Towards%20a%20High%20Quality%20Standards%20Development%20Process%20for%20Mobile%20Telephony

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Towards a High QualityStandards Development
Processfor Mobile Telephony

• Luigi Logrippo
• Telecommunications SE Research Group
• School of InformationTechnology and Engineering
  University of Ottawa, Canada
• luigi_at_site.uottawa.ca
• www.site.uottawa.ca/luigi

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Claudine Simson, NortelNetworks VP recently
identified
Correct and Unambiguous Standards and
Specifications
as one of the challenges to be addressed by the
Company
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Importance of a correctly specified standard

• Implementation is simplified (and possibly even
  automated)
• Reduced reliance on testing, last minute fixes
• Interworking between different implementations
  has a better chance
• Standard updates can be traced to affected code

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The three stages of the standardization process
in telecom

• Stage 1 Specification of requirements, main
  functionalities, user view
• Stage 2 Identification of components and
  messages. Protocol scenarios expressed in the
  form of Message Sequence Charts (MSCs)
• Stage 3 Detailed description of the protocol

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Issues

• How to guarantee a disciplined, high-quality,
  development process among the three stages
• How to specify properly each stage
• How to guarantee consistency and traceability
  among the stages
• How to obtain automatically implementations from
  Stage 3
• How to derive test cases from all stages
• How to do design-time performance assessments
  (work by Prof. M. Woodside, Carleton University).

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Relevant techniques at different design stages
UCM
MSC
LOTOS
SDL
TTCN
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Use Case Maps for Stage 1A semi-formal notation
for presenting sequences ofabstract
responsibilities in distributed systems.Matches
well the abstract descriptions of Stage
1.Assignment of responsibilities to components
to be added in stage 2.
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Use Case Maps basic notation
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LOTOS

• Language of Temporal Ordering Specification
• Formal Description Technique
• Process Algebra Properties
• Interprocess Synchronization (rendezvous)
• Appropriate for systems prototyping and
  validation
• Several possible specification/representation
  styles
• Higher level languages that map into LOTOS have
  been defined
• Clear representation of system structures
• Validation tools

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From UCM to LOTOS

• Processes
• operator
• Actions
• Processes
• operator
• Synchronization
• Special Action

• Stubs
• Or-Fork/Join
• Responsibilities
• Components/maps
• And-Fork/Join
• Rendezvous
• TimeOuts

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LOTOS Allows to Execute Stage 1

• Scenarios can be derived and validated
• Message Sequence Charts can be derived
• Functional Test Suites can be derived

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Bound UCM between Stages 1 and 2
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Stage 2 Message Sequence Chart Notation
(MSCs)an ITU-T standard
(Example taken from WIN)
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Stage 3 SDL

• ITU-Ts Specification and Description Language
• Appropriate for detailed specification of
  architectures and protocols
• MSCs can be input to SDL and validated
• Code can be obtained from SDL
• Test suites can be obtained from SDL

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Our method
Requirements
Architectural Model
UCM
Stage 1
scenarios
LOTOS
MSCs
scenarios
Stage 2
scenarios
SDL
Stage 3
SDL
Test Cases (TTCN)
Implementation
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Evaluation of method

• Not limited to standards.
• can be applied generally to software design
• and probably also to hardware design, with
  adaptations
• Intensive and rigorous at the design level
• Simplifies significantly implementation, testing
  and probably maintenance

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Patterns towards an architectural approach to
telecom software engineering (with R. Andrade)

• Focus on common solutions to recurring problems
  regarding mobile wireless communication systems
• requirements and analysis stages
• Capture common behavior and architectural
  elements
• documentation for legacy systems
• source of initial design decisions for new
  systems (Wireless IP, IMT-2000)
• Patterns can be validated (e.g. by using LOTOS
  methods)

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Finding Patterns authentication
Use Case Maps System Descriptions
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A Summary of the Authentication Pattern

• Problem Preventing unauthorized or fraudulent
  access to cellular networks by mobile stations
  illegally programmed with counterfeit
  identification and electronic serial number.
• Solution Perform an authentication operation in
  both the mobile station and the network sides
  based on an encryption algorithm and a secret key
  number.

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Pattern Language

• A collection of patterns that build on each other
  to generate a system

Starting pattern
potential sequences in which the patterns occur
exchanges of data between two patterns
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Reusability
Common Solutions for Protocol Design Problems
describes
Patterns for Mobility and Radio Resource
Management
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Approach for Pattern Reuse
2nd Development Cycle
1st Development Cycle
Requirements
Capture (Stage 1)
Analysis (Stage 2)
Design (Stage 2)
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Evaluation

• Our patterns represent established expertise in
  the design domain
• This method captures such expertise in a
  rigorous, implementation-independent way
• Future designers of similar systems wont have to
  reinvent the wheel