Mobile Devices Notes
Mobile Devices
Understanding Mobile Devices
Objectives:
Set up mobile devices and peripherals.
Configure mobile device apps.
Install and configure laptop hardware.
Troubleshoot mobile device issues.
Set Up Mobile Devices and Peripherals
Mobile Display Types
Mobile devices integrate system components and peripherals for video, sound, and input control.
Smartphones, tablets, and hybrid tablet/laptops use touch screens for input/output and system case for components like CPU, RAM, storage, networking, and power.
Liquid Crystal Displays (LCD)
Most mobile devices use flat-panel LCD screen technology.
Liquid crystal properties change with voltage application.
Each color LCD pixel comprises subpixels with red, green, and blue (RGB) filters.
Transistors address each pixel to vary intensity, creating the display's color range.
Thin Film Transistor (TFT) Technology
Liquid crystal elements and transistors are placed on a thin film transistor (TFT).
Three main types of TFT technology:
Twisted nematic (TN): Crystals twist or untwist based on voltage level; earliest type, faster response times to reduce ghosting and motion blur during high frame rates.
In-plane switching (IPS): Crystals rotate, delivering better color reproduction and wider (178/178 degree) viewing angles; early versions had slower response times, but high-quality IPS can match TN response times while retaining better color and viewing angles.
Vertical alignment (VA): Crystals tilt, supporting wide color gamut and best contrast ratio (difference in shade between black and white).
Example: IPS panel might support a contrast ratio, a VA panel would be or . Viewing angles aren't as good as IPS, and response times are worse than TN, causing more motion blur and ghosting.
LED Backlit Displays
LCDs need illumination to produce a clear image.
TFTs use an array of light-emitting diodes (LED) for illumination.
Smartphones/tablets use edge lighting (LEDs at top/bottom) + diffuser for even brightness.
Organic LED (OLED) Displays
Each pixel is generated by a separate LED (AMOLED).
No separate backlight required.
Better contrast ratios, thinner, lighter, and consume less power.
OLEDs can be made from plastic, allowing curved displays.
Manufacturers are experimenting with flexible, roll-up displays.
Drawbacks:
Maximum brightness may be lower than LCDs, reducing clarity in bright sunlight.
More susceptible to burn-in (static images cause persistent retention).
Digitizer Functions
Touch screen converts analog touch input to digital instructions.
Digitizer is placed between protective glass and display panel.
Analog signals are detected by sensor grid when tapping/swiping.
Information is sent via cable to a circuit that converts analog to digital signal.
Capacitive Digitizers
Modern mobile devices use capacitive digitizers.
Support multitouch (gestures like sweeping/pinching).
Newer devices provide haptic feedback (touch responsiveness).
Touchscreen covered by scratch/shock-resistant tempered glass (e.g., Gorilla Glass).
Screen protector can be applied, carefully to avoid interfering with touch.
Rotating and Removable Screens
Most devices can be used in portrait or landscape orientation.
Accelerometers/gyroscopes detect device position changes and adjust screen orientation.
Also used as control mechanisms.
Some laptops are tablet hybrids with fully flipped/rotated touch screens.
Microsoft Surface hybrids feature detachable keyboards.
Mobile Device Accessories
Touchpads: Embedded panel on laptops for pointer control; most support multitouch/gestures.
Trackpads: Similar to touchpads, but often larger, external devices.
Drawing pads (graphics tablets): Large-format touch devices for digital art.
Touch Pens (Styluses): Used for precise control, handwriting, and drawing.
Natural input
Various sizes, from smartphone styluses to full-size pens for tablets/graphics pads.
Drawing pad pens have interchangeable nibs for different pen/brush types.
Microphone, Speakers, and Camera/Webcam
Mobile devices have integrated audio/video input/output.
Microphone records audio/voice calls, speakers produce audio output.
Digital camera for video recording/web conferencing/still pictures.
Laptops: Microphone exposed by a small hole next to the camera lens.
Smartphones/tablets have front/rear-facing cameras for still pictures/webcams.
Microphone/speakers are usually on the bottom edge.
