The Role of Collective Perception and 5G NR-V2X Sidelink in Road Safety

• Road fatalities remain a major concern, motivating technologies and policies aimed at reducing transport deaths toward zero by 2050.Source: §I · p. 1
• Cooperation enables vehicles to overcome isolated sensing by exchanging information through V2X communications.Source: §I · p. 1
• Collective perception lets vehicles and RSUs broadcast both their own status and information about surrounding objects.Source: §I · p. 1
• Prior studies largely use synthetic object traces and earlier CPM rules, leaving real-object variability and perception–communication interaction insufficiently understood.Source: §I · p. 1
• The paper reviews recent CPS standardization and evaluates 5G NR-V2X sidelink under object-selection strategies using reliability, timeliness, congestion, and information-value measures.Source: §I · p. 1
• The article proceeds from vehicular communication alternatives and safety-service evolution to collective perception, performance results, and open research challenges.Source: §I · pp. 1–2

• IEEE and 3GPP provide the principal wireless access technologies underlying C-ITS.Source: A. Organizations and Standardization… · p. 2
• ETSI develops European ITS functional standards spanning the communication stack on which ITS applications rely.Source: A. Organizations and Standardization… · p. 2
• SAE performs a similar functional-standardization role in the United States for connected and automated mobility systems.Source: A. Organizations and Standardization… · p. 2
• C2C-CC, C-ROADS, and 5GAA support interoperability, deployment, cross-border harmonization, testing, and C-V2X promotion.Source: A. Organizations and Standardization… · p. 2

• IEEE 802.11p operates in the 5.9 GHz ITS band with 10 MHz channels, 3–27 Mbps raw rates, and listen-before-talk access.Source: B. Enabling Communication Technologies · p. 2
• IEEE 802.11bd enhances throughput, reliability, and latency with up to 40 MHz bandwidth, higher-order modulation, and new coding options.Source: B. Enabling Communication Technologies · p. 2
• 802.11bd is interoperable with 802.11p, supporting transition and coexistence in mixed vehicular networks.Source: B. Enabling Communication Technologies · p. 2
• 5G NR-V2X, specified in 3GPP Release 16, supports periodic and aperiodic traffic and unicast, groupcast, and broadcast communication types.Source: B. Enabling Communication Technologies · p. 2

Day 1

• Day 1 shares a connected road user’s identity, location, and changing dynamic attributes through messages broadcast within radio range.Source: C. The Progression · pp. 2–3

Day 2

• Vehicles or RSUs can detect and signal unconnected vulnerable road users, including pedestrians hidden from an approaching vehicle’s view.Source: Figure 1 · p. 3, C. The Progression · p. 3
• Day 2 collective perception shares locally sensed environments from cameras, lidars, and radars.Source: C. The Progression · p. 3
• Shared perception can extend a vehicle’s range by fusing received data with its own sensor measurements.Source: C. The Progression · p. 3

• Collective perception is a major road-safety research and standardization theme in Europe and is accompanied by related initiatives in China, Korea, and the United States.Source: C. The Progression · p. 3

Day 3

• Day 3 uses maneuver coordination messages for negotiated or infrastructure-prescribed cooperative operations.Source: C. The Progression · p. 3

C-ITS architecture

• The ETSI C-ITS stack has access, networking and transport, and facilities layers.The access layer transmits packets; networking and transport manage addressing, forwarding, and flow multiplexing; facilities contain services.Source: A. The C-ITS Stack and the Collective… · p. 3
• The access layer uses IEEE or 3GPP technologies to transmit packets over the wireless medium.Source: A. The C-ITS Stack and the Collective… · p. 3

Networking and transport

• GeoNetworking manages node addressing and multi-hop forwarding, while BTP multiplexes flows from higher layers.Source: A. The C-ITS Stack and the Collective… · p. 3

Facilities and services

• C-ITS services exchange structured messages and store data in dedicated databases such as the local dynamic map.Source: A. The C-ITS Stack and the Collective… · p. 3

CPM structure

• CPMs contain a header and payload composed of wrapped containers carrying station, sensor, region, and perception information.The management container provides reference time, position, and segmentation data; other containers describe the originating station and sensing capabilities.Source: B. Collective Perception Messages · pp. 3–4
• The CPM structure includes mandatory and optional containers for different categories of station and perception information.The figure identifies the header, payload, and mandatory and optional containers defined by ETSI TS 103 324 V2.1.1.Source: B. Collective Perception Messages · p. 3, Figure 2 · p. 4

Message generation

• CPM periodicity ranges from 100 ms to 1 s, with object inclusion governed by elapsed time and dynamic behavior.VRUs depend on time since last inclusion, while vehicles and motorcyclists also depend on dynamic behavior; these rules may produce large messages and high channel load.Source: C. The Issue of Redundancy Mitigation · p. 4

Object selection

• VoI-based selection prioritizes objects according to factors including proximity, motion unpredictability, timeliness, and information reliability.The paper contrasts a pedestrian suddenly entering the road with a stationary parked car and notes that VoI is application-dependent.Source: C. The Issue of Redundancy Mitigation · p. 4

Evaluation setup

• The evaluation uses object traces from real sensor measurements collected by moving vehicles.This supports a realistic assessment of collective perception traffic rather than relying only on synthetic object traces.Source: §IV · p. 4
• Network-level simulations use the open-source WiLabV2Xsim framework to study 5G NR-V2X delivery.Source: §IV · p. 4

