Why consider propagation?

2. Compatibility with other users

• strength of interfering signal(s)?

• physical area of interference?

• time period of interference?

• degradation in quality of wanted signal?

Is frequency sharing possible?

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• Second part of question takes account of fact that frequency bands are almost never exclusive; sharing almost always necessary; therefore must recognise possibility of interference:
  • is strength of interfering signal sufficiently below that of wanted signal?
  • does this situation occur within required coverage area?
  • does interference exist for acceptable period of time? (e.g. 0.1% for 99.9% availability).
  • is the distortion or error rate acceptably low?

• Ultimate question – is sharing possible?

• None of these questions can be answered without considering the propagation of the signals concerned (wanted and interfering).