Providing continuous connectivity to in-motion networks only with

Providing continuous connectivity to in-motion networks only with WiFi devices

Providing continuous connectivity to in-motionnetworks only with WiFi devices

Spiderman Handover and the High-Frequency Handover Problemin Homogeneous Wireless Networks

Juan-Carlos Maureira1 and Olivier Dalle1

1Join team MASCOTTE, I3S( CNRS-UNS)INRIA - Sophia Antipolis

Nov, 12th, 2009 / Web Seminar UNSA

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Outline

1 Problem

2 Proposed Solution

3 The High-Frequency Handover Problem and the SpidermanHandover

4 Better Approach to Mobile Ad-hoc Networking : B.A.T.M.A.N.

5 On-Going work and Perspectives

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Problem

Outline

1 Problem

2 Proposed Solution




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Problem

In-motion wireless networks

In-Motion wireless Networks

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Networked Devices inside the train

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Problem

Requirements

Requirements

Continuous connection to external networks

No packet loss when handover from one cell to anotherLow delay to infrastructure network (backbone)

Scalable

Large AP topologiesProper QoS for all in-motion clientsSupport speeds up-to 250 Km/h

Fault Tolerance

Access Point/Base Station FailureDeath routes

Easy to Deploy/Manage/Maintain

Small cell coverage⇒ large number of APsHigh failure ratio⇒ easy to repair

Low cost of implementation

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Problem

Requirements

Requirements

Continuous connection to external networksNo packet loss when handover from one cell to another

Low delay to infrastructure network (backbone)

Scalable


Fault Tolerance





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Problem

Requirements

Requirements

Continuous connection to external networksNo packet loss when handover from one cell to anotherLow delay to infrastructure network (backbone)

Scalable


Fault Tolerance





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Problem

Requirements

Requirements


ScalableLarge AP topologies

Proper QoS for all in-motion clientsSupport speeds up-to 250 Km/h

Fault Tolerance





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Problem

Requirements

Requirements


ScalableLarge AP topologiesProper QoS for all in-motion clients

Support speeds up-to 250 Km/h

Fault Tolerance





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Problem

Requirements

Requirements


ScalableLarge AP topologiesProper QoS for all in-motion clientsSupport speeds up-to 250 Km/h

Fault Tolerance





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Problem

Requirements

Requirements



Fault ToleranceAccess Point/Base Station Failure

Death routes




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Problem

Requirements

Requirements



Fault ToleranceAccess Point/Base Station FailureDeath routes




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Problem

Requirements

Requirements




Easy to Deploy/Manage/MaintainSmall cell coverage⇒ large number of APs

High failure ratio⇒ easy to repair


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Problem

Requirements

Requirements




Easy to Deploy/Manage/MaintainSmall cell coverage⇒ large number of APsHigh failure ratio⇒ easy to repair


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Problem

Requirements

Requirements




Easy to Deploy/Manage/MaintainSmall cell coverage⇒ large number of APsHigh failure ratio⇒ easy to repair


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Problem

Problems Outline

Problems Outline

Low cost implementation⇒ Small cells are cheap (WiFi)

Two Problems:

Handover Problem : Jump from one AP to the other without losspacketsManage a large AP topology in the backbone network

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Problem

Problems Outline

Problems Outline

Low cost implementation⇒ Small cells are cheap (WiFi)Two Problems:


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Problem

Problems Outline

Problems Outline


Handover Problem : Jump from one AP to the other without losspackets

Manage a large AP topology in the backbone network

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Problem

Problems Outline

Problems Outline



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Problem

Problems Outline

Problems Outline



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Proposed Solution

Outline

1 Problem

2 Proposed Solution




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Proposed Solution

Spiderman and B.A.T.M.A.N

Spiderman and B.A.T.M.A.NSuperheroes to the rescue

Handover Problem⇒ Spiderman Handover

Backbone Network⇒ B.A.T.M.A.N

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Proposed Solution





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Proposed Solution





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Proposed Solution





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Proposed Solution


Proposed Architecture

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Proposed Solution



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Proposed Solution



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Proposed Solution



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Proposed Solution



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Proposed Solution


Spiderman and B.A.T.M.A.NSolution’s Keys

Key Elements

Dual IEEE802.11b/g/n radio gateway device (Spiderman Device)

Wireless Switch Access Point (a modified version of an AP) toaccess the backbone network

New handover algorithm (exploit the dual radio hardware)focused on high-frequency handover

