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FRMCS – Radio network planning fundamentals

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Yahya Khaled, technical director at ATDI APAC, gives us his insights on the challenges in radio network planning and modelling an evolving technology.

FRMCS is an emerging next-generation standard set to replace GSM-R. Based on 5G technology, it promises to deliver high data rates, low latency, and network-slicing capabilities. FRMCS supports critical railway communication services including real-time control, safety-critical applications, high-definition video surveillance, and more.

With migration underway, many questions remain unanswered about the potential challenges facing network operators. With rail networks operating numerous communications systems across the country and over international borders, managing seamless communications and data exchanges can present significant challenges.

FRMCS standardisation is expected to be finalised in the next few years. What frequency bands will FRMCS use?

Yahya Khaled.

In September 2021, the European Commission announced the harmonised use of the paired frequency bands 874.4-880.0 MHz and 919.4-925.0 MHz and the unpaired frequency band 1,900-1,910 MHz for FRMCS in Europe. Consideration to share the 5GHz frequency band (5,875-5,925 MHz) for Urban Rail and ITS TC RT is also in progress.

Legacy networks and FRMCS will need to coexist during network migration. What issues might this present?

The migration to FRMCS underscores the vital role of interoperability, as legacy radio systems may not align with FRMCS. The complexities vary based on the chosen frequency band, especially the reverse bands that heighten uplink and downlink interference risks. To mitigate this, superior equipment and custom filters may be necessary, tailored to each country’s spectrum allocation. Reflecting on GSM-R’s extended band introduction, meticulous planning makes RF interference manageable.

RF planners may reinstate minimum separation distances or other mitigations, particularly near the proposed FRMCS frequency band, ensuring a successful transition while upholding railway communication reliability.

What challenges can we expect from FRMCS in terms of coverage? How will environmental conditions affect this?

FRMCS promises seamless communications and data exchanges across networks, contingent on diligent planning and execution. Achieving a comprehensive network coverage that encompasses remote and rural areas is a pivotal aspect of this technology. The effectiveness of 5G versus GSM-R in terms of coverage hinges on frequency band selection and is governed by the laws of physics. Higher frequency bands offer superior antenna gain and directivity, favourable for rail-type communications.

While designers adeptly tackle terrain challenges, they often overlook the impact of man-made structures like railway stations and bridges. Addressing these concerns necessitates high-resolution modelling and a 3D GIS dataset empowered by a deterministic propagation engine.

FRMCS promises improved data transfer rates for video and other railway data. How will FRMCS deliver sufficient capacity to manage the growing demands for data transmission?

FRMCS offers high data transmission capacity, enhancing rail operations control and enabling technologies like autonomous trains. 5G’s advantages include traffic prioritisation and flexibility, lower RTT delays, and robust communications. However, planning should consider sector loading, traffic type, and achievable Signal to Interference & Noise Ratio (SINR) for upload and download, especially for surveillance cameras that faced challenges in LTE. Proper modelling and realistic expectations are essential for FRMCS deployments.

Beamforming is a game-changer in 5G. How will this benefit the rail environment? 

Beamforming might not offer significant benefits for most FRMCS rail network deployments. Coverage along the rail corridor can be achieved with highly directive sectors, often static, with overlapping beams for multiple data streams. While 5G’s multi-spatial focus is used, it’s not impossible that we’ll encounter 8T8R port antennas with a single radiation beam.

ATDI is hosting a webinar on the Fundamentals of RF planning for FRMCS on 24 October at 10am CEST. To learn more, register today.

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