Draft Ietf 6lowpan Usecases 05

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6LoWPAN Working Group E. KimInternet-Draft ETRIExpires: May 13, 2010 D. Kaspar

Simula Research LaboratoryN. Chevrollier

TNOJP. Vasseur

Cisco Systems, IncNovember 9, 2009

Design and Application Spaces for 6LoWPANsdraft-ietf-6lowpan-usecases-05

Abstract

This document investigates potential application scenarios and usecases for low-power wireless personal area networks (LoWPANs). Thisdocument provides dimensions of design space for LoWPAN applications.A list of use cases and market domains that may benefit and motivatethe work currently done in the 6LoWPAN WG is provided with thecharacterisi tcis of each dimention. A complete list of practical usecases is not the goal of this document.

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This Internet-Draft will expire on May 13, 2010.

Copyright Notice

Kim, et al. Expires May 13, 2010 [Page 1]


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Internet-Draft 6LoWPAN Design and Applications November 2009

Copyright (c) 2009 IETF Trust and the persons identified as thedocument authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trusts LegalProvisions Relating to IETF Documents(http://trustee.ietf.org/license-info) in effect on the date ofpublication of this document. Please review these documentscarefully, as they describe your rights and restrictions with respectto this document. Code Components extracted from this document mustinclude Simplified BSD License text as described in Section 4.e ofthe Trust Legal Provisions and are provided without warranty asdescribed in the BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 31.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 41.2. Basic Network Configuration . . . . . . . . . . . . . . . 4

2. Design Space . . . . . . . . . . . . . . . . . . . . . . . . . 73. Application Scenarios . . . . . . . . . . . . . . . . . . . . 9

3.1. Industrial Monitoring . . . . . . . . . . . . . . . . . . 93.1.1. A Use Case and its Requirements . . . . . . . . . . . 103.1.2. 6LoWPAN Applicability . . . . . . . . . . . . . . . . 11

3.2. Structural Monitoring . . . . . . . . . . . . . . . . . . 133.2.1. A Use Case and its Requirements . . . . . . . . . . . 133.2.2. 6LoWPAN Applicability . . . . . . . . . . . . . . . . 14

3.3. Healthcare . . . . . . . . . . . . . . . . . . . . . . . . 153.3.1. A Use Case and its Requirements . . . . . . . . . . . 163.3.2. 6LoWPAN Applicability . . . . . . . . . . . . . . . . 17

3.4. Connected Home . . . . . . . . . . . . . . . . . . . . . . 183.4.1. A Use Case and its Requirements . . . . . . . . . . . 193.4.2. 6LoWPAN Applicability . . . . . . . . . . . . . . . . 20

3.5. Vehicle Telematics . . . . . . . . . . . . . . . . . . . . 213.5.1. A Use Case and its Requirements . . . . . . . . . . . 223.5.2. 6LoWPAN Applicability . . . . . . . . . . . . . . . . 22

3.6. Agricultural Monitoring . . . . . . . . . . . . . . . . . 233.6.1. A Use Case and its Requirements . . . . . . . . . . . 243.6.2. 6LoWPAN Applicability . . . . . . . . . . . . . . . . 25

4. Security Considerations . . . . . . . . . . . . . . . . . . . 275. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 286. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29

6.1. Normative References . . . . . . . . . . . . . . . . . . . 296.2. Informative References . . . . . . . . . . . . . . . . . . 29Authors Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30



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1. Introduction

Low-power and lossy networks (LLNs) is the term commonly used torefer to networks made of highly constrained nodes (limited CPU,memory, power) interconnected by a variety of "lossy" links (low-power radio links or powerline communication (PLC)). They arecharacterized by low speed, low performance, low cost, and unstableconnectivity. A LoWPAN is a particular instance of an LLN, formed bydevices complying with the IEEE 802.15.4 standard [5]. Their typicalcharacteristics can be summarized as follows:

o Limited processing capability: the smallest common LoWPAN nodeshave 8-bit processors with clock rates around 10 MHz. Othermodels exist with 16-bit and 32-bit cores (typically ARM7),running at frequencies in the order of tens of MHz.

o Small memory capacity: common RAM sizes for LoWPAN devices consistof a few kilobytes, usually 4K or 8K bytes. However, a widevariety of RAM sizes is available, reaching from 1K up to 256Kbytes.

o Low power: wireless radios for LoWPANs are normally battery-operated. Their RF transceivers often have a current draw ofabout 10 to 30 mA, depending on the used transmission power level.In order to reach common indoor ranges of up to 30 meters andoutdoor ranges of 100 meters, the used transmission power is setaround 0 to 3 dBm. Depending on the processor type, there is anadditional battery current consumption of the CPU itself, commonlyin the order of tens of milliamperes. However, the CPU powerconsumption can often be reduced by a thousandfold when switchingto sleep mode.

o Short range: the Personal Operating Space (POS) defined by IEEE802.15.4 implies a range of 10 meters. For real implementations,the range of LoWPAN radios is typically measured in tens ofmeters, but can reach over 100 meters in line-of-sight situations.

o Low bit rate: the IEEE 802.15.4 standard defines a maximum over-the-air rate of 250K bit/s, which is most commonly used in currentdeployments. Alternatively, three lower data rates of 20K, 40Kand 100K bit/s are defined.

As any other LLN, a LoWPAN does not necessarily comprise of sensornodes only, but may also consist of actuators. For instance, in anagricultural environment, sensor nodes might be used to detect lowsoil humidity and then send commands to activate the sprinklersystem.



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After defining common terminology in Section 1.1 and describing thecharacteristics of LoWPANs in Section 2, this document provides alist of use cases and market domains that may benefit and motivatethe work currently done in the 6LoWPAN WG.

1.1. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT","SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in thisdocument are to be interpreted as described in [1].

