The Proliferation Of Bluetooth In V2X Automotive Applications

A ubiquitous technology in consumer electronics is poised to boost communications in and around a vehicle.

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V2X, or “Vehicle to Everything,” applies to wireless communication between a vehicle and a specific entity or network. Although vehicle-to-vehicle communication projects can be traced back to the 1970s, more recently the IEEE WLAN V2X specifications released in 2010 and the 3GPP V2X specification published in 2016 have defined specific wireless standards for V2X communications. Most of the efforts with wireless vehicle communications have been driven by various Advanced Driver Assistance Systems (ADAS) initiatives and have been focused on what is generically referred to in the wireless industry as Wireless Local Area Networks (WLAN) or Wireless Wide Area Networks (WWAN). V2X wireless protocols, as it was originally defined, have been specifically centered around either IEEE 802.11p, which forms a vehicular ad-hoc network via dedicated short-range communications (DSRC), or more recently the 3GPP C-V2X, which is a cellular network standard initially based on LTE as defined in 3GPP Release 14 and enhanced in subsequent releases.

As electronics have proliferated and evolved in automobiles over the last decade, so has the need for wireless communications both in and around the automobile. To use this initial definition of V2X is a bit myopic and quite constraining with the advent of other automotive wireless use cases that have emerged.

Bluetooth enters V2X applications

Bluetooth technology is ubiquitous and found in most electronic devices we use today, most importantly our mobile phones. Bluetooth, or specifically Bluetooth Low Energy (BLE), is categorized as a Wireless Personal Area Network (WPAN) technology with the key attributes of extremely low power, low cost and short range. BLE devices are typically battery powered and may have up to 10 years of battery life.

When considering specific wireless use cases for vehicles, you must analyze the attributes of a given wireless protocol. Over the last couple of decades, I have been asked several times by the press and analysts, “which is the superior wireless technology?” or, “which wireless protocol will win?” My simple response has been a question back to them: “which is the best method of transportation, a bicycle, a car or an airplane?” They all do different things, their range, carrying capacity (payload), cost and energy use are all quite different. The same is true when looking at wireless applications in automobiles.

Where we have been: Automotive use of Bluetooth to date

Bluetooth is certainly not new to automobiles. We are all aware of applications such as hands-free phone use, synchronizing our phone contacts with the car, streaming music from our phone to the car’s infotainment system and the use of Bluetooth in GPS navigation systems, including Apple CarPlay or Android Auto. Other, more limited uses have been in diagnostics via the use of aftermarket modules for the ODBii port as well as data tethering to cloud gateways via Bluetooth to cellular communications. Several automotive makers have migrated from proprietary wireless protocols to the use of Bluetooth in key fobs.

While these are compelling uses of Bluetooth, they only scratch the surface of how Bluetooth will be used in the near future.

Emerging Bluetooth V2X applications

Let’s look at the basic classifications of automotive wireless communications. Figure 1 shows the classic six categories for V2X communications. I would argue that there is a 7th category which is defined as “in-vehicle” communications. Some folks also call this “in-cabin” communications.

Fig. 1: V2X wireless communication classifications.

BLE can be quickly eliminated as useful technology in three of the seven V2X categories simply because of its short range (30-100ft). Vehicle-to-Network (V2N), which is basically communicating long range to the cloud, is better served by cellular technologies. Likewise, more medium range applications (~1 kilometer) for Vehicle-to-Infrastructure (V2I) and Vehicle-to-Vehicle (V2V) applications cannot be serviced by Bluetooth.

This leaves the remaining four V2X categories that are viable for BLE applications:

  • In-Vehicle Communications (IVC)
  • Vehicle-to-Device (V2D)
  • Vehicle-to-Grid (V2G)
  • Vehicle-to-Pedestrian (V2P)

In Vehicle Communications (IVC) applications are well suited for BLE due to the short range the wireless signal must travel. A simple example of this is cable/connector replacement for sensors or solenoids/actuators. This can help reduce the weight of heavy and expensive cable harnesses and eliminate some of the reliability issues associated with conventional connectors. Many of these wired systems are historically CAN bus-based, which can be supported over a simple dedicated Bluetooth wireless link. Network architectures in automobiles are evolving from hundreds of individual Electronic Control Units (ECUs) in a flat topology to more domain-specific ECUs and ultimately zonal networks connected to a central processing unit via Ethernet. Despite this shift in network topologies, Bluetooth will play a role with connecting sensors to zonal gateways in different locations in the car.

Two of the more popular monitoring systems in vehicles that are migrating to BLE are Tire Pressure Monitor Systems (TPMS) and Battery Management Systems (BMS). TPMS have been historically low frequency propriety wireless protocols. TMPS systems are becoming more sophisticated by not only measuring tire pressure but temperature, vibration and even thread wear to better indicate when maintenance or replacement is required to prevent tire failure. Standardizing on BLE technology, including using the new Periodic Advertising with Response (PAwR) enhancement recently released in the 2023 Bluetooth 5.4 specification, will help increase reliability and extend battery life in TPMS systems.

