2C04 DECUS IT-Symposium 2006 Andreas-Roos · Consideration of extended and novel security & privacy mechanisms Consideration Integration of Quality of Service (QoS) mechanisms Consideration

IT-Symposium 2006 17. Mai 2006

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DECUS IT-Symposium 2006 in Neuss – Andreas RoosPotentials and challenges of multi-hop networksMay 17th, 2006, slide 1

DECUS IT-Symposium 2006

Potentials and challenges of multi-hop networks considering as example ad hoc and mesh networks

Andreas Roos, Profn. Sabine Wieland, Michael Flegl

Düsseldorf/NeussMay 17th, 2006


ContentOverview

� Introduction to wireless multi-hop networks� Ad hoc networks

� Mesh networks

� Benefit of wireless multi-hop networks

� Routing mechanisms

� Application scenarios and existing solutions

� Standardisation activities

� Challenges

� Conclusions


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Wireless multi-hop networksWhat are wireless multi-hop networks?

� Wireless communication between nodes – no wired connectivity.

� Multipoint-to-multipoint communication.

� Communication among nodes.� Single-hop communication – always possible.

� Multi-hop communication – usage of suitable routing protocols.

� Each node contains routing functionalities.

� Self-organizing network structure.� Distributed intelligence – no centralized managing.

� Each node is responsible for routing and connection establishment.

� Dynamic network topology.� Each node can be source, router and destination.

� Technologies for setup multi-hop networks� E.g. Bluetooth, WLAN, WiMAX.

Node (Source)

Node (Destination)

Node


Wireless multi-hop networksClassification of multi-hop networks

There are different kinds of multi-hop networks with different characteristics and

applications:

� Mobile Ad hoc Networks (MANETs)

� Wireless Mesh Networks (WMNs)

� Sensor networks

Important differences between ad hoc, wireless mesh networks and sensor networks:

� Routing protocols

� Networks equipment

� Energy behaviour

� Mobility support


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InternetInternet

Wireless multi-hop networksAd hoc network – characteristics

Mobile Ad hoc networks (MANETs) – client mesh networks

� Spontaneous formed networks consisting of mobile and wireless devices, e.g.

laptops, PDAs or mobile phones.

� High mobility – mobile and wireless devices.

� Limited energy supply – usage of battery or rechargeable battery.

� No infrastructure equipment necessary, e.g. base station, access point.

� Limited bandwidth.

� Application scenarios� Mainly used for local communications – connectivity to external networks needs special

gateways.

Gateway


Wireless multi-hop networksMesh network – characteristics

Wireless Mesh Networks (WMNs) – Infrastructure mesh network

� Network consists of infrastructure components, e.g. base stations.

� Low mobility.

� “Unlimited” energy supply – power supply via mains supply.

� Application scenarios� Transport network with connection to external networks, e.g. Internet.

� Separates access network and backhaul network, e.g. user access via 802.11 b/g and backhaul

802.11a.

InternetInternet

Backhaul connection

Access connection

Access networkBackhaul network


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Wireless multi-hop networks General characteristics

� Dynamic network topology� Mobility of user devices (ad hoc network).

� Backbone scalability of access network (mesh network).

� Partitioning and merging of networks.

� Changing characteristics of wireless channel (fading).

� Asymmetric / unidirectional connectivity� Quality of connection among source and destination can be different.

� Security mechanisms are difficult to apply� Interception of wireless channel.

� In case of multi-hop routing packets are processed by intermediate nodes.

Consideration of extended and novel security & privacy mechanisms

Consideration Integration of Quality of Service (QoS) mechanisms

Consideration of multi-hop routing mechanisms


� Low infrastructure costs� Wiring is a cost intensive factor.

� Wiring each Internet access point is expensive.

� Cheap establishment of multi-hop networks, e.g. IEEE 802.11 equipment.

� Multi-hop networks can reduce the number of expensive Internet connections.

� Many multi-hop nodes share few Internet connections.

� Additional multi-hop nodes can be easy installed.

� Reliability and Robustness� Redundant paths within the multi-hop network.

� Low transmit power� Small distances between nodes.

� Energy efficient, min. interference and spatial reuse.

� Easy extensible� No wired installation necessary.

� Auto configuration of multi-hop nodes.

Benefits of multi-hop networks (part 1)Overview


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� Coverage extension of base stations� Intermediate nodes forward packets to the Gateway.

� Far users can be covered.

� Enhancement of network performance� Higher performance for far users

� Poor performance on direct link to the base station.