Readers are expected to be familiar with all the terms and conceptsthat are discussed in "IPv6 over Low-Power Wireless Personal AreaNetworks (6LoWPANs): Overview, Assumptions, Problem Statement, andGoals" [3], and " Transmission of IPv6 Packets over IEEE 802.15.4

Networks" [4].

Readers would benefit from reading 6LoWPAN ND [6], 6LoWPAN headercompression [7], and 6LoWPAN Routing Requirements [8] for the detailsof the each 6LoWPAN work.

This specification makes extensive use of the same terminologydefined in 6LoWPAN ND [6] unless otherwise redefined below.

This document defines an additional terms:

LC(local-coordinator) node

A logical functional entity that performs the special role ofcoordinating its child nodes for local data aggregation, statusmanagement of local nodes, etc. Thus, the local coordinator nodedoes not need to coincide with a link-layer PAN coordinator andthere may be multiple instance in a LoWPAN.

1.2. Basic Network Configuration

The IEEE 802.15.4 standard distinguishes between two types of nodes,reduced-function devices (RFDs) and full-function devices (FFDs).However, as this distinction is not usually present in realdeployments, a LoWPAN can generally be understood as a network ofLoWPAN Hosts and LoWPAN Routers (or LoWPAN Mesh Nodes), all of whichare referred to as LoWPAN Nodes. LoWPAN Hosts only source or sink

IPv6 datagrams, and LoWPAN Mesh Nodes are special LoWPAN Hosts whichdo not forward IP datagrams, but some forward 6LoWPAN frames, whileLoWPAN Routers forward IP datagrams. Both LoWPAN Routers and LoWPANMesh Nodes forward data between source-destination pairs. Thedifference between LoWPAN Routers and LoWPAN Mesh Nodes is the layerthey operate in. While LoWPAN Routers perform IP routing, LoWPAN



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Mesh Nodes operate on top of the link layer and use link addressesfor their forwarding and multihop functionalities.

Example LoWPAN topologies are depicted in Figure 1 and Figure 2. Adefinition of how mesh topologies are obtained and maintained is outof scope of this document.

Communication to corresponding nodes outside of the LoWPAN isbecoming increasingly important for convenient data collection andremote control purposes. The intermediate LoWPAN nodes act as packetforwarders or LoWPAN routers and connect the entire LoWPAN in amulti-hop fashion. Edge Routers are used to interconnect a LoWPAN toother networks, or to form an Extended LoWPAN by connecting multipleLoWPANs. Before LoWPAN nodes obtain their IPv6 addresses and thenetwork is configured, each LoWPAN executes a link-layer

configuration either by the mechanisms specified in 6lowpan ND [6] orby using a coordinator who is responsible for link-layer shortaddress allocation. However, the link-layer coordinatorfunctionality is out of the scope of this document. Details ofaddress allocation of 6LoWPAN ND is in [6].

A LoWPAN can be configured as Mesh Under or Route Over (seeTerminology in Section 1.1). In a Route Over configuration, multihoptransmission is carried out by LoWPAN Routers using IP routing (seeFigure 2). In a Mesh Under configuration, the link-local scopereaches to the boundaries of the LoWPAN and all nodes in a LoWPAN areincluded in the scope (see Figure 1), and multihop transmission isachieved by forwarding data at the link layer or in an adaptationlayer. More information about Mesh Under and Route Over is in6LoWPAN ND [6] and 6LoWPAN Routing Requirements [8].

m h| | ER: LoWPAN Edge Router

ER --- m --- m --- h m: LoWPAN Mesh Node\ / \ h: other LoWPAN Host

m --- m

Figure 1: Example of a Mesh Under LoWPAN



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r h| | ER: LoWPAN Edge Router

ER --- r --- r --- h r: LoWPAN Router\ / \ h: LoWPAN Host

r --- r

Figure 2: Example of a Route Over LoWPAN



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2. Design Space

Inspired by [9], this section lists the dimensions used to describethe design space of wireless sensor networks in the context of the6lowpan Working Group. The design space is already limited by theunique characteristics of a LoWPAN (e.g., low-power, short range,low-bit rate) as described in [3]. The possible dimensions forscenario categorization used in this document are described asfollows:

o Deployment: LoWPAN nodes can be scattered randomly or they may bedeployed in an organized manner in a LoWPAN. The deployment canoccur at once, or as an iterative process. The selected type ofdeployment has an impact on node density and location. Thisfeature affects how to organize (manually or automatically) the

LoWPAN and how to allocate addresses in the network.

o Network Size: The network size takes into account nodes thatprovide the intended network capability. The number of nodesinvolved in a LoWPAN could be small (10 nodes), moderate (several100s), or large (over a 1000).

o Power Source: The power source of nodes, whether the nodes arebattery-powered or mains-powered, influences the network design.The power may also be harvested from solar cells or other sourcesof energy. Hybrid solutions are possible where only part of thenetwork is mains-powered.

o Connectivity: Nodes within a LoWPAN are considered "alwaysconnected" when there is a network connection between any twogiven nodes. However, due to external factors (e.g., extremeenvironment, mobility) or programmed disconnections (e.g.,sleeping mode), the network connectivity can be from"intermittent" (i.e., regular disconnections) to "sporadic" (i.e.,almost always disconnected network). Differences in L2 duty-cycling settings may additionally impact the connectivity due tohighly varying bit-rates.

o Multi-hop communication: The multi-hop communication factorhighlights the number of hops that has to be traversed to reachthe edge of the network or a destination node within it. A singlehop may be sufficient for simple star-topologies, but a multi-hop

communication scheme is required for more elaborate topologies,such as meshes or trees. In previous work by academia andindustry on LoWPANs, various routing mechanisms were introduced,such as data-centric, event-driven, address-centric, localization-based, geographical routing, etc. This document does not make useof such a fine granularity but rather uses topologies and single/



