Location Services Overview

About Location Services

LBS pinpoints the location of mobile users and can do so without requiring the installation of mobile applications by utilizing network-based methods to locate devices, allowing location pinging of smart and feature phones alike. Mobile users must opt in and provide explicit permission to have their device located before location pings can be made.

In instances when the service cannot retrieve an aGPS (assisted GPS) location fix, or the mobile device doesn’t have built-in aGPS functionality, Cell-ID methods can still provide valuable location data.

Example Use Cases

Just a few common examples of LBS use cases include:

  • Location-aware, device-agnostic workforce management
  • Mobile payment verification to combat fraud
  • Geo-relevant text messaging for localized content delivery
  • Parcel tracking
  • Fleet management
  • Vehicle tracking
  • Theft recovery tracking
  • Telemetry
  • Emergency services
  • Proximity marketing
  • Location-contextual gaming

Methods Overview

MethodDescriptionConditionsAccuracyRangeResponse
A-GPSDevice-assisted: Network calculates end-user location using user-device positioning measurements.

Requirements:
- GPS chipset in user device
- Network-assisted satellite tracking
- Device set to LBS “on” mode

Fallback: ECID
Sensitivity: High

Best:
- Outdoors
- Clear line of sight to sky

Avoid:
- Indoors
- Dense urbana (high-rise/underground)
- Dense woodland (tall trees)
Highest of network
-enabled techniques
Fixes from newer tower technologies (e.g. 4G/LTE) capable of 5-20m outdoors
50m (good conditions)15 - 40 sec
Enhanced Cell ID (ECID)Network-based: Network calculates user position using radio-related measurements.

Requirements: Must be supported by Network Cell Tower

Fallback: Basic Cell ID

Availability: generally available across diverse vendor products and networks


Best:
- Urbana
- Closely grouped cell towers
- Indoors & Outdoors
Localized to finer level than with CID
Dependent on cell size
50-1000m
50-250m average (urban/suburban)
0 - 20 sec
Cell ID (CID)Network-based: takes readings from nearby cell towers.

Requirements: Works with all phones

Availability: Widely available
Best:
- Urbana
- Closely grouped cell towers
- Indoors & Outdoors
Dependent on cell size
Can be poor in cells with large coverage areas
800m average
50m min (high tower density)
5000m+ (low tower density)
0 - 5 sec(Near-Real Time)

Positioning Methods

aGPS

aGPS stands for Assisted Global Positioning System, and can provide the most precise reading of a device’s location within a range of 15-50+ meters.

The most accurate readings come from aGPS phones with a clear line of sight to GPS satellites, such as those located outdoors or inside of a car near a window. While aGPS works on the same principles as a GPS, the difference is that aGPS gets the information for a location fix from the satellites by using mobile network resources, also called assistant servers. Since these servers are continually sending and receiving information and therefore log the exact orbit and time for the location of the satellites, there is little or no delay in receiving the requested information.

aGPS is a hybrid method that is both network-based and handset-based, in that the mobile device must possess GPS receiver chipsets. The Network Operator must also deploy aGPS servers at their base stations. These servers download the GPS orbital information from the satellite and store it in the database. An aGPS-capable device can connect to these servers and download this information upon request. The technique “assists” the handset in quickly finding the three closest satellites within its range through the help of the closest base station. This technique offloads some of the mobile device processing requirements of a typical GPS and can perform the calculations much more quickly and without battery drain.

Though standalone GPS receivers have become hugely popular and are very accurate, they require direct communication with satellites rather than cellular towers, and therefore work best in clear weather and in areas without mountains, valleys or structures blocking the path to the sky. aGPS receivers work better in these situations, provided that they have decent cellular service coverage. Some aGPS models have the ability to link up to GPS satellites directly in case the assistance server is not available or if it is out of cellular network coverage area.

