MAC Protocol for Ad-Hoc Networks
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Questions and Answers

What is a crucial aspect that a MAC protocol for ad-hoc networks should consider?

  • Fixed Location of Nodes
  • Constraint of ad-hoc networks (correct)
  • Central Coordination of nodes
  • Distributed Nature of the network

    • What is a primary goal of the MAC protocol in ad-hoc networks?

  • To maximize control packet transmission
  • To provide Quality of Service (QoS) support for real-time traffic (correct)
  • To minimize error-prone shared broadcast channels
  • To ensure hidden and exposed terminal problems

    • What is a major challenge in designing a MAC protocol for ad-hoc networks?

  • Distributed Nature of the network
  • Fixed Location of Nodes
  • Error-Prone Shared Broadcast Channel (correct)
  • Central Coordination of nodes

    • What should be achieved through the exchange of time synchronization among nodes?

    <p>Synchronization</p> Signup and view all the answers

    What is a key requirement for a MAC protocol in ad-hoc networks?

    <p>To ensure fair allocation of bandwidth to nodes</p> Signup and view all the answers

    What is a design goal of a MAC protocol for ad-hoc wireless networks?

    <p>To ensure the protocol is scalable to large networks</p> Signup and view all the answers

    What is the primary function of the link manager in the Bluetooth protocol stack?

    <p>To establish logical channels between devices and handle power management, authentication, and quality of service</p> Signup and view all the answers

    What is the main difference between the ZigBee3 radio specification and Bluetooth?

    <p>The cost and power consumption of the specification</p> Signup and view all the answers

    What is the function of the telephony protocol in the Bluetooth middleware layer?

    <p>To manage call setup and termination for the three speech-oriented profiles</p> Signup and view all the answers

    What is the purpose of the service discovery protocol in the Bluetooth middleware layer?

    <p>To locate services within the network</p> Signup and view all the answers

    What is the range of the ZigBee3 radio specification?

    <p>Up to 30 m</p> Signup and view all the answers

    What is the maximum number of devices that can be connected per network in the ZigBee3 radio specification?

    <p>255 devices</p> Signup and view all the answers

    What is the layer in the Bluetooth protocol stack that deals with radio transmission and modulation?

    <p>Physical radio layer</p> Signup and view all the answers

    What is the data rate supported by the ZigBee3 radio specification?

    <p>Up to 250 Kbps</p> Signup and view all the answers

    What are the primary factors that constrain wireless sensor nodes?

    <p>Energy, computation, and communication</p> Signup and view all the answers

    Why is ad-hoc deployment a significant consideration in wireless sensor networks?

    <p>Because it requires minimal infrastructure and maintenance</p> Signup and view all the answers

    What is a key difference between wireless sensor networks and other ad-hoc networks?

    <p>The emphasis on sensing and data processing</p> Signup and view all the answers

    Why is it essential to minimize energy consumption in wireless sensor networks?

    <p>Because nodes are battery-powered and replacing batteries is not feasible</p> Signup and view all the answers

    What is the primary reason for using data fusion and compression in wireless sensor networks?

    <p>To conserve energy by reducing data transmission</p> Signup and view all the answers

    What is a key characteristic of wireless sensor networks compared to other ad-hoc networks?

    <p>Wireless sensor networks have more densely deployed nodes</p> Signup and view all the answers

    Why is receiving data in wireless sensor networks considered costly?

    <p>Because it consumes energy equal to transmitting data</p> Signup and view all the answers

    What is a key difference in communication schemes between wireless sensor networks and other ad-hoc networks?

    <p>Wireless sensor networks use many-to-one communication</p> Signup and view all the answers

    What is the primary purpose of modulation in data transmission?

    <p>To encode information from a message source for transmission</p> Signup and view all the answers

    What is the result of modulating the carrier signal called?

    <p>Modulated signal</p> Signup and view all the answers

    What are the three characteristics of a carrier signal that can be varied in modulation?

    <p>Amplitude, frequency, and phase</p> Signup and view all the answers

    What is the process of extracting the baseband message from the carrier signal called?

    <p>Demodulation</p> Signup and view all the answers

    What is the relationship between frequency and period?

    <p>Frequency is inversely proportional to period</p> Signup and view all the answers

    What is the most popular analog modulation technique?

    <p>Frequency Modulation (FM)</p> Signup and view all the answers

    What type of signal has a limited frequency range?

    <p>Bandpass signal</p> Signup and view all the answers

    What is the term for the original signal that is being transmitted?

    <p>Modulating signal</p> Signup and view all the answers

    What is the definition of the index of refraction of one medium relative to another?

