Tr@Ins6 Trackside Communication Herman Claus
Transcript of Tr@Ins6 Trackside Communication Herman Claus
Handover solution for Pico-Cells
Herman Claus – based on work from Tom Van
Leeuwen
Siemens, Nokia Siemens Networks, OTN
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Outline
The Project and The Company
Problem statement
Existing solutions
Radio over Fibre solution
WLAN Fast Handover
Supporting Hardware
Future evolution
The Project and the Company
During the project, the Siemens Herentals company
went through a lot of changes
At the start, Siemens Herentals (formerly Atea) formed the
Com Division of Siemens Belgium
Two departments were interested in this project
Siemens OTN department : world leader in track-side communication
for metro, also interested in trains etc.
IP-on-trains for TGV by Siemens Services department
The project received a GO with a dual goal
Build up and exchange knowledge about IP-on-trains
Good partners
Own knowledge from Services
Build up knowledge about communication with metro
Experimental technology for OTN
IBBT knowledge
The Project and the Company
During the project
Siemens Com carved out from Siemens
Nokia Transmission Systems carved out from Nokia
Both merged to form Nokia Siemens Networks
The Project and the Company
In Herentals
Siemens Com merged with Nokia Transmission Systems
Corporate R&D at Herentals (with the exception of OTN) was
spun off (160 developers) and sold to Devoteam
11 june 2008, after several months of negotiations, it was
announced that the OTN group wil carve out and is due to be
independend july 1st 2008 (GIMV -> see www.gimv.be for
press releases and other information)
All this had its impact on the project
But with the help of he IBBT the project could be finalised
This presentation : only the OTN part of the project is
described
IP-on-trains : contact Walter van Brussel, is explained in the
other WPs
Problem statement
Communication with metro
Tunnels
Communication with trains
No cheap global wireless coverage
Cost of bandwidth for wireless is high
Bandwitdh x surface should somehow be related to cost
So : use pico-cells
For moving vehicles : handover problem
The faster the more problematic
Same solution for use in tunnels
So there is a technological problem
Remark : there is also an economical one
Base stations are expensive, so picocells are, too.
Problem statement
Pico-cells are a problem Speed of access point is no problem for most technologies
But handover between cells is
Eg : WiFi : cell of 200 m diameter, speed 120 kmh,
handover every 6 seconds, bad conditions at the edge
Normally handover takes time
Problems with VPN connections etc
What is needed is Seamless handover mechanism
Handover invisible to end-device and to network
Part of the problem solved by other WPs Making handover invisible to end user and network
Same problem as eg satellite etc.
So : concentrate on handover mechanism
Existing solutions
IST projects FIFTH and MOWGLY
DVB-S2, DVB-RCS
IBBT project FAMOUS
WLAN for fast moving users
InterAccess Point protocol modification proposed
Several algorithms studied
Predicting future access point
Easily adaptable to trains and metro
Making handover mechanism faster
Eg SyncScan algorithm for optimising scanning
Existing solutions
On the level of fast context switching
Solutions available
Our project
Fast re-association of wireless connection
Be as standard as possible
Two solutions developed by IBBT / Ghent
Radio over fibre based solution
WLAN GAP filler solution
Radio over Fibre solution
Not part of the project
Idea : between antenna and electronics of the base
station there is a wire
With fibre this wire can span hughe distances
So :
make many antennae, place them widely apart
connect them to one set of electronics
Use overlapping frequencies
neither base station, neither moving access point is aware of
the fact that the moving access point is moving
Radio over Fibre solution
Some manipulation of datastreams required
See article feb 2007 IEEE Communications Magazine
Problem : economical : cost of antennae-base stations
WLAN Fast Handover
Handover problem : wireless layer problem When moving from one cell to another cell
Old cell : communication dies
New cell : communication starts up
Dying and starting under bad conditions (low power budget)
Uses lots of time because of robust modulation, broadcast messages etc : normal communication in cell disrupted
Idea :
Separate the handover from normal communication in the cell
Cell 1 uses channel1 : high speed encoding
Cell 2 uses channel2 : high speed encoding
Cell 1 and Cell 2 also support channel3
Channel3 is used for handover,
overlaps in space between cells
Uses soft handover
Low-speed robust encoding
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Fast Roaming WLAN Switch for Rail Systems
Fast Roaming
WLAN AP
Fast Roaming
WLAN AP
Fast Roaming
WLAN AP
Fast Roaming
WLAN AP
Radius
ServerGateway
Fast Roaming
WLAN Client
Data – 802.11a/g Control - 802.11h
WLAN Fast Handover
WLAN Fast Handover
Client
1 interface
802.11a/g data channel
802.11h control channel
Lightweight Access Points
2 interfaces
same dedicated handover frequency
limited functionality
handoff limited to change in WLAN channel
Switch
association, authentication and security
Handover
The GAP filler solution
The problem it solves
The system handles frequency handovers under good signal
conditions
The handover frequency of Channel3 guarantees low speed
but continuous operation of wireless link
The handover does not disrupt the high speed
communication
Association with channel1, channel2 and channel3 can be
done while no data is being transmitted over this paricular
interface
Hardware
OTN developed a generic supporting hardware
Ethernet layer based data transport
Supporting TDM separated IP channels over one fibre
Transparant to all higher layers
Central switch can ‘directly’ connect to access points
Controlled delay
All channels can be serviced individually
Hardware
Port10Port1 Port2 Port9
Ethernet programmable
Switch logic
Backplane
Logic 1
Segment 1
10Mbps
Backplane
Logic 2
Segment 2
25Mbps
Backplane
Logic 10
Segment 12
30Mbps
Backplane
Logic 9
Segment 11
10Mbps
User side
Hardware
FPGA
10/100Mbps 1
2
10
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10/100/1000Mbps
10/100/1000Mbps
11
12
10/100Mbps
10/100Mbps
10 * max. 196 Mbps
2 * max. 784 Mbps
Backplane
Maximum 12 segments
Maximum 784 Mbps
Front-end
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Future
Merging of several technolgies needed
Fast handover
Billing and access control
VPN structures
The job ain’t finished yet