White Space Database Connectivity for Mobile Devices

First Experiments

P. Pawe lczak [with: N. Brouwers, A. Yousef Majid, N. Cicek, K. Langendoen]

TU Delft Embedded Software GroupSeptember 8, 2016

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Motivation

”spectrum sensing is expensive—in cost, energy consumptionand complexity of the circuitry.”

X. Ying et al., Exploring indoor white spaces in metropolises, in Proc. ACM MobiCom 2013

Use White Space Databases (WSDBs)!But is it really so simple?

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Research Question/Methodology

1 What is the cost of WSDB access for mobiles?2 Approach: Connect to WSDB through Android OS

I Access delay (query → response)I Size of responseI Energy consumed (per radio access, per smartphone)

3 MetodologyI Analyze data (from various WSDBs)I Model resultsI Suggest WSDB access strategies for mobile devices

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Limitations

Limited Interest to Industry

WSDB still immature/mobility is of low interest yet!

1 Current regulation: must query every X m as you move2 Experiments presented applicable for a special scenarios

1 Query WSDB through non-DSA interface for extra channel2 PAWS v20 (Section 7)

F Master asking for spectrum on behalf of Slave

3 Example: swarm of quadcopters forming ad hoc network

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WSDB Connection

WSDBs used in the experiment

https://www.google.com/get/spectrumdatabasehttp://tvws-demo.spectrumbridge.comhttp://whitespaces.msresearch.ushttp://tvwsdb.broadbandappstestbed.com/json.rpc

WSDBs not used in the experiment

Rest of the OFCOM trial WSDBshttp://specobs.ee.washington.eduhttp://whitespaces.cloudapp.net/WSFinder.aspxhttp://observatory.microsoftspectrum.com...

Open API for all WSDBs—query from anywhere possible

Save response data/time + energy consumed (Neat)

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Measuring Energy Consumption

Neat Power Measurement Toolkit

Custom-build power measurement platform [“Embedded Monsoon”]

Correlates system events with energy use

Andriod-based, 2 kHz sampling, SD Card storage, external battery

N. Brouwers et al., NEAT: A Novel Energy Analysis Toolkit for Free-Roaming Smartphones, in Proc. ACM

SenSys 2014

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Phone/RTL-SDR Dongle Connection

Platform: Samsung GT-I9250 + CyanogenMod 10.1.3 + Fitipower FC0013 tuner

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Results: WSDB Access Delay

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LA WV SC LE CB[GL]

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LA WV SC LE CB[BG]

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LA WV SC LE CB[SB]

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100x per location

LA, WV, SC, LE, CB: various locations in US

GL, BG, SB: google.nl, bing.com, spectrumbridge.com

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Results: WSDBs Message Size

CDF

PDF

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Measuring Single WSDB Query: Setup

Cellular: KPN, Vodafone, T-Mobile

WiFi: Eduroam

10549 query results at a fixed indoor location (two weeks)

WSDB querying intervalI T-Mobile, Vodafone: 30 sI KPN: 2 minI Eduroam: 10 s

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Results: Phone Energy Consumption

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GGL/NY GGL/SCSBI/NY SBI/SC

Symbols: ‘+’—Eduroam, ‘∆’—T-Mobile, ‘o’—KPN, ‘*’—Vodafone

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WSDB Access: Energy Model

Energy linear as time for WSDB reply passes (excluding tail)

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print_constraints: VPP: 1800 <--> 2500 mV at 1900 mV normal standbyprint_constraints: VAUX2_6030: 1200 <--> 2800 mV at 1800 mV normal standbyasoc: null-codec-dai <-> MultiMedia1 mapping okasoc: null-codec-dai <-> MultiMedia2 mapping okasoc: null-codec-dai <-> Voice mapping okasoc: null-codec-dai <-> Tones mapping okasoc: null-codec-dai <-> Vibra mapping okasoc: null-codec-dai <-> MODEM mapping okasoc: null-codec-dai <-> MultiMedia1 LP mapping okasoc: FM Digital <-> omap-mcbsp-dai.1 mapping okasoc: twl6040-dl1 <-> mcpdm-dl mapping okasoc: dit-hifi <-> omap-mcasp-dai mapping okasoc: twl6040-dl1 <-> mcpdm-dl1 mapping okasoc: twl6040-ul <-> mcpdm-ul1 mapping okasoc: twl6040-dl2 <-> mcpdm-dl2 mapping okasoc: twl6040-vib <-> mcpdm-vib mapping okasoc: Bluetooth <-> omap-mcbsp-dai.0 mapping okasoc: Bluetooth <-> omap-mcbsp-dai.0 mapping okasoc: FM Digital <-> omap-mcbsp-dai.1 mapping okasoc: MODEM <-> omap-mcbsp-dai.1 mapping okasoc: hdmi-audio-codec <-> hdmi-audio-dai mapping okOMAP4 PM: Static dependency added between MPUSS and DUCATI <-> L4_PER/CFG and L3_1.rpmsg_omx rpmsg-omx0: new OMX connection srv channel: 1024 -> 60!rpmsg_omx rpmsg-omx1: new OMX connection srv channel: 1024 -> 60!request_suspend_state: wakeup (3->0) at 13021911623 (2014-07-16 11:02:31.332214356 UTC)

