6LoWPAN Working Group                                             E. Kim
Internet-Draft                                                      ETRI
Intended status: Informational                                 D. Kaspar
Expires: July 22, 2011                        Simula Research Laboratory
                                                          N. Chevrollier
                                                             JP. Vasseur
                                                      Cisco Systems, Inc
                                                        January 18, 2011

               Design and Application Spaces for 6LoWPANs


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

Status of this Memo

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  5
     1.2.  Premise of network configuration . . . . . . . . . . . . .  5
   2.  Design Space . . . . . . . . . . . . . . . . . . . . . . . . .  7
   3.  Application Scenarios  . . . . . . . . . . . . . . . . . . . .  9
     3.1.  Industrial Monitoring  . . . . . . . . . . . . . . . . . .  9
       3.1.1.  A Use Case and its Requirements  . . . . . . . . . . . 10
       3.1.2.  6LoWPAN Applicability  . . . . . . . . . . . . . . . . 11
     3.2.  Structural Monitoring  . . . . . . . . . . . . . . . . . . 12
       3.2.1.  A Use Case and its Requirements  . . . . . . . . . . . 13
       3.2.2.  6LoWPAN Applicability  . . . . . . . . . . . . . . . . 14
     3.3.  Connected Home . . . . . . . . . . . . . . . . . . . . . . 15
       3.3.1.  A Use Case and its Requirements  . . . . . . . . . . . 15
       3.3.2.  6LoWPAN Applicability  . . . . . . . . . . . . . . . . 17
     3.4.  Healthcare . . . . . . . . . . . . . . . . . . . . . . . . 18
       3.4.1.  A Use Case and its Requirements  . . . . . . . . . . . 18
       3.4.2.  6LoWPAN Applicability  . . . . . . . . . . . . . . . . 20
     3.5.  Vehicle Telematics . . . . . . . . . . . . . . . . . . . . 20
       3.5.1.  A Use Case and its Requirements  . . . . . . . . . . . 21
       3.5.2.  6LoWPAN Applicability  . . . . . . . . . . . . . . . . 22
     3.6.  Agricultural Monitoring  . . . . . . . . . . . . . . . . . 22
       3.6.1.  A Use Case and its Requirements  . . . . . . . . . . . 22
       3.6.2.  6LoWPAN Applicability  . . . . . . . . . . . . . . . . 24
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 26
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 28
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 29
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 29
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 30

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1.  Introduction

   Low-power and lossy networks (LLNs) is the term commonly used to
   refer 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 are
   characterized by low speed, low performance, low cost, and unstable
   connectivity.  A LoWPAN is a particular instance of an LLN, formed by
   devices complying with the IEEE 802.15.4 standard [4].  Their typical
   characteristics can be summarized as follows:

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

   o  Small memory capacity: the smallest common LoWPAN nodes have a few
      kBytes of RAM with a few dozens of kBytes of ROM/flash memory.
      While the memory sizes of nodes continue to grow (e.g., IMote has
      64K SRAM, 512K Flash memory), the nature of small memory capacity
      for LoWPAN nodes remains a challenge.

   o  Low power: wireless radios for LoWPANs are normally battery-
      operated.  Their RF transceivers often have a current draw of
      about 10 to 30 mA, depending on the used transmission power level.
      In order to reach common indoor ranges of up to 30 meters and
      outdoor ranges of 100 meters, the used transmission power is set
      around 0 to 3 dBm.  Depending on the processor type, there is an
      additional battery current consumption of the CPU itself, commonly
      in the order of tens of milliamperes.  However, the CPU power
      consumption can often be reduced by a thousandfold when switching
      to sleep mode.

   o  Short range: the Personal Operating Space (POS) defined by IEEE
      802.15.4 implies a range of 10 meters.  For real implementations,
      the range of LoWPAN radios is typically measured in tens of
      meters, 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 current
      deployments.  Alternatively, three lower data rates of 20K, 40K
      and 100K bit/s are defined.

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

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

1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [1].

   Readers are expected to be familiar with all the terms and concepts
   that are discussed in "IPv6 over Low-Power  Wireless Personal Area
   Networks (6LoWPANs): Overview, Assumptions,  Problem Statement, and
   Goals" [2], and " Transmission of IPv6 Packets over IEEE 802.15.4
   Networks" [3].

