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GoT: Decreasing DCC Queuing for CAM Messages

Oscar Amador, Ignacio Soto, Manuel Urueña, Maria Calderon

TL;DR

The paper addresses CAM freshness under ETSI DCC queuing, which degrades in the presence of multi-traffic. It provides an analytical model showing that queue waiting times follow $T_q \sim U(0,t_{dcc})$ with $\overline{T_q}=t_{dcc}/2$, increasing $t_{e2e}$ and $t_{age}$ (where $t_{age(n-1)}=T_q(n)+t_{cam}(n)$). The authors propose Generate-on-Time (GoT), which delays CAM generation until the next gate opening time $t_{go}$ using a small buffer $\varepsilon$, aligning CAM generation with DCC and keeping the transmission rate. Simulation results in static and road scenarios show that GoT lowers $t_{e2e}$ and $t_{age}$ toward $\varepsilon$ while preserving CAM throughput, with notable improvements in information freshness especially under higher densities.

Abstract

Vehicular networks use Decentralized Congestion Control (DCC) mechanisms to operate effectively, but this mechanism may introduce queuing delays. Freshness of Cooperative Awareness Messages (CAMs) is critical for their usefulness. In this letter we explore how the presence of other types of traffic additional to CAMs, even with lower priorities, has an impact on the freshness of CAM messages due to DCC queuing. Finally, we propose Generate-on-Time (GoT), which is a simple mechanism that reduces DCC queuing delays for CAM messages without introducing any downside in other performance metrics.

GoT: Decreasing DCC Queuing for CAM Messages

TL;DR

The paper addresses CAM freshness under ETSI DCC queuing, which degrades in the presence of multi-traffic. It provides an analytical model showing that queue waiting times follow with , increasing and (where ). The authors propose Generate-on-Time (GoT), which delays CAM generation until the next gate opening time using a small buffer , aligning CAM generation with DCC and keeping the transmission rate. Simulation results in static and road scenarios show that GoT lowers and toward while preserving CAM throughput, with notable improvements in information freshness especially under higher densities.

Abstract

Vehicular networks use Decentralized Congestion Control (DCC) mechanisms to operate effectively, but this mechanism may introduce queuing delays. Freshness of Cooperative Awareness Messages (CAMs) is critical for their usefulness. In this letter we explore how the presence of other types of traffic additional to CAMs, even with lower priorities, has an impact on the freshness of CAM messages due to DCC queuing. Finally, we propose Generate-on-Time (GoT), which is a simple mechanism that reduces DCC queuing delays for CAM messages without introducing any downside in other performance metrics.
Paper Structure (9 sections, 3 equations, 5 figures, 1 table)

This paper contains 9 sections, 3 equations, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. End-to-end delay in CAMs
  3. Overview of CAM generation rules
  4. Analysis of CAM end-to-end delay with multi-traffic
  5. Generate-on-Time (GoT)
  6. Simulation Results
  7. Static Scenario
  8. Road Scenarios
  9. Conclusion

Figures (5)

  • Figure 1: ETSI ITS Architecture: DCC cross-layer and the CA basic service.
  • Figure 2: CAM generation under rules defined in etsiCAM
  • Figure 3: CAM generation with Generate-on-Time
  • Figure 4: Comparison between ETSI CAM and Generate-on-Time in a static scenario
  • Figure 5: Comparison between ETSI CAM and Generate-on-Time in a road scenario ($d\leq400m$)