    <p>The sine of the angle of incidence divided by the sine of the angle of refraction</p> Signup and view all the answers

    What is the effect of refraction on radio waves in the atmosphere?

    <p>They travel more slowly near the ground than at higher altitudes</p> Signup and view all the answers

    What is the purpose of the adjustment factor K in the formula for the effective, or radio, line of sight?

    <p>To account for the refraction of radio waves</p> Signup and view all the answers

    What is the effect of transmission impairments on analog signals?

    <p>They introduce random modifications that degrade signal quality</p> Signup and view all the answers

    What is the effect of transmission impairments on digital data?

    <p>They cause bit errors, transforming 1 into 0 and vice versa</p> Signup and view all the answers

    What is the formula for the optical line of sight?

    <p>d = sqrt(2 * h)</p> Signup and view all the answers

    What is the purpose of the formula for the effective, or radio, line of sight?

    <p>To calculate the maximum distance between two antennas for LOS propagation</p> Signup and view all the answers

    What is the value of the adjustment factor K in the formula for the effective, or radio, line of sight?

    <p>K = 4/3</p> Signup and view all the answers

    Study Notes

    MAC Protocol for Ad-Hoc Networks

    • The MAC protocol should maximize quality of service support for time-critical applications.
    • The protocol should consider the constraints of ad-hoc networks, such as synchronization, which can be achieved by exchanging time synchronization among nodes.
    • Control packets must not consume too much of the network bandwidth.

    Issues in Ad-Hoc Networks

    • Hidden and exposed terminal (fading) problems need to be addressed.
    • The protocol should avoid collision and error-prone shared broadcast channels.
    • Distributed nature and lack of central coordination are challenges in ad-hoc networks.
    • Mobility of nodes is a key issue, as nodes are mobile most of the time.

    Design Goals of a MAC Protocol

    • The protocol should operate in a distributed manner.
    • It should provide QoS support for real-time traffic.
    • Access delay should be kept low.
    • The available bandwidth should be utilized efficiently.
    • The protocol should ensure fair allocation of bandwidth to nodes.
    • It should be scalable to large networks.
    • Power control mechanisms should be included to manage energy consumption.

    Bluetooth Protocol Stack

    • The Bluetooth protocol architecture consists of a physical radio layer, baseband layer, link manager, and middleware layer.
    • The physical radio layer deals with radio transmission and modulation.
    • The baseband layer handles time slots and frame grouping.
    • The link manager handles logical channel establishment, power management, authentication, and QoS.
    • The middleware layer includes protocols such as telephony, service discovery, and more.

    ZigBee and IEEE 802.15.4

    • ZigBee is designed for lower cost and power consumption than Bluetooth.
    • The specification is based on the IEEE 802.15.4 standard.
    • The radio operates in the same ISM band as Bluetooth and can connect up to 255 devices per network.
    • The specification supports data rates of up to 250 Kbps at a range of up to 30 m.

    Wireless Sensor Networks

    • Wireless sensor networks are ad-hoc networks with self-organizing nodes that are randomly deployed.
    • Nodes are characterized by small size, low cost, and low power consumption.
    • Sensor networks have many more nodes and are more densely deployed than other ad-hoc networks.
    • Hardware must be cheap, and nodes are more prone to failures.
    • WSNs operate under strict energy constraints, and nodes are typically static.

    Lifetime of Wireless Sensor Networks

    • Nodes are battery-powered, and nobody is going to change the batteries.
    • Lifetime is crucial, and each operation brings the node closer to death.
    • To save energy, nodes should sleep as much as possible, acquire data only if necessary, use data fusion and compression, and transmit and receive only if necessary.

    Refraction and Optical Line of Sight

    • Refraction causes radio waves to bend toward the earth due to the decreasing refractive index of the atmosphere with height.
    • The optical line of sight can be expressed as a function of distance and antenna height.
    • The effective or radio line of sight is expressed as a function of distance, antenna height, and an adjustment factor to account for refraction.

    Modulation

    • Modulation is the process of encoding information from a message source into a bandpass signal suitable for transmission.
    • It involves translating a baseband message signal to a bandpass signal at frequencies very high compared to the baseband frequency.
    • Modulation can be done by varying the amplitude, phase, or frequency of a high-frequency carrier in accordance with the amplitude of the message signal.

    Demodulation

    • Demodulation is the inverse operation of modulation, extracting the baseband message from the carrier so that it can be processed at the receiver.

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    Description

    Designing a MAC protocol for ad-hoc networks requires consideration of quality of service support, synchronization, and bandwidth constraints. The protocol should maximize quality and address specific issues.

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