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Integrating Location Technology into Feature Phones

Dec. 15, 2020
Bringing hybrid-positioning functionality, typically found in smartphones, to feature phones generally requires smart design tactics to maintain their lower cost levels.

What you’ll learn:

  • The importance of location technologies in (feature) phones.
  • Why GPS alone isn’t enough for feature phones.
  • Design considerations for location in feature phones.

One critical component that feature-phone manufacturers look to add to their offerings is ubiquitous location. It may sound a bit surprising based on the maturity of positioning services as a core component of smartphone operating systems, but the addition of location, specifically hybrid positioning through providers like Skyhook, brings smartphone-like benefits to feature phones. It also adds a plethora of additional capabilities such as location-based applications, directions in hard-to-locate areas, and important emergency services. 

The Challenge of Location in Various Environments

A large percentage of device manufacturers that compete in this segment struggle to provide dependable positioning services and location results when users are indoors, in dense urban areas, or in other environments that may limit the effectiveness of the Global Navigation Satellite System (GNSS). GNSS is the standard term for any satellite navigation system that provides autonomous geo-spatial positioning with global coverage. With an estimated 400 million feature phones sold in 2019, there’s tremendous interest in creating devices with the functionality of a premium-priced smartphone but built with minimal hardware, at a fraction of the price. 

Hybrid-positioning solutions in smartphones are now expected, and in many countries even required, to meet local emergency requirements. Hybrid positioning combines positioning technologies (GNSS, Wi-Fi, and cellular positioning) to select the appropriate source, or combination—depending on signal availability and quality indicators—to provide the most accurate and efficient positioning fix in any environment. Smart feature-phone manufacturers, with devices running on mobile operating systems like KaiOS Technologies, can enhance their smart feature phones by integrating advanced device location capabilities that can position a device in any environment.

A Growing Feature-Phone Market

Recent growth in the market for feature phones is propelled by various industries and regions of the world seeing the value of a reliable, less expensive alternative to the standard smartphone, including:

  • Emerging phone markets currently affected by a “digital divide” that makes feature phones their most accessible choice due to the lower price point and availability.
  • Specialty industries where a smartphone with a touchscreen and multiple apps isn’t necessary.
  • Construction sites, where a rugged phone’s durable build mitigates the risk of breaking if dropped, and accurate location improves worksite safety and the ability to have employees working but contactable in various locations.
  • The hospitality and healthcare industries, where feature phones are used as organization-provided devices that offer extended battery life and have push-to-talk variants.
  • Outdoor adventurers who can take feature phones on trips without worrying about breaking them, while still being provided with directions to their destination, and the option to place a call if needed.

In emerging markets specifically, feature-phone devices can require the use of older 2G/3G networks, either due to coverage availability of more modern networks, or to reduce ongoing subscription costs. To prepare for this possibility, designers and original design manufacturers (ODMs) should consider what markets, bands, and network types they plan to target with their product. Therefore, they can have the most cost-effective hardware selected for the application that will function in that area.

For example, selecting an LTE modem that also has 2G/3G support may be a smart decision in some cases. However, in other instances, that selection could result in unnecessary additional costs for the component, based on the market the device is projected to be released in. 

How Does Wi-Fi Help GPS? 

A GPS module can boot in several modes, depending on things like whether or not the GPS has valid almanac and ephemeris data, the types of incoming signal levels, and the distance or time relative to the previous reported location. In some cases, this results in a device’s GPS (GNSS) receiver having what’s commonly called a “cold start” while it waits to acquire assistance data and/or receives information from enough satellites at one time to obtain an accurate fix. It can vary by device, but this “time to first fix” (TTFF) during a cold start can range from 1-4 minutes.

During that time, if the device has the available hardware and integrated hybrid-positioning software, it can perform a Wi-Fi scan and (in any areas with a Wi-Fi signal) acquire a fix within seconds. This is based on reference database information, which may also be previously downloaded or cached on the device. The device can use network-based positioning for tracking until an accurate GNSS fix is received, and it can potentially provide results to the GNSS interface as seed locations to accelerate location acquisition from that source. 

Why Is GPS Alone Not Enough? 

Smartphones have leveraged, and still do to this day, hybrid positioning since the iPhone first came out. GPS on its own can’t provide that level of accuracy, as it requires a clear satellite connection to provide accurate location and therefore isn’t a solid choice on its own for a phone offering. 

A device may have a high-quality GNSS fix in tracking mode, but when the device enters an indoor or dense urban environment, that can no longer be the case. The software on the device can detect when the attributes of the GNSS NMEA stream indicate quality is degrading (number of visible satellites, error estimates, HDOP, etc.). It then immediately corroborates with cellular-based positioning, as well as initiates a Wi-Fi Scan to provide Wi-Fi-based localization, and continues doing so to constantly track the device with the assistance of other sensors on the device (accelerometer, compass, etc). In this case, the software can also disable GNSS to conserve power until it’s indicated that that source may be more accurate and reliable than any network source.

Design Considerations for Feature Phones Looking to Incorporate Location

Feature-phone devices can often have cheaper components, modules, and antennas due to their lower price point and razor-thin margins. These less expensive or lower-tier components may magnify the need for good design that considers antennae placement and testing, as well as sensitivity or algorithm tuning to accommodate positioning services.

Such tuning can vary across hardware, memory, and power constraints, as well as common mobility behavior for the primary use case. One representative case is augmenting software and/or firmware to reduce variability in network measurements that are provided to positioning software solutions when other sensors (accelerometer, gyro, etc.) may not be available or are unreliable. 

One such example is having the underlying software perform repeated Wi-Fi scans based on the observed signal environment. This reduces variability between scans when they’re inconsistent in stationary scenarios. Efficiently combining consecutive scans, if necessary, can compensate for sensitivity issues more common in lower-tier modules and reduce jitter or inconsistency in location results. 

A similar example applies to cellular positioning results when no other location source is available. The ability to receive or induce back-to-back cellular signal observations, or network measurement readings, that include neighbor cell identifiers in addition to the connected cell information can help stabilize variability between fixes. It also provides the most accurate location available at that time. Other items involve things like the configuration of caching logic or power-saving algorithms based on available hardware and memory.

By partnering with an independent location provider, device manufacturers can be confident that they’re providing the most accurate location functionality available, optimized for their specific device. All the while, they have the freedom to create the phone they want that’s power-efficient at a highly competitive price point.

Nick Knelliger is Director of Product at Skyhook.

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