   Readers would benefit from reading 6LoWPAN ND [5], 6LoWPAN header
   compression [6], and 6LoWPAN Routing Requirements [7] for the details
   of the 6LoWPAN work.

   This document defines the following terms:

   LC (Local Controller)

      A logical functional entity that performs the special role of
      coordinating and controlling its child nodes for local data
      aggregation, status management of local nodes, etc.  There may be
      multiple instances of local controller nodes in a LoWPAN.

   LBR (LoWPAN Border Router)

      A border router is located at the junction of separate LoWPAN
      networks or between a LoWPAN network and another IP network.
      There may be one or more LBRs at the LoWPAN network boundary.  A
      LBR is the responsible authority for IPv6 Prefix propagation for
      the LoWPAN network it is serving.  An isolated LoWPAN also
      contains a LBR in the network, which provides the prefix(es) for
      the isolated network.

1.2.  Premise of network configuration

   The IEEE 802.15.4 standard distinguishes between two types of nodes,
   reduced-function devices (RFDs) and full-function devices (FFDs).  As
   this distinction is based on some MAC features that are not always in
   use, we are not using this distinction in this document.

   6LoWPAN networks can be deployed using either route-over or mesh-

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   under architectures.  As the choice of route-over or mesh-under does
   not affect the applicability of 6LoWPAN technologies to the use cases
   described in the document, we will use the term "6LoWPAN network" to
   mean either a route-over or mesh-under network.

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2.  Design Space

   Inspired by [8], this section lists the dimensions used to describe
   the design space of wireless sensor networks in the context of the
   6LoWPAN Working Group.  The design space is already limited by the
   unique characteristics of a LoWPAN (e.g., low-power, short range,
   low-bit rate) as described in [2].  The possible dimensions for
   scenario categorization used in this document are described as

   o  Deployment: LoWPAN nodes can be scattered randomly or they may be
      deployed in an organized manner in a LoWPAN.  The deployment can
      occur at once, or as an iterative process.  The selected type of
      deployment has an impact on node density and location.  This
      feature 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 that
      provide the intended network capability.  The number of nodes
      involved in a LoWPAN could be small (10 nodes), moderate (several
      100s), or large (over a 1000).

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

   o  Connectivity: Nodes within a LoWPAN are considered "always
      connected" when there is a network connection between any two
      given nodes.  However, due to external factors (e.g., extreme
      environment, 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 to
      highly varying bit-rates.

   o  Multi-hop communication: The multi-hop communication factor
      highlights the number of hops that has to be traversed to reach
      the edge of the network or a destination node within it.  A single
      hop 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 and
      industry 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 use
      of 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 and
      require 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 structural
      monitoring 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 induced
      factor (e.g., sensors in an automobile), hence not predictable, or
      a controlled characteristic (e.g., pre-planned movement in a
      supply 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 scenarios
   in terms of system design.  A complete list of practical use cases is
   not the objective of this document.

3.1.  Industrial Monitoring

   LoWPAN applications for industrial monitoring can be associated with
   a broad range of methods to increase productivity, energy efficiency,
   and safety of industrial operations in engineering facilities and
   manufacturing plants.  Many companies currently use time-consuming
   and expensive manual monitoring to predict failures and to schedule
   maintenance or replacements in order to avoid costly manufacturing
   downtime.  LoWPANs can be inexpensively installed to provide more
   frequent and more reliable data.  The deployment of LoWPANs can
   reduce equipment downtime and eliminate manual equipment monitoring
   that is costly to be carried out.  Additionally, data analysis
   functionality can be placed into the network, eliminating the need
   for manual data transfer and analysis.

   Industrial monitoring can be largely split into the following
   application fields:

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

      A plant's monitoring boundary often does not cover the entire
      facility but only those areas considered critical to the process.
      Easy to install wireless connectivity extends this line to include
      peripheral areas and process measurements that were previously
      infeasible or impractical to reach with wired connections.

   o  Machine Surveillance: ensuring product quality and efficient and
      safe equipment operation.  Critical equipment parameters such as
      vibration, temperature, and electrical signature are analyzed for
      abnormalities that are suggestive of impending equipment failure
      (see Section 3.2).

