External Vehicle Communications

cellular · GNSS · V2X · eSIM

An EV talks to the outside world over five radio links. The cellular link carries almost all the value, and it is the one regulators now control.

Diagram of five radio links from the vehicle, which carries a TCU, antennas and a secure element: cellular LTE and 5G for telemetry, OTA updates and remote commands over carrier networks; GNSS (GPS, Galileo, BeiDou) for receive-only position and time; C-V2X PC5 for direct car and roadside messages at 5.9 GHz without a network; Wi-Fi, Bluetooth and UWB for hotspot, phone-as-key and depot data offload; and eCall, the automatic crash call that has been mandatory in the EU since 2018. Most of these radios sit in or next to one module, the telematics control unit. FIVE RADIO LINKS FROM THE VEHICLE Vehicle TCU, antennas, secure element Cellular LTE / 5G telemetry, OTA, remote commands over carrier networks GNSS GPS, Galileo, BeiDou: position and time, receive-only C-V2X (PC5) direct car and roadside messages at 5.9 GHz, no network Wi-Fi, Bluetooth, UWB hotspot, phone-as-key, depot data offload eCall automatic crash call; mandatory in the EU since 2018 Most of these radios sit in or beside one module, the TCU.
EU eCall
new types since 2018
US 3G shutdown
2022
US C-V2X spectrum
30 MHz at 5.9 GHz
China NEV data reporting
GB/T 32960
Hub
Supply Chain

Finding

The cellular link is the vehicle's lifeline for OTA, fleet data and remote service, and network sunsets, sourcing bans and mandates now shape its hardware more than bandwidth does

External communications are separate from the in-vehicle network: they connect the vehicle to carriers, satellites, roadside units and phones. The cellular modem in the TCU carries telemetry, OTA images and remote commands; when AT&T, T-Mobile and Verizon shut down 3G in 2022, millions of older vehicles lost connected services because their modems could not be upgraded. Regulation now sets requirements at each link: eCall in the EU and ERA-GLONASS in Russia mandate crash calls, China requires every new-energy vehicle to stream operating data to a national monitoring platform under GB/T 32960, and the US bars Chinese and Russian connectivity hardware from model year 2030.

V2X has split by region. The FCC moved the upper 30 MHz of the 5.9 GHz band to C-V2X in November 2024 and retired the older DSRC standard, and US DOT published a national V2X deployment plan the same year. China has the deepest C-V2X rollout, with roadside units in pilot zones such as Wuxi and Beijing Yizhuang and C-V2X fitted to models from Hongqi, GAC Aion and others. In Europe, Volkswagen fits Car2X based on ITS-G5 (802.11p Wi-Fi) to the Golf and the ID family, while other makers wait for a regulatory decision.

On the hardware side, Qualcomm supplies most automotive modems and C-V2X chipsets, with MediaTek, Samsung, UNISOC and Huawei as alternatives; u-blox, Qualcomm, Broadcom, Unicore and Allystar make GNSS receivers. See the TCU page for module and Tier 1 suppliers.

Internal vs external

External communications vs the in-vehicle network

The two stacks meet at the TCU and gateway; mixing them up confuses both architecture and sourcing.

External communications vs in-vehicle network
StackConnectsPurposeTechnologies
In-vehicle network (IVN)Sensors, compute, controllers and actuators inside the vehicleReal-time internal data and controlAutomotive Ethernet, CAN FD, LIN, camera SerDes
External communicationsVehicle to cloud, fleet, roadside units, phones and satellitesTelemetry, OTA, remote commands, positioning, V2X, eCallLTE and 5G, GNSS, C-V2X, Wi-Fi, Bluetooth, UWB, eSIM, secure elements

Hardware

Hardware elements and suppliers

Most elements are integrated into or tightly coupled to the TCU, but each is a separate supply chain.

External communications hardware
ElementWhat it doesIntegrationSuppliers
Telematics control unitVehicle-side hub for telemetry, OTA transport and remote commandsStandalone ECU, sometimes merged with the gatewayLG Electronics, Harman, Aumovio, Denso, Bosch, Huawei, Flaircomm
Cellular modem (LTE / 5G)Wide-area uplink and downlinkInside the TCU, as a chipset or moduleQualcomm, MediaTek, Samsung, UNISOC; modules Quectel, Fibocom, Telit Cinterion
GNSS receiverPosition and timing for fleets, navigation and logsInside the TCU or shared with infotainmentu-blox, Qualcomm, Broadcom, STMicro, Unicore, Allystar
C-V2X radioVehicle-to-vehicle and vehicle-to-infrastructure messagesOptional; in the TCU or a separate unitQualcomm, Autotalks (acquired by Qualcomm), Huawei, CICT (Datang)
RF front-endFilters, amplifiers, switches and tunersCoupled to the modem and antennasQorvo, Skyworks, Murata, Qualcomm
Antenna systemCellular, GNSS and V2X coupling; shark fin or distributedRoof module or hidden antennasTE, Molex, Harada, Yokowo, Aumovio, Sunway
SIM / eSIMCarrier identity and remote provisioningEmbedded eUICC in the TCUThales, Giesecke+Devrient, Idemia; carrier platforms
Secure element / HSMKey storage, crypto, secure boot, signed OTA verificationInside the TCU or on the main boardNXP, Infineon, STMicro
Flash storageBuffers logs and stages OTA imagesInside the TCUMicron, Samsung, Kioxia, SK hynix

Fleet-grade

OTA duties and fleet-grade connectivity

Fleets stress the external link harder than private owners do, mostly in reliability and key management rather than raw modem speed.

OTA responsibilities and fleet requirements
FunctionConsumer vehicleFleet vehicle
Telemetry volumePeriodic uploadsFrequent events and operational metrics
OTA cadenceOccasional, owner-approvedFrequent, staged rollouts with monitoring
Update safetySigned images, secure boot, A/B partitionsSame, plus audit logs and fleet-wide rollback policy
Buffering and fault handlingBest effortStore-and-forward through coverage gaps
Key managementOEM-managedPer-fleet policy, auditability, access control for third parties

Sources

Sources and scope

Scope
External Vehicle Communications
Sources
FCC 5.9 GHz Second Report and Order (November 2024); US DOT National V2X Deployment Plan; EU eCall Regulation 2015/758; GB/T 32960; BIS connected vehicle rule; company disclosures
Updated
October 2026