Wireless Communication
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Questions and Answers

In wireless communication, what are the two spatial scales at which the wireless channel varies?

  • Large scale fading and small scale fading (correct)
  • Primary fading and secondary fading
  • Global fading and local fading
  • Macroscopic fading and microscopic fading

    • What is the time constant associated with variations in large-scale fading as the mobile moves?

  • Many seconds or minutes (correct)
  • Milliseconds
  • Nanoseconds
  • Hours

    • In free space, how does received power attenuate?

  • Exponentially
  • Like $1/r^2$ (correct)
  • Linearly
  • Like $r^2$

    • Which term is used to describe the attenuation of received power with reflections and obstructions?

    <p>Multipath fading</p> Signup and view all the answers

    What is the goal of the course mentioned in the text?

    <p>To study in a unified way the fundamentals and new research developments in wireless communication</p> Signup and view all the answers

    Which day of the course is dedicated to studying MIMO?

    <p>Day 2</p> Signup and view all the answers

    What is the focus of Day 3 of the course?

    <p>Wireless Networks</p> Signup and view all the answers

    Which concept is illustrated using examples from several modern wireless systems such as GSM, IS-95, and CDMA 2000 1x EV-DO?

    <p>The fundamentals as well as the new research developments</p> Signup and view all the answers

    What is the term used to describe the comparison of 3 systems in the context of multiple access and interference management?

    <p>Multiple Access and Interference Management</p> Signup and view all the answers

    What is the primary focus of the course outlined in the text?

    <p>Fundamentals, MIMO, and Wireless Networks</p> Signup and view all the answers

    Which type of channel has a capacity close to that of the AWGN channel when only receiver CSI is available?

    <p>Fast fading channel</p> Signup and view all the answers

    What is needed to address the unreliability and poor outage capacity in a slow fading channel?

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

    In which domain is waterfilling used for addressing the challenges in a slow fading channel?

    <p>Frequency domain</p> Signup and view all the answers

    What can have a capacity greater than that of the AWGN channel when full CSI is available in a fast fading channel?

    <p>Fast fading channel</p> Signup and view all the answers

    What type of channel provides more opportunities for performance boost when full CSI is available?

    <p>Fast fading channel</p> Signup and view all the answers

    In which regime does waterfilling in frequency domain occur?

    <p>Power limited regime</p> Signup and view all the answers

    What is a source of unreliability and very poor outage capacity?

    <p>Slow fading channel</p> Signup and view all the answers

    What is powerful in multiuser situations, providing more opportunities for performance boost?

    <p>Opportunistic communication</p> Signup and view all the answers

    What type of diversity is mentioned as a solution to address the unreliability in a slow fading channel?

    <p>Receive diversity</p> Signup and view all the answers

    What incurs only a small penalty in capacity when present in a fast fading channel with only receiver CSI?

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

    What is the primary driver behind wireless communication system design?

    <p>Understanding physical parameters such as carrier frequency, mobile speed, bandwidth, and delay spread</p> Signup and view all the answers

    What is the frequency response of the system shifted from the passband to the baseband for?

    <p>Processing at baseband</p> Signup and view all the answers

    What allows the system to resolve multipaths up to delays of 1/W?

    <p>Sampling the baseband-equivalent channel model</p> Signup and view all the answers

    What is crucial for increasing reliability in communication over flat fading channels?

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

    What is used to increase diversity and improve reliability in wireless communication?

    <p>Antenna diversity, space-time codes, and cooperative diversity</p> Signup and view all the answers

    What provides a fundamental characterization of coded performance in wireless communication?

    <p>Information theory</p> Signup and view all the answers

    Which method is used to obtain time diversity?

    <p>Interleaving and coding over symbols across different coherent time periods</p> Signup and view all the answers

    What is crucial for exploiting added diversity efficiently?

    <p>Time, frequency, and space diversity</p> Signup and view all the answers

    What is used to enhance wireless communication performance?

    <p>Frequency diversity approaches such as OFDM</p> Signup and view all the answers

    What are ai(t) and $\tau_i(t)$ used to represent in wireless channel modeling?

    <p>Gain and delay of path i</p> Signup and view all the answers

    What is the primary driver behind wireless communication system design?

    <p>Understanding how physical parameters impact wireless channel behavior</p> Signup and view all the answers

    What is the frequency response of the system shifted from the passband to the baseband in wireless communication?

    <p>$-W/2$ to $W/2$</p> Signup and view all the answers

    What is the limit for resolving multipaths by sampling the baseband-equivalent channel model?

    <p>Up to delays of 1/W</p> Signup and view all the answers

    Which statistical models are based on the statistical ensemble of channels in wireless communication?

    <p>Rayleigh flat fading and Rician models</p> Signup and view all the answers

    Which method is crucial for increasing reliability in communication over flat fading channels?

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

    How can time diversity be obtained in wireless communication?

    <p>By interleaving and coding over symbols across different coherent time periods</p> Signup and view all the answers

    Which method is used to increase diversity and improve reliability in wireless communication?

    <p>Antenna diversity, space-time codes, and cooperative diversity</p> Signup and view all the answers

    Which approaches are used to enhance wireless communication performance in frequency diversity?

    <p>Time-domain equalization, direct-sequence spread spectrum, and orthogonal frequency-division multiplexing (OFDM)</p> Signup and view all the answers

    What provides a fundamental characterization of coded performance in wireless communication?

    <p>Information theory</p> Signup and view all the answers

    What is the representation for the gain and delay of path i in wireless channels?

    <p>ai(t) and $\tau_i(t)$</p> Signup and view all the answers

    Study Notes

    Wireless Communication: Understanding Multipath Fading and Diversity

    • Wireless communication occurs at high carrier frequencies, leading to multipath fading due to constructive and destructive interference of transmitted waves.
    • Channel variation occurs when a mobile moves a distance of the order of the carrier wavelength, which translates to channel variation of the order of 100 Hz for vehicular speeds.
    • The primary driver behind wireless communication system design is to understand how physical parameters such as carrier frequency, mobile speed, bandwidth, and delay spread impact wireless channel behavior.
    • Wireless channels can be modeled as linear time-varying systems, with ai(t) and i(t) representing the gain and delay of path i.
    • Communication takes place at passband [f_c-W/2, f_c+ W/2], and processing at baseband [-W/2,W/2], with the frequency response of the system shifted from the passband to the baseband.
    • Sampling the baseband-equivalent channel model allows the system to resolve multipaths up to delays of 1/W, with fading occurring due to destructive interference of the multipaths contributing to a tap.
    • Statistical models based on the statistical ensemble of channels, such as Rayleigh flat fading and Rician models, are used for design and performance analysis.
    • Diversity is crucial for increasing reliability in communication over flat fading channels, with time, frequency, and space diversity being key methods for exploiting added diversity efficiently.
    • Time diversity can be obtained by interleaving and coding over symbols across different coherent time periods, with the amount of diversity limited by delay constraints and channel variation speed.
    • Antenna diversity, space-time codes, and cooperative diversity are methods used to increase diversity and improve reliability in wireless communication.
    • Frequency diversity approaches such as time-domain equalization, direct-sequence spread spectrum, and orthogonal frequency-division multiplexing (OFDM) are used to enhance wireless communication performance.
    • Information theory provides a fundamental characterization of coded performance in wireless communication, identifying the impact of channel resources and suggesting new communication methods.

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    Fundamentals of Wireless Communication PDF

    Description

    Test your knowledge of wireless communication with this quiz on understanding multipath fading and diversity. Explore concepts such as channel variation, time and frequency diversity, statistical channel models, and methods for increasing reliability in wireless communication.

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