Which type of wireless propagation tends to bounce respectively from the surface

Question

Which type of wireless propagation tends to bounce respectively from the surface of the Earth to the Ionosphere? a.________ sky wave b. _________ Ground wave c. _______ Line of sight d. ________ CAN waves Multipath propagation received affects received signal strength is what way a.________ Can only decrease received signal strength b. _______ can both increase and decrease received signal strength c. ____________ can only decrease received signal strength d. ________ cannot affect received signal strength but only affects the phase of the noise component of the received signal What is the purpose of "jam signal" as used in Ethernet When is the jam signal sent? a. ________ Immediately before a collision is detected b. ___________ Immediately after a collision is detected c. __________ At the end of the exponential backoff delay d. ___________ After the preamble signal is sent

Explanation / Answer

1.A. Sky wave propogation refers to the propogation by the reflection of wave from ionosphere back to the earth..

Ground wave is LOS communication or refelection caused by earth surface to atmosphere of earth.

2.In Multi path propagation there some disadvatages due to fading of signal. Those are

i.Rapid changes in signal strength over distances small or large

ii.Rapid frequency variations due to doppler effects.

iii.Time dispersion and multiple echoes generated dueto, multiple paths.

So, There is no definitive answer in this. so, I am going for option B. we can not say perticularly increase or decrease. It may increase or decrease in several conditions.

3. If a collision is heard over a telephone channel then Jam signal will be sent by the both ends to stop the transmission over the data line for some time. Purpose is to ensure both parties know about the collision and save the data transmission.

4.Jam Signal will be sent immediately after the collision is heard. SO, Option B.

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