Study of Network Coding for Multi-antenna
Switched Links-based Vehicle-to-Vehicle (V2V)
Communications
Wai Chen1, Ratul Guha1, Jasmine Chennikara-Varghese1, Rama Vuyyuru2,
Junichiro Fukuyama2
1Telcordia
Technologies
2Toyota InfoTechnology Center
March 2-3, 2011
1
Motivation
 DSRC / WAVE based networks:
 Contention-based media access
protocol
 Omni-directional antenna
 Complex to achieve reliable V2V
communications
Contention
Collision (multicasting/broadcasting)
 Radio and antenna technologies continue
to advance
L2
 60 GHZ radio, millimeter wave
B1
 Costs expected to drop
 => Switched-Links based Architecture
The Fully Networked Car
Geneva, 2-3 March 2011
L1
F1
R2
2
R1
Radio Interface Characteristics
L2
L1
B1
 Designation of radio interface
 Naming based on positions:




F1
R2
R1
Front: F1, F2,..
Left-side (driver): L1, L2,…
Right-side (passenger): R1, R2,…
Back: B1, B2,…
 Each vehicle has N antennas which can provide directional links.
 Each radio has the capability to detect and form a directional
link with another radio in the range.
 Each directional link is one-way; a bi-directional (full duplex)
link needs two directional (one-way) links.
 Radios communicate status through periodic beacons.
The Fully Networked Car
Geneva, 2-3 March 2011
3
Neighborhood Broadcasting
o Information sent to all vehicles and vehicles pick-up as
desired
o Support broadcasting, multicasting, and unicasting
• Broadcasting: use directional links to forward
messages – e.g., along a direction; all vehicles in
the neighborhood can receive the messages;
— Dissemination scope is enforced (e.g., stop at
maximum hop count)
• Multicasting/unicasting: use neighborhood
broadcasting to forward messages (all neighbors
hear the messages), but only multicast (or
unicast) members actually pick up the messages.
The Fully Networked Car
Geneva, 2-3 March 2011
4
Neighborhood Broadcasting – No Mesh
o Each vehicle passes each packet,
once, to each of its immediatelylinked neighbors
• Each vehicle drops duplicate
packets
• Dissemination scope is enforced
(e.g., stop at maximum hop count)
Packet OUT
L2
L1
Packet IN
B1
F1
Packet OUT
Packet OUT
R2
R1
Packet OUTPacket OUT
No mesh
The Fully Networked Car
Geneva, 2-3 March 2011
5
Network Coding
Input and Output
•
In the exemplary diagram below, packets A and B are received at the vehicle. The output is
obtained as a map from incoming packets A and B.
• For example, the mapping mi can be a linear combination with random coefficients
selected from a finite field.
Packet OUT “1A+1B ”
Packet IN
“A”
Packet OUT “2A+2B ”
Packet IN
“B”
•
Packet OUT “3A+3B ”
Diversified packet out: m(A,B)= A+B where coefficients  and  are randomly
chosen from a finite field. Each outgoing link transmits a different packet.
The Fully Networked Car
Geneva, 2-3 March 2011
6
Network Coding Scenario
o
High-bandwidth applications need to run in
the presence of other traffic in the network.
• As such the available capacity may be lower
than the requirements of the high-bandwidth
application
o
o
In the scenario, a single source sends highbandwidth traffic.
Node 1 in the leading edge of the road
segment broadcasts packets at 4.3 Mbps for
20 seconds
• The capacity of each link is 2 Mbps
o
We measure the performance at the other
vehicles on the roadway with and without
network coding (no-mesh approach).
