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RE: Proximity alarm interface

From: Thomson, Martin <Martin.Thomson@commscope.com>
Date: Wed, 29 Jun 2011 07:15:11 +0800
To: Steve Block <steveblock@google.com>, Doug Turner <doug.turner@gmail.com>
CC: Anne van Kesteren <annevk@opera.com>, Lars Erik Bolstad <lbolstad@opera.com>, "public-geolocation@w3.org" <public-geolocation@w3.org>
Message-ID: <8B0A9FCBB9832F43971E38010638454F040B26CA7E@SISPE7MB1.commscope.com>
SUPL provides similar functionality.  The idea is to trigger a notification if the device enters a target area.  As discussed, the main benefit is battery savings.

In that method, a server indicates the set of WiFi access points and/or cell identifiers that are either entirely within, or border on the area of interest.  When the device moves and is forced to hand off, it quickly checks this set.  If it sees an identifier that is entirely within, it fires the trigger; if it sees a bordering identifier, it initiates a GPS positioning attempt to help determine if it is in the target area.

This functionality is probably already available to a number of devices, but it requires server assistance in order to identify the set of interesting base stations.  

Without server assistance, the device has to send base station identifiers to a server each time that it hands off (or it could have a big database).  That reduces the battery savings, but probably only marginally, since the device is going to be awake at handoff time anyhow.

A device that honours enableHighAccuracy could produce something approximating the effect without needing an API change.

--Martin

On 2011-06-29 at 03:10:56, Steve Block wrote:
> > How much battery life savings is there?
> The argument we discussed at the face-to-face was that the UA could 
> simply check WiFi and/or Cell IDs until it got close to the relevant 
> location, and only then enable full location look-ups, possibly 
> including GPS. A JS implementation can't do this, especially if the UA 
> doesn't honour enableHighAccuracy.
> 
> Steve
> 
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Received on Friday, 1 July 2011 05:32:58 UTC

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