Waiting-time Displays for Bus Passengers

Team A: Huanwen Qu ,

Laurence Cabenda ,Kang Ning

Assignment

●The buses equip with GPS and mobile phones. Call into a central system to report their present location.●The bus stands will get LED displays controlled by a microprocessor which can also communicate by phone. ●The solution of communicating by phone was chosen●The central system knows the geography of the routes of all buses, the typical travel speed.

Requirements

● A high-level specification of the sytem● Give a briefing to the issue and aspects that may

be of importance for this.

Bus stand

Bus stand

Bus stand

Bus stand

Bus

Bus

Central System

Illustration

Central System

Mobilphone network

Auto phone

call

INTERFACE

System

control

Bus speed

calc

Route m

ap calc

Position calc

INTERFACE

Data process

Bus Speed

Bus Stand

Route Map

BUS with GPSBUS stand with LED

UML

Components

Central SystemBus

Bus Stand

Modules of Bus

GPS Receiver Bus Position Sender

Bus Position Report

GPS Receiver

● Contains GPS control system.● Receives bus position from GPS system● Exposes an interface which provides current bus

position to the Bus Position Report module.– GetPosition : POSITION

Bus Position Sender

● Contains mobile phone communication system.● Provides Wireless Data Link to the bus.● Exposes an interface to Bus Position Report

module.– SendPosition : POSITION

Receives position data and sends data to the Central System.

Bus Position Report

● Reports current bus position to Central System periodically.

● There is a timer in the module. When the timer is triggered, the module requests the current bus position from GPS Receiver module and sends this position to Central System through Position Sender module.

Timer --> SendPosition (GetPosition)

Modules of Bus Stand

Bus Distance Receiver

Bus Distance Display

LED Display

Bus Distance Receiver

● Contains mobile phone communication system.● Provides Wireless Data Link to the bus stand.● Receives bus distance from Central System.● Calls Bus Distance Display module to show

distance data when new data are received.– ShowDistance : DISTANCE

Bus Distance Display

● Shows bus distance data thought LED Display module.– LEDShow (LED)

● Converts bus distance data to LED display data.– DISTANCE -> LED

● Exposes an interface to Bus Distance Receiver module.– ShowDistance : DISTANCE

Converts DISTANCE to LED and shows it.

LED Display

● Shows the distance of the arriving buses on the LED display.

● Contains a LED display control system in the module.

● Exposes an interface which accepts bus distance data with type LED and shows the distance.– LEDShow : LED

Modules of Central System

Bus Position Trace

Route Map

Bus Distance Broadcast

Bus Distance Forecast

Bus Distance SenderBus Position Receiver

Bus Position Receiver

● Contains Mobile Phone Communication system.● Provides Wireless Data Link to the Central

System.● Receives bus positions for buses.● Calls Bus Position Trace module when new

position data arrives.– UpdatePosition position

Bus Distance Sender

● Contains Mobile Phone Communication system.● Provides Wireless Data Link to the Central

System.● Sends bus distance data to bus stands.● Exposes an interface to Bus Distance Broadcast

module.– SendDistance : DISTANCE

Accepts DISTANCE data and sends it to bus stands.

Bus Position Trace

● Manages position information of all buses dynamically

● Two interfaces:– UpdatePosition : POSITION

Updates a bus position.

– GetPosition : POSITION

Get a bus position from the trace.

Bus Distance Broadcast● Broadcasts bus distance data to all bus stands

periodically.● Manages a bus stands list.

– AllStands : STAND● There is timer in the module. When timer is

triggered, it calculates all bus distance data and sends them to all bus stands.

Timer --> for each stand in AllStands

distance = Forecast stand

SendDistance distance

Bus Distance Forecast

● Forecasts how much time it takes from a bus to a bus stands according to a typical bus speed and the route.

● The module can query bus position from Bus Position Trace module and query route map from Route Map module.

● Interface:– Forecast : STAND -> DISTANCE

Route Map

● Contains all information of bus routes and bus stands.

● Provides some interfaces for Bus Distance Forecast module to query data of bus routes and bus stands.

Discuss Requirements Accuracy

● Time intervals buses send GPS position● Time intervals server update the bus-stands● Accuracy versus time overhead.