Enhanced Cell-ID

Enhanced Cell-ID uses basic Cell-ID as well as a variety of Radio Frequency parameters and calculations such as Timing Advance to estimate a position within the cell-sector with an accuracy range of 40-400 meters, compared to the 100-5000 meter range of standard Cell-ID.

Based upon neighboring cell measurements, the network can estimate the part of the concentric ring that the mobile device is within.

Cell-ID

Cell-ID can approximate a mobile device’s location within 100-5000 meters using the geographical coordinates of the corresponding Base Station. It is the simplest way to describe the general location of a handset. It requires the network to identify the Base Transceiver Station (i.e. the cell tower to which the device is connected at the time). The network uses the cell site and the respective sector within the cell to estimate location.

The Cell-ID method operates in most types of cellular networks. It is the lowest cost method and is quick to yield a reading of a device’s location, however accuracy and consistency vary dramatically depending on cell site density. This is because the typical cell tower’s reach is anywhere from 2-20 kilometers in diameter. Since the mobile device can be anywhere within that area, the accuracy of this method depends on that size. Thus Cell-ID positioning is generally more accurate in urban areas with a dense network of smaller cells than in rural areas with fewer base stations.

This LBS method is best-suited to use-cases that do not require pinpoint accuracy, for instance, “What part of town am I in?”

Geofencing

To locate a mobile device you have to ping it directly, performing a “location fix.” Continuously performing that fix is cost prohibitive, but GeoFences solve that problem by only pinging devices located within a specific area. Schedule and frequency parameters defined by use case determine when and how often you want to locate the mobile device within your GeoFence.

Example Use-Cases

Ann’s fleet of delivery trucks are required return nightly to a home-base lot. To know when and if each vehicle returns, Ann set her GeoFence boundary to the parking lot’s location between 5pm and 7pm, Monday through Friday, and set her frequency to perform a location fix on the vehicles inside the Fence once every fifteen minutes. When a truck enters the fence, Ann knows within fifteen minutes because she can ping either the driver’s mobile phone or a vehicle-specific device installed into each truck. Aerialink’s Location API can then deliver the time stamp and x/y coordinate to Ann’s application for analysis, and/or send an SMS alert to the phone of her fleet/operations manager.

Setting Up a GeoFence

These are the key factors to be considered for each GeoFence program:

  • Schedule: When do you want to ping your users?
  • Frequency: How often do you want to locate user? (ex: once every 30 minutes, once every week, etc.)
  • Quantity: How many fences do you need? (if you have 50 stores, you would have 50 fences)
  • Fence Location: Where is the fence? The location can be determined by x, y coordinates. A geo-fence works best in urban areas where cell towers are closest together, but a large geo-fence is the exception to this rule.
  • Fence Shape: How big does the fence need to be? The use-case’s own variables will drive the size of the fence and often the shape. Most common shape is Radius. It is highly recommend that the fence be 5-10 miles or greater.
  • Messages: What are the auto-response messages that will be triggered when user enters fence?
  • Logic: What logic would you like built into your system? For instance, your program could have built-in logic so that it knows that once a user is within your geo-fence, that it should “stop looking for user A for X amount of time,” to prevent unnecessary pinging (e.g. Once a truck from the fleet we mentioned earlier checks into their location, they could be pinged once every couple of hours instead of once every fifteen minutes). Another logic example would be to send a user only one message per week regardless of the number of times they enter the fence (e.g. A user drives past a store twice daily on their way to and from work, and do not want to receive a promotional message every time they drive past that location).
  • Privacy: How will your users join the service? As always, location and privacy policy go hand in hand, the user must agree to the terms and policy before location can be served to application.

Positioning Fallback

If your plan includes aGPS transactions, then an aGPS fix will be the first attempted method of location. If the device has an aGPS chip and a hybrid of satellite and cell tower location-based information, the API will return an aGPS fix.

