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Indigenous 5G Standalone Captive Non-Public Network for Deep Subterranean Mass Rapid Transit: Architecture, Analytical Dimensioning and Field Validation on Mumbai Metro Line 3
Subject area: Science,Engineering and Technology · Area of research: 5G CNPN / 5G FWA, Telecom, Metro Communication
DOI: https://doi.org/10.64388/IREV10I2-1722256
Abstract
Deep subterranean mass rapid transit corridors constitute among the most adverse radio-frequency propagation environments encountered in civil infrastructure. Bored tunnels of restricted transverse dimension, reinforced concrete linings of high dielectric loss, pronounced horizontal curvature, densely metallic rolling stock and sustained vehicular motion act in combination to produce severe non-line-of-sight attenuation, rapid temporal channel variation and appreciable Doppler dispersion. The established remedies radiating coaxial feeder, fibre-fed distributed antenna systems and cable-intensive trackside transmission networks impose capital expenditure scaling linearly with route length, installation programmes constrained to non-revenue engineering possessions, and whole-of-life maintenance obligations commensurate with the quantity of consumable physical medium installed. This paper reports the architecture, analytical dimensioning, field implementation and experimental validation of a wholly indigenous 5G Standalone (5G-SA) Captive Non-Public Network (CNPN), integrated with a Fixed Wireless Access (FWA) last-mile layer, deployed across Section 1 of Mumbai Metro Line 3 (MML3, Aqua Line). The system operates in 3GPP band n78 and employs an O-RAN Alliance compliant Option 7.2a lower-layer functional split, with x86-based Centralized Unit and Distributed Unit processing, 4T4R Radio Units of Indian manufacture, a cloud-native Service-Based Architecture core hosted within a Micro Data Centre at the Aarey Operations Control Centre, and a passive 1:6 wavelength-division fronthaul multiplexing scheme permitting six-sector distribution over a single optical fibre core. Acceptance and User Acceptance Testing conducted across five operational domains depot and stabling yard, two underground stations, a 1.24 km bored tunnel alignment and in-motion measurement aboard revenue-configuration rolling stock established downlink throughput of 113.00–132.00 Mbps at station levels and 124.17–133.26 Mbps throughout the tunnel alignment, with round-trip latency confined to 16–25 ms and uninterrupted session continuity across all inter-cell transitions. Of particular significance, downlink throughput at the deepest point of the bored alignment was retained at 124.17 Mbps, a diminution of only 6.8 per cent relative to the tunnel portal a result constituting direct experimental corroboration of the guided-mode dimensioning developed herein, in which the analytically derived waveguide break-point distance of 101 m is shown to coincide with the 100 m radio unit spacing adopted. Three concurrently instantiated network slices, bearing operational control, video surveillance and commercial passenger traffic respectively, were verified for mutual isolation. The paper further presents a two-slope tunnel propagation treatment, a Doppler and handover dimensioning analysis, a decomposed latency budget, and a comparative capital expenditure framework indicating a projected reduction of 40–50 per cent relative to cable-intensive alternatives. To the authors’ knowledge, the conjunction of properties realised in this deployment has not previously been reported in the open literature; the specific claims of priority, and the evidence required to sustain each, are stated formally in Section 1.5.
Keywords
5G Standalone, Captive Non-Public Network (CNPN), O-RAN, Option 7.2a Functional Split, Fixed Wireless Access (FWA), Tunnel Waveguide Propagation, Mass Rapid Transit, Network Slicing, Communications-Based Train Control, Micro Data Centre, Indigenous Telecommunications Manufacture, Technological Sovereignty.
References
[1] 3GPP TS 23.501, "System architecture for the 5G System (5GS)," 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects.
[2] 3GPP TS 23.502, "Procedures for the 5G System (5GS)," 3rd Generation Partnership Project.
[3] 3GPP TS 38.300, "NR; NR and NG-RAN Overall Description; Stage 2," 3rd Generation Partnership Project.
[4] 3GPP TS 38.104, "NR; Base Station (BS) radio transmission and reception," 3rd Generation Partnership Project.
[5] 3GPP TS 38.214, "NR; Physical layer procedures for data," 3rd Generation Partnership Project.
[6] 3GPP TS 38.306, "NR; User Equipment (UE) radio access capabilities," 3rd Generation Partnership Project.
[7] 3GPP TS 22.261, "Service requirements for the 5G system; Stage 1," 3rd Generation Partnership Project.
[8] 3GPP TS 33.501, "Security architecture and procedures for 5G System," 3rd Generation Partnership Project.
[9] 3GPP TR 38.901, "Study on channel model for frequencies from 0.5 to 100 GHz," 3rd Generation Partnership Project.
[10] O-RAN Alliance, "O-RAN Control, User and Synchronization Plane Specification," O-RAN.WG4.CUS.0.
[11] IEEE Std 1588-2019, "IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems."
[12] ITU-T Recommendation G.8275.1, "Precision time protocol telecom profile for phase/time synchronization with full timing support from the network."
[13] IEEE Std 1474.1, "IEEE Standard for Communications-Based Train Control (CBTC) Performance and Functional Requirements."
[14] A. G. Emslie, R. L. Lagace, and P. F. Strong, "Theory of the propagation of UHF radio waves in coal mine tunnels," IEEE Transactions on Antennas and Propagation, vol. AP-23, no. 2, pp. 192–205, March 1975.