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multi-hop communication.

o Traffic Pattern: several traffic patterns may be used in LoWPANs.To name a few, Point-to-Multi-Point (P2MP), Multi-Point-to-Point(MP2P) and Point-to-Point (P2P).

o Security Level: LoWPANs may carry sensitive information andrequire high-level security support where the availability,integrity, and confidentiality of the information are crucial.This high level of security may be needed in case of structuralmonitoring of key infrastructure or health monitoring of patients.

o Mobility: Inherent to the wireless characteristics of LoWPANs,nodes could move or be moved around. Mobility can be an inducedfactor (e.g., sensors in an automobile), hence not predictable, or

a controlled characteristic (e.g., pre-planned movement in asupply chain).

o Quality of Service (QoS): for mission-critical applications,support of QoS is mandatory in resource-constrained LoWPANs.



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3. Application Scenarios

This section lists a fundamental set of LoWPAN application scenariosin terms of system design. A complete list of practical use cases isnot the objective of this document.

3.1. Industrial Monitoring

LoWPAN applications for industrial monitoring can be associated witha broad range of methods to increase productivity, energy efficiency,and safety of industrial operations in engineering facilities andmanufacturing plants. Many companies currently use time-consumingand expensive manual monitoring to predict failures and to schedulemaintenance or replacements in order to avoid costly manufacturingdowntime. LoWPANs can be inexpensively installed to provide more

frequent and more reliable data. The deployment of LoWPANs canreduce equipment downtime and eliminate manual equipment monitoringthat is costly to be carried out. Additionally, data analysisfunctionality can be placed into the network, eliminating the needfor manual data transfer and analysis.

Industrial monitoring can be largely split into the followingapplication fields:

o Process Monitoring and Control: combining advanced energy meteringand sub-metering technologies with wireless sensor networking inorder to optimize factory operations, reduce peak demand,ultimately lower costs for energy, avoid machine downtimes, andincrease operation safety.

A plants monitoring boundary often does not cover the entirefacility but only those areas considered critical to the process.Easy to install wireless connectivity extends this line to includeperipheral areas and process measurements that were previouslyinfeasible or impractical to reach with wired connections.

o Machine Surveillance: ensuring product quality and efficient andsafe equipment operation. Critical equipment parameters such asvibration, temperature, and electrical signature are analyzed forabnormalities that are suggestive of impending equipment failure(see Section 3.2).

o Supply Chain Management and Asset Tracking: with the retailindustry being legally responsible for the quality of sold goods,early detection of inadequate storage conditions with respect totemperature will reduce risk and cost to remove products from thesales channel. Examples include container shipping, productidentification, cargo monitoring, distribution and logistics.



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o Storage Monitoring: sensor systems designed to prevent releases ofregulated substances to ground water, surface water and soil.This application field may also include theft/tampering preventionsystems for storage facilities or other infrastructure, such aspipelines.

3.1.1. A Use Case and its Requirements

Example: Hospital Storage Rooms

In a hospital, maintenance of the right temperature in storage roomsis very critical. Red blood cells need to be stored at 2 to 6degrees Celsius, blood platelets at 20 to 24 C, and blood plasmabelow -18 C. For anti-cancer medicine, maintaining a humidity of 45%to 55% is required. Storage rooms have temperature sensors and

humidity sensors every 25m to 100m, based on the floor plan and thelocation of shelves, as indoor obstacles distort the radio signals.At each blood pack a sensor tag can be installed to track thetemperature during delivery. A LoWPAN node is installed in eachcontainer of a set of blood packs. In this case, highly densenetworks must be managed.

All nodes are statically deployed and manually configured with eithera single- or multi-hop connection. Different types of LoWPAN nodesare configured based on the service and network requirements.

All LoWPAN nodes do not move unless the blood packs or a container ofblood packs is moved. Moving nodes get connected by logicalattachment to a new LoWPAN. When containers of blood packs aretransferred to another place of the hospital or by ambulance, theLoWPAN nodes on the containers associate to a new LoWPAN.

This type of application works based on both periodic and event-driven notifications. Periodic data is used for monitoring thetemperature and humidity in the storage rooms. The data over orunder a pre-defined threshold is meaningful to report. Blood cannotbe used if it is exposed to the wrong environment for about 30minutes. Thus, event-driven data sensed on abnormal occurrences istime-critical and requires secure and reliable transmission.

LoWPANs must be provided with low installation and management costs,and for the transportation of boold containers, precise location

tracking of containers is important. The hospital network manager orstaff can be provided with an early warning of possible chainruptures, for example by conveniently accessing comprehensive onlinereports and data management systems.

Dominant parameters in industrial monitoring scenarios:



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o Deployment: pre-planned, manually attached

o Mobility: no (except for asset tracking)

o Network Size: medium to large size, high node density

o Power Source: most of the time battery-operated

o Security Level: business-cri tical. Secure and reliabletransmission must be guaranteed.

o Multi-hop communication: multi-hop mesh networking

o Connectivity: always on for crucial processes

o QoS: important for time-critical event-driven data

o Traffic Pattern: P2P (actuator control), MP2P (data collection)

o Other Issues: Sensor network management, location tracking, real-time early warning

3.1.2. 6LoWPAN Applicability

The network configuration of the above use case can differsubstantially by system design. As illustrated in Figure 3, thesimplest way is to build a star topology inside of each storage room,and connect the storage rooms with one link but overall networkconfiguration is with mesh topologies. Each LoWPAN node reaches theEdge Router (ER) by a pre-defined routing/forwarding mechanism.Local Coordinator nodes (LCs) play a role in aggregation of thesensed data. A LoWPAN LC is a logical entity that can be implementedtogether with an LoWPAN Edge Router or a LoWPAN Node. In case thatthe sensed data from an individual node is important, such as urgentevent-driven data, it will not be accumulated (and further delayed)by the LoWPAN LCs but immediately relayed. In Mesh under, link-layeraddresses in the mesh-header defined by RFC 4944 [4] are used fortransmission, and in Route Over, IP forwarding is used.