Backbone mesh routing protocol focused on linear topologies

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Proposed Solution



Key Elements





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Proposed Solution



Key Elements





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Proposed Solution



Key Elements





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The High-Frequency Handover Problem and the Spiderman Handover

Outline

1 Problem

2 Proposed Solution




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The High-Frequency Handover Problem

The High-Frequency Handover ProblemA Cocktail of High Speed and Small Cell Coverage

tc = coverage(i)v

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tc = coverage(i)v

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tc = coverage(i)v

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th = ts + ta

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th = ts + ta

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th = ts + ta13/44





Experimentally :

ts ≈ 2 seconds when scanning all the IEEE 802.11 channels

ta ≈ 1 seconds from the cell border

th ≈ 3 seconds

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Experimentally :



th ≈ 3 seconds

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Experimentally :



th ≈ 3 seconds

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Experimentally :



th ≈ 3 seconds

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Buffer while performing handover

tq ≈Qmax

(renq− rdeq)⇒ tq > 0→ Qsize ↑

tq < 0→ Qsize ↓Qsize = Qmax ⇒ Taildrop

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tq ≈Qmax

(renq− rdeq)

⇒ tq > 0→ Qsize ↑


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tq ≈Qmax



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tq ≈Qmax


tq < 0→ Qsize ↓

Qsize = Qmax ⇒ Taildrop

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tq ≈Qmax



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Without buffering when handover:

With buffering when handover:

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Without buffering when handover:

With buffering when handover:

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Consequences of Handover with buffer

Taildrop (packet losses when queue becomes full) at WirelessStations (STA)

Access Points Give up packets when STA exits from AP(i) andenters to AP(i+1)

⇓Break before Make HandoverBreak the connection with AP(i) before to make the connection with

AP(i+1)

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Consequences of Handover with buffer

Taildrop (packet losses when queue becomes full) at WirelessStations (STA)

Access Points Give up packets when STA exits from AP(i) andenters to AP(i+1)

⇓Break before Make HandoverBreak the connection with AP(i) before to make the connection with

AP(i+1)

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Make before break handover at high-speed mobility:

v =coverage(i)

tc

⇒ tc =coverage(i)

v⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec

IEEE 802.11 RadiosTx Power = 100 mWcoverage(i) = 150mLine-of-Sight

v = 250km/h

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v =coverage(i)

tc⇒ tc =

coverage(i)v

⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec


v = 250km/h

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v =coverage(i)

tc⇒ tc =

coverage(i)v

⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec


v = 250km/h

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v =coverage(i)

tc⇒ tc =

coverage(i)v

⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec


v = 250km/h

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v =coverage(i)

tc⇒ tc =

coverage(i)v

⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec


v = 250km/h

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v =coverage(i)

tc⇒ tc =

coverage(i)v

⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec


v = 250km/h

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v =coverage(i)

tc⇒ tc =

coverage(i)v

⇒

tc =150m

v

tc =150m

250km/h

tc = 2.16sec


v = 250km/h

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tc =coverage(i)

v⇒ tc = 2.13sec

tq =Qsize

(renq− rdeq)⇒ tq =

20∗Psize

Txrate

tq =20∗1518bytes

1Mbps

tq = 0.23sec

Psize = 1518 bytesBasic Tx Rate =1Mbps

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tc =coverage(i)

v⇒ tc = 2.13sec

tq =Qsize

(renq− rdeq)⇒

tq =20∗Psize

Txrate

tq =20∗1518bytes

1Mbps

tq = 0.23sec


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tc =coverage(i)

v⇒ tc = 2.13sec

tq =Qsize


20∗Psize

Txrate

tq =20∗1518bytes

1Mbps

tq = 0.23sec


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tc =coverage(i)

v⇒ tc = 2.13sec

tq =Qsize


20∗Psize

Txrate

tq =20∗1518bytes

1Mbps

tq = 0.23sec


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tc =coverage(i)

v⇒ tc = 2.13sec

tq =Qsize


20∗Psize

Txrate

tq =20∗1518bytes

1Mbps

tq = 0.23sec


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Operational Time : to = tc− ta− tq

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Operational Time : to = tc− ta− tq