� Higher performance on short links.� Higher performance for nodes without LOS (Line of Sight)

� Poor direct link because of obstacles.

� Routing around obstacles.

Benefits of multi-hop networks (part 2)Overview


Routing in multi-hop networksClassification of routing protocols

Proactive Hybrid Reactive

•DSDVDSDVDSDVDSDV

•OLSROLSROLSROLSR

•STARSTARSTARSTAR

•TBRPF TBRPF TBRPF TBRPF

•WRPWRPWRPWRP

•…

•DSRDSRDSRDSR

•AODVAODVAODVAODV

• TORATORATORATORA

• SSRSSRSSRSSR

• …………

Multi-hop routing protocols

•ZRPZRPZRPZRP

•CBRPCBRPCBRPCBRP

•FSRFSRFSRFSR

•CEDARCEDARCEDARCEDAR

•…………

� Proactive: Routing information to all network nodes always available.

� Reactive: Routing information to destination established on demand.

� Hybrid: Combines advantages of proactive and reactive routing protocols.

AODV (Ad hoc On-Demand Distance Vector)

OLSR (Optimized Link State Routing)


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Routing in ad hoc networks (part 1)Considering as example AODV

RREQ

AODV (Ad hoc On-Demand Distance Vector) – part 1:

� Source (orange node) sends Route Request message (RREQ).

� RREQ message is broadcasted within the network (nodes).

� Destination (blue node) receives RREQ message.

Node (Source)

Node (Destination)

Node


RREP

AODV Route Discovery – part 2:

� Destination (blue node) sends Route Reply message (RREP) to source via unicast.

� RREP is send to source via shortest route.

Node (Source)

Node (Destination)

Node

Routing in ad hoc networks (part 2)Considering as example AODV


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Routing in mesh networks (part 1)Considering as example OLSR

Benefit of Multipoint Relaying within OLSR (Optimized Link State Routing)

� Reduce the number of duplicate retransmissions while forwarding a

broadcast packet.

� Restricts the set of nodes retransmitting a packet from all nodes to a

subset of all nodes.

Multipoint Relay (MPR) selection

� Each node selects and keeps its own set of Multipoint relays.

� Rule of OSLR:� For all 2 hop neighbors n there must exist a MPR m.

� So n can be contacted via m.

Forwarding of traffic

� All nodes registers and maintains their MPR selectors.

� Rule of OSLR:� If OLSR-packet is received from a MPR selector

� Then all messages contained in that packet are to be forwarded if TTL > 0.

m

m

n

n

n

n

m

m

n

n

n

nForwarded traffic


Routing in mesh networks (part 2)Considering as example OLSR

Distribution of link-state information

� Traditional link-state routing protocols flood the network with link-state information

(Regular flooding).

� OLSR optimises this behaviour – Multipoint Relay flooding (MPR flooding)� Only MPRs selectors are declared in link-state messages – minimises size of link-state messages.

� Only nodes selected as MPRs generate link-state messages – minimises amount of link-state

messages.

� All nodes select their own MPRs� Number of MPR subset depends on network topology.

Regular flooding MPR floodingNetwork structure


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Application scenarios of wireless multi-hop networksOverview

Ad hoc networks

� Civil applications� Spontaneous network forming (e.g. Conference, Meetings, Enterprises)

� Rescue missions in disaster areas (e.g. destroyed infrastructure)

� Sensor networks (e.g. observation and monitoring)

� Inter car communication (e.g. FleetNet)

� Personal Area Networks (e.g. mobile phone, camera, printer, laptop).

Mesh networks

� Civil applications� Broadband Internet access

� In-house networking

� Extensions of network structures, e.g. Hotspots, cellular networks.

Ad hoc & mesh networks

� Military application� Communication between mission troops (e.g. soldier, tank).


Application scenario for ad hoc networksInter car communication

� Car-to-Car Personal Communication � Entertainment, e.g. telephone call, short messaging, chat.

� Car-to-Car Traffic Safety Communication� Warnings, emergency call, traffic jam information, platoon etc..

� Car-to-Infrastructure Personal Communication� Data download via Hotspots, payment of multi-storey car park, Location Based Services etc..

� Car-to-Infrastructure Traffic Safety Communication� Communication with traffic lights, traffic signs or barriers, downloading of actual traffic

information or car diagnostics.

