Contents Introduction What are Location-based services Working of Location-based services Location Tracking Technologies Power profiling a mobile phone Power consumption of location based services Minimizing the power consumption Future Aspects Conclusion 2

Introduction A successful Location-Based Service must not drain the battery of a mobile phone. Battery capacity is a scarce resource in mobile phones, because the capacity of batteries is not increasing at the same pace as the new power-demanding features are added to mobile phones. LBSs make heavy use of many power-consuming features of mobile phones, such as the screen to display maps, the radio to receive and send data, or a GPS receiver for positioning. 3

Location Based Services A location-based service (LBS) is an information or an entertainment service, which is accessible with mobile devices through the mobile network and which uses the information of the geographical position of the mobile device. LBS include services to identify location of a place or a person, eg. the nearest banking cash machine, the nearest subway or the whereabouts of a friend or an employee. LBS even includes location-based games. 4

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How they work?? Location based services work on the principles of Location Tracking Technology. Location Tracking Technology is a convergence of several technologies that can track the objects according to their geographical position. Current technologies being used for location-tracking and location-based systems include: 6

Location Tracking Technologies Geographic Information System (GIS) - For large- scale location-tracking systems, it is necessary to capture and store geographic information. Global Positioning System (GPS) - is a space- based satellite navigation system that provides location and time information in all weathers, anywhere on or near the Earth, where there is an unobstructed line of sight to three nearest GPS satellites. 7

Radio-frequency identification (RFID) chips use wireless non-contact system that uses radio- frequency electromagnetic fields to transfer data from a tag attached to an object, for the purpose of automatic identification and tracking. Wireless local area network (WLAN) links two or more devices using wireless distribution method and provides a connection through an access point to the wider internet. 7 14

Power profiling a mobile phone Features Processor 1% Processor 100% Bluetooth Microphone Screen Wi-Fi scan GPS 3G radio idle 3G radio sending Avg. Power [watt]

Power Consumption of Location Based Services 9 16

Power Consumption of Location Based Services Geotagging are services that attach location information to other digital material, e.g., pictures. Reactive location-based search are services that, when requested, search for information related to the user’s location. Maps and navigation are services that can show people where they are on map stations and provide navigation directions. 17

Location based games are games that use location as an element in the game play eg. finding physical caches using GPS. Sports trackers are services that log where and when you can exercise for sharing. Place and activity recognition are services that can register the whereabouts and activities of a user

Proactive location based search are services that push information to the user of query results when in proximity of them. Location based social networking are services that enable the user to link location to social networking

Minimizing the Power Consumption Firstly, for saving power, the user should relax the required positioning accuracy from the highest possible to what is necessary. Secondly, map services on mobile phones can limit the zoom level to a relevant accuracy limit. Thirdly, services can adjust their quality based on how much battery power is left

To implement these concepts, here are the two goals: Minimize needed position fixes. Use the least consuming feature for positioning. 23

Minimize Needed Position Fixes Model the error of the last known position to establish which position fixes can be avoided. As long as the modeled error does not exceed the accuracy limit, no positioning is necessary. This system also takes into account the delays associated with powering on and off features, which lowers the chance of exceeding accuracy limits

Least Consuming Feature for Positioning To save power, switch to the least-consuming positioning feature that provides the needed accuracy, which provides significant savings. Extend the approach to also minimize needed position fixes by mobility profiling, e.g., to guess the possible paths that a target is taking and then follow the nearest path

Future Aspects The area of LBSs is growing and new services are emerging all the time, which compile new types of knowledge from the positions of targets. Improvements in technology might also change the power consumption levels of specific features of LBSs. 26

Conclusion Understanding the importance of minimized power consumption of LBSs. How the different mobile phone features consume power, and applied this understanding to the power consumption of commercial LBSs. These methods are able to provide significant power savings of up to 85%, which corresponds to an increase in battery lifetime. 2ggg gd 27