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For a mobile speed of 250 km/h, the operational time within a smallcell:

to = tc− ta− tq ⇒ tc = 2.16sec, ta = 1sec, tq = 0.23sec

to = 2.16−1−0.23

to = 0.93sec

to = tc︸︷︷︸coverage(i)

v

− ta− tq︸︷︷︸C

to =coverage(i)

v−C

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to = 2.16−1−0.23

to = 0.93sec


v

− ta− tq︸︷︷︸C

to =coverage(i)

v−C

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to = 2.16−1−0.23

to = 0.93sec


v

− ta− tq︸︷︷︸C

to =coverage(i)

v−C

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to = 2.16−1−0.23

to = 0.93sec


v

− ta− tq︸︷︷︸C

to =coverage(i)

v−C

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Operational Time versus Speedto = coverage(i)

v −C

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Frequency of Handover at High-Speed in Large Scenarios

Figure: Marseille - Nice Railway : 200km long, 1700 APs, Trip time 2 Hours

frequency of handover = 17004800 = 0.35 APs

sec23/44





Frequency of Handover at High-Speed in Large Scenarios

Figure: Marseille - Nice Railway : 1700 APs, Trip time 2 Hours

frequency of handover = 17004800 = 0.35 APs

sec24/44

≈ 1 AP each 3 seconds!!!




Spiderman Device and Spiderman Handover AlgorithmThe Spiderman Device

Spiderman Device

Dual radio IEEE 802.11 Bridge Device with handover capabilities.

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Spiderman Device and Spiderman Handover AlgorithmThe Wireless Switch Access Point

Wireless Switch Access Point

IEEE 802.11 Access Point that handles STA associations as L2switched ports. It learns the MAC Addresses (clients behind theSpiderman Device) that are known on each port (association) andswitch packets according between ports according the MACaddress tables.

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Spiderman Device and Spiderman Handover AlgorithmThe Spiderman Handover Algorithm

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The Gratuitous ARP Loop

Algorithm that ensures the Layer 2 route propagation across theinfrastructure network.

Spiderman Device keep the ARP entries of each in-motion client(ARP Cache)

Once associated (with the passive radio) it dumps GratuitousARP Bursts at regular time intervals

Check the ARP burst return through the active radio

ARPs didn’t received are sent again in the next burst.

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Spiderman Device and Spiderman Handover AlgorithmSome Results

Queue Size in APs with Break before Make Handover

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Queue Size in APs with Spiderman Handover

S i m u l a t i o n T i m e ( s e c )

2 0 2 2 2 4 2 6 2 8

Qu

eu

e S

ize

0

2

4

6

8

1 0

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Gratuitous ARP loop delays

0

50

100

150

200

250

300

100 200 300 400 500 600 700 800 900 1000 1100

Hos

ts

Time (ms)

Gratuitous ARP delays in the Spiderman Loop

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RTT Ping delay from the in-motion network to the infrastructure

10 20

30 40

50 60

70 0 20

40 60

80 100

120 140

160

0 0.02 0.04 0.06 0.08 0.1

0.12 0.14

Pin

g R

TT

(se

c)

Speed

Simulation Time (sec)

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RTT Ping delay from the in-motion network to the infrastructure

10 20

30 40

50 60

70 0 20

40 60

80 100

120 140

160

0 0.02 0.04 0.06 0.08 0.1

0.12 0.14

Pin

g R

TT

(se

c)

Speed

Simulation Time (sec)

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Better Approach to Mobile Ad-hoc Networking : B.A.T.M.A.N.

Outline

1 Problem

2 Proposed Solution




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B.A.T.M.A.N.

Better Approach to Mobile Ad-hoc Networking : B.A.T.M.A.N.The Backbone Mesh Network

Nice - Marseille Railway

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B.A.T.M.A.N.


Nice - Marseille Railway - 1700 APs

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B.A.T.M.A.N.


Nice - Marseille Railway Section

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B.A.T.M.A.N.


Nice - Marseille Railway Section Zoom

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B.A.T.M.A.N.

Proposed Backbone Mesh Network Topology

Access Points Line (line n0)First Backbone Line (line n1)Second Backbone Line - Shortcut - (line n2). . .i th Backbone Line - Shortcut - (line ni , i = 1..(n + 1))

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B.A.T.M.A.N.

Proposed Backbone Mesh Network TopologyMesh Node

Dual IEEE802.11aDirectional Radio Links(Mesh network)

One IEEE802.11b/g/nfor the Wireless SwitchAccess Point

One Ethernet Port toUplink with backbone(line) nodes

Internal Switch Fabricto switch packetsamong all theseinterfaces

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B.A.T.M.A.N.

