Requirements “Needs” Statement"According to the National Center for Mission and Exploited Children for the year 2000, there were over 750,000 reports of missing children - roughly 2,100 children per day.”*
We will develop a system to
increase the recovery rate
of these children.*Source: http://www.ncmec.org/download/ar_2000.pdf
Requirements Elicitation Process
• We Developed Case Scenarios– Child wearing device 24x7 to various activities– Operation during abduction– Non-family child abduction– Operation during non-abduction
• We Used Functional Scenarios– Tracking operations– Reporting operations– Processes and procedures– Hardware, software– Performance
• We Performed Similar System Examinations– Cadillac OnStar® System
• OnStar add-on services
– Acura Navigation System– Volvo Navigation System– Lo-Jack Anti-Theft System
• We Solicited Stakeholder Inputs (Parental Survey)– 10 question survey to 5 mothers of children
Used a broad array of elicitation techniques . . .
Requirements Results• Developed ~90 unique requirements• Developed 6 functional areas (15 sub-functions)
–Power Management•Idle
•Activated
–Communications•Transmit/Receive EOC-MU
•EOC-Police
•EOC-Parents
–Tracking•Acquire GPS signals
•Calculate location
–Data Storage•Store location at EOC
•Store location in Mobile Unit
–Maintenance•EOC Maintenance
•Mobile Unit Maintenance
–Performance•Reliability
•Affordability
•Size/Weight
•Legal Compliance
Architectures: Requirements Mapping
Requirements Navigation System
Power Mgmt
Wearing of Device
Notifi-cation
Comm Ops Center
The WoRLD system shall map coordinates to area mapping systems.
The mobile unit shall be operated and worn continuously
The mobile unit shall self-activate
Operate in low power standby mode for a period of 72 hours
Establish a robust communication infrastructure to facilitate interstate cases and exchanges
The mobile unit shall report its system health status
The system shall transfer coordinate information to local, state, federal law enforcement agencies, or parents.
The mobile unit available in NFT five different sizes.
The mobile unit will be concealable.
The navigation data should promote good ranging properties, signal hiding and immunity to jamming.
The WoRLD system shall not transmit coordinate information until activation.
The EOC shall be capable of interrogating transmit devices.
The mobile unit will be difficult to remove.
The mobile unit designed with anti-tamper measures
The WoRLD shall be responsive to local, state and federal laws.
ArchitecturesFunctional System Areas Architecture Alternatives
Navigation
SystemGPS LORAN Orbcomm
Power
ManagementSolar Batteries Kinetic
Wearing of
DeviceImplant Obvious
ExternalHidden
ExternalNotification Operator Auto-
notificationDistance Trigger
Communications Cell-Analog
Cell Digital
Ops Center Central Distributed
* Total number of possible architectures: 3x3x3x3x2x2 = 324
Architectures: Alternatives• The 5 chosen architectures explore the
trade-space• Low, Mid, High Cost• Low, Mid, High Performance• High Value Option
• Architecture choices are based upon the following • Use Case Scenarios• Questionnaires• Student research of relevant technologies (lo-jack, LORAN,
Cell Analog, GPS)• Past experience of group
Architectures: Considerations…
Functional System Areas Architecture AlternativesNavigation
System
GPS
(High Cost)
(High Performance)
LORAN
(Mid Cost)
(Low Performance)
Orbcomm
(Mid Cost)
(High Performance)
Power
Management
Solar
(Mid Cost)
(Mid Performance)
Batteries
(Low Cost)
(High Performance)
Kinetic
(High Cost)
(Low Performance)
Wearing of Device Implant
(High Cost)
(High Performance)
Obvious External
(Low Cost)
(High Performance)
Hidden External
(Mid Cost)
(High Performance)
Notification Operator
(High Cost)
(High Performance)
Auto-notification
(Mid Cost)
(Mid Performance)
Distance Trigger
(Low Cost)
(Low Performance)
Communications Cell-Analog
(Low Cost)
(High Performance)
Cell Digital
(High Cost)
(Mid Performance)
Ops Center Central
(Mid Cost)
(High Performance)
Distributed
(High Cost)
(High Performance)
Arch. 1 High Cost/High Performance
Functional System Areas
Chosen Alternatives
Navigation System
GPS LORAN Orbcomm
Power Management
Solar Batteries Kinetic
Wearing of Device Implant Obvious Hidden External
Notification Operator Auto-notification Distance Trigger
Communications Cell-Analog Cell Digital
Ops Center Central Distributed
Arch. 2 Low Cost/High Performance
Functional System Areas
Chosen Alternatives
Navigation System
GPS LORAN Orbcomm
Power Management
Solar Batteries Kinetic
Wearing of Device Implant Obvious Hidden External
Notification Operator Auto-notification Distance Trigger
Communications Cell-Analog Cell Digital
Ops Center Central Distributed
Arch. 3 Mid Cost/High Performance
Functional System Areas
Chosen Alternatives
Navigation System
GPS LORAN Orbcomm
Power Management
Solar Batteries Kinetic
Wearing of Device Implant Obvious Hidden External
Notification Operator Auto-notification Distance Trigger