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

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

3.1.1.  A Use Case and its Requirements

   Example: Hospital Storage Rooms

   In a hospital, maintenance of the right temperature in storage rooms
   is very critical.  Red blood cells need to be stored at 2 to 6
   degrees Celsius, blood platelets at 20 to 24 C, and blood plasma
   below -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 the
   location of shelves, as indoor obstacles distort the radio signals.
   At each blood pack a sensor tag can be installed to track the
   temperature during delivery.  A LoWPAN node is installed in each
   container of a set of blood packs.  In this case, highly dense
   networks must be managed.

   All nodes are statically deployed and manually configured with either
   a single- or multi-hop connection.  Different types of LoWPAN nodes
   are configured based on the service and network requirements.
   Especially, LCs play a role in aggregation of the sensed data from
   blood packs.  In the extended networks, more than one LoWPAN LCs can
   be installed in a storage room.  In the case that the sensed data
   from an individual node is urgent event-driven data such as outrange
   of temparature or humidity, it will not be accumulated (and further
   delayed) by the LCs but immediately relayed.

   All LoWPAN nodes do not move unless the blood packs or a container of
   blood packs is moved.  Moving nodes get connected by logical
   attachment to a new LoWPAN.  When containers of blood packs are
   transferred to another place of the hospital or by ambulance, the
   LoWPAN 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 the
   temperature and humidity in the storage rooms.  The data over or
   under a pre-defined threshold is meaningful to report.  Blood cannot
   be used if it is exposed to the wrong environment for about 30
   minutes.  Thus, event-driven data sensed on abnormal occurrences is
   time-critical and requires secure and reliable transmission.

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

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   tracking of containers is important.  The hospital network manager or
   staff can be provided with an early warning of possible chain
   ruptures, for example by conveniently accessing comprehensive online
   reports and data management systems.

   Dominant parameters in industrial monitoring scenarios:

   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-critical.  Secure and reliable
      transmission must be guaranteed.

   o  Multi-hop communication: multi-hop 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 differ
   substantially by system design.  As illustrated in Figure 1, the
   simplest way is to build a star topology inside of each storage room.
   Based on the layout and size of the storage room, the LoWPAN can be
   configured in a different way of mesh topology as shown in Figure 2.

   Each LoWPAN node may reach the LBR by a predefined routing/forwarding
   mechanism.  Each LoWPAN node configures its link-local address and
   obtains a prefix from its LBR by an 6LoWPAN ND procedure [5].  LoWPAN
   nodes need to build a multi-hop connection to reach the LCs and LBR.

   The data volume is usually not so large in this case, but is
   sensitive to delay.  Data aggregators can be installed for each
   storage room, or just one data aggregator can collect all data.  To
   make a light transmission, UDP is likely to be chosen, but secure
   transmission and security mechanism MUST be added.  To increase
   security, link-layer mechanisms and/or additional security mechanisms

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   SHOULD be used.

   Because a failure of a LoWPAN node can critically affect the storage
   of the blood packs, network management is important in this use-case.
   A light weight management mechanism MUST be provided for the

   When a container is moved out from the storage room, and connected to
   the other hospital system (if the hospital buildings are fully or
   partly covered with LoWPANs), a mechanism to rebind to a new parent
   node and a new LoWPAN MUST be supported.  In the case that it is
   moved by an ambulance, it will be connected to an LBR in the vehicle.
   This type of mobility is supported by 6LoWPAN ND and routing

   LoWPANs MUST be provided with low installation and management costs,
   providing benefits such as reduced inventory, and precise location
   tracking of containers, and mobile equipment (moving beds at the
   hospital or ambulances).

