Telecommunication Modulation Techniques Quiz
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Questions and Answers

What does Quadrature Amplitude Modulation (QAM) combine?

  • Frequency modulation and signal modulation
  • Waveform modulation and amplitude modulation
  • Amplitude modulation and phase modulation (correct)
  • Phase modulation and frequency modulation

Which modulation scheme is used for encoding two-bit data into one of four phases?

  • BPSK
  • 64 QAM
  • QPSK (correct)
  • 16QAM

What is a consequence of the Hidden Terminal Problem?

  • Elimination of data collisions entirely
  • Improved signal strength among connected devices
  • Increased data transmission rate
  • Interference between stations that cannot detect each other (correct)

What modulation rate may impact achieving the desired Bit Error Rate (BER) in challenging RF environments?

<p>Modulation rate (C)</p> Signup and view all the answers

Which of the following frequency ranges is associated with Wi-Fi standards under IEEE 802.11?

<p>2.4 GHz and 5 GHz (C)</p> Signup and view all the answers

What is the primary function of the Home Subscriber Service (HSS) in a mobile network?

<p>To facilitate device authentication (A)</p> Signup and view all the answers

Which component of the 4G LTE architecture is responsible for providing NAT services?

<p>PDN Gateway (P-GW) (A)</p> Signup and view all the answers

What is a key goal of 5G technology compared to 4G?

<p>Increase peak bitrate significantly (A)</p> Signup and view all the answers

What does MIMO stand for and how does it enhance data transmission?

<p>Multiple-Input Multiple-Output, using multiple antennas (B)</p> Signup and view all the answers

Which of the following frequency bands is associated with 5G NR?

<p>450 MHz-6 GHz (D)</p> Signup and view all the answers

What application is associated with Extremely Low Frequency (ELF) waves?

<p>Underwater communication (D)</p> Signup and view all the answers

Which frequency band is primarily used for AM radio?

<p>Medium Frequency (MF) (D)</p> Signup and view all the answers

What is the frequency range of the Very High Frequency (VHF) band?

<p>30-300 MHz (A)</p> Signup and view all the answers

Which of the following waves is used in fiber-optic communication?

<p>Visible Light (C)</p> Signup and view all the answers

What application is widely associated with Super High Frequency (SHF) waves?

<p>Satellite communication (C)</p> Signup and view all the answers

Which of the following frequency ranges corresponds to the Very Low Frequency (VLF) band?

<p>3-30 kHz (D)</p> Signup and view all the answers

What is the frequency range for Ultra-High Frequency (UHF) waves?

<p>300-3,000 MHz (A)</p> Signup and view all the answers

Which statement about Ultraviolet waves is true?

<p>They have hazardous effects on humans. (C)</p> Signup and view all the answers

Which channel is explicitly banned in the USA and most of the world?

<p>Channel 14 (A)</p> Signup and view all the answers

What is a characteristic of wireless links that distinguishes them from wired links?

<p>Increased vulnerability to interference from various devices (D)</p> Signup and view all the answers

What is a significant disadvantage of the 2.4 GHz frequency band?

<p>Narrow band and interference (A)</p> Signup and view all the answers

How many non-overlapping channels exist in the 5 GHz frequency band?

<p>24 (D)</p> Signup and view all the answers

What occurs when a wireless signal travels through material?

<p>Path loss resulting in weakened signal strength (D)</p> Signup and view all the answers

What advantage does Quadrature Phase Shift Keying (QPSK) offer over standard Phase Shift Keying (PSK)?

<p>It effectively doubles the data capacity by using two bits per symbol. (B)</p> Signup and view all the answers

In which operating mode does a wireless network have no base stations?

<p>Ad-hoc mode (D)</p> Signup and view all the answers

Which of the following describes an example of a base station in a wireless network?

<p>802.11 access point (D)</p> Signup and view all the answers

Which modulation scheme transmits one bit per symbol?

<p>Amplitude Shift Keying (ASK) (C)</p> Signup and view all the answers

How can the signal-to-noise ratio (SNR) be effectively increased?

