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!