FAQ

1. DEFINITIONS

1.1 What is Sequitur?

SEQUITUR is a UWB real-time locating system (RTLS). It is an eco-system composed of hardware and firmware building blocks as well as end-user applications for high accuracy ranging, positioning, tracking and navigation.

1.2 What is UWB?

Ultra-wideband (UWB) systems are based on a new radio technology that uses very low energy pulses for short-range, high-bandwidth communications over a large portion of the radio spectrum (about 500 MHz). It is a new new technology allowing to accurately determine the position of objects/persons with centimeter-level precision. This technology is particularly useful for indoor environments, where traditional GPS systems are completely unusable or characterized by poor accuracy.

1.3 What does TWR mean?

TWR is the acronym of two-way ranging. It is a technique adopted for determining the distance between two devices. Basically, one device sends a packet to the second one, which responds immediately. Then, the first device can determine the time elapsed between the time instants related to the first transmission and the response reception (the so-called round-trip time). Since the speed of light is known, the distance can be directly estimated from the round-trip time measure. By combining several TWR measurements between anchors and the tag, a tag can be localized.

1.4 What does TDOA mean?

TDOA is the acronym of time-difference-of-arrival. It is a localization technique according to which the tag position is estimated by comparing the time delay between the reception of signals coming from different nodes (anchors), as done by GPS receivers with satellites signals.

1.5 What are Anchors?

Anchors are fixed devices placed in known position in the environment. They serve as reference for locating mobile nodes (tags or mini-tags), as satellites serve as reference for a mobile GPS receiver. Anchors are part of the Sequitur infrastructure, without which tags/mini-tags localization is impossible.

1.6 What are Tags?

Tags are mobile devices localized by Sequitur system. They autonomously estimate their position by communicating with anchors, so position is available at tag side. Every tag works independently from the others and a centralized server/localization software is not required.

1.7 What are Mini-Tags?

Mini-Tags are mobile devices being localized by the Sequitur system. Their position is not available at tag-side, but it is computed by an external Central Unit. They are battery-powered (rechargeable) and have been designed with a small form factor in order to be used as portable device for people and asset tracking.

1.8 What are nodes?

“Node” means the generic Sequitur devices (Anchor , Tag or Mini-Tag).

1.9 What is Sequitur Manager?

Sequitur Manager is an easy-to-use software which helps you to install, configure, manage and control your Sequitur RTLS.  Check and modify system parameters, reconfigure devices and upgrade firmware is quick and easy. Sequitur Manager embeds REST API in order to provide data to a third-party application and a ready-to-use web client (Sequitur Manager UI) for system configuration and tags monitoring.

1.10 What is Sequitur Manager UI?

Sequitur Manager UI is the graphical web interface of Sequitur Manager. It is completely based on Sequitur Manager REST API so users can evaluate what we can offer with this powerful interface. It includes also documentation of system parameters and the documentation of available API: UDP API (device level), and HTTP REST API (server level) documentation and a detailed guide for the GUI usage.

1.11 What is Sequitur Intracking Server?

Sequitur InTracking Server is the software which perform Mini-Tags localization. This software communicates with Sequitur anchors. As output interface the server offers an UDP socket for each Mini-Tag that reflects the tag UDP socket. In this manner we can offer a powerful abstraction tool allowing the communication with Tag and Mini-Tags in the same way.

1.12 What is Sequitur Core?

Sequitur Core is the full software suite which includes “Sequitur Manager” , “Sequitur Manager UI” and “Sequitur InTracking Server” software.

2. SEQUITUR RTLS

2.1 How does Sequitur work?

Sequitur exploits the innovative ultra-wideband (UWB) technology for realizing very precise measurements on the radio signals, such as determining the time instant at which a packet is received by a device. Such time measurements are realized with an accuracy of a few picoseconds. In this manner precise ranging between nodes can be carried out, and measurements can be fused to determine with centimeter-level accuracy the position of a mobile device (tag).

2.2 Can Sequitur be customized?

Yes. Sequitur is completely developed by UNISET. Software, Firmware, Hardware is totally under our control so we can offer a full customization. If you have special request please contact us.

2.3 Does Sequitur work indoor and/or outdoor?

Yes, Sequitur can work both indoor and outdoor. For outdoor applications, dedicated waterproof enclosures are available.

Sequitur is certified for the CE market according to the harmonized standard ETSI EN 302 065-2. Both LT1 (indoor only) and LT2 configurations (indoor+outdoor) are implemented (corresponding to UWB channel 2 and channel 5 of the IEEE 802.15.4a standard). For outdoor use, the user should check the local regulation.