External headsets/earbuds provide speaker microphone and headphone speakers.
Wired: 3.5 mm audio jack or USB/Lightning connector.
Wireless: Bluetooth.
Adapters can be used if no audio jack is supported.
Connections can also be used for external speakers.
Wi-Fi Networking
Enabling and Disabling Wi-Fi.
Airplane Mode
Wi-Fi Antenna Connector/Placement
Cellular Data Networking
Connect to the Internet via cellular radio and network provider.
Data rate depends on technology (3G, 4G, etc.).
Charges are based on data downloaded, especially when roaming internationally.
Discuss:
Global System for Mobile Communications vs. Code-Division Multiple Access
Cellular Networking Data Indicators
Enabling and Disabling Cellular Data
Mobile Hotspots and Tethering
A smartphone/tablet can be a personal hotspot to share cellular data.
Configure with access point settings (network name, security type, passphrase).
Tethering: Connecting another device via USB/Bluetooth to share cellular data.
Not all carriers allow tethering; some charge extra.
Connect via USB/Bluetooth, then configure tethering in settings.
Mobile Device Wired Connection Methods
Mobile devices support various connection methods.
Cabled and wireless interfaces allow peripheral attachment, data sharing, and charging.
Laptop Ports
Smartphone and Tablet Connectors
Serial Interfaces
Bluetooth Wireless Connections
Wireless connection for accessories.
Bluetooth creates a short-range personal area network (PAN).
Used to share data with a PC, connect to a printer, use a wireless headset, etc.
Enable, pair, and test Bluetooth connections.
Near-Field Communication (NFC) Wireless Connections
NFC chips for short-range data transmission (up to about 20 cm/8 in).
Low data rates for transactions not requiring large amounts of information.
Allows mobile payments via contactless PoS machines.
User enters credit card information into a wallet app.
The wallet app transmits a one-time token linked to customer account.
Major wallet apps: Apple Pay, Google Pay, and Samsung Pay.
Some PoS readers may only support specific wallet apps.
NFC enabled/disabled via settings on Android. Device must be unlocked for transactions over a certain amount.
NFC can configure other connections (e.g., pairing Bluetooth devices).
Tapping an NFC-enabled smartphone and headset automatically negotiates a Bluetooth connection.
Port Replicators and Docking Stations
Provide more connection methods for mobile devices.
Allows mobile devices to be used at a desk like a PC.
Port Replicator
Attaches via special connector or USB.
Provides ports for keyboards, monitors, mice, and network connections.
Does not add other functionality.
Docking Station
Sophisticated port replicator with add-in card/drive support via media bay.
Docked computer functions like a desktop or uses additional features.
Smartphone and Tablet Docks
Smartphones have processing power rivaling desktops.
Connects to monitor, external speakers, keyboard/mouse via USB or Lightning port.
Configure Mobile Device Apps
Mobile Apps
Installable programs extending mobile device functionality.
Written/compiled for a specific mobile OS.
Apps for Apple iOS cannot be directly installed on Android (developer must make a version for each OS).
Discuss:
iOS Apps
Android Apps
Permissions
Account Setup
Types of Data to Synchronize
Mobile device synchronization (sync) copies data between different devices.
PC and smartphone or smartphone, tablet, and PC.
Keeps information up to date.
Examples: Contacts, mail, pictures, videos, documents, apps, and passwords
Email Configuration Options
Email is an important feature of mobile devices.
Discuss:
Commercial Provider Email Configuration
Corporate and ISP Email Configuration
Synchronization Methods
Before cloud services, data was manually synchronized with a desktop PC.
Used PC to back up smartphone data and sync calendar/contacts.
Devices are now connected via cloud services.
Device OS and apps can back up data to the cloud with permission.
Signing into a new device syncs data from the cloud seamlessly.
Enterprise Mobility Management (EMM)
Applies security policies to mobile devices/apps in the enterprise.
Identifying and managing all devices is referred to as visibility.
Two main functions:
Mobile Device Management (MDM): Sets device policies for authentication, feature use (camera/microphone), connectivity; allows device resets and remote wipes.