SourceSourceSourceSource: : : : www.carwww.carwww.carwww.car----totototo----car.orgcar.orgcar.orgcar.org SourceSourceSourceSource: Andreas L: Andreas L: Andreas L: Andreas Lüüüübke, Volkswagen AG, Wolfsburgbke, Volkswagen AG, Wolfsburgbke, Volkswagen AG, Wolfsburgbke, Volkswagen AG, Wolfsburg


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Application scenarios of wireless mesh networksBroadband Wireless Internet Access (BWIA)

� Broadband internet access is not available everywhere� In places installed infrastructure does not support broadband internet access like DSL.

� Installing of required infrastructure is expensive.

� Wireless mesh networks offers important advantages� Low costs of Investments – no wired infrastructure needed.

� Customer Coverage – LOS to the base station is not required.

� Fast deployment – usage of wireless equipment.

� Reliability – connectivity via multiple wireless links.

� Communication among mesh nodes, e.g. for community and neighbourhood networking.

� Application scenarios� Providing of wireless DSL in undersupplied DSL areas – wireless technology e.g. WiMAX.

InternetInternet

InternetInternet

In-house networking


Application scenarios of wireless mesh networksIn-house networking

� In-house coverage is difficult� Interference of propagation due to obstacles – walls, objects, people, etc.

� Dead zones without coverage.

� Full wireless coverage is expensive – every access point (AP) needs wired connection to a central

hub.

� In-house networking with wireless mesh networks� All devices within the home network can share one Internet connection.

� Individual and flexible setup of mesh equipment.

� Mesh APs only need power supply.

� Application scenarios� Building automation – e.g. video observance, measurement value logging.

� Broadband in-house networking – backbone (data backup and storage) and support of

multimedia applications (e.g. video streaming, conferencing, online gaming).

InternetInternet

Mesh networkAccess network


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Application scenarios of wireless mesh networksCellular backhaul

� Bandwidth demand is constantly increasing� Number of users increases.

� Supply of multimedia services and applications increases.

� Mesh networks provides this demand� Flexible scaling and splitting of cells.

� Increasing network capacity and coverage.

� Application scenarios� Flexible connection of cellular BSs to the core network via mesh connections.

� Extension of cellular networks

� Easy and cheap installation of new cell locations

Cellular core

network

Cellular core

network

Backhaul connection

Extension of BackhaulAccess connection to network


Application scenarios of wireless mesh networksExisting mesh solutions

SourceSourceSourceSource: Microsoft, http://: Microsoft, http://: Microsoft, http://: Microsoft, http://research.microsoft.comresearch.microsoft.comresearch.microsoft.comresearch.microsoft.com/mesh//mesh//mesh//mesh/

BelAir Networks deployment example.

Challenges:� 6 building complexes, 529 rooms, over 23

acres.

� Limited room for deployment on the ocean

side and locations for mounting power

access.

Result:� Full WiFi coverage of the Sheraton property

with only 13 mesh boxes.

SourceSourceSourceSource: BelAir : BelAir : BelAir : BelAir networksnetworksnetworksnetworks, , , , http://http://http://http://www.belairnetworks.comwww.belairnetworks.comwww.belairnetworks.comwww.belairnetworks.com////

Microsoft� Self-Organizing Neighborhood Wireless Mesh

Networks – sharing of Internet access, local

communication.

� Microsoft focus on Software not Hardware.

� Goal is to implement the multihop functionality

in Microsoft Windows


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Standardisation activities – IEEE Wireless multi-hop networks

802.16-2004 (802.16a)802.15.4 (Zigbee)

802.15.5 (WPAN Mesh)

802.11s (ESS Mesh

Networking)Task GroupTask GroupTask GroupTask Group

802.16a ratified in 01/2003

802.16-2004 ratified in 06/2004

802.16e-2005 approved in

12/2005

802.15.4 standardized 11/2003

802.15.5 05/2004

First meeting 06/2004DatesDatesDatesDates

Mesh already included in the

current (802.16-2004) standard

– many limitations and open

issues

Proposals have been submitted

to enhance the 802.16 mesh

New Relay Task Group 802.16j

(03/2006)

802.15.4: native mesh support

802.15.5: Begin of

standardization process:

determine the necessary

mechanisms (in PHY & MAC)

WPANs to enable mesh

networking.

Joint proposal of SEE Mesh and

Wi-Fi Mesh – starting point of

802.11s standard

Standard is targeted to be

approved by 2008

Current Current Current Current

statestatestatestate

Phy & Mac layerPhy & Mac layerPhy & Mac layerFocusFocusFocusFocus

Metropolitan area networks802.15.4: Sensor networks

802.15.5: Wireless Personal area

networks

Local Area networksNetwork Network Network Network

typetypetypetype

802.16802.16802.16802.16802.15802.15802.15802.15802.11802.11802.11802.11


Standardisation activities – IETFWireless multi-hop networks

� A lot of multi-hop routing protocols are developed, e.g.� AODV (Ad hoc On-Demand Distance Vector)

� DSR (Dynamic Source Routing)

� DSDV (Destination Sequenced Distance Vector), etc.

