Blue Ravens (Bluetooth Ranging Access Vehicle Enablement System) is a system solution developed by NXP to assist customers in designing their own BLE-based car access solutions using NXP products. It is designed to support a variety of car access use cases through a modular approach. The main objective (but not limited) is to present all the capabilities and advantages of the Channel Sounding technology and NXP BLE Handover in an automotive use case.
- Channel Sounding is part of the new Bluetooth Low Energy (BLE) standard (BLE 6.0) as a highly accurate distance measurement solution, and available on the NXP KW47 chip.
- BLE Handover is an NXP proprietary feature developed by NXP to seamlessly transfer a BLE connection from one device to another, without disconnection, using and out of band channel (e.g. CAN). This transfer does not impact the peer device so interoperability is guaranteed. This feature can also be used to enable BLE connection RSSI sniffing to increase RSSI based system security. (KW45 & KW47)
Thanks to its modularity, this system can be used to address multiple use-cases, from simple BLE connection system, up to a full BLE Channel Sounding positioning system. Please, note that Channel Sounding is only supported on KW47 chip. KW45 can only be used for simple BLE system. By default, the system on KW47 covers a basic use of Channel Sounding to measure the distance between one remote device (Digital Key) and alternatively several different fixed devices (Car Anchor). At each instant in time, only one anchor is connected to the Digital Key. The other anchors (not connected) can be set in Connection RSSI Sniffing mode (based on Handover). This mode increase the system security by accessing the RSSI value of a connection instead of an advertising packet. These RSSI values can be used to estimated which anchor can be used in the round-robin or to keep the best BLE link around the Car.
The system is composed of multiple KW4x boards, each with a specific role. On board is used as Digital Key, to be caried by the user, the other represent the Car sub-system. On this Car Sub-system, all boards are connected to each other using the CAN bus. The CAN bus fulfills the purpose to power all boards with 12V and to allow communication between the boards:
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Control Unit (KW4x EVK-Board) |
Car Anchors (KW4x LOC-Board) |
Digital Key (KW4x LOC-Board) |
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Role: Central decision-making node Functionality: - Coordinates BLE anchors. - Triggers actions based on received data
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Role: BLE devices connected to the Control Unit via CAN bus Functionality: - Advertise BLE presence. - Wait for a Digital Key to connect. - Act as CS initiators during the session. |
Role: Acts as the remote BLE device Functionality: - Scans for BLE anchors. - Initiates connection with a Car Anchor. - Once connected, behaves as a CS reflector.
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A Desktop application is used to monitor the states and monitor the measurement done by the system:
Using the successive measurement on each anchors, the Car sub-system is able to estimate the Digital Key position (Disclaimer: this solution is not consider accurate in dynamic environments)
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Features |
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BLE connection |
Supporting 1 connection only for now (multiple peer plan) |
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BLE Channel Sounding (KW47 only) |
Yes |
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RSSI Sniffing |
Yes – All not connected anchors |
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Automatic exclusion of suboptimal anchors |
Yes |
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BLE Handover with CS context (No CS repeat) |
Yes |
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Trilateration algorithm |
Yes |
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Measurement filtering (real time) |
Yes |
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Detection area triggering action (e.g. Welcome zone) |
Yes |
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Car Anchor CAN Synchronization (radio core sync) |
No (planned for next release) |
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Channel Sounding Sniffing |
No (feasibility study ongoing) |
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KPIs |
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Number of Anchor |
From 2 to 8 |
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Number of Digital Key |
1 |
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BLE Connection Interval |
7.5ms – 4s (Default = 30ms) |
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BLE Handover connection transfer time (+CS context transfer) |
<60ms (CI=30ms) <50ms (CI=10ms) |
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CS start Delay |
(2+7)*CI |
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CS measurement and data transfer (Real Time) |
<70ms (CI=30ms) |
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CS Algo |
<30ms |
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Full cycle time (CS + Handover) [Algorithm runs asynchronously on the anchor after the handover is finished] |
390ms (CI=30ms) 190ms (CI=10ms) |
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Line Of Sight CS measurement range |
100m Max (at 10dBm) |
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Back Pocket CS measurement range |
10m (at 10dB) |
This solution is under development and improvement will be added in the future releases.
