Chirp Spread Spectrum (CSS)

Chirp Spread Spectrum RTLS, Location Tracking, & Positioning


Learn more about Chirp Spread Spectrum (CSS) and how this flexible radio-frequency technology offers a unique performance mix of accuracy, range, and reliability to create unparalleled indoor positioning and asset tracking — especially in industrial-grade environments.

What is Chirp (CSS) Technology?

HowInpixonUsesCSSChirp, or Chirp Spread Spectrum (CSS), is a long-range radio-frequency technology for wireless communication that can be leveraged to detect and track the location of people, assets, and devices both in and outdoors, across large-scale facilities. Its long-range performance with high-reliability, strong resistance to radio interference and low-power consumption, make chirp uniquely suited for applications in large, noisy environments, like industrial facilities. Like other communication protocols including UWB and Bluetooth, chirp can be used to transmit data between devices through radio waves. It does so by using a wideband modulation technique, that creates linear frequency modulated signals also known as chirps.

Chirp was designed to operate in the 2.45 GHz ISM band and belongs to the same category as other Spread Spectrum technologies. Originally purposed in military applications to help ensure secure and reliable communication more resistant to detection, jamming and interference, Spread Spectrum methods spread radio signals across a wider range of frequencies, producing signals with wider bandwidths while still preserving the initial signal power. Chirp technology increases the bandwidth of signals to multiples of the value stated in the “Shannon-Hartley” theorem, helping it enable communication more robust against interference. There are two types of chirp pulses implemented – upchirps and downchirps. For wireless communication, chirp pulses are dispatched from a transceiver to a receiver, or amongst transceivers that can both transmit and receive communications with one or more devices at the same time. Receiving devices analyze the patterns of incoming pulses and translate them into data. While this allows devices to reliably send data over long-ranges, chirps can also be used to accurately sense the location of devices. This makes it possible for chirp-enabled devices, such as RTLS anchors to pinpoint a transmitting device, such as an asset tracking tag, find its precise location and in certain applications enable location-aware communication and services.

In addition to being used by RTLS for real-time positioning of devices, like tracking tags, chirp technology can also enable two-way ranging and distance monitoring, as well as wireless communication applications. Through these types of applications, chirp technology helps power location-aware solutions that enable a multitude of use cases including asset tracking, collision avoidance, vehicle tracking, industrial automation, worker search and rescue and more, in a variety of types of facilities and industrial environments like factories, underground mines, warehouses and more.

History of Chirp Technology

Chirp pulses can be found all throughout our natural world, used by animals like dolphins and bats for communication and sensing. These same pulses were first adapted and patented into technological applications in the 1940s by a Professor Hüttmann, who used chirp for radar applications. The concept of using chirp spread spectrum in radar applications was further developed by Sidney Darlington, a lifetime IEEE fellow, in 1947, who’s research yielded pulse compression radar. In 1996, Canon continued the development of chirp technology, patenting chirp pulses for data transmission in fiber optic systems. Since the 1990s chirp technologies have seen continued advancements and improvements. Much of this was driven by further investigation and patents by nanotron technologies, a company that is now part of the Inpixon family. Today, Inpixon is the leader in chirp technology, providing chirp-enabled solutions that power real-time location tracking, two-way ranging and bi-directional communication applications that help organizations leverage location-awareness to enhance safety, efficiency and accelerate business results. Inpixon offers chirp-enabled RTLS solutions including flexible, long-range location tracking tags, anchors and its proprietary Inpixon nanoLOC location chip which serves as the foundation of many chirp technology locationing solutions worldwide.

Chirp's Unique Advantages

Chirp has many unique advantages that make it a flexible option suitable in deployments where long-range positioning, high-reliability and low-power performance requirements are of special importance.

Due to high system gain, as well as resistance to interference and multipath fading, CSS delivers its exceptional range for positioning (up to 500 m), even in noisy industrial facilities. This range extends both indoors and outdoors, offering solutions that work in both environments with no costly spectrum licensing required. Its long-range communication range and high channel capacity, paired with its accurate location determinacy between 1-2 m and very low latency, enable real-time locationing and two-way ranging/communication applications with a special performance mix many other common RF technologies can’t achieve.

Chirp-enabled technology also consumes very little power and was designed for low-power applications in particular, allowing you to build RTLS solutions with affordable and efficient hardware options, such as tracking tags with embedded batteries that can operate for multiple years without needing to be recharged or replaced.