<p>By increasing the transmission power (D)</p> Signup and view all the answers

Which feature of 5 GHz Wi-Fi affects its coverage area compared to 2.4 GHz Wi-Fi?

<p>Shorter range (A)</p> Signup and view all the answers

Which protocol is used to manage link access in a wireless network?

<p>Multiple Access Protocol (D)</p> Signup and view all the answers

What challenge does multipath propagation present in wireless communication?

<p>Signals arriving at different times due to reflections (B)</p> Signup and view all the answers

Which statement accurately reflects the characteristics of wireless hosts?

<p>They can run applications and may be either mobile or stationary. (D)</p> Signup and view all the answers

In a mesh network, what does a host typically rely on to connect to a larger internet?

<p>A series of relays through multiple wireless nodes (D)</p> Signup and view all the answers

Which statement accurately describes how SNR can change with mobility in wireless networks?

<p>Dynamically adapting transmission parameters can improve SNR. (B)</p> Signup and view all the answers

What characterizes the connection in an ad hoc network?

<p>No infrastructure is needed (C)</p> Signup and view all the answers

In Bluetooth technology, what role does a master device play in a piconet?

<p>Grants permission for slaves to send data (B)</p> Signup and view all the answers

How does Time Division Multiplexing (TDM) organize data transmission?

<p>Allocates a fixed time interval for each transmission (D)</p> Signup and view all the answers

Which of the following is true about Frequency Division Multiplexing (FDM) in Bluetooth?

<p>It employs 79 frequency channels for communication (C)</p> Signup and view all the answers

What is the primary function of an Access Point (AP) in a wireless network?

<p>To facilitate wireless communication and access to wired networks (C)</p> Signup and view all the answers

Which protocol is used by Ethernet to manage network collisions?

<p>CSMA/CD (D)</p> Signup and view all the answers

Which of the following best describes the frame structure of Wi-Fi?

<p>Comprises management and control frames as well as data frames (C)</p> Signup and view all the answers

What feature allows Bluetooth clients to conserve battery power?

<p>Parked mode (C)</p> Signup and view all the answers

Flashcards

ELF frequency range

3-30 Hz

SLF frequency range

30-300 Hz

VLF frequency range

3-30 kHz

LF frequency range

30-300 kHz

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MF frequency range

300-3,000 kHz

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HF frequency range

3-30 MHz

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VHF frequency range

30-300 MHz

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UHF frequency range

300-3,000 MHz

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QAM Modulation

A modulation scheme combining phase and amplitude modulation to transmit data.

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QAM-16

A modulation scheme encoding 4-bit data into one of 16 phases.

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Hidden Terminal Problem

A wireless network issue where stations can't see each other's interference.

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Modulation Rate

A factor affecting signal quality in wireless environments, particularly when distance increases.

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IEEE 802.11 Standards

Standards that define the various Wi-Fi versions, data rates, and frequency ranges.

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Bluetooth Piconet

A small wireless network formed by Bluetooth devices, where a master device manages communication with several slave devices.

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Bluetooth Master

The central device in a Bluetooth piconet that controls communication with slave devices.

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Bluetooth Slave

A Bluetooth device that sends data only when permitted by the master device.

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Ethernet Topology

The physical arrangement of devices in an Ethernet network, including BUS, Star, Ring, and Hybrid.

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Wi-Fi Medium

Wi-Fi uses radio waves (RF) to transmit data.

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Ethernet vs. Wi-Fi: Collision Handling

Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection), while Wi-Fi uses CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance).

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Access Point (AP) Function

An access point (AP) acts as a central point for devices to connect to a Wi-Fi network, similar to a switch in Ethernet. It bridges the wireless devices to the wired infrastructure.

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Ethernet vs. Wi-Fi: Layer 2 Devices

Ethernet uses switches, while Wi-Fi uses access points to manage data transmission at the data link layer (Layer 2).

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Wireless Network Infrastructure

Wireless networks that use a central base station (e.g., Wi-Fi access point, cellular tower) to connect devices to a larger network.