Based on the layout and size of the storage room, the LoWPAN can beconfigured in a different way of mesh topology as shown in Figure 4.More than one LoWPAN LCs can be installed in a storage room, and LCs

collect data as relay points to transmit the sensed data toward theLoWPAN ERs. LoWPAN Nodes need to build a multi-hop connection toreach the LCs and ER by either Mesh Under or Route Over. In MeshUnder, more than one LCs can be installed in the LoWPAN and the nodesplay role in transmission multi-point traffic (multicast) by unicastmethod, not only role in data collection. In Route Over, LoWPAN



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Routers will handle multicast traffic to their LoWPAN links.

Each LoWPAN node configures its link-local address and may get aprefix from its default router by an 6LoWPAN ND procedure [6].Routable addresses are needed to communicate with other LoWPAN nodesnot reachable over a single radio transmission. .

Packets are compressed by 6LoWPAN header compression mechanism [7].The data volume is usually not so big in this case, but it issensitive for delay. Data aggregators can be installed for eachstorage room, or just one data aggregator can collect all data. Tomake a light transmission, UDP (encapsulated in 6LoWPAN header or asit is) will be chosen, but secure transmission and security mechanismshould be added. To increase security, MAC layer mechanisms and/oradditional security mechanisms can be used.

Because a failure of a LoWPAN node can critically affect the storageof the blood packs, network management is important in this use-case.SNMP-lite or other mechanism should be provided for the management.

When a container is moved out from the storage room, and connected tothe other hospital system (if the hospital buildings are fully orpartly covered with 6LoWPANs), it should rebind to a new parent nodeand a new LoWPAN. 6LoWPAN ND [6] will support this procedure. Incase that it is moved by an ambulance, it will be connected to anedge router in the vehicle. LoWPANs must be provided with lowinstallation and management costs, providing benefits such as reducedinventory, and precise location tracking of containers, and mobileequipment (moving beds at the hospital or ambulances).

ER| ER: LoWPAN Edge Router

LC----------LC----------LC LC: Local Coordinator node/ | \ / | \ / | \ (Data Aggregator)

n n n n n n n n n n: LoWPAN Node

Figure 3: Storage rooms with a simple star topology



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GW+------------+-----------+ GW: Gateway| | | ER: LoWPAN Edge Router

ER ER ER(LC) LC: Local Coordinator node| | | (Data Aggregator)

n -- LC -- n LC -- n n n: LoWPAN Node| | | | | / \n LC -- n n -- n -- LC n - n| | \ | |\n --- n n -- n n -- n n

Figure 4: Storage rooms with a mesh topology

3.2. Structural Monitoring

Intelligent monitoring in facility management can make safety checksand periodic monitoring of the architecture status highly efficient.Mains-powered nodes can be included in the design phase of aconstruction or battery-equipped nodes can be added afterwards. Allnodes are static and manually deployed. Some data is not criticalfor security protection (such as normal room temperature), but event-driven emergency data must be handled in very critical manner.


Example: Bridge Safety Monitoring

A 1000m long concrete bridge with 10 pillars is described. Eachpillar and the bridge body contain 5 sensors to measure the waterlevel, and 5 vibration sensors are used to monitor its structuralhealth. The LoWPAN nodes are deployed to have 100m line-of-sightdistance from each other. All nodes are placed statically andmanually configured with a single-hop connection to the localcoordinator. All LoWPAN nodes do not move while the service isprovided. Except from the pillars, there are no special obstacles ofattenuation to the node signals, but careful configuration is neededto prevent signal interference between LoWPAN nodes.

The physical network topology is changed in case of node failure. Onthe top part of each pillar, an sink node is placed to collect thesensed data. The sink nodes of each pillar become data gatheringpoint of the LoWPAN hosts at the pillar as local coordinators.

This use case can be extended to medium or large size sensor networksto monitor a building or for instance the safety status of highwaysand tunnels. Larger networks of the same kind still have similarcharacteristics such as static node placement, manual deployment anddependent on the blue print of the structure, mesh topologies will be



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built with mains-powered relay points. Periodic and event-drivenreal-time data gathering is performed and the emergency event-drivendata MUST be delivered without delay.

Dominant parameters in structural monitoring applications:

o Deployment: static, organized, pre-planned

o Mobility: none

o Network Size: small (dozens of nodes) to large

o Power Source: mains-powered nodes are mixed with battery powered(mains-power nodes will be used for coordinators or relays).

o Security Level: safety-critical. Secure transmission must beguaranteed. Only authenticated users should be able to access andhandle the data.

o Multi-hop communication: multi-hop mesh networking should besupported.

o Connectivity: always connected or intermittent by sleeping modescheduling.

o QoS: Emergency notification (fire, over-threshold vibrations,water level, etc) is required to have priority of delivery andmust be transmitted in a highly reliable manner.

o Traffic Pattern: MP2P (data collection), P2P (localized querying)

o Other Issues: accurate sensing and reliable transmission areimportant. In addition, sensor status reports may be needed tomaintain a reliable monitoring system.


The network configuration of this use case can be very simple, butthere are many extended use cases for more complex structures. Theexample bridge monitoring case may be the simplest case. Dependenton the bridge size, the network will be configured by different sizewith mesh topology.

Each LoWPAN node configures its link-local address and may get aprefix from its default router by an 6LoWPAN ND procedure [6]. Eachpillar may have one local coordinator node(LC) for data collectionfrom each pillar. Each pillar network may be built as a stubnetwork, so that 16-bit addresses can be utilized [7]. Globally



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routable addresses should be allocated to communicate with otherLoWPAN nodes not reachable over a single radio transmission.