Mesh Routing ProtocolWhich one?

Optimized link state routing protocol - OLSR (RFC-3626)IP routing Protocol - Discarded

Ad hoc On Demand Distance Vector - AODV (RFC-3561)Reactive Protocol (Routes on Demand)The Connection setup delay is low - DiscardedIntermediary nodes may lead to inconsistent routes if theSeq.Num is too old.Periodic Beacons uses bandwidth

Better Approach to Mobile Ad-hoc Networking - BATMANProactive Protocol (Routes set in advance)Has the notion of “Direction”. Nodes only has the next hopaddressSlow in convergenceBi-directional / multi-interface support - Approved

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B.A.T.M.A.N.

Mesh Routing ProtocolBetter Approach to Mobile Ad-hoc Networking: B.A.T.M.A.N.

Direction of the link (forward or backward)

Uplinks with superior mesh lines (gateways)

Hello protocol to detect link failures

Multiple routes to reach one gateway

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B.A.T.M.A.N.






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B.A.T.M.A.N.






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B.A.T.M.A.N.

Mesh Routing ProtocolFailure Tolerance

Directional radios covering 2 or 3 nodes ahead

Bootstrap protocol to build topology

Hello protocol to change next hop route when anode fails (Link A→B fails)

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B.A.T.M.A.N.

Mesh Routing ProtocolFailure Tolerance

Directional radios covering 2 or 3 nodes ahead

Bootstrap protocol to build topology

Hello protocol to change next hop route when anode fails (Link A→B fails)

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B.A.T.M.A.N.

Proposed Backbone Mesh Network TopologyDelay Bound to Reach Gateways

Between two contiguous nodes:

delayi→(i+1) = delayforwarding + delaytransmission︸︷︷︸∆

(1)

Forwarding delay depends on the network technologyTransmission delay includes media access delay andretransmissions delay

Between node i to the node i + n

delayi→(i+n) =n

∑j=i

∆j→(j+1) (2)

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B.A.T.M.A.N.


for n and k fixed:

delayi→G =mn

∆1 +km

∆2 (3)

Minimun Delay

How many nodes must the second line have to minimize the delay?

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B.A.T.M.A.N.


for n and k fixed:

delayi→G =mn

∆1 +km

∆2 (3)

Minimun Delay


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B.A.T.M.A.N.


for n and k fixed:

delayi→G =mn

∆1 +km

∆2 (3)

Minimun Delay


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B.A.T.M.A.N.


for n and k fixed:delayi→G =

nm

∆1 +mk

∆2 (4)

∂

∂mdelayi→G =

√kn∆1

∆2(5)

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B.A.T.M.A.N.


Delay to reach G from the line 1∆1 = 500ns,∆2 = 50ns, n = 1700, k = 30

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

0 500 1000 1500 2000 2500 3000 3500 4000

de

lay

(ns)

Nodes in Line 2 (m)

Delay

m = 714

m = 714.142843 40/44


On-Going work and Perspectives

Outline

1 Problem

2 Proposed Solution




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On-Going work

On-Going Work

Extend mesh delay results to n lines

Match experimental results on gratuitous ARP loop withsimulated resultsKeep studding scenarios to validate the spiderman handover

Urban scenario (high interference)Rural scenario (low inter fence)Tunnel scenario (metro)

Verification of the infrastructure network by means of simulationDelay boundary in several configurationsSystem reaction in front of a high failure ratio of nodes

Try to test it in a real test-bed (who can borrow me a train?)

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On-Going work

Perspectives

Use MIMO phy to increment the uplink bandwidth between themobile and the infrastructureApplications

To have Internet on metro (subway) to use your PDA to read thejournalsCollaborative work when you are travelling in a inter-city tripIn-Route information for cars in highways

Traffic informationAccidentsCheap on-line GPS cartography

VoIP on trainsLive video streaming (Surveillance). . .

Show an attractive cost in maintenance

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Summary

Summary

An architecture to provide connectivity to in-motion networks in ahigh-frequency handover scenario with a reasonable (to bedemonstrated) cost in operation and maintenance

Key contributionsSpiderman DeviceWireless Switch Access PointSpiderman Handover AlgorithmGratuitous ARP Loop for Route UpdatesLinear Mesh Topology Protocol (Based on BATMAN)

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Documents

Providing continuous connectivity to in-motion networks only with