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It took five years until Deutsche Bahn (German railways) upgraded all their 800 intrain repeaters to support EGSM and GSM1800 which was completed only last year. But they still lack UMTS support (which perhaps would make little sense on the 2100 MHz band as there's little coverage along most high speed tracks).

Against this background I doubt Deutsche Bahn will soon install LTE-capable repeaters unless operators pay for the upgrade. But even then intrain coverage means competition to Deutsche Bahn's intrain WiFi service called "Railnet", which may result in an opposing attitude towards such ideas.

Besides the question of economics I wonder what the best solution would be from a technical point of view. Wouldn't it perhaps be better if there was a single wireless backhaul and all the operators ran femto cells in the waggons instead of running repeaters?

Interestingly Deutsche Telekom still owns a large chunk of the former C-Netz spectrum (451.30 – 465.74 MHz) which they soley use to provide a wireless backhaul to Deutsche Bahn's "Railnet" by a radio technology called Flash-OFDM whose spectral efficency is obviously subpar (delivers up to 5.1 MBit/s downlink and 1.8 MBit/s uplink). Couldn't one make better use of this spectrum? Unfortunately there seems to be no frequency band specified for LTE in this frequency range but I expect LTE could multiply capacity and would be less prone to high speeds than Flash-OFDM. With the increased capacity they could offer faster WiFi and/or connect UMTS/LTE femto cells to the core network.

Some further reading (in German):

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