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Communication Between Peer Wireless Sensor Networks over 2.5G/3G Mobile Networks

Srdjan Krco

R&D

Ericsson Ireland

srdjan.krco@ericsson.com

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About Ericsson Ireland

• 3G research and development;• Training center;• Applied Research Lab

– Network management;– Wireless sensor networks;– Ad-hoc networks;– Distributed systems;

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Acknowledgments

• Skylark project team• David Cleary• Daryl Parker

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Presentation outline

• Introduction;• Wireless sensor networks gateway architecture; • P2P sensor networks;• Conclusion;

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Introduction – Ericsson Interests

• Ericsson fields of interest:– Mobile infrastructure;– Mobile services – design and development of new services that

will increase number of mobile network subscribers;

• Sensor networks in mobile networks context;• Potential source of new traffic and hence revenue;• Issues:

– How to connect sensor networks to mobile networks;– How to enable easy access to sensor networks and information

they provide;– Impact of numerous sensors connected to a mobile network;

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Introduction – Wireless Sensor Networks

• Number of small nodes with sensing, computing and wireless communication capability;

• Data gathered in one node; • Hop-by-hop communication; • Redundant number of nodes;• Data fusion;• Querying and tasking;

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Introduction – Wireless Sensor Networks

• Gateway node – injects queries and tasks;– gathers responses;

• User-gateway communication– using short-range wireless technology or – wide area networks (fixed and mobile);

• Sensor networks deployed, maintained, operated and used by one organization;

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Introduction – Wireless Sensor Networks

Mobile Network(GPRS/UMTS)

PDA

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Introduction – Resarch Focus

• Popular research topics:– Routing; – MAC layer issues;– Data aggregation;– Security;– Middleware;

• Less popular:– Interaction with external networks;– Interaction between wireless sensors networks;

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Introduction – Standard Assumptions

• Users have applications designed for a particular sensor network;

• Available services known in advance (temperature monitoring, military vehicles tracking);

• Means for establishing communication links with gateways (protocol, gateway address, etc.) known in advance;

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Focus of Our Research

• Design and development of software and protocol architecture of a wireless sensor network gateway– Generic, supports various sensor types and data format;– Independent of underlying transmission technologies;

• Creation of a peer-to-peer sensor network over a 2.5/3G mobile network, where each sensor network represents one peer node– Peers able to exchange data and provide more complex services;– Users also peers or have access to services provided by any peer

via communication with one peer node only;

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Our Testbed

GPRS

MemoryBT

Controller

MemoryBT

Controller

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Smart Sensor

• Micro controller– Controls Bluetooth link;– Implements communication protocol for interaction with gateway; – Controls attached sensors;

• Memory– Stores sensor data temporarily;

• Sensors– One or more attached;– Described by attributes;

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WSN Gateway Implementation

• Linux OS laptop;• Java;• Bluetooth PCMCIA card;• GPRS PCMCIA card or infrared connection to a GPRS

enabled mobile phone;

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WSN Gateway

• Entry point into a sensor network;• Short-range wireless communication

– With sensors;– With users in the vicinity;

• Wide area network access– Remote users;– Other gateways;

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WSN Gateway

• Hides internal organization of the sensor network; • Aware of all sensor types in the network and their

characteristics– Sensor attributes (sensor type, location, data format, accuracy

etc.) described and transferred as XML string;– Sensor querying based on sensor attributes (XML based);– Describes supported functions (max, min, average);

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WSN Gateway Functionality

• Discovers smart sensors;• Gathers description of available sensors;• Controls communication with and functionality of sensors;• Creates an object for each available sensor

– Has methods for communication with the sensor;– Keeps an up to date description of the sensor;

• Provides API for access and control of the sensor network;

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WSN Gateway – Architecture

SN Comm InterfaceBluetooth

Sensor Network API

Network InterfaceGPRS

Abstraction LayerJXTA middleware

JXTA API

Cor

e Ser

vice

s

Applications

Sensor Network

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Core Services

• Common procedures and services required by all layers– Logging;– Scheduling;– Event subscription;– Services required for automatic application start and restart;

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Sensor Network Communication Interface

• Transmission technology specific;• Provides methods for data transfer to/from sensors over

the chosen communication interface;• Provides additional, interface specific methods (Inquiry,

Service Discovery);

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Sensor Network Abstraction Layer

• Each sensor in the network represented as one object:– Methods for sending and receiving data to/from sensors;– Stores the complete description of sensor’s capabilities;

• Data transmission specifics hidden from users;• Uses XML based communication protocol

– Discover sensors’ characteristics;– Transfer data and commands;– Change sensor settings;

• Applications access objects using SN interface;• Collected replies are formatted into a structured XML

document and forwarded to users;

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Sensor Network Abstraction Layer – GetData

<?xml version="1.0" encoding="UTF-8"?><getData>

<sensor> <sensorID>

2 </sensorID> <transmitMode>

<attribute name=”periodical”> <attribute name=”period”>

5 </attribute> <attribute name=”unit”>

min </attribute></attribute>

</transmitMode></sensor>

</getData>

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<sensorProfile><attributeProfile>

<attribute name="location"><attribute name="town">

Dublin</attribute><attribute name="building">

<attribute name="name">Woodpark

</attribute></attribute><attribute name=“floor">

3</attribute><attribute name="room">

<attribute name="name">Conference room

</attribute><attribute name="number">

12394</attribute>

</attribute></attribute>

</attributeProfile>

Sensor Profile

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<dataProfile><dataAttribute>

<name>temperature

</name><unit>

Celsius</unit><sampleLength>

4</sampleLength>

</dataAttribute></dataProfile></sensorProfile>

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Sensor Network API

• Generic methods, provide consistent interface regardless of sensor type and characteristics;