The LoWPAN Nodes are installed on the place after manual optimizationof their location. Static data paths to the data gathering pointscan be set in the commissioning phase. If the network does not use aRoute Over mechanism, the 6LoWPAN mesh-header described in RFC 4944[4] may be used for static data forwarding, unless other mesh undermechanisms are provided.

A logical entity of data gathering can be implemented in each LC.Communication schedules must be set up between leaf nodes and theirLC to efficiently gather the different types of sensed data. Eachdata packet may include meta-information about its data, or the typeof sensors could be encoded in its address during the address

allocation. The data gathering entity can be programmed to triggeractuators installed in the infrastructure, when a certain thresholdvalue has been reached. This type of application works based on bothperiodic and event-driven notifications. The data over or under apre-defined threshold is meaningful to report. Event-driven datasensed on abnormal occurrences is time-critical and requires secureand reliable transmission. For energy conservation, all nodes mayhave periodic and long sleep modes but wake up on certain events.

Packets are compressed by 6LoWPAN header compression mechanism [7].Due to the safety-critical data of the structure, authentication andsecurity are important issues here. Only authenticated users shouldbe allowed to access the data. Additional security should beprovided at the LoWPAN ER for restricting the access from outside ofthe LoWPAN. The LoWPAN ER may take charge of authentication ofLoWPAN nodes. Reliable and secure data transmission should beguaranteed.

ER -- LC ----- LC ------ LC ER: Edge Router/| | | LC: Local Coordinator node

h n n -- n -- n n -- n r: LoWPAN Router (Route Over)/\ | | | | n: LoWPAN Node

h h n -- n n -- n -- h h: LoWPAN host

Figure 5: A LoWPAN with a mesh topology

3.3. Healthcare

LoWPANs are envisioned to be heavily used in healthcare environments.They have a big potential to ease the deployment of new services bygetting rid of cumbersome wires and simplify patient care in



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hospitals and for home care. In healthcare environments, delayed orlost information may be a matter of life or death.

Various systems, ranging from simple wearable remote controls fortele-assistance or intermediate systems with wearable sensor nodesmonitoring various metrics to more complex systems for studying lifedynamics, can be supported by LoWPANs. In the latter category, alarge amount of data from various LoWPAN Nodes can be collected:movement pattern observation, checks that medicaments have beentaken, object tracking, and more. An example of such a deployment isdescribed in [10] using the concept of Personal Networks.


Example: healthcare at home by tele-assistance

A senior citizen who lives alone wears one to few wearable LoWPANNodes to measure heartbeat, pulse rate, etc. Dozens of LoWPAN Nodesare densely installed at home for movement detection. A LoWPAN ER athome will send the sensed information to a connected healthcarecenter. Portable base stations with LCDs may be used to check thedata at home, as well. The different roles of devices have differentduty-cycles, which affect node management.

Multipath interference may often occur due to the patients mobilityat home, where there are many walls and obstacles. Even duringsleeping, the change of the body position may affect the radiopropagation.

Data is gathered both periodically and event-driven. In thisapplication, event-driven data can be very time-critical. Thus,real-time and reliable transmission must be guaranteed.

Privacy also becomes an issue in this case, as the sensed data isvery personal. In addition, different data will be provided to thehospital system from what is given to a patients family members.Role-based access control is needed to support such services, thussupport of authorization and authentication is important.

Dominant parameters in healthcare applications:

o Deployment: pre-planned

o Mobility: moderate (patients mobility)

o Network Size: small, high node density



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o Power Source: hybrid

o Security Level: Data privacy and security must be provided.Encryption is required. Role based access control is required tobe support by proper authentication mechanism

o Multi-hop communicaton: multi-hop for homecare devices, startopology on patients body. Multipath interference due to wallsand obstacles at home must be considered.

o Connectivity: always on

o QoS: high level of support (life and death implication), role-based

o Traffic Pattern: MP2P/P2MP (data collection), P2P (localdiagnostic)

o Other issues: Plug-and-play configuration is required for mainlynon-technical end-users. Real-time data acquisition and analysisare important. Efficient data management is needed for variousdevices which have different duty-cycles, and for role-based datacontrol. Reliability and robustness of the network are alsoessential.


In this use case, the local network size is rather small (less than10s of nodes). The home care system is statically configured withmulti-hop paths and the patients body network can be built as a startopology. The LoWPAN Edge Router(ER) at home is the sink node in therouting path from sources on the patients body. A plug-and-playconfiguration is required. Each home system node will get a link-local IPv6 address according to the auto-configuration described inRFC 4944 [4]. As the communication of the system is limited to ahome environment, both 16-bit and 64-bit can be used for IPv6 link-local addresses. An example topology is provided in Figure 6.

Multi-hop communication can be achieved by either Mesh Under or RouteOver mechanisms. When a Route Over routing mechanism is used, therouters deployed in the home environment will form a mesh of IPv6links. In Mesh Under, more than one LCs can be installed in the

LoWPAN and the nodes play role in transmission multi-point traffic(multicast) to unicast method. In Route Over, LoWPAN Routers willhandle multicast traffic to their LoWPAN Link.

The patients body network can be simply configured as a startopology with a LC dealing with data aggregation and dynamic network



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attachment when the patient moves around at home. As multipathinterference may often occur due to the patients mobility at home,the deployment of LoWPAN nodes and transmission paths should be wellconsidered. At home, some nodes can be installed with power-affluence status, and those LoWPAN Nodes can be used for relayingpoints or data aggregation points.

The sensed information should be maintained with the identificationof the patient no matter if the patient visits the connected hospitalor stays at home. If the patients LoWPAN uses globally unique IPv6address, the address can be used for the identification, however, thehome system itself does not require globally unique IPv6 address butcould be run with link-local IPv6 address. In this case, thehospital LoWPAN needs to operate additional identification system.