Due to higher bandwidth chirp pulses and CSMA support, chirp-based systems are highly resistant to RF interference including both narrowband and broadband disturbances. Frequency spreading of chirps also make chirp systems highly resistant against multipath fading. With most narrowband RF technologies, the original signal from a transmitter will typically reach a receiver with several reflections from buildings or other environmental surroundings. This often results in frequencies being amplified or attenuated, as well as destructive interference which may cause a disconnect in the communication link of a narrowband system. CSS is different, because the energy contained in transmitted symbols is distributed uniformly over the bandwidth, meaning the communication link will not be disconnected when the interfering entity is not blocking the whole bandwidth of the channel. Unlike other RF technologies, chirp is also resistant to the doppler effect which causes a frequency shift of the transmitted signals. Its wide bandwidth nature also helps to enhance the quality of reception with almost any antenna position. These unique qualities allow chirp to deliver high performance applications in noisy environments like industrial facilities where reliability and robustness against disturbances are required.

CSS Signals can also be used for time-of-arrival (ToA) estimation and time difference of arrival (TDoA) position calculation, delivering accurate system performance for scalable solutions capable of supporting thousands of concurrently tracked entities. Chirp solutions also offer cost-effective hardware and require less infrastructure than other technologies, delivering high ROI and further adding to its distinct ability to offer highly scalable enterprise deployments.

How Does Chirp (CSS) Positioning Work?

Chirp makes it possible to determine location via distance-based methods, rather than other common techniques that rely on less accurate calculations based on received signal strength. This can precisely measure distance between transceivers by calculating the time it takes for signals to travel amongst the devices. In certain scenarios the X,Y, and Z coordinates of a device’s location can be detected, adding an additional dimension to the localization chirp can provide. Based on the use case or application, the exact distance-based calculation technique can differ.

For chirp positioning, there are two primary techniques that can be used: time difference of arrival (TDoA) and two-way ranging (TWR).

Diagram illustrating how Time Difference of Arrival (TDoA) works in positioning.

Time Difference of Arrival (TDoA)

In RTLS, TDoA utilizes location data, collected by chirp (CSS) RTLS anchors from transmitting RTLS tags, to calculate the real-time positions of the tagged entities. A RTLS tag will continuously send out RF signals, also known as location blinks at regular intervals. Multiple RTLS anchors within the communication range of the transmitting tag will receive these location blinks and timestamp their exact time-of-arrival (ToA). The anchors then forward this time-stamped location data to the central location engine software. To work properly, the fixed anchors need to be accurately synchronized to run on the same clock.

The location engine will analyze each anchor’s data and the differences in arrival times to each anchor and use multilateration to calculate the tag’s coordinates. Those coordinates can be used to visualize the location of the device on an indoor map of your space or leveraged for other uses depending on the specific application.

Diagram illustrating how Two Way Ranging (TWR) works in positioning.

Two Way Ranging (TWR)

While in TDoA multiple fixed anchors work together to determine the location of a mobile object, TWR primarily uses two-way communication between two devices, such as location tracking tags deployed to people, object or vehicles, for real-time monitoring of the distance between them.

With TWR, when a device is in close proximity to another, the two devices will start ranging with each other to determine their distance, even as they communicate. The time it takes for signals to travel between them is then multiplied by the speed of light and used to continuously determine their relative positions.

The determined location from one device to another is then harnessed depending on the specific application. TWR can also be used by fixed anchors and tracking tags, however the TWR process can only use one ranging partner to locate the device at a time.

How Accurate is Chirp Positioning?

Chirp TDoA-based indoor positioning allows for location accuracy between 1-2 meters for high-performance RTLS that delivers real-time results with very low latency. Its unparalleled reliability, through characteristics like its resistance against RF disturbances, multipath fading and the doppler effect, enable Chirp to uniquely deliver reliable wireless communication that ensures accurate position calculations in RTLS.

What is the Range of Chirp Technology?

One of chirp’s most powerful advantages is its ability to enable positioning over long ranges of typically up to 500 meters. This provides accurate, low latency real-time locationing across large areas in facilities like factories, warehouses and even underground mines. Its high reliability also ensures accurate wireless communication over these long ranges.

Chirp’s range can be extended into both indoor and outdoor areas, for in and outdoor support with no spectrum license required.

In certain scenarios and under ideal conditions, Inpixon has been able to achieve ranges of up to 1000 meters with its chirp RTLS technology.

Compared to other common positioning technologies, Chirp yields superior range. Other standards typically cover areas much more limited in size, requiring more deployed infrastructure such as RTLS anchors. 

How is Chirp Different From Other Positioning Technologies?

Chirp vs. UWB

Chirp and UWB have many common attributes – low power, strength as an asset tracking technology, high reliability and performance well matched for industrial environments. Both are advanced options for true real-time locating systems, but have distinct advantages that make each suitable in different scenarios. Chirp excels at providing accurate long-range positioning, while UWB is best suited for precise applications. Chirp is a 2.4 GHz RF technology, while UWB operates at a higher bandwidth over a very wide frequency spectrum. Both can be used for TDoA-based calculations to accurately determine the position of tracked entities. The two are very reliably performing technologies and feature strong protection against RF interferences and disturbances. Though chirp and UWB are different technologies that present their own unique advantages, both can be combined in RTLS deployments via Inpixon’s mixed technology, enabling users create high-performance and versatile solutions that can power a wide array of location-aware use cases and allow you to experience the benefits of both UWB and chirp at the same time.