• List of sensors in the network;• Description of available sensors (sensor attributes);• XML querying based on description of required data;• Listeners:

– Sensor has been added/removed from the network;– New data available;

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Sensor Network API – Query

• Users define data they are interested in (for example: temperature on the first floor in the HQ building) instead of defining the network address of a particular sensor;

• Query definition similar to the sensor attribute profile;• Constraints given in the query compared against

characteristics (attributes) of available sensors and returns a list of sensor IDs that correspond to the query;

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Sensor Network API – Query<?xml version="1.0" encoding="UTF-8"?><querySensors>

<constraint attrName="location"><constraint attrName="building">

<constraint attrName="name"><equals>

HQ House</equals>

</constraint></constraint><constraint attrName="level">

<moreThan>1

</moreThan><lessThan>

4</lessThan>

</constraint></constraint>

</querySensors>

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P2P Sensor Networks

• Sensor networks – Deployed on ad-hoc basis by various entities;– Appear and disappear based on the operator needs, requirements

and schedule;

• Short-range (Bluetooth) and wide-range (UMTS) wireless interface for communication with users;

• Users interact with networks in an ad-hoc manner based on theirs needs at a given moment and location;

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P2P Sensor Networks

Mobile Network(GPRS/UMTS)

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P2P Sensor Networks

• Users are external to the network– do not know about the existence of the network or services they

provide;– Sensor network’s characteristics, type or format of data unknown;

• Sensor network detection, service discovery and service provision mechanisms required;

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P2P Sensor Networks

• Numerous services– Traffic congestion info;– Water pollution of a river;– Weather info;– Personal health care network;– Free spaces in a car park;

• Not feasible to have a central service listing server;

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P2P Sensor Networks

• Individual sensor networks – Cooperate;– Form groups;– Provide more comprehensive service;– Available to more users;

• Users – Communicate with one sensor network gateway;– Able to get information about/from all other sensor networks in the

group;

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P2P Sensor Networks

• Possible scenarios:– Users access sensor network over a short-range wireless interface

(Bluetooth):• Bluetooth Inquiry;• Access to information from via the gateway;

– Users access sensor network over a mobile network:• Join peer group;• Access to information using P2P protocols;

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P2P Sensor Networks and Users

Mobile Network(GPRS/UMTS)

PDA

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P2P Sensor Networks

• Issues– Detection of other sensor networks;– Information exchange between sensor networks;– Description of sensor network services;– Forwarding users request and sensor network responses to/from

proper sensor network;

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JXTA

• Network programming and computing platform for creating interoperable P2P applications and services;

• Designed for ad-hoc, pervasive, multi-hop P2P networks;• Allows any connected heterogeneous device on the

network (mobile phone, PDA, PC et.) to communicate and collaborate with one another;

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JXTA - Architecture

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JXTA – Core Layer

• Peers: any networked device that implements JXTA;• Peer Groups: collection of peers that have a common set

of interests;• Pipes: the basic communication means – a virtual

unidirectional connection between peers;• Advertisements: Describe all entities (resources), such

as peers, peer groups, pipes, or services;– XML structured documents;

• Network Transport: provides a mechanism to handle the transmission of data over the network;

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JXTA – Protocols

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JXTA – Protocols

• Peer Resolver Protocol – mechanism by which a peer can send a generic query to other peers;

• Peer Discovery Protocol (PDP) – used to discover any published resources represented as advertisements. The PDP is based on the use of rendezvous peers;

• Peer Membership Protocol – mechanism by which peers can organize themselves to form groups. Peer groups are discovered using the PDP;

• Pipe Binding Protocol – used to establish pipe connections between peers;

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JXTA - Protocols

• Rendezvous Protocol – propagates messages within the specified group on behalf of peers from within the same group– primary purpose is to provide a service whereby peers can

connect to a rendezvous peer to avail of a service that will propagate messages on their behalf;

• Rendezvous Peers – Special type of peers with the ability to cache advertisements and forward requests to help peers discover resources;– Interact with different rendezvous peers;

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JXTA Services

• Discovery Service– Provides access to the PDP;– Limited to the context of the peer group;– Searches for JXTA resources;

• Pipe Service – Manages and creates virtual channels of communication between

peers in a peer group– Limited to the context of the peer group;

• Resolver Service– Implements the resolver service to distribute queries among peers;

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Platform Specific Services

• Position Service– Provides peer-positioning services by querying the MPS (Mobile

Positioning Service) for a given MSISDN embedded within a PeerID;• Scheduler service

– Allows tasks to be remotely scheduled on peers within our network (scheduled code updates, scheduled migration of services between peers);

• Sensor Service– JXTA wrapper service around the WSN Gateway functionality;

– Communication between peer sensor networks over GPRS network;

– Provides remote querying of sensor networks and individual sensors as well as providing sensor event subscription mechanisms;

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Example

• Gateway gathers sensor profiles, compiles a list of available services/sensors characteristics (type, location, accuracy, …) and structure it as its advertisement;

• Rendevouz peer has information about all available sensor services in the peer group;

• User interacts with a gateway over a short-range interface or becomes a mobile peer;

• Gets information about all services in the peer group from the local gateway or a rendevouz peer;

• Query network based on description of available services;

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Conclusion

• Gateway architecture:– Supports various types of sensors;– Easily adaptable to different communication technologies;– XML structured sensor profiles and communication protocol;– WSN API supports attribute based querying;

• JXTA platform can be used as a P2P middleware layer, but: – Poor performance;– Slow, consumes large amount of memory, quite unreliable;

• Prototype scaling-down required;