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Google I/Oߦ͖ͬͯ·ͨ͠(Wi-Fi RTTʹ͍ͭͯ)
@sasamihoo
2018.5.27 Google I/O 2018 Θ͍Θ͍ใࠂձ 1
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profile
4 sasami(@sasamihoo )
4 intern(Android Engineer)
4 IoTܥͷݚڀࣨ(M2)
4 Androidྺ1.5͘Β͍
4 ࠓճGoogle I/OॳࢀઓͰ͢
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Google I/Oߦ͖ͬͯ·͠
ͨ!!
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Target session
How to get one-meter location-accuracy from Android
devices
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Overview of the
session
4 1-meter level accuracy of
indoor location positioning
4 API available in Android P
Wi-Fi RTTΛར༻͢Δ͜ͱͰ1m͝ͱͰ
ͷࣨͷAndroidͷσόΠεͷҐஔΛ
ଌఆͰ͖ΔΑ͏ʹͳͬͨ
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Current approach for detecting indoor
positioning
4 gyro
4 Wifi-RSSI
4 Cell NLP
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Current critical problem for getting
fine location
4 Wifi-RSSI are affected by human activity(2.4Ghz)
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What is Wifi RTT?
4 IEEE 802.11mc protocol
4 Using Time-of-Flight
technology
4 get distance from total time of
packet’s round trip
ڑ = (total time * speed-
of-light(c)) / 2
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How it works?
4 get total time from timestamp
from the access point
2 * distance = ((t4-t1) -
(t3-t2))*c
t4-t1 = ΞΫηεϙΠϯτଆͷ࣌ؒͷ
ࠩ
t3-t2 = σόΠεଆͷ࣌ؒͷࠩ
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how to get the device’s position?
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Calculate Positioning
4 multilateration
4 more ranges, more
constraints and get more
accurate position
4 at least more 4 ranges
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multilateration
estimation
case of no exact solution to that
equation(no intersect)
- squares solution
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Demo
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How to add RTT in our application?
4 IEEE 802.11mc protocol’s support of both Wi-Fi
device and a mobile phone
4 location permission(ACCESS_FINE_LOCATION)
4 Wi-Fi scan available
4 no need to connect to the Wi-fi(using beacon
packet)
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Check the device support RTT?
val packageManager: PackageManager = context.getPackageManager()
rttSupported: Boolean =
packageManager.hasSystemFeature(PackageManager.FEATURE_WIFI_RTT)
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Check the access point support RTT?
public fun filterRttApp(){
val scanResult: List = wifiManager.getScanResults()
for (scanResult: ScanResult in scanResults) {
if (scanResult.is80211mcResponder()){
}
}
}
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Start Ranging
val request: RangingRequest = RangingRequest.Builder()
.addAccessPoints(scanResults)
.build()
rttManager.startRanging(request, executor, RangingResultCallback(){
fun onRangingFailure(code: Int){ /* handle error*/ }
fun onRangingResult(results: List){
for (result: RangingResult in results){
doSomethingWithResults(
result.getStatus(),
result.getMacAddress(),
result.getDistanceMs()
)
}
}
})
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RTT Ranging Results
type function name
int getDistanceMm()
int getDistanceStdDevMm()
MacAddress getMacAddress()
long getRangingTimestampMillis()
int getRssi()
int getNumAttemptedMeasurements()
int getNumSuccessfulMeasurements()
available in Android Preview P(https://developer.android.com/reference/android/net/wifi/
rtt/RangingResult)
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Integration to Fused Location
Provider(In the future)
4 enable to use Wifi-RTT collaborate with other
solutions(GPS, gyro, Wifi-RSSI)
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What devices and access points can use
Wifi-RTT?
needs support of IEEE 802.11mc protocol
4 Pixel phones
4 Google Wifi will support soon
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Recap
4 Using Wifi RTT, 1-meter location accuracy is available
4 both access points and devices need to support of
IEEE 802.11mc protocol
4 Available in Android P preview
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Thanks!
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