Mobile Application Management (MAM): Sets policies for apps processing corporate data; prevents data transfer to personal apps; configures an enterprise-managed container or workspace.
When enrolled with MAM software, devices can be configured into an enterprise workspace mode allowing only authorized corporate applications to run.
Messages/attachments might be subject to data loss prevention (DLP) controls to prevent unauthorized forwarding.
Two-factor Authentication (2FA)
Most smartphones/tablets are single-user devices.
Access control via screen lock (password, PIN, swipe pattern).
Many devices support biometric authentication (fingerprint, facial/voice recognition).
Enrolled devices might have to re-authenticate to access the corporate workspace.
Corporate policy might require stronger methods, such as 2FA.
2FA means using two different kinds of credentials (fingerprint and PIN).
Account configured with authenticator device/app, trusted email account, or registered phone number.
When using a new device or when workspace policy requires 2FA, the user authenticates normally.
If accepted, an email, text, or phone call is generated on the trusted device.
The message includes a one-time password code for the user to input for confirmation.
Location Services
Geolocation: Using network attributes to identify the physical position of a device.
Mobile devices operate a location service to determine current position.
Two systems:
Global Positioning System (GPS): Determines latitude/longitude based on information received from satellites via a GPS sensor.
Indoor Positioning System (IPS): Works out a device's location by triangulating its proximity to other radio sources (cellular radio towers, Wi-Fi access points, Bluetooth/RFID beacons).
The location service stores personal data and is only available to apps with specific user permission.
Install and Configure Laptop Hardware
Laptop Disassembly Processes
Specific issues to consider for upgrades/replacements.
Hand Tools and Parts
Laptops use smaller screws than desktops; use precision screwdrivers and hand tools.
Screws can easily strip so use the appropriate sized screwdriver.
Document screw locations and ribbon cable orientation for reassembly.
Form Factors and Plastics/Frames
Laptop chassis incorporates the motherboard, power supply, display screen, keyboard, and touchpad.
Plastics/aluminum frames cover internal components.
Secured using small screws or pressure tabs; screws may be covered by rubber/plastic tabs.
Obtain manufacturer's service documentation before upgrades/replacements to explain disassembly, without damaging the chassis.
Only perform this work if no warranty is available.
Battery Replacement
Portable computers can work off building power and battery operation.
AC Adapters
Convert AC supply to DC voltages.
AC adapters are normally universal (or auto-switching) and can operate from any VAC Hz supply; check the label to confirm.
Battery Power
Laptop computers use rechargeable Lithium ion (Li-ion) battery packs. available in 6-, 9-, or 12-cell versions, with more cells providing for a longer charge.
Connector and battery-pack form factors are specific to the laptop vendor and to range/model.
Turn off and unplug the machine before inserting or removing the battery pack, which is usually removed by releasing catches.
The battery recharges when connected to the AC adapter and is trickle charged when laptop is in use.
Laptop includes a power management driver to ensure charging regime and prevent trickle charging from damaging it.
Li-on battery life is affected by being fully drained of charge and by being held continually at % charge. Balanced power charging stops trickle charging at %. Li-ion batteries are also sensitive to heat. If storing a Li-ion battery, reduce the charge to % and store at below oC.
RAM and Adapter Replacement
Laptops have fewer field-replaceable units (FRU) than desktops.
Using components sourced from the laptop vendor is recommended, but basic upgrade options, such as system memory and fixed disks, have become much simpler.
Upgrading RAM Modules
Laptop DDRx SDRAM is packaged in small outline DIMMs (SODIMMs).
A given SODIMM slot will only accept a specific type of DDR (e.g., DDR4 SODIMM in a DDR3 slot).
Slots are keyed to prevent incompatibilities.
Upgrading Adapter Cards
Adapters for modems, wireless cards, and SSD storage cards may be accessible and replaceable via screw-down panels.
Adapter formats: Mini PCIe, mSATA, and M.2 (none are compatible).
Can obtain mini PCIe or M.2 adapters for Wi-Fi, Bluetooth, and/or cellular data connectivity.