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Wireless Mesh Network

A wireless network where multiple wireless nodes (acting as routers) relay data to connect devices to a larger network without a central point.

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Path Loss

Decrease in signal strength as wireless signals travel through materials.

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Signal-to-Noise Ratio (SNR)

The ratio of signal strength to noise strength in a wireless communication system.

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SNR and BER Tradeoffs

Higher SNR usually results in lower Bit Error Rate (BER). Increasing power increases SNR and decreases BER, while choosing a correct physical layer (with the correct modulation technique) based on the required BER is crucial.

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Wireless Link Interference

Other devices using the same wireless frequencies leading to disruptions in a wireless network.

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HSS

A network element that stores information about mobile devices and their home network. It works with the MME to authenticate devices.

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S-GW

A gateway that lies on the data path between a mobile device and the internet. It handles data traffic and ensures smooth communication.

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P-GW

A gateway that connects the mobile cellular network to the internet. It works like a standard internet router, providing NAT services and allowing access to the web.

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Control Plane

The part of a cellular network responsible for managing device authentication, mobility, and security.

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Data Plane

The part of a cellular network responsible for carrying actual data and information between devices and the internet.

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2.4 GHz Wi-Fi Channels

The 2.4 GHz frequency band is divided into 14 fixed frequency channels, each 20 MHz wide. Some channels (like 12, 13) are globally allowed, but power limitations might apply. Channel 14 is restricted in most areas except Japan.

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5 GHz Wi-Fi Channels

The 5 GHz band uses 24 non-overlapping channels, organized into different frequency ranges (like U-NII-1, U-NII-2A, U-NII-2C, U-NII-3, ISM).

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Wireless Host

A device that runs applications and connects to a wireless network, such as a laptop, smartphone, or IoT device.

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Base Station

The central point of connection, usually connected to a wired network, providing the main point of access for wireless devices.

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Wireless Link

The connection between a wireless host and a base station or between multiple devices in an Ad-hoc network. It can also be a backbone link.

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Infrastructure Mode

A wireless network setup where a base station connects wireless devices to a wired network, allowing for handoffs between base stations.

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Ad-hoc Mode

A wireless network configuration without a central base station. Devices connect directly to each other within range.

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Wireless Network Taxonomy

A classification system for wireless networks based on factors like infrastructure (central hub vs. peer-to-peer), number of hops, and connection examples.

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Study Notes

Wireless Network Lecture 10

  • Objectives include understanding the electromagnetic spectrum, radio frequency ranges, differences between 2.4 GHz and 5 GHz bands, wireless network elements, modulation, active/passive scanning, Wi-Fi (802.11 wireless LANs), wireless frame addressing, personal area networks, and cellular network components/technology.

Overview of Wireless Network

  • A wireless network uses radio frequency (RF) connections between network nodes.
  • The number of wireless (mobile) phone subscribers now exceeds wired subscribers (5-to-1 ratio).
  • The number of wireless internet-connected devices equals the number of wired internet-connected devices.
  • Key challenges include communication over a wireless link and handling mobile users changing network attachment points.

Electromagnetic Waves

  • RF waves are used for communication, they're not harmful to humans.
  • The ionosphere reflects RF waves.
  • Skywaves bounce between the Earth's surface and the ionosphere.
  • Microwaves communicate with satellites, and anything outside Earth's atmosphere.
  • Ground waves propagate over the Earth's surface (used in TV/AM/FM broadcasts).

Types of RF Waves

  • Different frequency bands have different applications and wavelength ranges ranging from extremely low frequency (ELF) to extremely high frequency (EHF).

Other Electromagnetic Waves

  • Infrared used for short-range communication (TV remotes, etc.).
  • Visible light used in fiber-optic communication.
  • Ultraviolet has hazardous effects.
  • X-rays and gamma rays are highly harmful but used in medical purposes.