[GsmSST] RAT switched HSPAP -> HSDPA at cell 47647146

[GsmSST] RAT switched HSDPA -> UMTS at cell 47647146

[GsmSST] RAT switched UMTS -> HSPAP at cell 47647145

uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4request_suspend_state: sleep (0->3) at 66457824710 (2014-07-16 11:03:21.889058350 UTC)uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4

[GsmSST] RAT switched HSPAP -> UMTS at cell 47647145

DCH->FACH

FACH->IDLE

FACH->IDLE

FACH->IDLE

DCH->FACH

FACH->IDLE

DCH->FACH

FACH->IDLE[GsmSST] RAT switched HSPAP -> UMTS at cell 47754403 hub 1-0:1.0: activate --> -22uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4request_suspend_state: wakeup (3->0) at 3701864259839 (2014-07-16 17:00:43.948106503 UTC)uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4[GsmSST] RAT switched HSPAP -> UMTS at cell 47647146uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4

uid: 1000 action: z -> 7 state: 3 -> 3 retry: 4

[GsmSST] RAT switched UMTS -> HSPAP at cell 47647146

[GsmSST] RAT switched HSPAP -> UMTS at cell 47647146

1m:5s 1m:10s 1m:15s 1m:20s 1m:25s

FACH TailDCH TailDCHQuery

R/U

CPU Wake

E[E ] = cqE[t] + aq, t ∈ [tmin, tmax]I cq: connection energyI aq: ramp-up

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Results: Combined Measurement

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TMB TMB BFR BFR VDF VDF EDR EDR RTL RTLGGL SBI GGL SBI GGL SBI GGL SBI USB BTR

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Symbols: TMB—T-Mobile, VDF—Vodafone, BFR—KPN, GGL—Google,SBI—SpectrumBridge, EDR—Eduroam, RTL—SDR, BTR—battery

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WSDB and Mobiles

To save energy, query size, etc.: the Idea

When mobile—Query many locations at once (duh!)

No WSDB (we know) does multi-location query the right way

1 Discovery: Google (PAWS v6) JSON-RPC batch modeI Google: “This isn’t a supported mode of operation, though

it’s nice to find out that it does appear to work.”

2 Future: PAWS v201 Area query2 Multi-locations query

F ’’location": { ’’point’’: { ’’center’’: {’’latitude’’: X,

’’longitude’’:Y, ’latitude’’: Z, ’’longitude’’: W, . . .} . . . }

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Results: Delay vs Multiple Locations

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Multi-Locations Query Algorithm

Proposal

WSDB query rate throttle depending on the movement pattern[patent pending]

Reference algorithms:

1 Query as You Go: query WSDB with every d m

2 Multi: one-shot WSDB query from start to furthest point

3 Oracle: know your path exact and do not use localization

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Multi-Location Query: Experiment

1 Samsung Galaxy S2; 10 minute car drive (Almere, Netherlands)

2 Google WSDB; ≈0.5×106 WSDB queries generated

3 Mapping of locations in NL to US

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Multi-Location Query: Results

Symbols: SL—Query as You Go; ML—Proposed; PML—Multi; OPML—Oracle

Symbols: Yellow—WSDB query only; Blue—Total (including GPS)

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Summary

1 DSA will drain your battery—if you’re not careful2 Energy consumed

I Depends on the situationI Use WiFi if possibleI In multi-location query: cost of localization non-negligible!

3 Mobility and WSDBs: There is enough space at thebottom, so...

... we’re not done yet!

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