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Zorluk: Çok zorWireless Networking Standards and Technologies

A network technician is diagnosing performance degradation on a 2.4 GHz wireless network in an office environment. A wireless spectrum analyzer shows that three neighboring access points are configured to use Channel 1, Channel 2, and Channel 6. Users connected to the access point on Channel 2 experience severe packet drops and frame corruption, while users on Channels 1 and 6 maintain stable connections despite high traffic volume. Which of the following best explains why Channel 2 exhibits significantly higher frame corruption than Channels 1 and 6?

  1. Channel 2 causes adjacent channel interference with Channels 1 and 6, generating uncoordinated RF noise that disrupts CSMA/CA clear-channel assessments.Cevap
  2. B
    Channel 2 is restricted to a maximum 10 MHz channel bandwidth in the 2.4 GHz spectrum, causing throughput bottlenecks during peak utilization.
  3. C
    Channel 2 experiences co-channel interference that forces access points to automatically disable OFDM modulation and fall back to DSSS.
  4. D
    Channel 2 operates at a lower central frequency transmit power limit under regulatory guidelines compared to primary channels 1, 6, and 11.

Cevap

Channel 2 causes adjacent channel interference with Channels 1 and 6, generating uncoordinated RF noise that disrupts CSMA/CA clear-channel assessments.
The correct option identifies that Channel 2 creates adjacent channel interference (ACI) with both Channels 1 and 6. In the 2.4 GHz ISM band, each 20 MHz channel spacing requires 25 MHz separation between center frequencies to avoid overlap. Because Wi-Fi radios on Channel 2 cannot decode preamble headers from signals centered on Channels 1 or 6, they treat those transmissions as raw noise. Consequently, CSMA/CA clear-channel assessment fails to defer transmission, resulting in high rates of frame collisions and retransmissions.

Adım Adım Çözüm

1
Analyze the 2.4 GHz Wi-Fi channel allocation and frequency overlap bounds.
In North America, standard 20 MHz channels in the 2.4 GHz band have center frequencies separated by 5 MHz. The standard non-overlapping channels are 1 (2412 MHz), 6 (2437 MHz), and 11 (2462 MHz).
Channels must be separated by at least 25 MHz between center frequencies to prevent spectral overlap.
2
Evaluate the effect of placing an access point on Channel 2 (2417 MHz center frequency).
Channel 2 heavily overlaps with Channel 1 (2412 MHz) and partially overlaps with Channel 6 (2437 MHz).
Overlapping frequencies cause radio frequency energy from adjacent channels to spill over into the passband.
3
Differentiate between Co-Channel Interference (CCI) and Adjacent Channel Interference (ACI).
Devices on the exact same channel (CCI) can decode Wi-Fi preamble headers and use CSMA/CA to take turns transmitting. Devices on adjacent overlapping channels (ACI) perceive each other's signals as raw, undecodable RF noise, breaking CSMA/CA contention mechanisms and causing severe packet collisions.
ACI is significantly more destructive to performance than CCI because CSMA/CA backoff algorithms cannot properly parse the interfering signal's duration.

Anahtar Kavram

Adjacent Channel Interference vs. Co-Channel Interference in 2.4 GHz Wireless Networks
Tahmini Süre:2m 0s
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Wireless Networking Standards and Technologies

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