Indoor Positioning and Navigation

Introduction

In the modern world, the majority of individuals possess smartphones that excel in providing precise outdoor navigation. However, the task of indoor navigation remains a persistent challenge. Nevertheless, the implementation of an Indoor Navigation System (INS) can prove immensely beneficial, particularly in crowded environments like hospitals. Enabling the tracking of equipment and staff and facilitating patients’ arrival at their treatment locations, an indoor navigation system holds significant value in enhancing overall efficiency and convenience within healthcare facilities.

In manufacturing facilities, workers typically cover an average distance of 6 km per day while searching for and collecting parts for assembly. Implementing an Indoor Navigation System (INS) can greatly assist in expediting and streamlining this process, reducing downtime. By providing interactive maps of the facility, an INS enables workers to locate parts swiftly and efficiently. Furthermore, worker tracking functionality enhances emergency response times in critical situations.

At airports, travelers can benefit from an INS that guides them to their designated gates, information points, and baggage claims. Utilizing an INS also enables data analysis to improve queue management, minimize waiting times, optimize routes, and swiftly identify incidents.

These examples represent only a fraction of the potential use cases wherean INS can generate significant value. Building an effective navigation system necessitates precise object positioning. Given that GPS signals are attenuated indoors, alternative technologies are required for an Indoor Positioning System (IPS). In the following discussion, we explore several technologies that can be utilized for this purpose.

Radio Frequency (RF) Based Technologies

RF-based systems are widely adopted for indoor localization due to their favorable attributes such as accuracy, cost-effectiveness, energy efficiency, and the ability to penetrate obstacles like walls and bodies. However, it’s important to avoid RF-based localizations in critical locations such as hospitals and airplanes due to electromagnetic compatibility concerns. Nevertheless, they are ideal for industrial or automotive applications.

Bluetooth Low Energy

BLE is a standard technology for indoor positioning, operating within the 2.4 GHz frequency band for short-range wireless communications. It offers low energy consumption, a range of up to 40 meters, and an accuracy of 2–15 meters. Localization is achieved through Received Signal Strength (RSS) measurements of nearby devices. While BLE focuses on energy efficiency, it may face challenges in material penetration and accuracy in the presence of obstacles. Some IPS solutions utilize real-time calibration with RSS mapping to achieve an accuracy of 2 meters.

WiFi

WiFi, a widely adopted wireless networking technology operating at 2.4 GHz and 5 GHz, offers a potentially low-cost infrastructure as the necessary hardware is already widely deployed. Indoor localization using WiFi relies on Received Signal Strength (RSS) measurements. The coverage range can extend up to 100 meters.

ZigBee

ZigBee is employed for short-distance transmission within a wireless mesh network, utilizing different frequency bands depending on the region. It operates at 868 MHz in Europe, 915 MHz in the USA and Australia, and 2.4 GHz in other regions. ZigBee estimates distance between devices using RSS information. The indoor range can reach up to 100 meters, while it extends up to 300 meters outdoors.

RFID

RFID technology involves an RFID reader that emits electromagnetic pulses detected by RFID tags, which can be active, passive, or semi-active. Passive tags do not contain built-in batteries and instead reflect the signal received from the reader. Passive RFID is useful for sub-meter detection. Active RFID technology is less reliable for sub-meter localization but provides a range of approximately 100 meters. While RFID systems excel at detecting the presence of objects, they do not provide tracking information. Hence, they are often used in conjunction with other technologies.

5G

With its higher bandwidth and larger antenna arrays for massive MIMO, 5G offers high accuracy for positioning within a single cell. However, it requires dense base station deployment due to the limited penetration of the 5G mmWave bandwidth through walls. Indoor localization with 5G utilizes beam steering to estimate range through Round Trip Time (RTT) and angle of arrival (AoA) to determine precise positions within that range. While the initial setup costs might be higher, 5G enables localization accuracy of less than 1 meter.

Long Range Wide Area Network (LoRaWAN)

LoRaWAN is a Low Power WAN (LPWAN) technology specifically designed for IoT devices. It operates in license-free frequency bands, such as 867–869 MHz in Europe and 902–928 MHz in the USA. Indoor localization with LoRaWAN can be achieved by evaluating Received Signal Strength Indication (RSSI) from different LoRa gateways. The range indoors typically falls between 55–100 meters, with an accuracy of 3–4 meters.

