Indoor location services are evolving, and so are expectations. Legacy methods like BLE RSSI and Wi-Fi RSSI gained early traction due to low cost and ease of use, but in complex environments where accuracy, scalability, and consistency matter, these technologies hit their limits.
Cisco’s latest high-performance Wi-Fi 7 access points (CW9178 and CW9176 series) now integrate Ultra Wideband (UWB) technology (see Figure 1 for the Qorvo chipset), enabling precise indoor navigation and enterprise-grade asset tracking. UWB works alongside the existing wireless infrastructure to elevate location services to the next level.
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Figure 1 – Cisco Wireless 9178 Series Access Point with integrated UWB radio technology in-device.
What Sets UWB Apart: Precision at scale
While actual performance may vary based on environmental factors, such as physical obstructions, and deployment conditions, UWB provides sub meter accuracy in environments optimized for its use. UWB uses time difference of arrival (TDoA) techniques in both uplink and downlink. This accuracy is possible because UWB messages consist of series of short pulses, as you can see in Figure 2.
Figure 2 – UWB pulse structure.
This structure has significant advantages for positioning applications that rely on time of flight (the travel time between signal transmission and reception):
- Because the pulse is very short, the receiver can know with high accuracy when the pulse arrives. Each pulse is 2 nanosecond-long, and that’s the entire pulse. With pulse shape correlation and other techniques, the receiver can determine the pulse timing with a precision of up to 100ps or less, which is about 3 cm (just over an inch).
- The sequence of the first pulses is known, and the pulses are repeated a few times. A receiver that may have missed the first part of the message can still, from the part of the message it starts from, recompute when exactly the message is supposed to have started, making the technology highly efficient even in difficult or noisy environments.
While Wi-Fi FTM uses travel time techniques, it requires multiple two-way message exchanges between the client and infrastructure, which increases airtime usage and limits scalability. With FTM, the client first needs to request ranging from the AP. As can be seen in Figure 3, the AP then sends a message, (sent at time t1) that the client receives (at time t2) and replies to (t3). The response reaches the AP at time t4. In a subsequent exchange, the AP sends the (t1, t4) timestamps. The process works well but consumes airtime (and requires the client to send multiple messages).
Figure 3 – Wi-Fi Fine-Time Measurement (FTM) based on Two-Way Ranging (TWR) message exchanges.
In contrast, UWB uses a one-way TDoA mechanism in both directions, where a single message from either the infrastructure or the tag is sufficient for localization. This approach significantly reduces airtime usage and network load, enabling high concurrency and making UWB well suited for dense deployments.
Asset tags configured for tracking send at regular interval a short message called a “blink”, that simply carries the tag identifier and a timestamp. As you can see in Figure 4, several infrastructure radios (called anchors in UWB terminology) receive this message and write down the time of arrival. Then a location engine uses the difference between these times of arrival to deduce the relative distance of the tag to the anchors using hyperbolic math, and therefore the location of the tag.
Figure 4 – Asset tag sends Blink message in UWB-Based Uplink TDoA and APs send the received timestamps of blink as well as timestamps of synchronization messages to location engine.
TDoA for navigation works with the same logic, in the opposite direction. Several anchors send, one after the other and in response to a trigger from one anchor (the initiator), a short message that carries the anchor identity, location and the time of transmission, as you can see in Figure 5. The client device (think of your smartphone) receives each message, notes the time of arrival, reads the time of transmission, and computes the travel time of the message from the anchor to the client. By comparing the travel time from each anchor, the client device also uses hyperbolic math to compute its relative distance to the anchors. Then, using the anchors location, the client deduces its own location.
Figure 5 – In UWB-Based Downlink TDoA, the phone passively listens to the one-way ranging (OWR) inter-AP message exchanges to determine its own location.
In addition to the lightness of the process, a great advantage of TDoA for navigation is that the client does not need to send any message: it simply listens to the anchor communications. This silence not only allows the system to scale to infinity (you could have an infinite number of client devices performing navigation in a given environment - as they do not send any message, there is no risk of collision and therefore no upper number limitation), but also ensures that the clients can maintain privacy (they do not need to send any UWB message).
You can see the idea behind TDoA calculation in Figure 6. The determination of the relative distance (1 meter closer etc.) is either made by the smartphone in the navigation (Downlink TDoA) case, or by the location engine for asset tracking (Uplink TDoA) case.
Figure 6 – Determining the location by time difference of arrival and intersection of hyperbolas.
UWB’s pulse-based communication avoids the beacon and probe congestion seen with BLE and Wi-Fi RSSI methods. It supports real-time location updates for many devices with minimal collisions. This efficiency enables stable tracking in environments where large numbers of users or asset tags operate concurrently.
Contrary to other radio technologies where any device (client or infrastructure) may be sending any message, of any length, at any time,UWB anchors operate within structured time periods called ranging blocks. Each block is divided into multiple ranging rounds, divided into smaller periods that determine which device(s) are supposed to transmit. This division in blocks allows nearby groups of UWB APs (they are called anchors) to operate on the same channels and share the spectrum without collision as you can see in Figure 7.
Figure 7 – UWB ranging blocks, and rounds.
