Velocity Connect: Passive In-Coach Relaying for 5G NR High-Speed Railway Evaluation

This repository contains the final reproducibility package for the paper:

Passive In-Coach Relaying for 5G NR Connectivity in High-Speed Railways: A Reproducible System-Level Evaluation

The code provides an ns-3 / 5G-LENA based system-level framework for evaluating in-coach 5G NR connectivity under coach penetration loss and high mobility. The final release focuses on three coach scenarios:

• metallic coach baseline
• composite coach baseline
• Velocity Connect passive in-coach relaying

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1. What this repository provides

The repository includes:

• a reproducible ns-3 / 5G-LENA simulation setup for a single-cell high-speed railway downlink
• an effective-loss model for passive in-coach relaying
• a fixed-seed speed sweep at 500 m
• a multi-seed distance sweep at 300 km/h
• a scalability sweep with increasing UE count
• CSV logging for throughput, packet delivery ratio, latency and fairness
• plotting scripts used to regenerate the paper figures

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2. Final paper configuration

The final paper results are based on the following configuration:

• Carrier frequency: 3.5 GHz
• Bandwidth: 100 MHz
• Subcarrier spacing: 30 kHz
• gNB transmit power: 40 dBm
• Traffic: UDP downlink
• Packet size: 1024 Bytes
• Offered load per UE: 8.19 Mbps
• Simulation time: 2 s
• Application start time: 0.5 s
• Channel model: 3GPP UMi street canyon
• LOS: enforced
• Shadowing: disabled
• Scheduler: ns3::NrMacSchedulerOfdmaRR
• RLC mode: UM

Coach assumptions used in the paper:

• metallic coach: 60 dB penetration loss
• composite coach: 20 dB penetration loss
• Velocity Connect: effective loss ≈ 5 dB

Velocity Connect effective-loss model:

[ L_{\mathrm{eff}} = \max\left(0,;L_{\mathrm{cable}} + L_{\mathrm{coupling}} + L_{\mathrm{indoor}} - (G_{\mathrm{donor}} + G_{\mathrm{service}})\right) ]

Default component values:

• donor antenna gain = 8 dBi
• service antenna gain = 2 dBi
• feeder loss = 3 dB
• coupling / connector loss = 8 dB
• indoor distribution loss = 4 dB

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3. Required simulator version

The final workflow was run with:

• ns-3.46
• 5G-LENA NR 5g-lena-v4.1.1

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4. Repository layout

.
├── hsr_apps.h
├── hsr_io.h
├── hsr_nr.h
├── hsr_runner.h
├── hsr_stats.h
├── hsr_types.h
├── hsr_velocity_connect.cc
├── scripts
│   ├── run_hsr_campaign_singleproc.py
│   ├── run_distance_sweep_multiseed.py
│   ├── plot_hsr_results.py
│   └── plot_distance_multiseed.py
├── paper
│   ├── figures
│   └── results
├── legacy
└── README.md