2.4 What are the main differences between TWR and TDOA techniques?

TWR is a localization scheme using the measurement of the distance from a tag with respect to several anchors in order to compute the tag position. Every distance corresponds to a circle around the anchor. The interception of the circles identifies the tag’s position (trilateration). TDOA is a localization scheme using the measurement of the difference of travelling time involving a tag and a couple of anchors. It can be operated according to a centralized or decentralized architecture.

TDOA allows a larger number of tags, both in the centralized and decentralized architectures. Moreover, it enables low-energy consumption strategies (small, battery-powered tags).

TWR guarantees enhanced robustness and accuracy, and it is more robust than TDOA also outside the perimeter of anchors and for 3D positioning.

2.5 What are the differences between TDOA decentralized / centralized / coexistence?

For the centralized architecture, a tag transmits a signal, and a couple of anchors measure the difference in time related to the reception of the same signals at the 2 different locations. This time difference is related to the tag position.

For the decentralized architecture, a couple of anchors transmit signals (e.g. at the same time instant), and a tag measures the time elapsed among the reception of the 2 received signals. This time difference is, again, related to the tag position. GNSS systems operate according to this principle.

Then, in TDOA decentralized (Sequitur InGPS) the position is computed by the tag and unlimited tags can coexist. in TDOA centralized (Sequitur InTracking) the position is computed by a Central Unit, and small tags (Mini-Tags) only transmit short blink packets.

The coexistence mode allows combining the 2 architectures and the different type of tags.

2.6 Does Sequitur interfere with Wi-Fi or Bluetooth or any other RF system?

No. Sequitur is based on ultra-wideband (UWB) signals, transmitted at very low power and with very wide spectra. Such weak signals do not interfere with classical narrowband communication systems such as Wi-Fi of Bluetooth. Moreover, the frequency bands are located between 3 and 7 GHz, where the most common radio-based services do not operate.

2.7 What is the ranging accuracy?

Sequitur provides a ranging accuracy of a few centimeter.

2.8 What is the localization accuracy?

Sequitur provides a localization of centimetres/decimetres in line-of-sight conditions. Moreover, beyond-state-of-the-art tracking algorithms are employed for enhanced performance in the presence of moving tags.

2.9 What is the maximum communication range?

The maximum communication range depends on several parameters, such as the radio channel, the bit rate used and on the propagation environment. In general:
– The use of radio channel 2 at lower frequency enhances the communication range.
– The use of radio at lower data rate enhances the communication range.
During normal operations, in the best conditions (line-of-sight), up to 40 m of communication range is available by fulfilling the regulations on spectral emissions.

2.10 How many Tags / Mini-Tags can be localized simultaneously?

The number of tags localized simultaneously is unlimited for InGPS TDOA, while traded with the update rate and tag density for InGPS TWR.

Sequitur InTracking provides a large number of Mini-Tags (but not unlimited) depending on the selected position refresh rate and radio configuration. The high flexibility of Sequitur allows adapting the configuration to the specific user need.

2.11 What is the maximum localization refresh rate?

Up to 20 new position estimates per second per tag are available.

2.12 Is the localization 3D or 2D?

Sequitur InGPS works in 3D by default. User can select 2D localization when tags are kept at a fixed and known height for enhanced performance. Moreover, Sequitur can work in 2.5D, with variable but known height (e.g., provided by an external radar-altimeter). Finally, the pressure sensor can be also used to compute the height or refine the estimation.

Sequitur InGPS TWR is more robust for 3D localization. Reliable 3D localization with TDOA can be realized with multiple Anchors at different heights.

2.13 Is it possible to upgrade Anchors / Tags firmware after the installation?

Yes. All Sequitur devices can be upgraded with new firmware releases without the need of replacing them.

Sequitur Manager software allows simple and fast upgrade of nodes connected to the same network. This enables a complete support for customers regarding bug fixing or special customizations.

2.14 Does Sequitur needs “master nodes” for proper operations?

No. Master nodes are special anchors necessary in most of traditional RTLS solutions. Sequitur infrastructure does not use master nodes in order to provide a complete and true scalable solution. All Sequitur anchors are equal and the architecture is completely distributed. This allow us to localize tags even in case of anchors failure.

2.15 Why Sequitur is a complete scalable system?

Sequitur is a complete scalable system because no master nodes are required and the addition/replacement of anchors or the upgrade of a pre-existent installation does not involve the reconfiguration of the entire system. To expand the localization area user just add new anchors and configure them. No system replanning is required.

3. PRODUCTS

3.1 What does Sequitur InGPS TWR offer?

Sequitur InGPS TWR allows the localization of one or more Tags with the two-way-ranging technique. The Tag drives the localization process, so the position is available at tag side. This is fundamental to control robots, drones and machines since it is a reliable and low-latency scheme. TWR is more robust than TDOA for 3D localization and outside the perimeter of anchors. Moreover, in the absence of 3 anchors (when positioning cannot be guaranteed) the explicit tag-anchor distance information is still available. This is useful when presence detection or gate control is required, without the need of exact positioning.

