Download Service-Oriented Software Architecture for Sensor

Service-Oriented Software
Architecture for Sensor Networks
Jan Blumenthal
University of Rostock
4. IuK Tage Rostock
Rostock, 20th June 2003
Outline
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Introduction to sensor networks
Requirements
Software Engineering
Approach
Conclusion
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Evolution of sensor nodes
Sensor,
Actuator
Battery
Processor
HF
PC
Picoradio
(UCB)
WINS
(UCLA)
Blue-Node
(UoR) Smart Piece of
Dust Silicon
3
(UCB)
Characteristics of Sensor Nodes
• Limited capacity of
– Battery (Lifetime: days – 10 years)
– Processing capabilities
– Transmission range (5…20
meters)
• Data rates: Bit/s … KB/s
• Transmission methods:
– Bluetooth
– ZigBee
– nanoNET
Coming up sensor
nodes
• One specific application
• Price: some cents
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Characteristics of Sensor Networks
Properties:
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Wireless sensor nodes connect together autonomously
Distributed organization
Contain one or more data sinks
Huge number of nodes to compensate transmission range (density: 0.1
- 20 nodes/m2)
• Nodes may move around
Tasks:
• Cooperative data acquisition:
– Cooperative data collection and preprocessing
– Running distributed applications regionally
– Forwarding of results to higher application levels
• Adaptive reactions on environment modifications
• Network has to behave robustly and fault-tolerant to:
– Failure on single nodes
– Transmission errors and distortion through obstacles
– Intrusion and jamming
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Applications
Protecting flood dam with sandbags
Stress Monitoring
Sensor Node
Measurements in Fluids
Intra Corporal Measurements
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Requirements of Sensor Networks
1. Self-Organization
– Ad hoc network formation
– Autonomous connection establishment
2. Network Maintenance
– Addressing of nodes
– Routing facilities
– Compensation of network failures
3. Cooperative Processing
– Context awareness
– Location positioning and location awareness
– Preprocessing of collected raw data
4. Security Mechanisms
5. Energy Optimizations
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Context Awareness
Context Awareness: Adapts the behavior of the node to the
current environment
• Infrastructure context
– Refers to the infrastructure around the node
– Example: Perception of bandwidth and reliability
• Domain context
– Refers to the current environment of the node
– Example: Knowledge of next data sink in the network
Data sink node
Simple node
Transmission
range
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Cooperative Algorithms
• Reduction of data by preprocessing and aggregation
• Minimization of data stream to data sinks
Example: Positioning

