Virtual Labs

Handoff

1. What is the primary reason a handover mechanism is necessary in a cellular network?

a: To allow users to change their phone numbers. Explanation

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b: To ensure call quality remains stable for stationary users. Explanation

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c: To maintain a call connection for a mobile user moving between cells. Explanation

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d: To bill the user based on their location. Explanation

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2. What is the 'ping-pong effect' in the context of handovers?

a: A user's call bounces between the voice and data network. Explanation

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b: A user is rapidly handed over back and forth between two adjacent cells. Explanation

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c: A call is dropped and immediately reconnected. Explanation

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d: The network signal strength rapidly increases and decreases. Explanation

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3. A very high 'handover probability' would most likely be caused by...

a: a very high handover margin. Explanation

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b: a very low handover margin. Explanation

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c: the user not moving. Explanation

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d: the call drop probability being zero. Explanation

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4. What is a likely consequence of setting the 'handover threshold' too low (i.e., the signal must be very poor before a handover is triggered)?

a: The handover probability will increase significantly. Explanation

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b: The call drop probability will increase. Explanation

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c: The SINR for the user will always be very high. Explanation

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d: The 'ping-pong effect' will become a major problem. Explanation

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5. A successful handover should ideally result in the user experiencing...

a: a higher SINR from the new cell. Explanation

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b: a lower SINR from the new cell. Explanation

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c: an immediate increase in call drop probability. Explanation

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d: no change in SINR or call quality. Explanation

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6. How does a user's speed (e.g., walking vs. driving) typically affect handover probability?

a: Speed has no effect on handovers. Explanation

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b: A faster-moving user will likely have a lower handover probability. Explanation

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c: A faster-moving user will likely have a higher handover probability. Explanation

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d: Only users who are stationary can perform a handover. Explanation

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7. What is the main trade-off when adjusting the handover threshold?

a: Initiating the handover early (better SINR) vs. initiating it late (lower call drop risk). Explanation

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b: The cost of the handover vs. the user's data speed. Explanation

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c: The risk of dropping the call (if set too low) vs. the risk of a ping-pong handover (if set too high). Explanation

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d: Handover probability vs. handover margin. Explanation

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8. What does a high 'handover probability' imply for the network's signaling load?

a: It decreases the signaling load. Explanation

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b: It has no effect on the signaling load. Explanation

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c: It increases the signaling load because each handover requires network messages. Explanation

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d: It only affects the voice channel, not the signaling channel. Explanation

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9. A user at the edge of a cell experiences poor SINR, but their call is not handed over and is eventually dropped. What is a possible cause?

a: The handover margin is set too low. Explanation

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b: The handover threshold is set too high (i.s., signal must be good). Explanation

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c: The handover margin is set too high. Explanation

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d: The SINR from the new cell is too good. Explanation

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10. The objectives aim to study the effect of parameters on 'SINR', 'call drop probability', and 'handover probability'. Which of these is a measure of connection quality?

a: SINR Explanation

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b: Call drop probability Explanation

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c: Handover probability Explanation

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d: All of the above Explanation

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