3.2 What does Sequitur InGPS TDOA offer?

Sequitur InGPS TDOA allows the localization of as many Tags you need simultaneously, also in the same area and at the maximum refresh rate. It is a decentralized architecture based on the time-difference-of-arrival technique. The Tag computes its position. This is fundamental to control robots, drones and machines since it is a reliable and low-latency scheme. It is the key-player in control and navigation applications. No limits in the number of tags are present, so it is the true fully scalable solution. Neither servers nor connections among anchors are needed, so the system can be deployed very quickly and easily. The architecture is completely distributed and self-configuring.

3.3 What does Sequitur InTracking TDOA offer?

Sequitur InTracking TDOA allows the localization of a large number of Mini-Tags. It is a centralized architecture based on the time-difference-of-arrival technique. The Mini-Tag transmits only a short blink packet which is received by the anchors and forwarded to the Central Unit. Tags are very small and they do not need power supply. The position is available only at the Central Unit side. This configuration is the key-player in asset and people tracking (e.g., sport tracking and warehouses).

3.4 What does Sequitur InGPS + InTracking TDOA offer?

The configuration is the union of Sequitur InGPS TDOA and Sequitur InTracking TDOA. This product enables combining different types of tags. Both Tags and Mini-Tags can operate in the same environment with the same infrastructure (Anchors). For this configuration the position of Mini-Tags is available only at Central Unit side whereas that of Tags is available at Tag side. The Sequitur Manager software allows real-time monitoring of every type of tag thanks to Sequitur API. A typical use concerns large industrial contexts and warehouses: Tags (InGPS) are attached to machines and forklifts to monitor trajectories, handle the storage of pallets and bins; Mini-Tags (InTracking) are attached to people, goods, trolleys carrying spare parts,…

3.5 How to choose the right Sequitur product?

The key questions are:

  • Do I need a very large number of tags in the same area? If yes, InGPS TDOA provides this feature.
  • Do I need a very easy deployment, no server and no connection among anchors? If yes, InGPS TWR and InGPS TDOA provide these characteristics.
  • Do I need small, battery-powered tags, with very long battery life? If yes, InTracking TDOA is the best solution.
  • Do I need position on the tag (eg for control and navigation? If yes, InGPS is the right solution.
3.6 I already have Sequitur. Can I change configuration and/or type of tags?

Yes. The same set of anchors can handle every configuration of the Sequitur RTLS and every type of tag.

4. ANCHORS

4.1 Why do I need Anchors?

The Anchors provide the data for localization to Tags. They work similarly as satellites do for GPS.

Each time a tag wants to localize, at least data from 3 anchors are required.

4.2 How can Anchors be powered?

Anchors can be powered in 3 different ways:

  • Standard 5 V USB micro-B plug
  • 9 V to 24 V power supply via the auxiliary connector
  • 3af PoE

The devices require typically less than 5 W at tune time.

4.3 How can I connect with Anchors?

Anchors have 2 network interfaces: Ethernet and Wi-Fi. Ethernet interface supports 10/100 Mbps connectivity (with PoE 802.3af). Wi-Fi interface supports 802.11 b/g/n networks (operates only with 2.4 GHz Wi-Fi networks).

Moreover, each device can be connected with RS485/UART.

4.4 Do Anchors require a network connection at run-time?

When using Sequitur InGPS, the Anchors, once configured, do not strictly require a network connection, just power supply. However, for system monitoring, maintenance and diagnostic, we encourage the connection of Anchors to a network (either Ethernet or Wi-Fi).

Network connection is required for Sequitur InTracking and coexistence mode.

5. TAGS

5.1 How can Tags be powered?

Tags can be powered in 3 different ways:

  • Standard 5 V USB micro-B plug
  • 9 V to 24 V power supply via the auxiliary connector
  • 3af PoE

The devices require typically less than 5 W at tune time.

5.2 How can I connect with Tags?

Tags have 2 network interfaces: Ethernet and Wi-Fi. Ethernet interface supports 10/100 Mbps connectivity (with PoE 802.3af). Wi-Fi interface supports 802.11 b/g/n networks (operates only with 2.4 GHz Wi-Fi networks).

Moreover, each device can be connected with RS485/UART.

5.3 Where the Tag position is computed?

Tags include a powerful quad-core processor allowing on-board position calculation. This allows a vehicle equipped with Sequitur to know its own position, without relying on the connection with a server.

Differently, position of Mini-Tags is computed by an external Central Unit connects to the Anchors.

5.4 How can I retrieve the position by a Tag?

Position computed by a Tag can be obtained using simple and well-documented API running over UDP or serial port.

