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Mobile Infrastructure & Security > Lesson 1 (Mobile Sensors) > Flashcards

Lesson 1 (Mobile Sensors) Flashcards

1
Q

What kind of mobile sensors are there? (10)

A

Temperature, GPS, Magnetic field, Accelerometer, Gyroscope, Proximity, Pressure, Pedometer, Light and (Microphone/camera)

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2
Q

What does the accelerometer do and how does it work?

A

Provides the total force applied on the device. Stationary gives +1g gravinational force. Used to determine device orientation. Accelerometer values minus gravity force gives acceleration in SI: m/s2 (acceleration m/s per time unit). Used on different axes (xyz)

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3
Q

What does the magentic field sensor do and how does it work?

A

Measures the ambient magnetic field on the xyz axes. Measured in Micro Tesla (uT). This can determine which way is north. Also called compass sensor..

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4
Q

What does the Gyroscope sensor do and how does it work?

A

Measures the rate of rotation around an axis (xyz). Pitch x, Roll y, Azimuth z. Used for example for games.

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5
Q

What does the pressure sensor do and how does it work?

A

Measures the barometric pressure. Used to measure altitude. Units in hPa (millibar)

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6
Q

What does the gravity sensor do and how does it work?

A

The gravity sensor is not separate. It removes the acceleration data from the accelerometer to measure the gravity power.

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7
Q

What does the light sensor do and how does it work?

A

Small dot on the front of the phone. Units in lux. Measures the amount of light in the front of the phone.

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8
Q

What does the proximity sensor do and how does it work?

A

Measures the distance between an object and the phone itself. Usually in centimeters. Used to put the screen off while calling.

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9
Q

What interface is implemented by various sensor classes and how do they run on the device?

A

They run as a background service. Implementing the Listener interface. You can register callbacks here to receive updates from the sensor. These are async callbacks.

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10
Q

Which two sensor manager classes are there in Android?

A

LocationManager (GPS) and SensorManager (accelerometer, gyroscope, proximity, light sensors). Th

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11
Q

How can you request a sensor manager from an Android app?

A

By calling getSystemService(SENSOR_SERVICE) in an activity.

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12
Q

What types of locations does the GPS location listener keep track of? What interface is used?

A

GPS location and network location. LocationListener interface. The location provider matters for power usage. GPS uses more power than network location. Its possible to register passivly, which means that if another app requests the location, you will get it as well to save battery.

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13
Q

What options can be set for requesting location updates and how is this method called?

A

calling: requestLocationUpdates(). Options are x meters distance, x time elapsed, x minimum accuracy. Accuracy is how many meters in a diameter from the returned position the phone can actually be.

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14
Q

What properties does the Location object have?

A

altitude, longitude, latitude, speed and time

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15
Q

How do you (un)register a listener?

A

Calling the getSystemService().getDefaultSensor(type) and registering a sensor listener class to this sensor manager. You can also unregister using this sensor manager

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16
Q

What method from the SensorListener interface is called for updates from the sensor?

A

onSensorChanged(SensorEvent evt). Contains values that came from the sensor.

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17
Q

How do services run?

A

In a different thread. Can’t run on the GUI thread. It’ll run in the background.

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18
Q

How is the thread-like way on the GUI thread called and used for?

A

Handler. Its a thread/task which is running on the current (usually GUI) thread.

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19
Q

How can you access the GUI from a service?

A

By either implementing the interface in an activity or calling a Handler, to do it as a background task but on the GUI thread.

20
Q

What sensor is used to count steps?

A

STEP_COUTER or STEP_DETECTOR. This is not a physical sensor. This is called a Pedometer.

21
Q

What is Bluetooth?

A

Bluetooth is a set of specs for common short range wireless applications

22
Q

Who maintains bluetooth?

A

Bluetooth SIG. Over 2500 members. (Special Interest Group)

23
Q

What is the latest version of Bluetooth?

A

4.x

24
Q

What is the range of bluetooth?

A

10-100m

25
Q

What is the unique identifier of a bluetooth chip?

A

an 48 bit address. Like the BT address, device address or Mac address. Its used in all layers of BT communication.

26
Q

What is a less power consuming bluetooth technology?