Evaluation scenario

• The scenario models a congested highway where many CPS-capable vehicles share information about surrounding objects.Source: §IV · p. 4

Dataset

• The Cirrus dataset provides annotated scenes sampled at 1 Hz from a vehicle driving on highways and urban streets in Palo Alto.The recording vehicle used an RGB camera, and the dataset is repurposed here to characterize perception traffic.Source: A. Perceived Objects from Real Sensor… · p. 4
• The analysis asks how the number of perceived objects varies over time and uses that variability as input for perception-traffic characterization.Source: A. Perceived Objects from Real Sensor… · p. 5

Object extraction

• Tracking annotated bounding boxes identifies objects entering and leaving the vehicle’s field of view.Detected objects may or may not be included in CPMs depending on the message-generation strategy.Source: A. Perceived Objects from Real Sensor… · p. 5

Packet modeling

• Packet size is calculated from CPM containers and ITS headers, with the PerceivedObjectContainer contributing 13 bytes per detected object.The listed components include a 6-byte CPM header, management and station containers, sensor information, and BTP and GNW headers.Source: A. Perceived Objects from Real Sensor… · p. 5

Selection strategies

• Three strategies are examined: including all detected objects, randomly selecting a subset, and selecting the highest-VoI objects within Smax.The baseline is the reference; random inclusion uses pincl, while VoI-rank inclusion enforces a predefined maximum message size.Source: B. Object Inclusion Strategies · p. 5
• VoI-rank inclusion follows the ETSI approach of ranking objects by VoI and filling messages until the maximum size is reached.The maximum size may be dynamically provided by a radio resource management entity.Source: B. Object Inclusion Strategies · p. 5

Evaluation metrics

• Communication performance is assessed using PRR, packet inter-reception time, and channel busy ratio.PRR measures successful receptions by distance, packet inter-reception time measures gaps between successful packets, and CBR measures the fraction of busy subchannels.Source: B. Object Inclusion Strategies · p. 5

Trace-derived CPMs

• Figure 3 derives included-object counts, packet sizes, and required subchannels from real perception traces over time.The figure starts from dataset object annotations and compares how the inclusion strategies shape generated CPMs.Source: Figure 3 · p. 5

Evaluation metrics

• The received VoI ratio measures the average fraction of full-information perception delivered at a given distance.It combines object selection, CPM generation frequency, and communication reliability in one metric.Source: B. Object Inclusion Strategies · p. 5

Scenario and radio settings

• Vehicles are randomly distributed across six highway lanes at an average density of 150 vehicles/km, with speeds centered at 70 km/h.Vehicle speeds follow a Gaussian distribution with a 7 km/h standard deviation, and all vehicles transmit and receive CPMs.Source: C. Simulation Settings and Results · p. 6
• The sidelink simulation uses a 20 MHz channel, 30 kHz subcarrier spacing, up to five subchannels per slot, and MCS 12.MCS 12 uses 16-QAM with coding rate 0.43 and supports packets up to 1180 bytes without fragmentation.Source: C. Simulation Settings and Results · p. 6

CPM generation

• VoI-rank messages use Tgen = 200 ms and Smax = 400 bytes, while random inclusion uses pincl = 0.5.The 400-byte limit corresponds to the largest packet size fitting in two subchannels; security certificates cause occasional changes in the included-object count.Source: C. Simulation Settings and Results · p. 6

Communication performance

• The 100 ms baseline disseminates all objects most frequently but experiences the fastest PRR degradation with distance; longer periods improve PRR range at the cost of less frequent updates.VoI-rank further benefits from a limited and stable packet size, while its PIR distribution limits the probability of large reception gaps.Source: C. Simulation Settings and Results · p. 6

Information delivery

• VoI-rank provides a more stable RVR over distance by limiting message size while prioritizing higher-VoI objects.The 100 ms baseline performs best close to the transmitter but decreases rapidly with distance; random inclusion also loses transmitted VoI.Source: C. Simulation Settings and Results · p. 7

Channel occupancy

• Less frequent or smaller CPMs reduce channel congestion, but reducing channel load generally also reduces the number of objects shared per second.The results therefore support relevance-guided object selection rather than minimizing traffic alone.Source: C. Simulation Settings and Results · p. 7

Overall trade-off

• The most suitable strategy depends on balancing selected information value, message generation frequency, communication reliability, and channel occupancy.No single strategy is identified independently of these factors.Source: C. Simulation Settings and Results · p. 7

Contributions and findings

• The study integrates real-world object traces into a network-level simulator to evaluate CPM reliability, timeliness, resource occupancy, and valuable-information delivery.It considers different object-inclusion strategies over 5G NR-V2X sidelink.Source: §V · p. 7
• Message-size variations significantly affect 5G NR-V2X sidelink performance, while VoI-rank inclusion yields substantial communication gains.The strategy shapes perception traffic in line with current ETSI standardization and delivers valuable information with limited distance-related loss.Source: §V · p. 7

Cross-layer design

• The proposed design lets the access layer notify packet-size resource availability while the facility layer ranks objects by relevance and fills messages accordingly.This separates resource-size constraints from CPS object ranking.Source: §V · p. 7

Future directions

• Future work must determine optimal message sizes across physical- and access-layer configurations and CPM traffic conditions.The current study does not settle one optimal message size for all configurations.Source: §V · p. 7
• Future research should improve VoI definitions to capture accuracy, timeliness, and receiver relevance, and use datasets covering alternative settings such as urban areas.Large-scale field experiments remain necessary before practical deployment can be pursued.Source: §V · p. 7