Λߟ͑ͯݟ·͠ΐ͏ɻ
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ఱจ͔࣌Βܭࢉͨ࣌͠ࠁ
TAI
UT1
ఱจ͔࣌Βܭࢉ
ͨ࣌͠ࠁ
x13 x13 x13
x13 x13 X13
1ͷ͕͞13 SIඵͷ 1ͷ͕͞13 SIඵͷ 1ͷ͕͞16 SIඵͷ
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Մมඵ
͠ɺʮ̍ͷ͞ͷ86400 ׂʯΛඵͰఆٛͯ͠͠·͏ͱɺʹΑͬ
ͯ̍ඵͷ͕͞ҧ͖ͬͯͯ͠·͍·͢ɻ
͜Εɺৗੜ׆ΛૹΔ্Ͱ͋Γ·ͤΜ͕ɺཧ࣮ݧΤϯδ
χΞϦϯάʹେ͖ͳࢧো͕Ͱ·͢ΑͶɻ
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̍ͷ͞ͷมಈ
̍ΛSIඵͰදࣔͨ͠ͷɻ͍ͱ͍Ͱ 5msͷ͕ࠩ͋Δ͜ͱ͕Θ
͔Δɻ
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UTC
TAI
UT1
UTC
x13 x13 X13+3
x13 x13 X13
1ͷ͕͞13 SIඵͷ 1ͷ͕͞13 SIඵͷ 1ͷ͕͞16 SIඵͷ
͏Δ͏ඵ
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͏Δ͏ඵ
Leap second : ͏Δ͏ඵ
TAIͱఱจ༝དྷͷ࣌ࠁΛ͋ΘͤΔͨΊʹUTCʹૠೖ͞ΕΔ
UTCͷӡ༻։͔࢝Βద༻͞Εɺࠓ·Ͱ37ճ͔Βૠೖ͞Ε͍ͯΔ
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Leap second in iOS and macOS
iOSͱMac OSͷ෦࣌ܭɺ͓ΑͼFoundationͷDateΫϥεLeap second
ʹରԠ͍ͯ͠·ͤΜɻ
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Leap second in iOS and macOS
લճͷ͏Δ͏ඵɺ2016/12/31 23:59:60 UTCͰͨ͠ɻ
2016/12/31 23:59:59 UTC
2016/12/31 23:59:60 UTC
2017/01/01 00:00:00 UTC
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Leap second in iOS and macOS
let calendar = Calendar(identifier: .gregorian)
// 2016/12/31 23:59
var dateComp20162332235959 = DateComponents()
dateComp20162332235959.calendar = calendar
dateComp20162332235959.year = 2016
dateComp20162332235959.month = 12
dateComp20162332235959.day = 31
dateComp20162332235959.hour = 23
dateComp20162332235959.minute = 59
dateComp20162332235959.second = 59
dateComp20162332235959.date?.timeIntervalSince1970 // => 1483196399
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Leap second in iOS and macOS
let calendar = Calendar(identifier: .gregorian)
// 2016/12/31 23:60
var dateComp20162332235960 = DateComponents()
dateComp20162332235960.calendar = calendar
dateComp20162332235960.year = 2016
dateComp20162332235960.month = 12
dateComp20162332235960.day = 31
dateComp20162332235960.hour = 23
dateComp20162332235960.minute = 59
dateComp20162332235960.second = 60
dateComp20162332235960.date?.timeIntervalSince1970 // => 1483196400
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Leap second in iOS and macOS
let calendar = Calendar(identifier: .gregorian)
// 2017/01/01 00:00
var dateComp20170101000000 = DateComponents()
dateComp20170101000000.calendar = calendar
dateComp20170101000000.year = 2017
dateComp20170101000000.month = 1
dateComp20170101000000.day = 1
dateComp20170101000000.hour = 0
dateComp20170101000000.minute = 0
dateComp20170101000000.second = 0
dateComp20170101000000.date?.timeIntervalSince1970 // => 1483196400
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Leap second in iOS and macOS
// 2016/12/31 23:59
dateComp20162332235959.date?.timeIntervalSince1970 // => 1483196399
// 2016/12/31 23:60
dateComp20162332235960.date?.timeIntervalSince1970 // => 1483196400
// 2017/01/01 00:00
dateComp20170101000000.date?.timeIntervalSince1970 // => 1483196400
2016/12/31 23:60ͱ2017/01/01 00:00෦తʹ͍͠ɻ
ʹɹ͏Δ͏ඵʹରԠ͍ͯ͠ͳ͍ɻ
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Leap second in iOS and macOS
ݫີʹɺMaciPhoneʢͦͷଞͷଟ͘ͷσδλϧσόΠεʣͯ͢
TAIʹ༝དྷ͢Δಠࣗͷݪࢠ࣌ͷ࣌ࠁͰɺඪ४ిNTPͳͲͷ֤छٕज़ʹ
ΑͬͯɺUTCʹಉௐ͢ΔΑ͏ʹௐ͞Εͨ࣌ࠁΛ͖͟ΜͰ͍ΔΘ͚Ͱ
͢ɻ
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What is GPS Time?
