Online Anomaly Detection in Roadside-Unit Communication Streams with Delay-Aware Cluster Updates
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Keywords

Roadside unit security
vehicular communication streams
online anomaly detection
delayed cluster updating
V2I monitoring
data stream mining
connected transportation security

Abstract

Roadside units in connected transportation systems generate continuous communication streams from vehicle messages, signal controllers, traffic sensors, edge servers, and cooperative perception services. These streams are affected by traffic density, weather, road events, handover behavior, and temporary communication congestion. Repeated abnormal communication patterns, such as spoofed message bursts or unstable vehicle-to-infrastructure links, may be gradually treated as normal by conventional online clustering models. This study proposes a delay-constrained cluster updating method for roadside unit communication stream anomaly detection. The method constructs online clusters from message frequency, packet interval, vehicle-density context, signal-phase state, handover count, retransmission rate, and source-location consistency. A delayed update mechanism restricts cluster movement when suspicious communication patterns appear repeatedly within short temporal windows. Experiments are conducted on a roadside communication dataset containing 420 roadside units, 68 signalized corridors, 1.86 million vehicle identifiers, and 42 communication indicators collected over 76 days. The dataset includes 529 million message-flow records and 3,180 annotated abnormal episodes, including spoofed safety-message bursts, abnormal retransmission storms, unstable handover sequences, malicious location inconsistency, and edge-link congestion. The proposed method reduces median detection delay from 8.6 minutes to 2.1 minutes compared with streaming k-means. False alerts are limited to 3.6 cases per corridor-month. The clustering engine processes 116,000 message records per second, and the median update latency remains 19 ms per roadside unit window. The delayed update mechanism prevents 2,480 suspicious communication patterns from being prematurely absorbed into normal clusters during rush-hour traffic. The results demonstrate that anti-habituation cluster updating can improve anomaly detection in dynamic vehicle-to-infrastructure data streams.

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