2.4 GHz Band

  • Divided into 14 channels, each 20MHz wide.
  • Channels 12 and 13 are allowed worldwide (with lower power restrictions in the USA).
  • Channel 14 allowed in Japan but banned in other countries.
  • Offers better signal over longer distances and through solids.
  • Cons include narrow band, interference with other devices, more congestion and noise.

5 GHz Band

  • Divided into non-overlapping 24 channels, each 20MHz wide, organized into four frequency bands: U-NII-1, U-NII-2A, U-NII-2C (Extended), and U-NII-3, as well as ISM (Industrial, Scientific, Medical).
  • Covers less distance and isn't as good at penetrating solid objects as 2.4 GHz Wi-Fi.

Elements of a Wireless Network

  • Wireless Hosts: Laptops, smartphones, IoT devices. Can be stationary or mobile; Wireless does not always mean mobility.
  • Wired Network Infrastructure: Provides wired connections to the network.
  • Base Station: Connects to the wired network and relays packets between wired and wireless hosts. Examples include cell towers and 802.11 access points.
  • Wireless Link: Typically connects mobile devices to a base station or acts as a backbone link. It co-ordinates connections across various frequency bands and transmission distances with multiple access protocols.
  • Infrastructure Mode: Base station connects mobile devices into the wired network. Handoff allows mobile devices to change base stations while connected to the wired network.
  • Ad-hoc Mode: No base station; nodes organize themselves within the range of transmission and route data amongst each other.

Wireless Network Taxonomy

  • Single Hops: Hosts connect directly to a base station (e.g., Wi-Fi, cellular) which then connects to the internet.
  • Multiple Hops: Hosts may relay through several wireless nodes to reach the internet (e.g., mesh networks).
  • Infrastructure mode and Ad-hoc mode: used for multiple access
  • Signal degradation as it moves through matter (path loss).
  • Interference from multiple devices (e.g., 2.4 GHz).
  • Multipath propagation: signals reflected from objects, affecting signal strength and arrival time.

Wireless Modulation

  • Various modulation schemes including ASK, PSK, and FSK.
  • QPSK (quadrature phase-shift keying): allows more data than PSK.
  • QAM (quadrature amplitude modulation): combines phase and amplitude modulation for increased data capacity.
  • Modulation rate decreases for extended wireless range/difficult RF environment.

Avoiding Collisions

  • Sender reserves channel using short RTS (request-to-send) and CTS (clear-to-send) packets.
  • Other stations defer transmission.
  • The base station broadcasts clear-to-send.

802.11 Wireless LANs - Frame Addressing

  • Frames contain addressing information, control information, and data.
  • The frame structure supports different types of frames.

802.11 Mobility

  • Devices remain in the same IP subnet unless they change APs.
  • Self-learning switches maintain a record of the device locations for connectivity.

Power Management

  • Devices can enter a sleep mode between beacon frames to reduce power consumption.

Personal Area Networks (Bluetooth)

  • Based on IEEE 802.15.
  • Small diameter (less than 10m).
  • Ad-hoc (no infrastructure needed).
  • Uses 2.4/2.5 GHz ISM band; up to 3 Mbps transfer speeds.
  • Master/slave architecture: Slaves request permission to transmit to the master device.
  • TDM (time division multiplexing) and FDM (frequency division multiplexing) are used.

Ethernet vs Wi-Fi

  • Direct comparison of wired (Ethernet) and wireless (Wi-Fi) technologies
  • Features of the two technologies are contrasted

Cellular Networks

  • MSC connects to the wired telephone network.
  • Functions in cellular network architecture are presented visually.
  • FDMA/TDMA allows for shared spectrum.
  • CDMA (code division multiple access) is shared spectrum technique.

4G LTE Architecture

  • Mobile devices use LTE radio.
  • Mobile device identifies with a SIM card.
  • Elements of 4G LTE cellular architecture.

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Lecture 10: Wireless Network PDF

Description

Test your knowledge on key concepts of modulation techniques used in telecommunications, including QAM, MIMO, and various frequency bands. This quiz covers fundamental topics related to Wi-Fi, 4G, and 5G technologies. Explore how these concepts impact data transmission and network performance.

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