A

BLE, Bluetooth Low Enegery. Its part of Bluetooth 4.x

27
Q

3 Reasons why bluetooth is popular…

A

No network (LAN) is necessary, not other equipment. Just direct access.

28
Q

Where is Bluetooth used for? (3)

A

Wireless data transmittion. Unlimited syncing between devices in a short range. Handsfree calling/controlling of devices.

29
Q

2/3 Cutting edge Bluetooth apps…

A

iBeacons for advertising when you’r near. Also Payment / key authorization over bluetooth. (also health devices like wearables)

30
Q

Where is Bluetooth Low Energy (BLE) designed for? (4)

A

Small chunks of data. No support for streaming. Client-service architecture. 10mW RF-power.

31
Q

Bluetooth v1.2 keypoints… (3)

A
  1. Backward compatible with v1.1, faster connection and discovery.
  2. Recovered confrontation to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
  3. Data transmission speed up to 721 kbit / s.
32
Q

Bluetooth v2.0 keypoints… (3)

A
  1. Backward compatible with the previous v1.2.
  2. Enhanced Data Rate (EDR) for faster data transfer.
  3. The nominal rate of EDR is about 3 Mbit / s
33
Q

Bluetooth v3.0 keypoints… (3)

A
  1. Backward compatible with v2.1.
  2. Bluetooth 3.0 provides theoretical data transfer speeds of up to24 Mbit / s.
  3. For high data rate traffic this version uses the adjacent 802.11 link.
34
Q

Bluetooth v4.0+ keypoints… (4)

A
  1. Backward compatible with v3.0. Bluetooth 4.0 defines two modes:Blue tooth classic and blue tooth low energy. Some devices only have one mode, other devices support both modes (dual mode devices)
  2. Provides faster speed in data transmission than the earlier version.
  3. It comes with greatly reduced power consuming, as if it does not require any power at all to function.
  4. It provides more security in data transmission than the earlier version.
35
Q

What forms of bluetooth classic are there? (2)

A

BR = Basic Rate, EDR = Enhanced Data Rate.

36
Q

Which modes does Bluetooth 4.0 have? (2)

A
  1. a dual mode device which is able to support Bluetooth LE in addition to the regular Bluetooth BR/EDR (bluetooth classic)
  2. a single mode device, which supports only Bluetooth LE protocol.
37
Q

What are the three bluetooth classes?

A

Class 1: Ontworpen voor lange afstandsverbindingen (tot ~100m) - 100mW power
Class 2: Voor normaal gebruik (tot ~10m) - 2.5mW power
Class 3: Voor korte afstanden (10 cm - 1 m) - 1mW power

38
Q

Main difference between BLE (Bluetooth Low Energy) and Bluetooth classic

A

In summary, Bluetooth and Bluetooth Low Energy are used for very different purposes. Bluetooth can handle a lot of data, but consumes battery life quickly and costs a lot more. BLE is used for applications that do not need to exchange large amounts of data, and can therefore run on battery power for years at a cheaper cost. It all depends on what you’re trying to accomplish.

39
Q

What do we need to put in the android manifest to get bluetooth access?

A
40
Q

What low power operations does bluetooth have? (3 sorted on power consuming)

A

Hold: node sleep for a specified interval
Sniff: slave low-duty cycle mode. Will ocasionally run with a fixed interval.
Park: lowest power mode. Will not listen anymore, but periodically listen for broadcasts so it can unpark.

41
Q

What are Apple iBeacons?

A

Devices that can send unique code for enabling location based services, like advertising when you’re near.

42
Q

What are the different iBeacon ranges?

A

Immediate: Within a few cms
Near: within a couple of meters
Far: Greater than 10 meters

43
Q

What are the major/minor types of a ibeacon?

A

major = a value that can identify a group of beacons
minor = a value that can identify an individual beacon
within a group.

44
Q

What is the iBeacons unique address format?

A

30 bytes hex address. They can be used as a fixed prevux or a proximity UUID.

45
Q

When is a mobile phone accelerometerin a horizontal position?

A

When the X and Y axis are both 0g.

46
Q

Which sensor is used to measure device orientation?

A

Accelerometer

47
Q

How can an iBeacon estimate the distance between the client and the beacon?

A

Transmitted power value is used to calculate the distance from the ibeacon (TX-power from ibeacon + measured signal strength)

Mobile Infrastructure & Security (7 decks)

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