                         |                     LBR: LoWPAN Border Router
             LC----------LC----------LC        LC: Local Controller node
            / | \       / | \       / | \          (Data Aggregator)
           n  n  n     n  n  n     n  n  n      n: LoWPAN node

            Figure 1: Storage rooms with a simple star topology

           |            |           |         LBR: LoWPAN Border Router
          LBR          LBR         LBR(LC)     LC: Local Controller node
           |            |           |             (Data Aggregator)
          LC - n       LC - n      n            n: LoWPAN Node
        /  |   |        |   |     / \
       n   n - LC   n - n - n    n - n
       |       | \          |    |\
       n       n  n - n     n    n n

               Figure 2: Storage rooms with a mesh topology

3.2.  Structural Monitoring

   Intelligent monitoring in facility management can make safety checks
   and periodic monitoring of the architecture status highly efficient.
   Mains-powered nodes can be included in the design phase of a

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   construction or battery-equipped nodes can be added afterwards.  All
   nodes are static and manually deployed.  Some data is not critical
   for security protection (such as normal room temperature), but event-
   driven emergency data (such as a fire alarm) MUST be handled in a
   very critical manner.

3.2.1.  A Use Case and its Requirements

   Example: Bridge Safety Monitoring

   A 1000m long concrete bridge with 10 pillars is described.  Each
   pillar and the bridge body contain 5 sensors to measure the water
   level, and 5 vibration sensors are used to monitor its structural
   health.  The LoWPAN nodes are deployed to have 100m line-of-sight
   distance from each other.  All nodes are placed statically and
   manually configured with a single-hop connection to the local
   coordinator.  All LoWPAN nodes are immobile while the service is
   provided.  Except from the pillars, there are no special obstacles of
   attenuation to the node signals, but careful configuration is needed
   to prevent signal interference between LoWPAN nodes.

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

   This use case can be extended to medium or large size sensor networks
   to monitor a building or for instance the safety status of highways
   and tunnels.  Larger networks of the same kind still have similar
   characteristics such as static node placement, manual deployment and
   dependent on the blue print of the structure, mesh topologies will be
   built with mains-powered relay points.  Periodic and event-driven
   real-time data gathering is performed and the emergency event-driven
   data 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 local coordination or relays).

   o  Security Level: safety-critical.  Secure transmission must be
      guaranteed.  Only authenticated users must be able to access and

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      handle the data.

   o  Multi-hop communication: multi-hop mesh networking is recommended
      to be supported.

   o  Connectivity: always connected or intermittent by sleeping mode

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

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

   o  Other Issues: accurate sensing and reliable transmission are
      important.  In addition, sensor status reports should be
      maintained in a reliable monitoring system.

3.2.2.  6LoWPAN Applicability

   The network configuration of this use case can be done by simple
   topologies, however, there are many extended use cases for more
   complex structures.  The example bridge monitoring case may be the
   simplest case (an example topology is illustrated in Figure 3).

   The LoWPAN Nodes are installed on the place after manual optimization
   of their location.  As the communication of the leaf LoWPAN nodes may
   be limited to the data gathering points, both 16-bit and 64-bit can
   be used for IPv6 link-local addresses [3].  Each pillar may have one
   LC for data collection from each pillar.  Communication schedules
   should be set up between leaf nodes and their LC to efficiently
   gather the different types of sensed data.  Each data packet may
   include meta-information about its data, or the type of sensors could
   be encoded in its address during the address allocation.

   This type of application works based on both periodic and event-
   driven notifications.  The data over or under a pre-defined threshold
   is meaningful to report.  Event-driven data sensed on abnormal
   occurrences is time-critical and requires secure and reliable
   transmission.  For energy conservation, all nodes may have periodic
   and long sleep modes but wake up on certain events.  The data
   gathering entity can be programmed to trigger actuators installed in
   the infrastructure, when a certain threshold value has been reached.

   Due to the safety-critical data of the structure, authentication and
   security are important issues here.  Only authenticated users MUST be
   allowed to access the data.  Additional security SHOULD be provided
   at the LBR for restricting the access from outside of the LoWPAN.

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   The LBR may take charge of authentication of LoWPAN nodes.  Reliable
   and secure data transmission must be guaranteed.

   LBR - LC ----- LC ------ LC           LBR: LoWPAN Border Router
         /|        |        |            LC: Local Controller node
        n n    n - n - n    n - n        n: LoWPAN Node
          /\       |   |    |   |
         n  n      n - n    n - n - n

                  Figure 3: A bridge monitoring scenario

3.3.  Connected Home

   The "Connected" Home or "Smart" home is with no doubt an area where
   LoWPANs 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 dozen
   and probably in the near future a few hundreds of nodes of various
   nature: sensors, actuators and connected objects.