� The focus of these protocols are mobile ad hoc networks (MANETs) and thus

optimized for:� High mobility

� Dynamic networks

� Less overhead

� Energy efficient

� Low bandwidth

The behaviour of these protocols has to be optimized for WMNs

Currently no standardization activity specialized on mesh routing protocols


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Challenges (part 1)Research activities

Security & privacy

Wireless medium simplifies attacks.

� Secure communication between multi-hop nodes has to be established to provide� Confidentiality – Access to information for allowed users only.

� Integrity – Information is complete and not be changed by a third person.

� Authenticity – A person is assignable to an information.

� Non-repudiation – To ensure that transferred information has been sent by a person claiming to

have transferred this message.

� Privacy – There are different parts of privacy like,

� Communication privacy – Hide exchanged information of person (e.g. voice)

� Location privacy – Hide residence of person (actual location/address).

� Identity privacy – Hide personal information of person (user name, password).



Security & privacy

� Routing protocols for wireless multi-hop networks have to be improved� Avoiding malicious users and freeloaders.

� Guard against Dos (Denial of Service) attacks.

� Congestion of network by malicious users.

� Avoiding of man-in-the-middle attacks.

� Malicious multi-hop node is placed between two valid multi-hop entities.

� Forwarding of manipulated data.

� Changing of routing tables by misuse of routing messages.

� Prevention of passive monitoring.

� Ethernet sniffing and eavesdropping.


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Multi-hop routing

� Route selection� Most of the current routing protocols only consider hop count as metric.

� Further possible metrics: traffic situation, delay, jitter, bandwidth, link quality, error rate, etc.

� Load balancing� Distribution of network traffic – multi-path routing.

� Considering congested network areas.

� Backup routes� Maintenance of communications between nodes.

� Routing Security



Quality of Service (QoS)

� Resource reservation� Problematic of wireless channel

� Fast changing wireless conditions.

� Multi-hop network characteristics

� Unknown behaviour of wireless condition within the next hop.

� Resource allocation – Scheduling� Fairness

� Spatial reuse

� Interference avoidance

� Actual channel conditions.

� Capacity enhancement on PHY layer� Directional and smart antennas

� MIMO (Multiple Input Multiple Output) systems.



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Conclusion Wireless multi-hop networks

� Introduction to wireless multi-hop networks� Ad hoc networks

� Mesh networks

� Benefit of wireless multi-hop networks

� Routing mechanisms� AODV – Proactive routing protocol

� OLSR – Reactive rouging protocol

� Application scenarios and existing solutions� Ad hoc networks – Inter car communication

� Mesh networks – Broadband Internet access

– In-house networking

– Extensions of network structures

� Brief overview of standardisation activities� IEEE and IETF

� Issues of challenges� Security & privacy

� Multi-hop routing

� Quality of service

Huge potential of

wireless multi-hop

networks for future

communication

systems,

however, a lot of

developments

have to be done!


Thank you for your attention!

�Questions & annotations?

Andreas Roos

Office address: Deutsche Telekom Fachhochschule Leipzig

Gustav-Freytag-Straße 43-45

04277 Leipzig

Phone: +49 (0)6151/937-3381

Fax: +49 (0)6151/937-4611

E-mail: [email protected]


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Backup


� AODV - Ad hoc On-Demand Distance Vector

� CBRP - Cluster Based Routing Protocol

� CEDAR - Core Extraction Distributed Ad hoc Routing

� DSR - Dynamic Source Routing protocol

� DSDV - Destination-Sequenced Distance Vector

� FSR - Fisheye State Routing protocol

� OLSR - Optimized Link State Routing protocol

� SSR - Signal Stability Routing protocol

� STAR - Source Tree Adaptive Routing protocol

� TBRPF - Topology Broadcast based on Reverse-Path Forwarding routing

protocol

� TORA - Temporally-Ordered Routing Algorithm routing protocol

� WRP - Wireless Routing Protocol

� ZRP - Zone Routing Protocol

AbbreviationsRouting protocols

2C04 DECUS IT-Symposium 2006 Andreas-Roos · Consideration of extended and novel security & privacy mechanisms Consideration Integration of Quality of Service (QoS) mechanisms Consideration

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