Reconnect the antenna wires or install a new antenna kit; wires run around the screen in the laptop lid and are delicate.
Disk Upgrades and Replacement
Laptops typically support one internal mass storage device; extra storage is attached to an external port.
To upgrade, there must be a plan for what to do with existing data:
Migration: Use backup software to create an image/clone of the old drive and store it on USB media; restore image to new drive.
A system image is technology neutral, so an image of an HDD can be applied to an SSD.
However, the new drive must be the same size or larger than the old one, unless using a cloning tool that can shrink the source image.
Replacement: Back up only the data; install OS and apps on the new drive, then restore user data.
Keyboard and Security Component Replacement
Mechanical devices like the keyboard, touch pad, and biometric sensors can easily be damaged.
Replacing damaged components can be more cost-effective than buying a new laptop.
Discuss: Keyboard and Touchpad Replacement, Key Replacement, Biometric Security Components, Near-field Scanner
Troubleshoot Mobile Device Issues
Power and Battery Issues
If experiencing problems working from AC power, first test the outlet with a “known good” device (such as a lamp).
Next, check that an LED on the AC adapter is green.
If there is no LED, check the fuse on the plug, and if available, try testing with a known good adapter.
If a mobile device will not power on when disconnected from building power, first check that the battery is seated properly in its compartment.
Also check whether the battery contacts are dirty; clean them using swabs.
If the battery is properly inserted and the mobile device does not switch on or only remains on for a few seconds, it is most likely completely discharged.
A battery exhibiting poor health will not hold a charge, meaning that the battery is at the end of its useful life.
You can test this by using a known good battery.
If a known good battery does not work, then there is something wrong with the power circuitry on the motherboard.
While laptop batteries are replaceable, few smartphones or tablets come with removable battery packs.
Most vendors try to design their devices so that they will support “typical” usage for a full day without charging.
As the battery ages, it becomes less able to hold a full charge.
If it is non-removable, the device will have to be returned to the vendor for battery replacement.
Improper Charging Symptoms
Care for the battery to prolong life and mitigate health/safety risks.
Use the battery charger provided by the manufacturer or an approved replacement charger.
Using an incorrect battery charging cable or exposing a battery to extreme heat carries risks of fire or even explosion.
An improper charging routine will reduce the usable life of a battery.
Follow manufacturer instructions on the proper charging and discharging of the battery.
Make use of power management features included with your device/OS to prolong battery life.
A Li-ion battery should not be allowed to fully discharge regularly or be kept persistently at 100% charge, as this reduces battery life.
As batteries age, the maximum charge they can sustain decreases, so short battery life will usually indicate that the battery needs replacing.
If the battery is not old or faulty, you could suspect that an app is putting excessive strain on the battery; you can use an app to check battery utilization.
Swollen Battery Symptoms
If you notice any swelling from the battery compartment, discontinue use of the mobile device immediately.
Signs include a device that wobbles when placed flat or a deformed touchpad/keyboard.
A swollen battery indicates a problem with the charging circuit, which is supposed to prevent overcharging.
If a device is exposed to liquid, this could also have damaged the battery.
Li-ion batteries are designed to swell to avoid bursting or exploding, but great care must be taken to avoid further damage.
A swollen battery is a fire hazard and could leak hazardous chemicals—do not allow these to come into contact with your skin or your eyes.
If the battery cannot be released safely and easily from its compartment, contact the manufacturer for advice.
You should also contact the manufacturer for specific disposal instructions.
A swollen battery should not be discarded via standard recycling points unless the facility confirms it can accept batteries in a potentially hazardous state.
Hardware Failure Issues
Overheating Symptoms
The compact design of mobile devices makes them vulnerable to overheating.
The bottom surface of a laptop becomes hot when improperly ventilated.
This can easily happen when laptops are put on soft surfaces, on people's laps, or in places where there is not enough room between the vents and a wall.
Laptop cooling (or chiller) pads are accessories that are designed to sit under the laptop to maximize airflow and protect a user from getting a burn from a device overheating.
Dust trapped in vents acts as an insulator and can prevent proper cooling.
Handheld devices use passive cooling and therefore can become quite warm when used intensively.