http://leapsecond.com/java/gpsclock.htm
UTC 04:02:45
GPS 04:02:45
TAI 04:03:22
0:00:19 ???
0:00:37 ͏Δ͏ඵ
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GPS Time
ࠃࡍݪࢠ࣌ (TAI) ʹ༝དྷ͢Δݪࢠ࣌ܥͷ࣌ࠁͰɺ1980/1/6ʹUTCͱಉظ͠
͍ͯΔ࣌ࠁΛࢦ͢ɻ
ॳͷGPSӴଧ্͕ͪ͛1978ɻ
͏Δ͏ඵͷิਖ਼ߦͳ͍ͬͯͳ͍ɻʢTAIͱͷࠩҰఆʣ
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ඵͷ͞ ͏Δ͏ඵิਖ਼ ӡ༻ظؒ
TAI SIඵʢݻఆʣ ͳ͠ 1970~
GPS Time SIඵʢݻఆʣ ͳ͠ 1980~
UTC SIඵʢݻఆʣ ͋Γ 1972~
چUTC มಈ ͳ͠ 1961~1971
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Special relativity in GPS
−(v/c)2/2 = − 8.4 × 10−11
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General relativity in GPS
ΔU/c2 = 5.27 × 10−10
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Relativity in GPS
−4.45 × 10−10
−(v/c)2/2 = − 8.4 × 10−11
ΔU/c2 = 5.27 × 10−10
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࣮ࡍͷiOS DeviceͰଌఆͯ͠ΈΔ
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ۀػີ
ۀػີ
ۀػີ
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iOS Systemͷ࣌ࠁ߹Θͤਫ਼ࠓճඞཁ
ͳਫ਼ʹରͯ͠NGͰͨ͠ɻ
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Ͳ͏ͬͯSync͢Δ?
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Peer to Peer Time Sync on BT
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BTʹΑΔใڞ༗
CoreBTͰPeripheralͱCentralؒͰදࣔใΛڞ༗͢Δɻ
ͱͳΔPeripheralʹଞͷ͕Centralͱͯ͠ଓɻ
Peripheral͔Βଓͨ͠CentralʹදࣔใΛૹ৴ɻ
BTʹ͓͍ͯPeripheral-CentralؒͰૹ৴Ͱ͖Δใྔগͳ͍ͨΊɺը
૾σʔλΛૹ৴͢ΔΘ͚Ͱͳ͘ɺ͋Β͔͡Ίʹอ࣋͢Δը૾
Λมߋ͢Δํࣜͱ͢Δɻ
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BTʹΑΔใڞ༗
Peripheral͔ΒCentralʹ࣮ࡍʹૹ৴ͯ͠Έͨͱ͜Ζɺฏۉͯ͠20~40
msecͷԆ͕ੜ͡ɺཁٻ͞ΕΔ16.66 msecͷൣғʹ͓͞·Βͳ͔ͬ
ͨɻ
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t
Peripheral
Central 1
Central 2
Central 3
20~40 msec
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௨৴࣌ͷԆΛফڈ͢Δ
BT௨৴ʹ͔͔Δॲཧ࣌ؒ
ͷॲཧ࣌ؒ + ௨৴࣌ؒ
௨৴࣌ؒ ∝ PeripheralͱCentralͷڑ
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௨৴࣌ͷԆΛফڈ͢Δ
Central
Peripheral
Peripheral͔ΒCentralʹTAIΛجຊͱͨ͠ಠࣗͷ࣌ࠁ
ܥΛఆظతʹૹ৴͠ɺCentral͔ΒPeripheralଆʹ
ࣗσόΠεͷ࣌ࠁΛૹ৴͢Δɻ
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
? ? ? ? ? ?