Chirp vs. BLE

Chirp and BLE have common attributes - low power, low cost, long-running effectiveness as an asset tracking technology. However, chirp can deliver far superior performance characteristics including positional accuracy, achievable communication range and communication reliability than Bluetooth. This is in large part due to Chirp’s ability to enable applications that determine location and relative distance via TDoA and ToF-based two-way ranging, respectively. BLE positioning technology typically locates devices via received signal strength indicator (RSSI), which estimates positions and yields a considerably lower level of accuracy based on whether a device is transmitting a strong or weak signal relative to a beacon or sensors. BLE also has a much shorter range and data rate than chirp and is more prone to signal interference. Bluetooth does have an enormous ecosystem and has been a leading indoor positioning technology for quite some time. It is used by so many of today’s wireless devices and a very popular option for locationing, offering an extensive set of flexible hardware options that can easily be implemented, such as BLE beacons. However, it is very limited, especially in industrial environments, which are areas where chirp spread spectrum excels.

Chirp vs. Wi-Fi

Wi-Fi’s ubiquitous presence in our devices and indoor spaces have made it a key RF technology for indoor location. In advanced location-based scenarios, Wi-Fi can be limited due to its low accuracy and flexibility. Chirp excels in these more advanced applications where accuracy, range and latency are key requirements. Wi-Fi’s accuracy is far less than chirp, because it typically measures location not by distance, but rather RSSI, just as Bluetooth. It is also more likely to experience signal interference, which Chirp has strong protection against. Chirp also requires less power, allowing for more useful and affordable tools, such as asset tracking tags that can be powered by long-lasting embedded batteries. However, the wide array of Wi-Fi enabled devices and ability to leverage existing infrastructure, such as Access Points, make it an important and very popular indoor positioning technology, especially when a high degree of accuracy is not required.

Chirp (CSS)

Location Accuracy*
Chirp (CSS) 1-2 m
UWB +/- 40 cm
BLE < 5 m
Wi-Fi < 10 m
Chirp (CSS) Optimal: 10-500 m
Up to 1000 m
UWB Optimal: 0-50 m
Up to 200 m
BLE Optimal: 0-25 m
Up to 100 m
Wi-Fi Optimal: 0-50 m
Up to 500m
Chirp (CSS) < 1 ms to get location
UWB < 1 ms to get location
BLE Typically 3-5 s to get location
Wi-Fi Typically 3-5 s to get location
Power Consumption
Chirp (CSS) Very low, option for embedded cell battery in select hardware options
UWB Low, option for embedded cell battery in select hardware options
BLE Very low, option for embedded cell battery in select hardware options
Wi-Fi Moderate
Chirp (CSS) $
UWB $$
BLE $$
Wi-Fi $$$ ($ with Wi-Fi access points)
Chirp (CSS) ISM-band 2.4 GHz (2.4-2.4835)
UWB 3.1 – 10.6 GHz
BLE 2.4 GHz
Wi-Fi 2.4, 5 GHz
Data Rate
Chirp (CSS) Up to 2 Mbps
UWB Up to 27 Mbps
BLE Up to 2 Mbps
Wi-Fi Up to 1 Gbps

* With optimal conditions and deployment

Key Benefits

Long-Range Positioning Both Indoors and Out

Chirp delivers long-range positioning of up to 500 meters, powering location-aware use cases across large facilities and indoor and outdoor areas.

Real-Time, Low-Power

Chirp delivers low latency and power-efficient performance, enabling highly scalable, true real-time applications that allow you to instantly sense location, movement, and motion of personnel, assets, equipment, and vehicles and leverage long-lasting hardware.

Superior Reliability

Chirp’s unparalleled reliability allows it to protect against narrow and broad band disturbances, multipath fading, the doppler effect and more, enabling accurate RTLS in harsh, noisy RF environments.

"Identec’s Asset Agent provides the best possible location accuracy and reliability, even in harsh environments with many metal installations. Inpixon's long range and interference resistant Chirp Spread Spectrum (CSS) radio technology is key to our outstanding location performance."

Christian Aadal | Product Manager Asset Agent, IDENTEC SOLUTIONS NORWAY AS

"Working with Inpixon's Chirp is a no-brainer as it allows the integration of a wide range of applications within our IMAGINETM solution suite. These applications, including asset tracking, collision awareness, ventilation on demand, traffic management and many more, increase safety and productivity for the mining industry while contributing to the reduction of greenhouse gases."

Kim Valade | General Manager, MegLab

Use Cases for Chirp

Chirp Supported Inpixon Hardware

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