• Two layouts are shown on the right
The Fully Networked Car
Geneva, 2-3 March 2011
7
23
25
24
12
13
14
1
2
3
Vehicles in road segment =9
3-Lanes
56
57
58
59
60
61
45
46
47
48
49
50
34
35
36
37
38
39
25
26
27
28
23
24
12
13
14
15
16
17
1
2
3
4
5
6
Vehicles in road segment =36
6-lanes
Network Coding Scenario
Simulation Parameters
Application
Parameter
Simulation
Parameter
Value
Simulation Time
60 seconds
Link Bandwidth
2 Mbps
4.3 Mbps
Radio Range
Switched-link
Wired
2000 Bytes
Number of
vehicles
9,36
Road length
300 meters
Number of
vehicles per lane
3, 6
Lane width
3 meters
Number of lanes
3,6
Number of
sources
1
Application
Rate
Packet Size
Packet
5 seconds
generation start
time
Packet
generation end
time
Value
25 seconds
 In the subsequent charts “no coding” denotes the performance of switched link system with no-mesh
 “Coding” refers to the performance of the switched link system with no-mesh in the presence of network
coding
The Fully Networked Car
Geneva, 2-3 March 2011
8
Network Coding
3-lane case with 9 vehicles
23
24
25
12
13
14
1
2
3
Receiving Rate
4
2.5
2.5
Mbps
Mbps
12
13
14
1
2
3
no coding
coding
3.5
3
2
1.5
2
1.5
1
1
0.5
0.5
0
2
3
12
13
14
23
24
0
25
2
3
Vehicle ID
o
25
4
3
o
24
Receiving Rate
no coding
coding
3.5
23
13
14
23
24
25
Vehicle ID
Vehicles in shaded area ( on a diagonal path
from source) are able to leverage the
benefits from coding
PDR for coding and no coding is 100%
The Fully Networked Car
Geneva, 2-3 March 2011
12
o
o
o
9
Based on link selection, specific nodes
benefit from coding
All nodes have 100% PDR
Node 24 benefits from coding
Network Coding With Link Selection
3-lane case with 9 vehicles
23
24
25
23
24
25
12
13
14
12
13
14
1
2
3
1
2
3
Receiving Rate
Receiving Rate
4
3.5
3
3
2.5
2.5
2
2
1.5
1.5
1
1
0.5
0.5
0
0
2
3
12
13
14
23
24
no coding
coding
3.5
Mbps
Mbps
4
no coding
coding
2
25
3
o
o
o
We can select node to benefit from coding
All nodes have 100% PDR
Node 24 benefits from coding
The Fully Networked Car
Geneva, 2-3 March 2011
13
14
23
24
Vehicle ID
Vehicle ID
o
12
o
10
All nodes have 100% PDR
Node 25 benefits from coding
25
Network Coding with Link Selection
3-lane case with 9 vehicles
23
24
25
12
13
14
1
2
3
o
o
Using unidirectional links increases benefits at
unicast destinations
Only target nodes have 100% PDR with coding
Receiving Rate
4
no coding
coding
3.5
3
Mbps
2.5
2
1.5
1
0.5
0
2
3
12
13
14
Vehicle ID
The Fully Networked Car
Geneva, 2-3 March 2011
11
23
24
25
Network Coding
6-lane case with 36 vehicles
o
56
57
58
59
60
61
45
46
47
48
49
50
34
35
36
37
38
39
25
26
27
28
13
14
15
16
17
2
3
4
5
6
23
12
1
24
o
o
Vehicles on specific paths from the source are
able to leverage the benefits from coding
The benefit decreases for vehicles farther away
on the diagonal path
PDR for coding and no coding is 100%
Receiving Rate
4
no coding
3.5
coding
3
Mbps
2.5
2
1.5
1
0.5
0
2
3
4
5
6 12 13 14 15 16 17 23 24 25 26 27 28 34 35 36 37 38 39 45 46 47 48 49 50 56 57 58 59 60 61
The Fully Networked Car
Geneva, 2-3 March 2011
Vehicle ID
12
Summary
o A novel architecture has been proposed to support
multiple directional radios
• The architecture provides a setup to enable highthroughput and low-overhead communications.
o The architecture supports efficient dissemination of
messages among roadway vehicles
• 100% PDR
• Low Delay
o Network coding over well-defined switched links enhances
network performance
• Link selection can be used to benefit certain nodes.
The Fully Networked Car
Geneva, 2-3 March 2011
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