The connection between the LoWPAN ER at home and the ER at Hospitalmust be reliable and secure, as the data is privacy-crit ical. Toachieve this, additional policy for security is recommended betweenthe two LoWPAN.

n --- n I: Internet| | ER: Edge Router

ER --- I --- ER --- n --- n --- LC LC: Local coordinator node/|\ | | /|\ n: LoWPAN Node

.. . .. n --- n h h h h: LoWPAN Host

(hospital) (home system) (patient)

Figure 6: A mobile healthcare scenario.

3.4. Connected Home

The "Connected" Home or "Smart" home is with no doubt an area whereLoWPANs can be used to support an increasing number of services:

o Home safety/security

o Home Automation and Control

o Healthcare (see above section)

o Smart appliances and home entertainment systems

In home environments LoWPAN networks typically comprise a few dozenand probably in the near future a few hundreds of nodes of variousnature: sensors, actuators and connected objects.



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Example: Home Automation

The home automation and control system LoWPAN offers a wide range ofservices: local or remote access from the Internet (via a securededge router) to monitor the home (temperature, humidity, activationof remote video surveillance, status of the doors (locked or open),...) but also for home control (activate the air conditioning/heating, door locks, sprinkler systems, ...). Fairly sophisticatedsystems can also optimize the level of energy consumption thanks to awide range of input from various sensors connected to the LoWPAN:light sensors, presence detection, temperature, ... in order tocontrol electric window shades, chillers, air flow control, airconditioning and heating with the objective to optimize energy

consumption.

With the emergence of "Smart Grid" applications, the LoWPAN may alsohave direct interactions with the Grid itself via the Internet of theGrid network to report the amount of KWatts that could be load shed(Home to Grid) and to receive dynamic load shedding information if/when required (Grid to home): this application is also referred to asDemand-Response application. Another service known as Demand SideManagement (DSM) could be provided by utilities to monitor and reportto the user its energy consumption with a fine granularity (on a perdevice basis). Other inputs such as dynamic pricing can also bereceived by the user from the utility that can then turn on and offsome appliances according to its local policy in order to reduce itsenergy bill.

In terms of home safety and security, the LoWPAN is made of motion-and audio-sensors, sensors at doors and windows, and video cameras towhich additional sensors can be added for safety (gas, water, CO,Radon, smoke detection). The LoWPAN typically comprises a few dozenof nodes forming an ad-hoc network with multi-hop routing since thenodes may not be in direct range. It is worth mentioning that thenumber of devices tends to grow considering the number of newapplications for the home. In its most simple form, all nodes arestatic and communicate with a central control module but moresophisticated scenarios may also involve inter-device communication.For example, a motion/presence sensor may send a multicast message toa group of lights to be switched on, or a video camera will be

activated sending a video stream to a gateway that can be received ona cell phone.

Ergonomics in Connected Homes is a key and the LoWPAN must be self-managed and easy to install. Traffic patterns may greatly varydepending on the applicability and so does the level of reliability



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and QoS expected from the LoWPAN. Humidity sensing is typically notcritical and requires no immediate action whereas tele-assistance orgas leak detection is critical and requires a high degree ofreliability. Furthermore, although some actions may not involvecritical data, still the response time and network delays must be onthe order of a few hundreds of milliseconds to preserve the userexperience (e.g. use a remote control to switch a light on). Aminority of nodes are mobile (with slow motion). With the emergenceof energy related applications it becomes crucial to preserve dataconfidential ity. Connected Home LoWPAN usually do not require multi-topology or QoS routing and fairly simple QoS mechanisms must besupported by the LoWPAN (the number of Class of Services is usuallylimited).

Dominant parameters for home automation applications:

o Deployment: multi-hop topologies

o Mobility: some degree of mobility

o Network Size: medium number of nodes, potentially high density

o Power Source: mix of battery and AC powered devices

o Security Level: authentication and encryption required

o Multi-hop communication: no requirement for multi-topology or QoSrouting

o Connectivity: intermittent (usage-dependent sleep modes)

o QoS: support of limited QoS (small number of Class of Service)

o Traffic Pattern: P2P (inter-device), P2MP and MP2P (polling)


In the home automation use case, the network topology is made of amix a battery operated and main powered nodes that both communicationwith each other and to outside of the LoWPAN via the LoWPAN ERs.That being said it is expected that most LoPWAN nodes willcommunicate with a LC that will process the data and will communicate

with outside after potential data processing, filtering, etc.

In home network, installation and management must as extremely simplefor the user.

Link local IPv6 addresses can be used by nodes with no external



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communication but it also needs routable addresses to communicatewith other LoWPAN nodes not reachable over a single radiotransmission.

n --- n I: Internet| | ER: Edge Router

Internet/ ------- ER/LC -- n --- n ---- LC LC: Local coordinator nodeUtility network | | /|\ n: LoWPAN Node

n ---- n h h h h: LoWPAN Host

(outside) (home automation system)

Figure 7: Home Automation scenario

In some scenarios, the traffic will be sent to a LC for processingthat may in turn decide of local actions (switch a light on, ...).In other scenarios, all devices will send their data to the LCs thatmay also act as the ER for data processing and potential relay ofdata to outside of the LoWPAN. For the sake of illustration, some ofthe data may be processed to trigger local action (e.g. switch off anappliance), simply store and sent once enough data has beenaccumulated (e.g. energy consumption for the past 6 hours for a setof appliances) or could trigger an alarm immediately sent to adatacenter (e.g. gas leak detection).