Communications Cell-Analog Cell Digital
Ops Center Central Distributed
Arch. 4 High Cost/Mid Performance
Functional System Areas
Chosen Alternatives
Navigation System
GPS LORAN Orbcomm
Power Management
Solar Batteries Kinetic
Wearing of Device Implant Obvious Hidden External
Notification Operator Auto-notification Distance Trigger
Communications Cell-Analog Cell Digital
Ops Center Central Distributed
Arch. 5 Mid Cost/Mid Performance
Functional System Areas
Chosen Alternatives
Navigation System
GPS LORAN Orbcomm
Power Management
Solar Batteries Kinetic
Wearing of Device Implant Obvious Hidden External
Notification Operator Auto-notification Distance Trigger
Communications Cell-Analog Cell Digital
Ops Center Central Distributed
Expert Choice: Values toward Goal
1: Power Management
2: Performance of Device in Different Locations
3: Performance under Certain Scenarios
4: RMA
5: Human Factors
6: Performance under 3 activation scenarios
Expert Choice: Trade Analysis
Arch Cost Perf
5 Mid Mid
2 Low High
1 High High
4 High Mid
3 Mid High
Overall
Inconsistency: 0.02
Expert Choice: Sensitivity• Analysis indicates Architecture Performance is
Sensitive to following Evaluation Criteria– Power
• Change of importance from 0.4 to 0.5 makes Architecture 2 preferred alternative vice Architecture 5
• More important Power becomes, less desirable Architecture 5 becomes
– Performance of Device in Different Locations• The more important this criteria becomes, the less desirable Architecture
5 becomes, however there is very little change in other Architectures
– Performance Under Certain Scenarios• Really Changes Outcome of Preferred Alternative
– Increase from 0.2 to 0.3 makes order 2, 5, 1– Increase from 0.2 to 0.4 makes order 2, 4, 1, 5– Increase from 0.2 to 0.5 makes order 4, 2, 1, 5
– Performance Under Different Activations• Increase of importance from 0.05 to .2 makes Architecture 1 the
preferred alternative (the only time this occurs)
Most Sensitive
Expert Choice: Pros/Cons
Arch. Pros Cons1 •Device is hard to remove
•Good power management•Good protection against parental abduction
•High cost•Very low user acceptance•Upgrades would be difficult and invasive
2 •Low cost•Good power management•Performs well when child gets lost and self activates
•High maintenance•Device is larger in size and easier to remove•Higher maintenance needs
3 •Low cost•Responds well to Call Center activation•High performance outside of buildings
•High maintenance•Device has low performance inside and over long distances•Performs lower during non-parental abductions
4 •Low scheduled and unscheduled maintenance•Device is small and difficult to remove•Waterproof
•High cost•Device upgrades would be difficult and invasive•LORAN technology is becoming obsolete
5 •High system reliability•Low scheduled and unscheduled maintenance•High user acceptance
•Difficult to upgrade•Bad power management when in idle state•Performed poorly in most abduction scenarios
Lifecycle Cost Basis of Estimate
• Estimate based on Fairfax County, VA– Approximately 250,000 children in the county,
estimate was scaled to 100,000 children.
• Estimate based on 5-year Lifecycle– 1st year slated for development of system and
training of personnel– Years 2 through 5 the system was operational
• Approximately 2,000 children missing each day, or roughly 7 per day for area the size of Fairfax county– Modeled ~ 100 calls per day across all
scenarios, assumed at least 7 would be “emergency calls”
Arch Initial
Est.
Estimated
Cost
1 High $303M
2 Low $154M
3 Mid $154M
4 High $328M
5 Mid $245M
Final Analysis: Pros/Cons• Top 2 Alternatives: Architectures 2 and 5
– Mixed Pros & Cons with Each– Even trade offs
• Arch-2: 0.246• Arch-5: 0.252
Different Locations
Certain Scenarios
Under 3 Activation Scenarios
Final Analysis: CostEffectiveness vs Cost for WoRLD System
Architectures
0
0.05
0.1
0.15
0.2
0.25
0.3
0 50 100 150 200 250 300 350
Cost (millions)
Eff
ec
tiv
en
es
s
Architecture 1
Architecture 2
Architecture 3
Architecture 4
Architecture 5
1
4
2
5
3
Good
Fair
Poor
Best Performance for the money . . .
Final Analysis: Ranking• Architecture 2: Highest “Value Index”Arch Cost Trade
Value
Value
Index
2 Low - $154M .246 1.605 Mid - $245M .252 1.03
1 High - $303M .233 0.77
3 Low – $154M .088 0.57
4 High - $328M .181 0.55
Functional System Areas Chosen Alternative
Navigation System Orbcomm
Power Management Batteries
Wearing of Device Obvious
Notification Auto-Notification
Communications Cell-Analog
Ops Center Central
Architecture 2 -
Class Exercise
Assignment: Architect a solution to the problems caused by the potential installation of XYZ Cellular Corp’s Base Station.
1. Create a problem(s)/need(s) statement
2. Decompose into a basic requirement set (~10-20)
3. Allocate requirements across a Functional set (~5)
4. Develop design alternatives for each function (~3)
5. Develop alternate system architectures (~3)
6. Evaluate alternatives vs. criteria (~5)
7. Select & recommend a preferred alternative
Top Related