If a device does not have any aGPS technology, then Enhanced Cell ID (ECID) will be used to triangulate the location of the device according to the nearest cell towers and the relative signal strength between them. If your plan does not include aGPS transactions, then ECID will be the first method attempted.

If the cellular towers in the area do not support Enhanced Cell ID, then basic Cell ID will be used.

Network Accuracy Variables

Tower Concentration

The accuracy of network-based techniques is dependent upon the concentration of base station cell towers (with urban environments achieving the highest possible accuracy) and the implementation of up-to-date current timing methods (varies by station due to installation of hardware and software within the operator’s infrastructure).

In rural areas, or even the fringes of urban ones, there are fewer cellular towers available. With fewer than three towers, location pings will lose some of their precision.

A distance radius can be established using a cell tower’s known location. Without the intersection of circles from a second or third cell tower position, the device’s location can only be narrowed to somewhere within the circumference created by the tower’s distance radius. When towers are not equipped with triangulation software, location is approximated to a circle area representing the zone covered by the primary cell tower in contact with the phone. Rural areas with fewer cell towers display larger locational circles while urban areas show much smaller areas.

Triangulation

In a best-case-scenario, a cell phone’s signal may be picked up by three or more cell towers, enabling “triangulation.” Operators can estimate the distance of the phone from each tower based upon the lag time between pings being sent out and received.

Tower Technology

Network technology, 2G, 3G, 4G, HSPA+ and LTE and supporting location technology varies by network and cell tower. The expansion of faster, higher capacity, and more accurate technologies is being implemented on a continual basis.

  • A-GPS requires both the device and the Base Transceiver Stations (BTSs) to be equipped with GPS receivers.
  • Standard and Enhanced Cell-ID only require towers have radio measurement technology.

Directional Antennae

Some towers possess the capability to use directional antennae which can determine the direction of a cell phone’s signal.

Service Availability

If the mobile device is roaming on another network, location pings may be incorrect or unavailable. Accuracy is dependent upon the mobile device being served by its home network towers.

Device Accuracy Variables

Geographic Position

The position of the device within a cell area and its surroundings (e.g., indoor vs outdoor, open space vs near tall structures). In cases where a cell user is inside a large structures underground, GPS signal may be unavailable, rendering cell tower triangulation the only available location method. In rural areas, tower coverage can vary from about a quarter of a mile to several miles, depending upon how obstacles could be blocking the tower’s signal. In addition, a cellular device can be associated with a different cell tower as it moves near the edge of overlapping signal regions, or as cell signal fluctuates, causing the fix to shift rapidly from one pinpoint location to another. Enhanced Cell-ID and Cell-ID assume that the mobile device is always connected to the closest BTS (cell tower). However, a device may be connected to a farther BTS due to multipath propagation, BTS transmission power variation and the behavior of cell selection algorithm.

Signal Strength

Signal strength is used to predict the distance of a device from various cell towers. Location accuracy may lessen if the mobile device is in an area with weak wireless signal.

Known Location Issues

Verizon

Verizon only supports A-GPS if their Location Agent has been downloaded to the handset. Most of their newer models come pre-loaded with their app, meaning that A-GPS is possible, but if the app is not downloaded to the device, only Cell-ID location is available.

There are also some known issues with locating some Verizon devices while on LTE. The iPhone 6 and the Samsung Galaxy S7 both have single radios and are only locatable when in an area without LTE coverage. Verizon hasn’t rolled out LTE location yet, but most of their phones have dual radios and when connected to LTE, Verizon is still able to connect to the 3G radio to get location. Unfortunately, some of their newer devices (like the two mentioned) only have one radio and when connected to LTE they won’t be locatable.

Aerialink recommends that end-users turn off the LTE in their settings. If their device isn’t locatable while on LTE and they can’t turn it off, then there are really only two possibilities: they can download a third-party app from the app store that allows LTE to be disabled, or they can switch to a different phone model (or wireless carrier) that allows LTE to be turned off or is otherwise more locatable.