Although in the majority of cases nodes within the LoPWAN will be indirect range, some nodes will reach the ER/LC with a 2-3 hops pathusing Mesh Under or very likely a Route Over solution (with theemergence of several low power media such as low power PLC) in whichcase LoWPAN routers will be deployed in the home to interconnect thevarious IPv6 links.

The home LoWPAN must be able to provide extremely reliablecommunication in support of some specific application (e.g. fire, gasleak detection, health monitoring) whereas other application may notbe critical at all (e.g humidity monitoring). Similarly someinformation may require the use of security mechanisms forauthentication, confidentiality).

3.5. Vehicle Telematics

LoWPANs play an important role in intelligent transportation systems.Incorporated in roads, vehicles, and traffic signals, they contributeto the improvement of safety of transporting systems. Throughtraffic or air-quality monitoring, they increase the possibilities interms of traffic flow optimization and help reducing road congestion.



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Example: Telematics

As shown in Figure 8, scattered LoWPAN Nodes are included in roadsduring their construction for motion monitoring. When a car passesover these nodes, the possibility is then given to track thetrajectory and velocity of cars for safety purposes. The lifetime ofthe LoWPAN Nodes incorporated into roads is expected to be as long asthe life time of the roads (10 years). Multihop communication ispossible between LoWPAN Nodes, and the network should be able to copewith the deterioration over time of the node density due to powerfailures. Sink nodes placed at the road side are mains-powered,LoWPAN Nodes in the roads run on battery. Power savings schemesmight intermittently disconnect the nodes. A rough estimate of 4

nodes per square meter is needed. Other applications may involvecar-to-car communication for increased road safety.

Dominant parameters in vehicle telematics applications:

o Deployment: scattered, pre-planned

o Mobility: none (road infrastructure), high (vehicle)

o Network Size: large (road infrastructure), small (vehicle)

o Power Source: mostly battery powered

o Security Level: low

o Multi-hop communication: multi-hop, especially ad-hoc

o Connectivity: intermittent

o QoS: support of limited QoS

o Traffic Pattern: mostly Point-to-Point (P2P), Point-to-Multi-Point(P2MP)


For this use case, the network topology includes fixed LoWPAN Edge

Routers that are mains-powered and have a connection to a gateway inorder to reach the transportation control center. These LoWPAN ERsare logically combined with LC nodes as data sinks for a number ofLoWPAN Nodes inserted in the tarmac of the road.

In contrast to the LoWPAN ERs, the LoWPAN Nodes can generally operate



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with link-local IPv6 addresses as no direct access from outside theLoWPAN is established to the LoWPAN Nodes, while they needs routableaddresses to communicate with other LoWPAN nodes not reachable over asingle radio transmission. Globally unique IPv6 addresses can beallocated during the network setup procedure described in RFC 4944[4] and 6LoWPAN ND [6]. In Infrastructure LoWPANs, each ER isconnected by a backbone link and additional registration proceduresmay be required for management of multiple LoWPANs. Details of thisregistration are described in 6LoWPAN ND .

In this topology, a LoWPAN with one LoWPAN ER forms a fixed networkand the LoWPAN Nodes are installed by manual optimization of theirlocation. Static data paths to the data gathering point can be setin the commissioning phase. If the network does not use a Route Overmechanism, the 6LoWPAN mesh under forwarding is used. Forwarding/

Routing tables are not changed unless a node failure occurs.

+----+| ER |----------------------------- ER ...+----+ (at the road side)

-------|------------------------------|

n -- n --- n --- n +---|---+ ER: LoWPAN Edge Router/ \ | | h-n-h | n: LoWPAN Node

n n n +---|---+ h: LoWPAN Host(cars)

--------------------------------------

Figure 8: Multi-hop LoWPAN combined with mobile star LoWPAN.

3.6. Agricultural Monitoring

Accurate temporal and spatial monitoring can significantly increaseagricultural productivity. Due to natural limitations, such as afarmers inability to check the crop at all times of day orinadequate measurement tools, luck often plays a too large role inthe success of harvests. Using a network of strategically placedsensors, indicators such as temperature, humidity, soil condition,can be automatically monitored without labor intensive fieldmeasurements. For example, sensor networks could provide preciseinformation about crops in real time, enabling businesses to reduce

water, energy, and pesticide usage and enhancing environmentprotection. The sensing data can be used to find optimalenvironments for the plants. In addition, the data on the plantingcondition can be saved by sensor tags, which can be used in supplychain management.



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Example: Automated Vineyard

In a vineyard with medium to large geographical size, a number of 50to 100 LC nodes are manually deployed in order to provide full signalcoverage over the study area. An additional number of 100 to 1000leaf nodes with (possibly heterogeneous) specialized sensors (i.e.,humidity, temperature, soil condition, sunlight) are attached to theLCs in local wireless star topologies, periodically reportingmeasurements to the associated LoWPAN LCs. For example, in a 20-acrevineyard with 8 parcels of land, 10 LoWPAN Nodes are placed withineach parcel to provide readings on temperature and soil moisture.The LoWPAN Nodes are able to support a multi-hop forwarding/routingscheme to enable data forwarding to a sink node at the edge of the

vineyard. Each of the 8 parcels contains one data aggregator tocollect the sensed data. Ten intermediate nodes are used to connectthe sink nodes to the main gateway.

Localization is important for geographical routing, for pinning downwhere an event occurred, and for combining gathered data with theiractual position. Using manual deployment, device addresses can beused. For randomly deployed nodes, a localization algorithm needs tobe applied.

There might be various types of sensor devices deployed in a singleLoWPAN, each providing raw data with different semantics. Thus, anadditional method is required to correctly interpret sensor readings.Each data packet may include meta-information about its data, or atype of a sensor could be encoded in its address during addressallocation.