3.3.1.  A Use Case and its Requirements

   Example: Home Automation

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

   With the emergence of "Smart Grid" applications, the LoWPAN may also

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   have direct interactions with the Grid itself via the Internet 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 as Demand-
   Response application.  Another service known as Demand Side
   Management (DSM) could be provided by utilities to monitor and report
   to the user its energy consumption with a fine granularity (on a per
   device basis).  Other inputs such as dynamic pricing can also be
   received by the user from the utility that can then turn on and off
   some appliances according to its local policy in order to reduce its
   energy 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 to
   which additional sensors can be added for safety (gas, water, CO,
   Radon, smoke detection).  The LoWPAN typically comprises a few dozen
   nodes forming an ad-hoc network with multi-hop routing since the
   nodes may not be in direct range.  It is worth mentioning that the
   number of devices tends to grow considering the number of new
   applications for the home.  In its most simple form, all nodes are
   static and communicate with a central control module but more
   sophisticated scenarios may also involve inter-device communication.
   For example, a motion/presence sensor may send a multicast message to
   a 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 on
   a cell phone.

   Ergonomics in Connected Homes is a key and the LoWPAN must be self-
   managed and easy to install.  Traffic patterns may greatly vary
   depending on the applicability and so does the level of reliability
   and QoS expected from the LoWPAN.  Humidity sensing is typically not
   critical and requires no immediate action whereas tele-assistance or
   gas leak detection is critical and requires a high degree of
   reliability.  Furthermore, although some actions may not involve
   critical data, still the response time and network delays must be on
   the order of a few hundreds of milliseconds to preserve the user
   experience (e.g. use a remote control to switch a light on).  A
   minority of nodes are mobile (with slow motion).  With the emergence
   of energy related applications it becomes crucial to preserve data
   confidentiality.  Connected Home LoWPAN usually do not require multi-
   topology or QoS routing and fairly simple QoS mechanisms must be
   supported by the LoWPAN (the number of Class of Services is usually

   Dominant parameters for home automation applications:

   o  Deployment: multi-hop topologies

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   o  Mobility: some degree of mobility

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

   o  Power Source: mix of battery and mains-powered devices

   o  Security Level: authentication and encryption required

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

   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)

3.3.2.  6LoWPAN Applicability

   In the home automation use case, the network topology is made of a
   mix of a battery operated and mains-powered nodes that both
   communication with each other and a LBR provides connectivity to the
   outside of world for control management (Figure 4).

   In home network, installation and management must as extremely simple
   for the user.  Link local IPv6 addresses can be used by nodes with no
   external communication and the LBR allocates routable addresses to
   communicate with other LoWPAN nodes not reachable over a single radio

                           n --- n              I: Internet
                           |     |             LBR: LoWPAN Border Router
Internet/ ------- LBR/LC -- n --- n ---- LC     LC: Local controller node
Utility network     |      |            /|\     n: LoWPAN Node
                    n ---- n           n n n

   (outside)       (home automation system)

                    Figure 4: Home Automation scenario

   In some scenarios, the traffic will be sent to a LC for processing
   that may in turn decide of local actions (switch a light on, ...).
   In other scenarios, all devices will send their data to the LCs that
   may also act as the LBR for data processing and potential relay of
   data to outside of the LoWPAN.  It does not mean that every device
   gets through the LC and LBR for communicating each other.  For the

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   sake of illustration, some of the data may be processed to trigger
   local action (e.g. switch off an appliance), simply store and sent
   once enough data has been accumulated (e.g. energy consumption for
   the past 6 hours for a set of appliances) or could trigger an alarm
   immediately sent to a datacenter (e.g. gas leak detection).

   Although in the majority of cases nodes within the LoWPAN will be in
   direct range, some nodes will reach the LBR/LC with a 2-3 hops path
   (with the emergence of several low power media such as low power PLC)
   in which case LoWPAN routers will be deployed in the home to
   interconnect the various IPv6 links.