[15] D. G. Dudley, M. Lienard, S. F. Mahmoud, and P. Degauque, "Wireless propagation in tunnels," IEEE Antennas and Propagation Magazine, vol. 49, no. 2, pp. 11–26, April 2007.
[16] K. Hrovat, G. Kandus, and T. Javornik, "A survey of radio propagation modeling for tunnels," IEEE Communications Surveys & Tutorials, vol. 16, no. 2, pp. 658–669, 2014.
[17] EN 50121-4, "Railway applications Electromagnetic compatibility Part 4: Emission and immunity of the signalling and telecommunications apparatus," CENELEC.
[18] Department of Telecommunications, Government of India, "Guidelines for obtaining licence for establishing Captive Non-Public Network (CNPN)," June 2022.
[19] ITU-R Recommendation P.1238, "Propagation data and prediction methods for the planning of indoor radiocommunication systems and radio local area networks."
[20] Mumbai Metro Rail Corporation Ltd. and Bharat Sanchar Nigam Limited, "Quantum 5G Wireless: SpectraX Metro Rail Communications," Technical Report, 2026.
[21] delaPlex Limited and BSNL, "Acceptance Test Report: MMRCL Project Data Connectivity using Quantum 5G Spectrum (CNPN/FWA)," Inspection Document v1.0, March 2026.
[22] BSNL Telangana Circle, "High Level Solution Design for MML3 5G SA Network," Technical Architecture Document, 2026.
[23] MMRCL, "Joint Inspection Confirmation for BSNL Quantum 5G SIM-less FWA and Micro Data Center Solution," Project Acceptance Letter, March 2026.
How to cite this paper
@article{1722256,
author = {Dr. Hari Pratap Elduri, Sudhir Sahare},
title = {Indigenous 5G Standalone Captive Non-Public Network for Deep Subterranean Mass Rapid Transit: Architecture, Analytical Dimensioning and Field Validation on Mumbai Metro Line 3},
journal = {Iconic Research And Engineering Journals},
year = {2026},
volume = {10},
number = {2},
pages = {793-814},
issn = {2456-8880},
url = {https://www.irejournals.com/formatedpaper/1722256.pdf},
abstract = {Deep subterranean mass rapid transit corridors constitute among the most adverse radio-frequency propagation environments encountered in civil infrastructure. Bored tunnels of restricted transverse dimension, reinforced concrete linings of high dielectric loss, pronounced horizontal curvature, densely metallic rolling stock and sustained vehicular motion act in combination to produce severe non-line-of-sight attenuation, rapid temporal channel variation and appreciable Doppler dispersion. The established remedies radiating coaxial feeder, fibre-fed distributed antenna systems and cable-intensive trackside transmission networks impose capital expenditure scaling linearly with route length, installation programmes constrained to non-revenue engineering possessions, and whole-of-life maintenance obligations commensurate with the quantity of consumable physical medium installed. This paper reports the architecture, analytical dimensioning, field implementation and experimental validation of a wholly indigenous 5G Standalone (5G-SA) Captive Non-Public Network (CNPN), integrated with a Fixed Wireless Access (FWA) last-mile layer, deployed across Section 1 of Mumbai Metro Line 3 (MML3, Aqua Line). The system operates in 3GPP band n78 and employs an O-RAN Alliance compliant Option 7.2a lower-layer functional split, with x86-based Centralized Unit and Distributed Unit processing, 4T4R Radio Units of Indian manufacture, a cloud-native Service-Based Architecture core hosted within a Micro Data Centre at the Aarey Operations Control Centre, and a passive 1:6 wavelength-division fronthaul multiplexing scheme permitting six-sector distribution over a single optical fibre core. Acceptance and User Acceptance Testing conducted across five operational domains depot and stabling yard, two underground stations, a 1.24 km bored tunnel alignment and in-motion measurement aboard revenue-configuration rolling stock established downlink throughput of 113.00–132.00 Mbps at station levels and 124.17–133.26 Mbps throughout the tunnel alignment, with round-trip latency confined to 16–25 ms and uninterrupted session continuity across all inter-cell transitions. Of particular significance, downlink throughput at the deepest point of the bored alignment was retained at 124.17 Mbps, a diminution of only 6.8 per cent relative to the tunnel portal a result constituting direct experimental corroboration of the guided-mode dimensioning developed herein, in which the analytically derived waveguide break-point distance of 101 m is shown to coincide with the 100 m radio unit spacing adopted. Three concurrently instantiated network slices, bearing operational control, video surveillance and commercial passenger traffic respectively, were verified for mutual isolation. The paper further presents a two-slope tunnel propagation treatment, a Doppler and handover dimensioning analysis, a decomposed latency budget, and a comparative capital expenditure framework indicating a projected reduction of 40–50 per cent relative to cable-intensive alternatives. To the authors’ knowledge, the conjunction of properties realised in this deployment has not previously been reported in the open literature; the specific claims of priority, and the evidence required to sustain each, are stated formally in Section 1.5.},
keywords = {5G Standalone, Captive Non-Public Network (CNPN), O-RAN, Option 7.2a Functional Split, Fixed Wireless Access (FWA), Tunnel Waveguide Propagation, Mass Rapid Transit, Network Slicing, Communications-Based Train Control, Micro Data Centre, Indigenous Telecommunications Manufacture, Technological Sovereignty.},
month = {August},
doi = {https://doi.org/10.64388/IREV10I2-1722256}
}