1
- -
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
0.4 1.4 2.4 3.4 4.4 5.4
1
1
- -
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.4
0.4 1.4 2.4 3.4 4.4 5.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.4
2.6
0.4 1.4 2.4 3.4 4.4 5.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.4
2.6 3
2.6 1.4
0.4 1.4 2.4 3.4 4.4 5.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3
2.6 1.4
3 + ( 2.6 - 1.4) / 2
= 3.6
3.0
0.4 1.4 2.4 3.4 4.4 5.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6 > 3.0
3.0
0.4 1.4 2.4 3.4 4.4 5.4
3
2.6 1.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6 > 3.0
3.6
0.4 1.4 2.4 3.4 4.4 5.4
3
2.6 1.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6 > 3.0
3.6
1.0 2.0 3.0 4.0 5.0 6.0
3
2.6 1.4
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6
4.0
1.0 2.0 3.0 4.0 5.0 6.0
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6
4.0
4.6
1.0 2.0 3.0 4.0 5.0 6.0
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6
4.0
4.6
5
4.6 4.0
1.0 2.0 3.0 4.0 5.0 6.0
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6
4.0
4.6
5 + (4.6 - 4.0) / 2
= 5.3
5.6
1.0 2.0 3.0 4.0 5.0 6.0
5
4.6 4.0
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௨৴࣌ͷԆΛফڈ͢Δ
Peripheral
Central
1 2 3 4 5 6
1.2
2.6
3.6
4.0
4.6
5.3 < 5.6
5.6
1.0 2.0 3.0 4.0 5.0 6.0
5
4.6 4.0
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௨৴࣌ͷԆΛফڈ͢Δ
Centralଆ͔ΒPeripheralʹࣗσόΠεͷ࣌ࠁΛૹ৴͠ɺPeripheralଆ͔Β
ͦͷࠩΛৗʹCentralଆʹૹ৴͢ΔΑ͏ʹઃఆɻ
ఆظతʹޡࠩΛૹΔ͜ͱͰɺ࣌ؒࠩΛऩଋͤ͞Δɻ
͜ΕʹΑΓɺPeripheral - Central ؒͷޡࠩΛ10 msecఔʹ͢Δ͜ͱ͕Մ
ೳͱͳͬͨɻ
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͔͠͠ɺ·ͨผͷ੍ݶ͕……
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ଓτϥϒϧ
1ͷPeripheralʹରͯ͠ɺ4ͷCentral·
Ͱଓ͢Δ͜ͱ͕Ͱ͖͕ͨɺ5ͷ
CentralΛଓ͢Δ͜ͱ͕Ͱ͖ͳ͔ͬͨɻ
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Appleʹ͍߹Θͤ
1ͷPeripheralʹଓͰ͖ΔCentralɺ্੍༷ݶ͕ͳ͍͕࣮ӡ༻
্વ੍ݶ͕͋Δɻ
ͦͷଓɺσόΠεͷεϖοΫڥʹΑܾͬͯ·ΓɺҰҙʹఆ
ٛ͢Δ͜ͱͰ͖ͳ͍ɻ
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Single Layer Structure
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MultiLayer Structure
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Multilayer Structure
͜ΕͰ10ఔͷSyncՄೳͱͳͬͨɻ
ͨͩ͠ɺPeripheralͱCentralΛ͔Ͷͨͷଓ͕ෆ҆ఆɻ
Centralଆ͔ΒPeripheralͷଓ͕ޭ͢Δ͕ɺҰఆ࣌ؒʢඵʙॏ
ඵʣͨͭͱࣗવʹdisconnect͢Δ߹͕͋Δɻ
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·ͱΊ
BT૬ޓ௨৴Ͱ࣌ࠁࠩΛऩଋͤ͞ΔΈʹΑΓɺؒͷ࣌ࠁࠩΛ10
msecఔ·Ͱʹ͢Δ͜ͱ͕Ͱ͖ͨɻ
MultiLayer StructureΛͱΔ͜ͱʹΑΓɺBTͷଓ੍ݶΛ͑ͨଟͷ
ؒͰͷSyncͷՄೳੑײ͡Δɻ
ͨͩ҆ఆʹ͕͋Γɺݱঢ়Ͱ100ͷʹΑΔSyncԕ͍ɻ
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References
•ը૾
͍Β͢ͱ
https://www.irasutoya.com/
•GPSͷ૬ରิਖ਼ʹ͍ͭͯ
GPS ͱཧʢଜ ਗ਼ӳʣ
http://maya.phys.kyushu-u.ac.jp/~knomura/museum/GPS/node11.html