ELEC-E7120 – Wireless Systems

Cellular coverage problem in the metro of Helsinki

Jere Kaiku (295178)

Aapo Poutanen (78999u)

Theodosis Makris (465658)

Agrasagar Bhattacharyya (463964)

Observation and Hypothesis

Coverage problem in the metro of Helsinki

• Sudden change in signal strength from very good to very bad in certain areas(especially in tunnels).

• When metro trolley starts moving, a huge drop in experienced in QoS can be noted.

• Few second connection drops when reaching the end of WLAN range and phone switches to cellular data.

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Measurement champaign

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Graph of the measurements from Ruoholahti to Kulosaari and back

15:40-15:42 at Ruoholahti15:44 at Kamppi15:45 at Railwaystation15:46 at University of Helsinki15:48 at Hakaniemi15:50 at Sörnäinen15:52 at Kalasatama15:54 at Kulosaari15:57 at Kalasatama15:59 at Sörnäinen16:01 at Hakaniemi16:03 at University of Helsinki16:05 at Railwaystation16:07 at Kamppi16:09-> at Ruoholahti

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Measurements with 1 sec interval from Ruoholahti to Railway station and back

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09:42-09:45 at Ruoholahti09:47 at Kamppi09:48-09:55 at Railwaystation09:56 at Kamppi09:59 at Ruoholahti

Closer look at the strangeness in the tunnel

Very short handovers, and finally stuck at very low signal

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Analysis 1

Bad coverage in certain areas along the train lines

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Solution 1

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High power eNB

Analysis 2

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The signal gets affected in tunnels

Large penetration loss due to the shield of the train

Solution 2

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Analysis 3

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The network faces reduced handover success rate and increased power consumptions of UEs

Handover cases

Frequent handover Too late handover

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A B A B

Solution 3 – Mobile Relay Nodes

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Backhaul MRNPredictor Antenna

THE END

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