5.5 Which sensors are embedded on Tags?

Each Tag embeds the following sensors:

  • 3-axis accelerometer
  • 3-axis magnetometer
  • 3-axis gyroscope
  • Absolute Barometer

All IMU/sensors data are available through UDP API and REST API (on Sequitur Manager).

5.6 Is orientation provided together with position?

Yes. The Tag computes its own position with Sequitur InGPS. Using the embedded sensors, we also compute the absolute orientation quaternion. By fusing the position information of multiple tags, orientation on the local coordinate system is provided.

6. MINI-TAGS

6.1 What is the battery duration of a Mini-Tag?

Mini-Tag battery duration depends on position refresh rate and radio configuration parameters. Table of battery duration for different position refresh rate is listed below:

Up to 2 years or 22’000’000 update positions.

Up to 12 days (24h/24h) @ 20 Hz refresh rate.

Up to 44 days (24h/24h) @ 5 Hz refresh rate.

Up to 160 days (24h/24h) @ 1 Hz refresh rate.

Refresh rate and radio configuration parameters can be programmed into Mini-Tags in any time according to specific application specification in order to fulfil battery duration requirements.

6.2 How can I change the Mini-Tag configuration?

For change the Mini-Tag configuration, Sequitur InTracking Server and Sequitur Manager software are needed. Parameters can be modified at any time but they take effect on the Mini-Tag only when it is placed on his charging pad.

6.3 Can I reset my Mini-Tag to default factory conditions?

Yes. To perform factory reset you must turn off the Mini-Tag, then click the button 5 times and then keep it pressed for 10 seconds (during this operation the Mini-Tag turn on). At the button release a fixed blue user led will confirm the factory reset.

6.4 Does Mini-Tag have any built-in sensor?

Yes. Mini-Tags have an on-board ultra-low power accelerometer to detect movements and increase/decrease refresh rate, in order to save battery. Accelerometer configuration, movements or steady states with different refresh rates are totally configurable to meet user specifications and find the best trade-off between localization precision and battery duration.

6.5 Where Mini-Tag position is calculated and how can I obtain that?

Mini-Tags have not an on-board position calculation. Mini-Tag position estimation is performed by  the Sequitur InTracking Server running on the Central Unit connected to Anchors. Positions is available in 2 different ways:

  • Low-level UDP API as output of the Sequitur InTracking Server software.
  • High-level HTTP REST API as output of the Sequitur Manager software.
6.6 What are the main Mini-Tag applications?

Mini-Tags can be used in all those applications in which position is not needed at tag side.

Asset tracking, goods traceability, safety monitoring of employees, cameras control, forklifts localization/identification, access control, sport tracking and many others.

7. INSTALLATION

7.1 Is localization possible only inside the perimeter of Anchors? What happens if the tag moves away from the Anchors?

No, localization is possible also outside the perimeter described by Anchors. However, the localization accuracy decreases moving away from anchors. Sequitur InGPS TWR is more robust than TDOA solutions when the tag moves outside the perimeter of Anchors.

7.2 How many Anchors are necessary for localize Tags?

The number of Anchors depends on the environment dimensions and complexity. At least 4 Anchors are recommended. The minimum number of anchors is 4 for a 2D localization or 5 for a 3D localization.

7.3 Do I have to measure manually the coordinates of Anchors?

It depends on the target accuracy. For the maximum accuracy, a laser-based measure using a 3D laser or total station is suggested. For complex environments, Sequitur Manager UI allows placing directly Anchors on the map using drag-and-drop. This allows an extremely fast system configuration also in the presence of numerous walls.

8. SOFTWARE

8.1 On which system can I run Sequitur software?

Sequitur Core (embedding Sequitur Manager and Sequitur InTracking Server) is written in Java and can run on Linux, Windows and MacOS machines. A Java VM is required (minimum required version is Java 8 update 121).

Currently, Sequitur InTracking Server is limited to Windows machines.

8.2 What are the minimum computing requirements for software?

Sequitur Core will run on almost any recent (2012+) machine with at least 4 GB of RAM. The performance will vary with system size (number of Anchors, Tags and Mini-Tags) and with the user activity (e.g., the number of concurrent access to UI and data).

8.3 How to install the software?

The software is provided a zip-file. Simply extract the zip file content into a folder.
Then, a suite of script are provided (.bat for Windows, .sh for Unix-like systems) for launching the different application modes (Sequitur Manager, Sequitur InTracking Server).

A quick guide on how to install Sequitur as a Window service is present in the readme file (readme.htm).

8.4 I installed the software. Where can I find the user manual?

In the installation folder there is a simple first-start manual (file readme.htm).

The Sequitur Manager UI manual is accessible in Sequitur Manager UI by clicking the Help button in the navigation bar.