Within each round, UWB defines periods when anchors can send traffic like broadcast and anchor-to-anchor messages, and periods where asset tags can send messages. These periods are fairly short (a few milliseconds) which makes sure that no side is starved of channel access. All these messages are focused on distance measurements and are also very short. This orchestration allows the coexistence of a large number of anchors and client devices in the same location, with minimal risk of collision.
Cisco, in collaboration with our chipset vendor Qorvo, phone OEMs, and others has been working to enhance the FiRa specification to enable accurate indoor location using UWB in large buildings. Throughout 2024 and 2025, Cisco and its partners have submitted several change requests to the FiRa spec to support this goal.
Robust and secure
With encrypted ranging via Scrambled Timestamp Sequences (STS), UWB protects against spoofing and passive tracking. With STS, the timestamps used for ranging are encoded in a cryptographically scrambled way, with a key agreed upon between the anchors and the (legitimate) clients. An observer cannot read the time in these messages. For navigation, this protection means that an attacker cannot pretend to be an anchor and send forged messages and lead the client to conclude on a wrong location. For asset tracking, this protection means that a passive observer cannot use the tag messages to deduce the tag position. STS is a reliable option for regulated industries and privacy-conscious environments. This level of protection is particularly valuable for deployments in sectors such as healthcare, finance, and critical infrastructure.
Reliable in real-world conditions
While BLE and Wi-Fi RSSI are highly sensitive to wall materials, crowds, and interference, UWB maintains consistent performance across various environments. This is because of UWB’s repeated pulse structure. The travel time does not change significantly when the signal traverses obstacles like walls. Theoretically, the speed of light (and therefore of any signal in the spectrum, including UWB signals) changes slightly when the traversed medium changes, and is slower in a concrete wall than in the air. However, the difference is so small that a one foot (roughly 30 cm) concrete wall would change the measured distance by only half an inch (1.5 cm) or so. The pulse structure of UWB allows the receiver to determine the time of arrival of the signal with high precision. As the pulses are repeated several times, the receiver can add all these signals and overcome the effect of interreferences and multipath. Its resilience to multipath distortion and dynamic interference makes UWB ideal for use in complex indoor spaces like airports, hospitals, and industrial facilities.
Deployment Considerations
With these technical advantages established, it's important to understand the practical considerations for implementing UWB technology in real-world environments. UWB is a highly accurate and advanced indoor location technology, but it comes with specific deployment considerations. UWB is low power. Its shorter effective range means it requires a higher density of anchors compared to BLE or Wi-Fi-based location systems. For both uplink and downlink TDoA, accurate positioning depends on receiving a signal from a minimum of four well-placed access points or anchors. While this may increase infrastructure requirements, it is a purposeful tradeoff that enables high-resolution positioning, faster update rates, and more reliable performance in precision-critical scenarios.
To fully leverage UWB's capabilities, it is important to consider deployment factors. For example, achieving optimal performance may require an increase in access point density to support UWB location services. By making these adjustments, we can unlock UWB's potential to deliver exceptional accuracy and reliability.
Use Case Highlights
Indoor Navigation
- Smooth and responsive updates for turn-by-turn guidance, enabling intuitive movement through complex indoor layouts.
- Low-latency tracking ensures real-time responsiveness, critical for time-sensitive applications like emergency guidance or indoor way-finding.
- Minimal network impact thanks to passive, single-message ranging that avoids congestion from probes or beacons.
Asset Tracking
- High-resolution tracking capable of distinguishing individual items or tools, enabling operational accuracy and reducing asset loss along precise geofencing.
- Secure and scalable design supports thousands of concurrently tracked tags without overwhelming the RF environment
- Motion-aware localization enables tags to transmit location data only when movement is detected, reducing unnecessary transmissions and conserving battery life.
Cisco Spaces
Cisco Spaces is a leading cloud-based location services platform that leverages Cisco’s wireless infrastructure. Cisco Spaces turns wireless network into a powerful location intelligence platform helping you track assets, navigate indoors, and make smarter, data-driven decisions. Cisco’s UWB technology is natively integrated into Cisco Spaces, making it easy to deploy UWB for both indoor navigation and asset tracking.
For more information on how Cisco Spaces leverages Wi-Fi 7 access points to enable smart, connected environments, visit Overview of Wi-Fi 7 for smart spaces.
You can also learn more about the benefits and capabilities Wi-Fi 7 APs in Smart Spaces here.
Figure 8 – Cisco Spaces Interactive Dynamic 3D maps
The Bigger Picture
UWB enhances, rather than replaces, other location technologies. BLE and Wi-Fi RSSI remain valuable for coarse-grained awareness and background telemetry. UWB brings the precision layer—filling the gap for use cases that demand accuracy, low latency, and directional context.
As we continue to build intelligent indoor environments, Cisco’s unified platform with UWB at the core offers the flexibility and precision required to support future-facing experiences.
Acknowledgment
This blog was jointly developed with Jerome Henry. Special thanks to Jerome, who, as a FiRa Board Member, contributed significantly to UWB standardization, helping make this technology ready for mainstream enterprise adoption.
