1. Onboard communication
Frederik Vermeulen
(f.vermeulen@televic.com)
Televic NV

2. Mobility scenarios
Mobility scenarios
Legend:
E
D D F
B B B B
A A
C C C
Legend
A: personal WiFi device D: vehicle wireless connection point
B: on-board WiFi hotspot E: way-side wireless connection point
C: on-board services switch F: station WiFi hotspot

3. Mobility scenarios (1)
Mobility scenarios (1)
 User moving inside train
E
D
B B2 B3
1
A
C C C
E
D
B B2 B
1 3
A
C C C

4. Mobility scenarios (2)
 Train moving -> handover
E
D D F
B1 B2 B3 B
A A
C C C

5. Mobility scenarios (3)
 User leaving the train
D F D F
B B
A A

6. Tr@ins architecture
Train management
Internet
AAA NAT
Mobility
DHCP
Management
Mobility
Management
Local content
6

7. Onboard network
components
Train Train
Switch Switch
WiFi WiFi WiFi WiFi WiFi WiFi
BS BS BS BS BS BS
Mobility On-board server:
Management - voice/video communication,
passenger information, entertainment
- content server
- web, mail cache
- TCP accelerator
Wayside - crew authentication, gateway
link - train management (TCMS) interface
technologie
s

8. Onboard use cases
Seamless connectivity and Quality of Service for
- crew moving through the train
- passengers moving through the train
I. Moerman, B. Jooris, A. Schoutteet, F.Vermeulen
8

9. Applications on train
Applications
Passengers + Crew
• on-board content
• e-ticketing
(web/MM)
• maintenance, man
• email
• CCTV
• internet
• video/audio streaming
• VoIP

10. Two layer 2 handovers
 Vertical handovers when a crew terminal switches
between the wired and the wireless connection
WLAN
Satellite
G PR S
AP x A P-
A P- A P-
MAR A P-
A P- BS A P- BS BS A PP--
A
x OSS OSS OSS content
WL AN
Satellite
GP RS
AP x A P-
A P- A P-
MAR A P-
A P- BS A P- BS BS A PP--
A
x OSS OSS OSS content

11. Two layer 2 handovers
 Horizontal handover when a user is moving inside
the train
WLAN
Satellite
G PR S
AP x A P-
A P- A P-
MAR A P-
A P- BS A P- BS BS AAPP--
x OSS OSS OSS content
WL AN
Satellite
GP RS
A P- AP x
A P- A P- MAR A P-
A P- BS A P- BS BS AAPP--
x
OSS OSS OSS content

12. Connectivity requirements
Requirements
 bandwidth
 latency
(< 50 ms for voice)
 continuous connectivity
(=guaranteed <50ms latency at
handover)
available solutions 500 ms
 compatible with standards 802.3, 802.11

13. Vertical handover: wired-wireless
Convergence layer:
1 Device
Operating principle HS1 HS2 OK1 OK2 PS COL-
1 2 3 4 5 6 7 8 910 12
11
Switch
CONSOLE
 One virtual interface
ACT-
STA-
Gratuitous ARP
 One MAC and one IP address
ETH WLAN
MAC MAC
CL-MAC
Decision module
CL-IP
1 Interface

14. Horizontal handover
 Visualization of the horizontal handover
 MAP.html

15. Horizontal handover
 BS = AP + extra functionality
 Extra WLAN NIC (passive)
 listens to neighbor channel
 info per received Terminal
 the MAC address
 a flag passive/active
 list with the last received RSSIs
 time of the last received packet
 IP address
 IP address of the BS
 RSSI per neighbor
 Inter BS protocol
 Terminal info protocol
p. 15

16. Details: horizontal handover
 Vendor independent software package
Channel of the RSSI of
terminal terminal
measured on
the
serving BS
RSSI of terminal
measured on the
neighbor BSs,
with their
Sends beacons to the access channels
network every X ms

17. Demo setup
P
BS X
A
Asterisk Terminal
Switch
P P
A A
BS Z BS Y

18. Evaluation
• Sending 20Mb/s UDP with iPerf from server to
terminal
• Simulate motion → handoff every 15 seconds
• Average of 15 lost packets per handoff
• Lost packets ranged from 10 to 50 packets
• 30 of the 37 handoffs → less 14 lost packets
• Results in < 10ms disconnection time
Content SB ATT 4:1 2:1 Attenuation
BS A 1 Terminal
ATT 1-2
X
2 in SB ATT 3-4
P
ATT 5-6
BS A 3 Time
Y
P 4
BS A 5
Z
Switch P 6

19. Quality of Service onboard the train
BS
OSS
Provide QoS for Crew and Passenger
applications

20. QoS AP with dynamic mapping of
5 Access Classes to 4 Access Queues
AP / Crew node Public node
Access Queues: Access Access Queues:
• AQ_VO Classes:
• AQ_VI • Alarm • AQ_VO
• AQ_BE • Voice • AQ_VI
• AQ_BK • Video • AQ_BE
• AQ_BK
• Best Effort
•
EDCA parameters provided by QAP:
Background
CWmin[A CWmax[A AIFS[AC TXOP[A
AC
C] C] ] C]
Alarm 1 2 1 2048 ms
Voice 2 3 1 1504 ms
Video 3 4 2 3008 ms
Best
4 10 3 2048 ms
Effort
Backgrou
4 10 7 0
nd

21. QoS results: Public and Crew Video,
Downlink
Two Public video streams One Public and one Crew video
stream
100 100
90 90
80 80
% of Maximal Throughput
AC_VI
% of Maximal Throughput
70 70
60 60
AC_VI
50 50
40 40
30 30
20
AC_VI AC_VI AC_VI 20
AC_VI AC_BE AC_VI
10 10
0 0
1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171 181
Time (s) time (s)
Public Video Traffic Stream 1 Public Video Traffic Stream 2 Public Video Traffic Stream Crew Video Traffic Stream

22. Conclusions
 Onboard voice communication and
multimedia have strict requirements
 Fast handover: new mechanisms developed
 QoS: dynamic class mappings
 Layer 2 solutions for onboard network
 scope of onboard communication provider
 compatible with standard terminals

23. Q&A &
Demo