Dominant parameters in agricultural monitoring:

o Deployment: pre-planned

The nodes are installed outdoors or in a greenhouse with highexposure to water, soil, dust, in dynamic environments of movingpeople and machinery, with growing crop and foliage. LoWPAN nodescan be deployed in a pre-defined manner, considering the harshenvironment.

o Mobility: all static

o Network Size: medium to large, low to medium density

o Power Source: all nodes are battery-powered except the sink, orenergy harvesting



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o Security Level: business-cri tical. Light-weight security or aglobal key management can be used depending on the businesspurpose.

o Mutli-hop communication: mesh topology with local starconnections.

o Connectivity: intermittent (many sleeping nodes)

o QoS: not critical

o Traffic Pattern: Mainly MP2P/P2MP. P2P for Gateway communicationor actuator triggering.

o Other issues: Time synchronization among sensors are required, but

the traffic interval may not be frequent (e.g. once in 30 minutesto 1 hour).


The network configuration in this use case might, in the most simplecase, look like illustrated in Figure 9. This static scenarioconsists of one or more fixed LoWPAN ER that are mains-powered andhave a high-bandwidth connection to a gateway via a backbone link,which might be placed in a control center, or connect to theInternet. The LoWPAN ERs are strategically located at the border ofvineyard parcels, acting as data sinks. A number of LC nodes areplaced along a row of plants with individual LoWPAN Hosts spreadaround them.

While the LoWPAN ERs implement the IPv6 Neighbor Discovery protocol(RFC 4861), the LoWPAN Nodes operate a more energy-considering NDdescribed in [6], which includes basic bootstrapping and addressassignment. Link-local addresses are used for communication withinthe network while routable addresses are needed to communicate withother LoWPAN nodes not reachable over a single radio transmission.Each LoWPAN ER can have predefined forward management information, ifnecessary.

The intermediate nodes must implement a multi-hop forwarding/routingprotocol (Mesh Under or Route Over) and they are responsible totransmit the measured data at the LoWPAN hosts to the LoWPAN ERs. In

this simplest case, the LoWPAN Routers (not edge routers) or Meshnodes can build static forwarding/routing paths, and all end-nodescan be placed in one radio hop distance from its forwarder. In moreadvanced setups, mesh routing is used for data distribution. Packetsare forwarded to each router or mesh node and relayed to the LoWPANER.



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LoWPAN nodes may send event-driven notifications when readings exceedcertain thresholds, such as low soil humidity; which mayautomatically trigger a water sprinkler in the local environment.For increased energy efficiency, all LoWPAN Nodes are in periodicsleep state. However, the LoWPAN LCs need to be aware of suddenevents from the leaf nodes. Their sleep periods should therefore beset to shorter intervals. Communication schedules must be set upbetween master and leaf nodes, and global time synchronization isneeded to account for clock drift.

Also, the result of data collection may activate actuators. Context-awareness, node identification and data collection on the applicationlevel are necessary.

+----+| GW |+----+

| h h h h h h h h h GW: Gateway| \|/ \|/ \|/ ER: LoWPAN Edge Router

ER---- LC-------LC------LC CN: Local Coordinator node| /|\ /|\ /|\ h: LoWPAN Host| h h h h h h h h h

ER...

Figure 9: An aligned multi-hop LoWPAN.



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4. Security Considerations

Security requirements differ by use case. For example, industrialand structural monitoring applications are safety-crit ical. Securetransmission must be guaranteed, and only authenticated users shouldbe able to access and handle the data. Lightweight key mechanismscan be used. In health care system, data privacy is an importantissue. Encryption is required, and role-based access control isrequired to be supported by a proper authentication mechanism.



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5. Acknowledgements

Thanks to David Cypher for giving more insight on the IEEE 802.15.4standard and to Irene Fernandez for her review and valuable comments.



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6. References

6.1. Normative References

[1] Bradner, S., "Key words for use in RFCs to Indicate RequirementLevels", BCP 14, RFC 2119, March 1997.

[2] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,September 2007.

[3] Kushalnagar, N., Montenegro, G., and C. Schumacher, "IPv6 overLow-Power Wireless Personal Area Networks (6LoWPANs): Overview,Assumptions, Problem Statement, and Goals", RFC 4919,August 2007.

[4] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,"Transmission of IPv6 Packets over IEEE 802.15.4 Networks",RFC 4944, September 2007.

[5] IEEE Computer Society, "IEEE Std. 802.15.4-2006 (as amended)",2007.

6.2. Informative References

[6] Shelby, Z., Thubert, P., Hui, J., Chakrabarti, S., Bormann, C.,and E. Nordmark, "6LoWPAN Neighbor Discovery",draft-ietf-6lowpan-nd-07 (work in progress), October 2009.

[7] Hui, J. and P. Thubert, "Compression Format for IPv6 Datagramsin 6LoWPAN Networks", draft-ietf-6lowpan-hc-06 (work inprogress), October 2009.

[8] Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "ProblemStatement and Requirements for 6LoWPAN Routing",draft-ietf-6lowpan-routing-requirements-04 (work in progress),July 2009.

[9] Roemer, K. and F. Mattern, "The Design Space of Wireless SensorNetworks", December 2004.

[10] den Hartog, F., Schmidt, J., and A. de Vries, "On the Potential

of Personal Networks for Hospitals", May 2006.



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Authors Addresses

Eunsook KimETRI161 Gajeong-dongYuseong-guDaejeon 305-700Korea

Phone: +82-42-860-6124Email: [email protected]

Dominik KasparSimula Research Laboratory

Martin Linges v 17Snaroya 1367Norway

Phone: +47-4748-9307Email: [email protected]

Nicolas G. ChevrollierTNOBrassersplein 2P.O. Box 5050Delft 2600The Netherlands

Phone: +31-15-285-7354Email: [email protected]

JP VasseurCisco Systems, Inc1414 Massachusetts AvenueBoxborough MA 01719USA

Phone:Email: [email protected]



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