BMS is a fairly new BLE use case with growing significance. eVehicles have anywhere from 5000–9000 individual cells that are grouped together in several dozen modules within the overall EV battery pack. For effective cell management, modules must be monitored separately with their own charge controller to ensure proper cell operation for optimal capacity, life and cell protection/safety. Current and voltage must be monitored to ensure the cells are operating in the safe operating area (SOA). Temperature along with current charging rates are measured to determine the cell’s state of health (SOH). Because cells charge and discharge at different rates, the cell’s state of charge (SOC) must be monitored to insure that charging currents are going to the cells that require charging the most while full cells are not being over charged. This is called “cell balancing” and is depicted in the diagrams below. Running wires to all these individual charge controllers/sensors can become quite onerous. BMS vendors are now designing BLE based controllers to handle the communication wirelessly to simplify the wiring nightmare.

Fig. 2: Cell balancing.

An additional consideration for BLE is related to infotainment systems. We are all familiar with Bluetooth wireless speakers. To date, these have been based on the older Bluetooth “Classic” standard, also known as BR/EDR, which is a point-to-point connection to a single speaker or headset. With the advent of LE Audio (Audio over BLE), the audio quality has increased, the energy savings/battery life can increase by up to 90% and, most importantly, the BLE signal can be broadcast to multiple headsets in a vehicle. This is the Auracast initiative, which is essentially a BLE radio station that can be received by multiple headsets or earbuds, that has been recently promoted by the Bluetooth Special Interest Group.

Vehicle to Device (V2D) is the exchange of information between a vehicle and any electronic device that may be connected to the vehicle, most likely the owner’s mobile device. As mentioned previously, we use this today to stream audio in our car or communicate with the navigational system. Key fobs have now evolved to use your mobile device as a key (Phone as a Key or “PaaK”). On the near horizon is the distribution of digital keys to authorized users of your car. This could also apply to rental cars and trucking fleet management systems. Wireless digital key protocols, which include BLE, have been defined by the Car Connectivity Consortium (CCC) in the western world and other standards organizations in Asia. BLE can be used by itself or in conjunction with Near Field Communications (NFC) or Ultra-Wideband (UWB) wireless protocols. The newest Bluetooth specification due for release in mid-2024 will include Channel Sounding, which is a new BLE feature for High Accuracy Distance Measurement (HADM). This enables more precise distance measurement than simply measuring the radio signal strength. Accurately measuring the proximity of the user to their car enhances security measures associated with access and digital key distribution.

With BLE in every smartphone, we are only an “App” away from providing other functionality over a BLE wireless connection to various systems in a vehicle. This can include smart phone applications that show real-time diagnostics and performance information both for the driver and for auto shop mechanics. Other use cases include passenger comfort phone apps that allow driver customization with smart seats and other electronically controlled settings in a car, like mirror positioning and radio station preferences. These settings would be changed as the driver approaches the car versus waiting until they have opened the door or are already seated in the car. Automakers are looking at the use of Bluetooth during the manufacturing process as well as downloading maintenance history and owner information during service calls.

Vehicle to Grid (V2G) is a wireless application that is in its infancy. The demand for power to charge eVehicles could increase the load on power grids by significant proportions over the next decade. There have been documented cases where shipping companies have been denied approval to convert their trucking fleets over to battery power simply because the local power utility cannot provide enough power to charge their fleet overnight. The concept of V2G is that eVehicles can potentially be back-up power storage devices to supply power back into electrical grids. Likewise, bidirectional charging stations could manage the push and pull energy consumption from connected vehicles based on the energy demands at any given time. There have also been recent articles about charging coils being placed in the asphalt of roads to charge a vehicle while driving down the road or stopped at traffic lights. Regardless of the charging methodology, it is expected that BLE will be used as a backchannel communication protocol to communicate between the vehicle and the charging system. A simpler V2G application that is already deployed is the use of BLE to communicate with and pay for charging services in parking lots via your mobile device. BLE can be the bridge between the car’s battery management system and the charging station next to the car to monitor the charging status and battery heath all while being observed on the owner’s mobile device.

Vehicle to Pedestrian (V2P) is the last category for discussion. As our planet becomes more populated with both people and automobiles, it is easy to comprehend why injury and deaths to pedestrians and bicyclists continue to rise yearly (excluding the COVID years). Safety organizations around the world, automobile makers and several other agencies/companies are looking for solutions. The Ford Motor company has been evaluating the use of BLE to detect pedestrians via cell phone detection when in close proximity to cars. This is an extremely complicated issue to solve and may eventually involve several technologies, but I am sure that Bluetooth will be used in some manner to provide at least a portion of the ultimate solution.

Bluetooth solutions

Synopsys is actively supporting all BLE automotive applications including suppling Automotive grade (AG) RFPHYs with the appropriate AEC-Q100, HTOL, Misson Profiles and DRC/Temperature and aging requirements. We currently support the Bluetooth BT5.4 specification and will be early to market with Channel Sounding support in the upcoming next Bluetooth specification release in mid-2024.

Our RFPHYs and Link Layer Controller IP have excellent power, performance and area (PPA) specifications. They are silicon proven and in production with several tier 1 IoT silicon vendors. Sourcing both the RFPHY and Link Layer Controller from Synopsys will greatly reduce the risk and integration complexities in supporting the upcoming new Bluetooth enhancements over the next few years.

Conclusion

The definition of V2X is evolving to include short range wireless applications both in and around a vehicle. Bluetooth, and specifically Bluetooth Low Energy, is present in our mobile phones, which makes it the de-facto standard for short range wireless communications. The use of BLE in various use cases discussed in this paper highlight just some of the Bluetooth applications that are expected to be deployed in automobiles over the next couple of years. Only the future will tell us what’s in store for us beyond that.



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