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Giornata di studio sui White Spaces, che si è tenuta lunedì 24 ottobre 2011, 9.30 - 17.00 – Sala Agorà, Incubatore d’Imprese Innovative del Politecnico di Torino (I3P).
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La Sperimentazione White Spaces in Piemonte Applicazioni per Reti Veicolari
Claudio Casetti Dipartimento di Elettronica Politecnico di Torino
Goals
¤ ITS (Intelligent Transportation Systems) environment
¤ Design a roadside downloading application for vehicles with prefetching of content
¤ Exploit long-range UHF coverage for signalling traffic (vehicle position, content requests)
¤ Exploit short-range, high-bandwidth 5GHz links for content downloading
Starting Point
¤ VICSUM project ¤ funded by Regione Piemonte in 2007-09
¤ partners: Politecnico di Torino, CSP, CRF
¤ The VICSUM legacy ¤ Hand-on expertise in VANETs
¤ Designing mobile applications
¤ Living testbeds (Villa Gualino)
¤ The “VICSUM cars”
Network Architecture
¤ Infrastructure ¤ Central Controller (CC)
¤ Roadside Units (RSU)
¤ Long-Range Unit (LRU)
¤ Vehicle On-Board Units (OBU)
RSU1 RSU2
Network Architecture
¤ Control Plane ¤ Common channel shared by CC (though LRU) and Vehicle
OBUs (700 MHz)
¤ High-bit rate communication on point-to-point link between CC and RSU
¤ User Plane ¤ RSU to vehicles OBU communication (5 GHz)
The LFT Protocol
¤ We designed and implemented a communication protocol called Locate-Fetch-Transfer (LFT)
¤ LFT operates among RSUs, CC and OBUs
¤ LFT incorporates control and user plane
LFT Protocol Overview (1)
¤ Vehicle notifies to CC over 700 MHz link:
¤ own position
¤ content requests
¤ CC fetches requested content and dispatches it to the nearest RSU
¤ Vehicle associates to RSU and downloads as much as possible
RSU1 RSU2
LFT Protocol Overview (2)
¤ When moving out of RSU coverage, the download stops
¤ RSU reports the outcome of the download
¤ If incomplete, the CC schedules the download to continue at the next RSU
¤ Remaining file is dispatched to the next RSU
RSU1 RSU2
The Test
¤ The OBU requests the download of a 200-MB file
¤ The download is completed over several “contacts” with RSUs
¤ We measured ¤ the number of contacts to complete the transfer
¤ the coverage time
¤ the achieved throughput
The Test
¤ Preliminary tests at Villa Gualino (Torino) ¤ Signalling traffic on a 2.4-GHz (802.11b) channel
¤ Data channel on a 5-GHz (802.11a) channel
¤ Final tests in Val di Viù
Val di Viù Testbed
Results
0
5
10
15
20
25
0 100 200 300 400 500 600 700
Thro
ughp
ut [M
bps]
Time [s]
vehicle request and vehicle configurationvehicle configuration
0
5
10
15
20
25
0 200 400 600 800 1000 1200
Thro
ughp
ut [M
bps]
Time [s]
vehicle request and vehicle configurationvehicle configuration
20 km/h 40 km/h
Comparison with simple transfer
Access Point AP1 AP2 AP2 AP1 AP1 AP2 AP2 AP1 AP1 AP2 # of downloaded chunks
from the CC 35000 35000 35000 35000 35000 35000 35000 35000 35000 17379 # of downloaded chunks 17890 22887 26080 21261 29190 19903 32574 27438 26555 17379
Coverage time [s] 38 40 48 46 35 36 40 38 39 21 Throughput [Mb/s] 3.68 3.77 5.37 3.75 6.41 3.45 7.81 5.8 5.39 4.52
Access Point AP1 AP2 AP2 AP1 AP1 AP2 AP2 # of downloaded chunks
from the CC 35000 35000 35000 35000 35000 35000 18494 # of downloaded chunks 32850 30430 24750 18686 12650 28950 18494
Coverage time [s] 39 32 41 48 33 31 20 Throughput [Mb/s] 8.33 9.4 5.97 3.85 3.79 9.23 9.14
Our protocol: 7 contacts needed to transfer content
Simple transfer: 10 contacts needed to transfer content
Conclusions
¤ LFT is not a Cognitive Radio application but could work with any CR system
¤ Sustained throughput comparable to ADSL speeds to mobile users
¤ Use of today’s technology
¤ Future work: lots of optimization to do!
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