High screen brightness and use of the flashlight function will rapidly increase heat.
A mobile device will start to overheat quickly when exposed to direct sunlight.
Devices have protective circuitry that will initiate a shut down if the internal temperature is at the maximum safe limit.
You can also use an app to monitor the battery temperature and then compare that to the operating limits.
Generally speaking, approaching C is getting too warm.
Liquid Damage Symptoms
Some mobile-device cases provide a degree of waterproofing. Waterproofing is rated on the Ingress Protection (IP) scale.
A case or device will have two numbers, such as IP67.
The first (6) is a rating for repelling solids, with a 5 or 6 representing devices that are dust protected and dust proof, respectively.
The second value (7) is for liquids, with a 7 being protected from immersion in up to 1 m and 8 being protected from immersion beyond 1 m.
If a mobile device is exposed to liquid damage, there may be visible signs of water under the screen.
The screen might display graphics artefacts or not show an image.
Even if there is no visible sign, power off the device immediately if you suspect liquid damage.
Dry as much excess liquid as possible.
If you suspect that the internal components have been exposed, the device must be disassembled to fully dry.
Once dry, clean the circuit boards and contacts.
The battery will usually need to be replaced.
Physically Damaged Port Symptoms
Improper insertion and removal of connectors can easily damage the external ports of a mobile device.
If a port is damaged, the connector may be loose or may no longer fit.
There may be no data connection at all, or it might be intermittent.
The device may fail to charge properly.
Educate users to remove a connector by holding the connector and pulling it straight; a connector should not be jiggled to remove it.
USB-C and Lightning connectors are reversible, but other connector types should be oriented properly before plugging them in.
Screen and Calibration Issues
When you are troubleshooting a mobile display issue, you will often need to take into account the use of the integrated display and/or an external display and how to isolate a problem to a particular component, such as the graphics adapter, display panel, backlight, and digitizer.
If there is no image on the screen, check that the video card is good by using an external monitor.
Alternatively, there should be a very dim image on the display if the graphics adapter is functioning, but the backlight has failed.
Most screens use LED backlights; older laptops might use an inverter component to power a fluorescent backlight.
Discuss: Broken Screen Issues, Digitizer Issues, Cursor Drift/Touch Calibration Issues
Connectivity Issues
Wi-Fi and Bluetooth connectivity issues on a mobile can be approached in much the same way as on a PC.
Problems can generally be categorized as either relating to “physical” issues, such as interference, or to “software” configuration problems.
Consider these guidelines when you are troubleshooting issues with communication and connectivity:
Verify that the adapter is enabled. Check the status of function key toggles on a laptop, or use the notification shade toggles on a mobile device to check that airplane mode has not been enabled or that the specific radio is not disabled.
If a laptop has been serviced recently and wireless functions have stopped working, check that the antenna connector has not been dislodged or wrongly connected.
If a wireless peripheral such as a Bluetooth mouse or keyboard that has been working stops, it probably needs a new battery.
If you experience problems restoring from hibernate or sleep mode, try cycling the power on the device or reconnecting it and checking for updated drivers for the wireless controller and the devices.
If you are experiencing intermittent connectivity issues:
Try moving the two devices closer together.
Try moving the devices from a side-to-side or up-and-down position to a different position or changing the way in which the device is held.
Consider using a Wi-Fi analyzer to measure the signal strength in different locations to try to identify the source of interference.
Malware Issues
Whenever a device does not function as expected, you should assess whether it could be infected with malware.
Discuss the following scenarios:
Malware or rogue apps are likely to try to collect data in the background.
They can become unresponsive and might not shut down when closed.
Such apps might cause excessive power drain and high resource utilization, potentially leading to overheating problems.
Another tell-tale sign of a hacked device is reaching the data transmission overlimit unexpectedly.
Most devices have an option to monitor data usage and have limit triggers to notify the user if the limit has been reached.
This protects from large data bills but should also prompt the user to check the amount of data used by each application in order to monitor their legitimacy.
Malware may try to use the camera or microphone to record activity, so check that the camera LED is not activated.