   The home LoWPAN must be able to provide extremely reliable
   communication in support of some specific application (e.g. fire, gas
   leak detection, health monitoring) whereas other application may not
   be critical at all (e.g humidity monitoring).  Similarly some
   information may require the use of security mechanisms for
   authentication, confidentiality.

3.4.  Healthcare

   LoWPANs are envisioned to be heavily used in healthcare environments.
   They have a big potential to ease the deployment of new services by
   getting rid of cumbersome wires and simplify patient care in
   hospitals and for home care.  In healthcare environments, delayed or
   lost information may be a matter of life or death.

   Various systems, ranging from simple wearable remote controls for
   tele-assistance or intermediate systems with wearable sensor nodes
   monitoring various metrics to more complex systems for studying life
   dynamics, can be supported by LoWPANs.  In the latter category, a
   large amount of data from various LoWPAN nodes can be collected:
   movement pattern observation, checks that medicaments have been
   taken, object tracking, and more.  An example of such a deployment is
   described in [9] using the concept of Personal Networks.

3.4.1.  A Use Case and its Requirements

   Example: healthcare at home by tele-assistance

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

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   Multipath interference may often occur due to the mobility of the
   patients at home, where there are many walls and obstacles.  Even
   during sleeping, the change of the body position may affect the radio

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

   Privacy also becomes an serious issue in this case, as the sensed
   data is very personal.  In addition, different data will be provided
   to the hospital system from what is given to a patient's family
   members.  Role-based access control is needed to support such
   services, thus support of authorization and authentication is

   Dominant parameters in healthcare applications:

   o  Deployment: pre-planned

   o  Mobility: moderate (patient's mobility)

   o  Network Size: small, high node density

   o  Power Source: hybrid

   o  Security Level: Data privacy and security MUST be provided.
      Encryption is required.  Role based access control is required to
      be supported by light weight authentication mechanism

   o  Multi-hop communication: multi-hop for homecare devices, star
      topology on patients body.  Multipath interference due to walls
      and obstacles at home must be considered.

   o  Connectivity: always on

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

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

   o  Other issues: Plug-and-play configuration is required for mainly
      non-technical end-users.  Real-time data acquisition and analysis
      are important.  Efficient data management is needed for various
      devices which have different duty-cycles, and for role-based data
      control.  Reliability and robustness of the network are also

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3.4.2.  6LoWPAN Applicability

   In this use case, the local network size is rather small (less than
   10s of nodes).  The home care system is statically configured with
   multi-hop paths and the patient's body network can be built as a star
   topology.  The LBR at home is the sink node in the routing path from
   sources on the patient's body.  A plug-and-play configuration is
   required.  As the communication of the system is limited to a home
   environment, both 16-bit and 64-bit can be used for IPv6 link-local
   addresses [3].  An example topology is provided in Figure 5.

   The patient's body network can be simply configured as a star
   topology with a LC dealing with data aggregation and dynamic network
   attachment when the patient moves around at home.  As multipath
   interference may often occur due to the patients' mobility at home,
   the deployment of LoWPAN nodes and transmission paths should be well
   considered.  At home, some nodes can be installed with power-
   affluence status, and those LoWPAN nodes can be used for relaying
   points or data aggregation points.

   The sensed information MUST be maintained with the identification of
   the patient no matter if the patient visits the connected hospital or
   stays at home.  If the patient's LoWPAN uses globally unique IPv6
   address, the address can be used for the identification.  However, it
   causes cost for privacy and security.  The hospital LoWPAN where the
   patient's information is transferring needs to operate additional
   identification system together with strong authority and
   authentication mechanism.  The connection between the LBR at home and
   the LBR at Hospital must be reliable and secure, as the data is
   privacy-critical.  To achieve this, additional policy for security is
   recommended between the two LoWPAN.

                         n - n               I: Internet
                         |   |             LBR: Edge Router
      LBR --- I -- LBR - n - n - LC         LC: Local controller node
      /|\           |    |       /|\         n: LoWPAN Node
    .. . ..         n -- n      n n n

   (hospital)       (home system)  (patient)

                  Figure 5: A mobile healthcare scenario.

