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E8C15

SIGNALS AND EMISSIONS · Digital signals: digital communication modes; information rate vs. bandwidth; error correction; constellation diagrams

E8C15E8C →

What technique do individual nodes use to form a mesh network?

  1. AForward error correction and Viterbi codes
  2. BActing as store-and-forward digipeaters
  3. CDiscovery and link establishment protocols
  4. DCustom code plugs for the local trunking systems
Why A mesh network is self-organizing: each node runs protocols that discover neighboring nodes within radio range, establish links with them, and share routing information so traffic can hop node to node. That automatic discovery and link establishment is what distinguishes a mesh from a fixed, manually configured network. Amateur mesh systems such as AREDN use exactly this approach, with routing protocols exchanging neighbor and route data continuously.
Watch out Store-and-forward digipeating describes older packet radio repeating, where a station simply retransmits a frame addressed through it; that alone gives no automatic route discovery. Forward error correction and Viterbi decoding are link-layer error control, not network formation, and code plugs belong to commercial trunked land mobile radios.
Mesh nodes must first find each other: think discover, link, route.
HamSandwich explanation, first draft. The question and answers are the NCVEC text.
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The rest of E8C

  1. E8C01 What is Quadrature Amplitude Modulation or QAM?
  2. E8C02 What is the definition of symbol rate in a digital transmission?
  3. E8C03 Why should the phase of a PSK signal be changed at the zero crossing of the RF signal?
  4. E8C04 What technique minimizes the bandwidth of a PSK31 signal?
  5. E8C05 What is the approximate bandwidth of a 13-WPM International Morse Code transmission?
  6. E8C06 What is the bandwidth of an FT8 signal?
  7. E8C07 What is the bandwidth of a 4,800-Hz frequency shift, 9,600-baud ASCII FM transmission?
  8. E8C08 How does ARQ accomplish error correction?
  9. E8C09 Which digital code allows only one bit to change between sequential code values?
  10. E8C10 How can data rate be increased without increasing bandwidth?
  11. E8C11 What is the relationship between symbol rate and baud?
  12. E8C12 What factors affect the bandwidth of a transmitted CW signal?
  13. E8C13 What is described by the constellation diagram of a QAM or QPSK signal?
  14. E8C14 What type of addresses do nodes have in a mesh network?
  15. E8C15 What technique do individual nodes use to form a mesh network?
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