UGC NET CSE | December 2014 | Part 2 | Question: 46

Question

Consider the following statements $S1$ and $S2$ :

$S1$ : A hard handover is one in which the channel in the source cell is retained and used for a while in parallel with the channel in the target cell.

$S2$ : A soft handover is one in which the channel in the source cell is released and only then the channel in the target cell is engaged. 

• A. $S1$ is true and $S2$ is not true. 
• B. $S1$ is not true and $S2$ is true. 
• C. Both $S1$ and $S2$ are true. 
• D. Both $S1$ and $S2$ are not true. 

Answer 1

ans is D   

Hard handover

Is one in which the channel in the source cell is released and only then the channel in the target cell is engaged. Thus the connection to the source is broken before or 'as' the connection to the target is made—for this reason such handovers are also known as break-before-make. Hard handovers are intended to be instantaneous in order to minimize the disruption to the call. A hard handover is perceived by network engineers as an event during the call. It requires the least processing by the network providing service. When the mobile is between base stations, then the mobile can switch with any of the base stations, so the base stations bounce the link with the mobile back and forth. This is called 'ping-ponging'.

Soft handover

Is one in which the channel in the source cell is retained and used for a while in parallel with the channel in the target cell. In this case the connection to the target is established before the connection to the source is broken, hence this handover is called make-before-break. The interval, during which the two connections are used in parallel, may be brief or substantial. For this reason the soft handover is perceived by network engineers as a state of the call, rather than a brief event. Soft handovers may involve using connections to more than two cells: connections to three, four or more cells can be maintained by one phone at the same time. When a call is in a state of soft handover, the signal of the best of all used channels can be used for the call at a given moment or all the signals can be combined to produce a clearer copy of the signal. The latter is more advantageous, and when such combining is performed both in the downlink (forward link) and the uplink (reverse link) the handover is termed as softer. Softer handovers are possible when the cells involved in the handovers have a single cell site.

https://en.wikipedia.org/wiki/Handover

Comments

In cellular telecommunications, the terms handover or handoff refer to the process of transferring an ongoing call or data session from one channel connected to the core network to another channel. In satellite communications it is the process of transferring satellite control responsibility from one earth station to another without loss or interruption of service.

Answer 2

D) Both S1 and S2 are not true...

 

A hard handover is one in which the channel in the source cell is released and only then the channel in the target cell is engaged…

A soft handover is one in which the channel in the source cell is retained and used for a while in parallel with the channel in the target cell. Both given statement are wrong...