3.5.  Vehicle Telematics

   LoWPANs play an important role in intelligent transportation systems.
   Incorporated in roads, vehicles, and traffic signals, they contribute
   to the improvement of safety of transporting systems.  Through

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   traffic or air-quality monitoring, they increase the possibilities in
   terms of traffic flow optimization and help reducing road congestion.

3.5.1.  A Use Case and its Requirements

   Example: Telematics

   As shown in Figure 6, scattered LoWPAN Nodes are included in roads
   during their construction for motion monitoring.  When a car passes
   over these nodes, the possibility is then given to track the
   trajectory and velocity of cars for safety purposes.

   The lifetime of the LoWPAN Nodes incorporated into roads is expected
   to be as long as the life time of the roads (about 10 years).  Multi-
   hop communication is possible between LoWPAN Nodes, and the network
   should be able to cope with the deterioration over time of the node
   density due to power fails.  Sink nodes placed at the side of road
   are most likely mains-powered, LoWPAN Nodes in the roads run on
   battery.  Power saving schemes might intermittently disconnect the
   nodes.  A rough estimate of 4 nodes per square meter is needed.
   Other applications may involve car-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: hybrid

   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

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3.5.2.  6LoWPAN Applicability

   For this use case, the network topology includes fixed LBRs that are
   mains-powered and have a connection to high speed networks (e.g.,
   Internet) in order to reach the transportation control center
   (Figure 6).  These LBRs may be logically combined with LC as a data
   sink to gather sensed data from a number of LoWPAN Nodes inserted in
   the tarmac of the road.  In the road infrastructure, a LoWPAN with
   one LBR forms a fixed network and the LoWPAN nodes are installed by
   manual optimization of their location.

           | LBR |----------------------------- LBR ...
           +-----+    (at the road side)
      n -- n --- n --- n   +---|---+       LBR: LoWPAN Border Router
          / \          |   | n-n-n |        n: LoWPAN Node
         n  n          n   +---|---+

                      Figure 6: Telematics scenario.

3.6.  Agricultural Monitoring

   Accurate temporal and spatial monitoring can significantly increase
   agricultural productivity.  Due to natural limitations, such as a
   farmers' inability to check the crop at all times of day or
   inadequate measurement tools, luck often plays a too large role in
   the success of harvests.  Using a network of strategically placed
   sensors, indicators such as temperature, humidity, soil condition,
   can be automatically monitored without labor intensive field
   measurements.  For example, sensor networks could provide precise
   information about crops in real time, enabling businesses to reduce
   water, energy, and pesticide usage and enhancing environment
   protection.  The sensing data can be used to find optimal
   environments for the plants.  In addition, the data on the planting
   condition can be saved by sensor tags, which can be used in supply
   chain management.

3.6.1.  A Use Case and its Requirements

   Example: Automated Vineyard

   In a vineyard with medium to large geographical size, a number of 50
   to 100 LC nodes are manually deployed in order to provide full signal

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   coverage over the study area.  An additional number of 100 to 1000
   leaf nodes with (possibly heterogeneous) specialized sensors (i.e.,
   humidity, temperature, soil condition, sunlight) are attached to the
   LCs in local wireless star topologies, periodically reporting
   measurements to the associated LCs.  For example, in a 20-acre
   vineyard with 8 parcels of land, 10 LoWPAN Nodes are placed within
   each parcel to provide readings on temperature and soil moisture.
   The LoWPAN Nodes are able to support a multi-hop forwarding/routing
   scheme to enable data transmission to a sink node at the edge of the
   vineyard.  Each of the 8 parcels contains one data aggregator to
   collect the sensed data.

   Localization is important for this type of LoWPAN where installed in
   a geographically large area, for pinning down where an event
   occurred, and for combining gathered data with their actual position.
   Using manual deployment, device addresses can be used for identifying
   the position and localization.  For randomly deployed nodes, a
   localization algorithm needs to be applied.

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

   Dominant parameters in agricultural monitoring:

   o  Deployment: pre-planned

      The nodes are installed outdoors or in a greenhouse with high
      exposure to water, soil, dust, in dynamic environments of moving
      people and machinery, with growing crop and foliage.  LoWPAN nodes
      can be deployed in a pre-defined manner, considering the harsh

   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, or
      energy harvesting

   o  Security Level: business-critical.  Light-weight security or a
      global key management can be used depending on the business

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   o  Multi-hop communication: mesh topology with local star

   o  Connectivity: intermittent (many sleeping nodes)

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

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

   o  Other issues: Time synchronization among sensors are required, but
      the traffic interval may not be frequent (e.g. once in 30 minutes
      to 1 hour).

