Using SysML modeling, the authors modeled a highway control system to link operational requirements to the design of an LTE wireless network. Key aspects of the model-based systems engineering approach included: (1) eliciting operational requirements and mapping them to system elements in the SysML model, (2) using parametric diagrams to connect radio link budget calculations to requirements, and (3) allowing tradeoff analysis by linking design parameters like camera resolution and frequency bandwidth to operational constraints. This integrated modeling approach improves design quality and reusability compared to document-driven processes.

1. Using Modelling Tools for Highway Control Operations
Padma Kamath and Michael Liem
Alcatel-Lucent
Introduction Method Results Conclusions
The Systems Engineering process is executed within the SysML Model. The model The SysML model allows linking of Operational requirements to individual model The model based approach enforces a high level of rigor in the description of the
ABSTRACT
becomes more detailed as each phase is executed. elements. By using Parametric Diagrams in the model, the dimensioning of the LTE system. It allows describing the operational scenarios thoroughly before making
Highway traffic control systems can be considered as complex. Often the Systems that
network through the Radio linkbudget can be connected to the requirements. architecture and technology decisions. We were able to link operational properties to
are built do not meet operational requirements fully. A SysML based Engineering Requirement Analysis Phase the verification of the design decision for the Wireless LTE technology. The verification
approach is proposed for building a Highway Control System. We demonstrate how Elicitation of operational requirements was done directly within the system model by using parametric diagrams. Even though
the Telecom Network Design (here LTE) will be linked in the model to the operational Mapping to the System requirements
Transmit Power
The linkbudget determines the
Max UE transmit Power Losses the telecommunication system is transparent to the rest of the system in most
requirements to achieve an optimal Design solution. Requirements become elements in the Maximum Allowable and Margins Maximum Path Loss (MAPL)
Pathloss
cases, the concept of parametric diagrams within SysML allows connecting network
model. Interference margin
Gains
With a radio propagation formula the capacity and dimensioning aspects directly to operational requirements of the
extra cell interference
Poor User Requirement Elicitation Mixing Requirements and Design Gains - Losses- Margins
Reference
Sensitivity inter-site distance can be determined applications which use the network.
‘Black Box’ View ‘White Box’ View Reference Sensitivity Interference
cell radius
System Designs often fail because of •= MAPL
Poor involvement by operations people MAPL j dB = PMaxTX dBm
+ Txgain dB − Txloss dB PL = K1+K2 log (R) Operational Requirements Operational Requirements
System
Requirements System Design
Non separation of Requirements and System features are grouped into Use + Rxgain dB − Rxloss dB − Bodyloss dB Derive Requirements for LTE Network
− Penetration dB − Sensitivity dBm Where:
Document Driven Error Prone Process No Requirement traceability Solution Cases − Interferen ceMargin dB K1: 1km path loss
Error prone processes Only the principal Use case is considered − ShadowingM argin dB + HOGain dB
K2: Path loss exponent
Lack of requirements traceability here + FSSGain dB System LTE Network Design System
Model Model
LTE Network
Design
MBSE MBSE
Systems Engineering process
The Linkbudget formula will be
according to ISO/IEC 15288
Proper Systems Engineering process implemented in the SysML model (see
Requirement System Analysis
is key for Design quality. This includes:
Process Input
Analysis and Control
(Balance)
diagram on the right) System Design System Design
Requirements
Requirement Analysis
Loop
Functional Analysis
Functional Analysis Phase Verification that LTE supports a given
Functional Analysis
and Allocation
Design
The System is considered as a “Black bandwidth is also implemented (see
Design Synthesis
Verification Loop
Design Process Box” diagram below )
Synthesis Output
System behavior is described using This integrated Design approach has a high potential for re-usability of models and
Flow charts (Activity Diagram) should reduce the effort for design and improve the design quality.
Requirement SysML Model
Validation &
Model Based Systems Engineering Message sequence Diagrams are
Acceptance
Analysis
with SysML is the state-of-the-art in generated automatically (not shown)
The CCTV camera throughput is linked
Functional
Verification
Systems Engineering System Functions and Operations are
defined to the inter-site distance (see diagram on Bibliography
Analysis
The diagram on the left shows it as the left)
applied to the Design of a Highway The “Black Box” model can be executed 1.Friedenthal,S.,Moore,A., Steiner,R.,A Practical Guide to SysML, OMG Press; 2009
Design
Synthesis Implementation
for validation Also the number of CCTV cameras and
Control System the length of the highway is also linked to 2.Hoffmann, H.-P., Deskbook - Model based Systems Engineering with Rational
the linkbudget Rhapsody and Rational Harmony for Systems Engineering, IBM, 2010
Weather
Sensor
Design Synthesis Phase 3.Lescuyer, P., Lucidarme, T., Evolved Packet System (EPS): The LTE and SAE
Central Control
The System Architecture is defined. Evolution of 3G UMTS, John Wiley & Sons, Chichester, UK, 2008.
(see System Block Diagram) Using a mathematical solver (e.g. Maxima or Mathematica) we can now trade-off 4.Papageorgiou,M., Papamichail,I., Handbook of Ramp Metering, EuropeanRamp
Highway Control System used for our Wireless BaseStation
Operations and functions are camera resolution against required frequency bandwidth against number of sites. We Metering Project, 2007
study consists of the following:
allocated to Subsystem elements have linked key dimensioning parameters through the SysML model to operational 5.IEEE1220 - Standard for Application and Management of the Systems Engineering
Ramp Metering with CCTV as traffic Speed Limit/Lane Gates
“White Box” message sequence constraints. One could further link the camera resolution to the parameters of the Ramp Process, 2005
sensor CCTV traffic flow
Diagrams are generated Metering algorithm such as maximum speed.
LTE Wireless networks to interconnect
Parametric Diagrams are defined to
elements of the system Ramp Signal
do trade-off Analysis (see results)