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HP-MOSys 2012

25 October

Fábio Gameiro





Motivation (1/5)

Air Quality is increasingly becoming a concern for

public health officials and the citizens themselves;

3.3 millions of deaths related to air polution;

Reducing the air polution levels better public

health conditions and less expense in healthcare;

Source: World Health Organization (WHO)

3October 2012 - HP-MOSys 2012



Motivation (2/5)

Importance of air

quality

monitoring

4

- Register air pollutants concentration;

- Forecast based on statistical/

numerical models;

- Trigger alerts in case of high

concentrations;

- Support the creation of environmentlegislation / policies and verify their

results;

October 2012 - HP-MOSys 2012



Motivation (3/5)






Motivation (5/5)

7

Source: http://www.qualar.org

http://www.carris.pt

Bus 44 – 19 km

Bus 742 – 15 km

Bus 716 – 7 km

Bus 714 – 17 km

Bus 717 – 15 km

TOTAL

5 Buses

73 km


http://www.qualar.org/

http://www.carris.pt/

http://www.carris.pt/





URBISNET (1/7) Atmospheric monitoring with mobile stations of small

size and cost;

Mobile stations installed in urban buses;

Data acquisition using atmospheric sensors andsending data to a central server;

8

- Small dimensions;

- Low cost;

- Mobility;

- Greater spatial densityof samples;

- Inferior quality of

samples;- Fewer atmosphericcomponents (noparticles, sulfurdioxide, etc.);




URBISNET (2/7)

Create online air-quality maps;

Estimate pollution fields within Lisbon’s city limits;

Monitor and configure the mobile stations remotely,

through the web;




URBISNET (3/7)

?

10

Central Server

(CS)

Mobile

Station (MS)

Mobile

Station (MS)- Send atmospheric data

- Configure operations




URBISNET (4/7)

11

Central Server

(CS)

InternetMobile

Station (MS)

Mobile

Station (MS)

GPRS

Mobile Operator

Network

- Send atmospheric data





12

MS

Communications:

General PacketRadio Service

(GPRS)Wi-Fi 802.11 b/g

High connectivity and

availability

Usage costs

No usage costs

Sparse network= limited

connectivity

URBISNET (5/7)




URBISNET (6/7)

13

Central Server

(CS)

InternetMobile

Station (MS)

Mobile

Station (MS)

GPRS

802.11

Wi-Fi

Mobile Operator

Network

?October 2012 - HP-MOSys 2012

- Send atmospheric data




URBISNET (7/7)

14

Central Server

(CS)

Internet

Gateway

(GW)

Mobile

Station (MS)

Mobile

Station (MS)

GPRS

802.11

Wi-Fi

802.11

Wi-Fi

802.3

Ethernet

Mobile Operator

Network

- Send atmospheric data - WIFI

- Configure operations - GPRS




Architecture – MS (1/2) Requirements:

Atmospheric samples acquired periodically;

Georeferencing of samples;

Send the samples to the central server;

Provide remote monitoring and configuration

Characteristics:

Sensors: carbon dioxide (CO2), carbon monoxide (CO), ozone

(O3), nitrogen dioxide (NO2), temperature and relative humidity;

GPS;

GPRS and Wi-Fi communications;

ARM processor with Linux;




Architecture - MS (2/2)




Architecture – CS

Data Base to store samples;

Web Server as a platform tovisualize samples and preform

remote configuration of the

mobile stations;

Internet connection with

registered web domain and static

public IP address;




Architecture – GW (1/2)

Requirements:

Compact Size;

Wi-Fi 802.11b/g and Ethernet

interfaces;

Characteristics:

Desktop Asus EEEBox of reduced

size;

Built in Wi-Fi and Ethernet interfaces;




Architecture – GW (2/2)

Equipment configured to work autonomously as a

gateway between the mobile stations and the central

server;




Architecture - GPRS

20

- Supports monitoring and configuration operations

requested by the central server;

- The IP address of each MS is sent to the central server in

order to receive requests from it;

Star network topology since every MS canbe addressed by the central server;




Architecture - WiFi (1/6)

21

Used to send the atmospheric samples between MS and GW;

Network characteristics:

High mobility of MS nodes ;

Connectivity between nodes very limited;

Very sparse network;

Gateways placed in bus stops so most buses have direct

connectivity to them;

Data has only one destination, the central server;





22

The referred characteristics led to a communication protocol with the

following specifications:

Ad-hoc architecture;

Opportunistic communication;

Forwarding based on viral dissemination of information, using a

“store and forward” scheme;

Atmospheric sample is the basic unit of information;





23

Every network node sends a periodic broadcast message with

the type of node and identification;

Node type

Identification is unique for each type of node

NODE1 – mobile stations

GW - Gateways





24

After broadcasting, mobile stations exchange data between each

other or between mobile station and gateway;

Between mobile stations, the one with lowest id starts the data

exchange;

After data exchange, each mobile station adds the other station’s

address in a temporary exclusion list to avoid continuous data

exchange when in range;





25

Between mobile station and gateway, the mobile station always

initiates the communication, sending all of its data to the

gateway;

After receiving an acknowledge from the gateway, the mobile

station deletes the sent samples, assuming that all the data

will arrive at the central server;




Architecture – WiFi (6/6)

26

Information dissemination is tunable

by 2 parameters:

Time To Live (TTL) – controls

the maximum number of hopsthat a sample may take in the

network;

Max Times Sent – Controls the

number of times each sample issent from the same network

node;






Evaluation (2/5)

28

Results of the first test:

- 8 samples gathered were sent to the

central server;

- Successful line of sight

communication within a range of 140

meters.




Evaluation (3/5)

29

For the Wi-Fi performance test two mobile stations were used in

two cars (MS1 and MS2) and one gateway (GW);

6 trials were performed with different configurations (vehicle

speed and volume of data), in order to understand the efficiency

and effectiveness of the protocol in these situations;

Data files:

Small – 5 samples;

Medium – 20 samples; Large – 40 samples;

Speed:

20 km/h;

40 km/h;




Evaluation (4/5)






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