3.6.2.  6LoWPAN Applicability

   The network configuration in this use case might, in the most simple
   case, look like illustrated in Figure 7.  This static scenario
   consists of one or more fixed LBR that are mains-powered and have a
   high-bandwidth connection to a backbone link, which might be placed
   in a control center, or connect to the Internet.  The LBRs are
   strategically located at the border of vineyard parcels, acting as
   data sinks.  A number of LCs are placed along a row of plants with
   individual LoWPAN nodes spread around them.

   While the LBRs implement the IPv6 Neighbor Discovery protocol (RFC
   4861) to connect the outside of the LoWPAN, the LoWPAN Nodes operate
   a more energy-considering ND described in [5], which includes basic
   bootstrapping and address assignment.  Each LBR can have predefined
   forward management information to a central data aggregation point,
   if necessary.

   LoWPAN nodes may send event-driven notifications when readings exceed
   certain thresholds, such as low soil humidity; which may
   automatically trigger a water sprinkler in the local environment.
   For increased energy efficiency, all LoWPAN Nodes are in periodic
   sleep state.  However, the LCs need to be aware of sudden events from
   the leaf nodes.  Their sleep periods should therefore be set to
   shorter intervals.  Communication schedules must be set up between
   master and leaf nodes, and global time synchronization is needed to
   account for clock drift.

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

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        |    n n n   n n n   n n n         I: Internet
        |     \|/     \|/     \|/        LBR: LoWPAN Border Router
       LBR----LC------LC------LC          LC: Local Controller node
        |     /|\     /|\     /|\          n: LoWPAN node
        |    n n n   n n n   n n n

                  Figure 7: Automated vineyard scenario.

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4.  Security Considerations

   Security requirements differ by use case.  For example, industrial
   and structural monitoring applications are safety-critical.  Secure
   transmission MUST be guaranteed, and only authenticated users MUST be
   able to access and handle the data.  Lightweight key mechanisms can
   be used.  In health care system, data privacy is an important issue.
   Encryption is required, and role-based access control is required to
   be supported by a proper authentication mechanism.

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5.  IANA Considerations

   This document contains no actions for IANA.

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6.  Acknowledgements

   Thanks for David Cypher for giving more insight on the IEEE 802.15.4
   standard, and Irene Fernandez, Shoichi Sakane and Paul Chilton for
   intensive review and valuable comments.

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7.  References

7.1.  Normative References

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

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

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

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

7.2.  Informative References

   [5]  Shelby, Z., Chakrabarti, S., and E. Nordmark, "Neighbor
        Discovery Optimization for Low-power and Lossy Networks",
        draft-ietf-6lowpan-nd-15 (work in progress), December 2010.

   [6]  Hui, J. and P. Thubert, "Compression Format for IPv6 Datagrams
        in 6LoWPAN Networks", draft-ietf-6lowpan-hc-13 (work in
        progress), September 2010.

   [7]  Kim, E., Kaspar, D., Gomez, C., and C. Bormann, "Problem
        Statement and Requirements for 6LoWPAN Routing",
        draft-ietf-6lowpan-routing-requirements-08 (work in progress),
        November 2010.

   [8]  Roemer, K. and F. Mattern, "The Design Space of Wireless Sensor
        Networks", December 2004.

   [9]  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 Kim
   161 Gajeong-dong
   Daejeon  305-700

   Phone: +82-42-860-6124
   Email: eunah.ietf@gmail.com

   Dominik Kaspar
   Simula Research Laboratory
   Martin Linges v 17
   Snaroya  1367

   Phone: +47-4748-9307
   Email: dokaspar.ietf@gmail.com

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

   Phone: +31-15-285-7354
   Email: nicolas.chevrollier@tno.nl

   JP Vasseur
   Cisco Systems, Inc
   1414 Massachusetts Avenue
   Boxborough  MA 01719

   Email: jpv@cisco.com

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