Ultra-Wide Band (UWB)

UWB technology utilizes an extremely wide bandwidth exceeding 500 MHz, transmitting across various spectral bands from 3.1 to 10.6 GHz. UWB determines positions based on Time of Flight (ToF) measurements rather than RSS. It offers high accuracy, ranging from 0.01 to 1 meter, along with low latency. However, UWB solutions generally entail higher costs compared to other alternatives.

Inertial Measuring Units (IMUs)

IMUs incorporate sensors like accelerometers, gyroscopes, and magnetometers into a single integrated circuit (IC) to determine location and directional movement. They provide initial information about position, velocity, and angle. IMU-based localization requires sophisticated signal processing and filtering. Due to their tendency to accumulate errors over time, IMUs are often used in conjunction with other localization systems. For instance, in the absence of GPS satellite contact, a car can navigate within a tunnel for a limited period using IMUs.

Infrared Light

Infrared light-based systems utilize light pulses to detect the presence of objects. They require a clear line of sight (LOS) between the anchor and tag, and the signals cannot penetrate walls. Consequently, they are commonly used as room detectors. To achieve precise positioning, multiple installed anchors are necessary.

Ultrasound

Ultrasound-based systems utilize ultrasound waves, which do not interfere with electromagnetic waves, for localization. They typically involve a set of anchors and tags. Distance estimation is accomplished through Time of Flight (ToF) measurements, and with a minimum of three anchors, position calculation through trilateration becomes possible. Ultrasound systems can achieve submeter accuracy, but they are susceptible to interference from solid objects.

Marker and Computer Vision Based

Marker and computer vision-based systems determine the location of a camera-enabled mobile device by decoding location coordinates from visual markers. In this approach, markers are strategically placed throughout a venue, encoding coordinates such as latitude, longitude, and height off the floor. By measuring the visual angle from the device to the marker, the device can estimate its own location coordinates relative to the marker. This includes latitude, longitude, level, and altitude off the floor.

Overview

When selecting a technology for an Indoor Positioning System (IPS), several factors need to be taken into consideration. Among these, accuracy plays a crucial role in most IPS mapping systems. Higher accuracy typically necessitates the deployment of new hardware, which can result in increased costs. However, if pinpoint accuracy is not a critical requirement, alternative technologies can be employed. In cases where existing infrastructure is already in place, technologies such as Wi-Fi can be utilized without significant additional hardware investments.

Coverage, the extent of the area where location information is available, is the second most important characteristic of an Indoor Positioning System (IPS). There is often a trade-off between accuracy and coverage when selecting an IPS solution. The coverage can vary from a small-scale, such as a single room, to larger areas like warehouses or airports, where comprehensive coverage is required.

In addition to accuracy and coverage, scalability and adaptiveness to a changing environment are crucial considerations when selecting an Indoor Positioning System (IPS). It is essential to carefully evaluate the costs associated with deployment, operation, and maintenance. Some technologies offer mobility advantages, while others may require the installation of new fixed infrastructure.

Tools Required for indoor navigation

To implement a navigation system based on an IPS, an additional software stack is necessary for analytics and navigation purposes. These tools include:

1. Setup Tools: The setup tool is utilized to define the building’s outlines, rooms, and Points of Interest (PoIs). A content management system allows users to add, edit, and manage location-based data for PoIs within the indoor mapping solution.
2. Analytics and Wayfinding Tools: The Analytics and Wayfinding Tool enables real-time visualization of devices on the floor plan. It also calculates the shortest paths and provides wayfinding assistance for various PoIs.
3. SDKs and Web Services: SDKs (Software Development Kits) and web services are provided to support integration with other systems using REST/SOAP interfaces. These services also offer support for mobile devices.

Conclusion

Building effective indoor localization and navigation systems requires careful consideration of the technology choice, which should align with the specific use case and environment. For instance, if high precision is crucial and cost is not a limiting factor, a 5G solution may be the optimal choice. On the other hand, if conserving battery life on embedded devices is a priority, Bluetooth LE can be a suitable option. For covering large areas with lower accuracy but lower costs, WiFi may be a feasible choice. Currently, there is no single technology that can be universally applied to all Indoor Navigation Systems.