E3
N2
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E1

• Transfer E3 to N 3
N1

E2
N3
• Measurement the field

strengths of E1 and E 2
• Triangulation / multilateration
• Transfer of determined
positions to data sink
• Max. 6 transmissions
• Decentralized positioning
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Network Maintenance
• Attribute based addressing
– Assignment of data to location of data mining
– Location awareness necessary
– ID based addressing unfavorable
• Random node distribution
• Routes become obsolete quickly due to mobility
– Example: Temperature at location (x, y) ?
• Cooperative network behavior
– Data aggregation
– Address resolution / location awareness
– Adaptive routing strategy depends on mobility of nodes
• Communication reduction / avoidance
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Connectionless transmission
Prevent network traffic through data aggregation
Event based communication in contrast to request / reply
Polling avoidance
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Services
Definition: Little program accessed by standardized
interfaces over the network.
• Discovering and using services
• Cascading of services without previous knowledge of each
other
Service infrastructure for remote access:
Surface profile service
Surrogate Host
Service Proxy
Sensor C
Sensor B
Sensor A
Bluetooth
Physical
Request
Surface profile ?
LAN
Client
Physical
Request
Reply
Proprietary protocol TCP/IP
Reply
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Software Engineering
Network Maintenance
Services
Cooperative Algorithms
Context Awareness
Hardware Abstraction
Middleware
Common Middleware:
• Hides the complexity of the distributed system
• Standardized API to node application
• Provides access to services on remote nodes
Goal: Same middleware on different platforms
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Middleware Properties
Scalable Middleware
• Customization of data types during compile time
• Removing of unused components
Generic Middleware
• Platform independent middleware leads to increased number of
complex interfaces
• Adaption of interfaces instead of programs
Non Generic Middleware
void setBaudrate(int handle, int baudrate)
{
hardware_addr=getIOAddress(handle);
hardware_addr->BTR0=baudrate;
}
Generic Middleware
void setBaudrate(int baudrate)
{
// getIOAddress(handle);
BTR0=baudrate;
}
Valid only, if one interface present
Savings: parameter delivery, function call, stack operation, return value
assignment, field operation
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Middleware Properties II
Adaptive Middleware
• Mobility and changes in infrastructure require adaptions to the software
– Cluster head selection requires additional routing software
– Changing measurement methods leads to new programs
• Exchange and run components dynamically
– Start of new services
Reflective Middleware
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Ability to understand and influence itself
Application layers are not affected
Inspection: Analyze behavior via logging / debugging
Adaptation: Changing behavior of internal layers.
Example:
Customizing routing strategy depending on mobility
!
To overcome all the mentioned requirements
we designed a software model
!
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Definitions
Sensor Application
• Measurements and
storage of data
• Hardware dependant
• Example:
– Software driver for
temperature sensor
Node Application
• Application specific parts
• Middleware (routing,
discovering nodes)
• Contains sensor
application
Sensor Network Application
• Describes main tasks of the entire network
• Contains several node applications
• Optional administration interface
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Node Application
Host Middleware
Algorithms
Modules
Services
VM
Middleware Management
Operating System
Dynamic components
Internal interface
(generic middleware)
Sensor Driver
Sensor application
CPU
Sensor
No individual high level application, because:
• Nodes provide services only to the network
• Focus: Success of sensor network application instead of
node application
• Cooperative behavior of nodes
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Example
Middleware
Node
Sensor
Specific
Driver
OS Modules
Hardware
Sensor
Middleware
Middleware
Middleware
Node
Sensor
Specific OS
Driver
Modules
Node
Sensor
Specific
Driver
OS Modules
Node
Specific
OS Modules
ARM
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Sensor Node
Model
Temperature
Sensor
ARM Microcontroller
Temperature Sensor
68HC11
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Pressure
Sensor
68HC11 Microcontroller
Pressure Sensor
68HC11
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68HC11 µC
No Sensor
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Sensor Network Application
Administration Terminal
boot, logging
Sensor Network Application
Distributed Middleware
Node A
Node B
Node C
Middleware
Middleware
Middleware
Operating System
Operating System
Operating System
Hardware
Hardware
Hardware
systemwide
interfaces
customized
node‘s software
different node
hardware
• Middleware and Operating System are compiled and optimized to each
hardware
• Sensor Network Application
– Composition of all node services
• Optional administration terminal to manage the entire network
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Sensor Network Design
Components
Design & Edit
Compile/Link
Resource
Hardware
driven
• Create hardware-optimized software
components (driver, operating system)
• Create hardware-independent software
components (middleware, services)
• Combining of predefined components
• Source code generation
• Removing unused components
• Optimization of interfaces
• Optimization to node‘s hardware
• Distribution of nodes in different
environments
Distribute
Execute/Administrate
Monitoring
Evaluation
Optimization
• Monitoring the execution
• Creation of logfiles
• Evaluation of logfiles
Development Studio
Changes to common design methods.
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Conclusion
• New challenges of software development in sensor
networks
• Optimization of node‘s software based on
– Interface design
– Adaptive and reflective middleware
• Design of service-oriented middleware in sensor networks
• Future work
– Realization of presented software concept
– Development studio
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Thank you
Any questions ?
Our Approach
• Adaption of program to the application task
instead
adaption of application task to the program
• Adaption of interfaces to the program
instead
adaption of the program to the interfaces
• Application-dependent customized software
components
instead
multipurpose software on each node
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Software Architecture
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Desktop Model
Resource optimized
Application
Application
Middleware
Middleware
Operating System
Application Specific
OS Modules
Hardware
Hardware
Independent
applications
Standardized
middleware
Standardized
operating system
Example: Jini
Not optimized
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Independent
applications
Standardized
middleware
Standardized
interfaces
Unused components
removed
(Partly) optimized modules
Sensor Node
Middleware
Node
Sensor
Specific
Driver
OS Modules
Hardware
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Sensor
No independent
applications
Customized
middleware
Proprietary interfaces
Optimized driver
software
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