---
title: "Short note: Handover"
subject: "Wireless Communication"
chapter: 2
key: "semester_7/wireless_communication:short-note-handover"
source: https://www.bctengineer.com/q/semester_7/wireless_communication/short-note-handover
site: BCT Engineering
---

# Short note: Handover

Wireless Communication · Chapter 2: Cellular Mobile Communication Concepts

- Asked in: 2073 Magh, 5 marks
- Video: [Handoff | Handover | Hard Handoff | Soft Handoff | Mobile Computing](https://www.youtube.com/watch?v=WyRgu_F2i9c) — Dr. Ankit Verma
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/wireless_communication/short-note-handover
- Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-2

## Question

Write a short note on handover.

## Short answer

Handover transfers an ongoing call to another channel or base station without interruption when signal falls. It uses a handoff margin to balance unnecessary handoffs and dropped calls. Types include hard (break-before-make), soft (make-before-break), and mobile-assisted. Guard channels and queuing prioritise handoffs to prevent dropped calls.

## Answer

**Handover (handoff)** is the process of transferring an ongoing call or data session from one channel or base station to another without interruption, when the mobile moves into another cell or the signal quality falls.

**Process**
- The serving base station monitors signal strength. When it falls to the **handoff threshold** Pr,handoff, the MSC looks for a better neighbouring cell and a free channel.
- The call must be transferred before the signal falls to the **minimum usable level** Pr,min. The difference Δ = Pr,handoff − Pr,min is the handoff margin; too large Δ causes unnecessary handoffs, too small Δ causes dropped calls.
- In 1G, base stations measured the mobile's signal; in 2G (GSM) the mobile measures neighbours and reports them (**mobile-assisted handoff, MAHO**).

```text
 Power  BS1                BS2
  │ \                     /
  │   \ Pr,handoff      /
  │     \  Δ         /
  │.......\ Pr,min /........
  └──────────────────────── distance
```

**Types**
- **Hard handover** (break before make) – GSM, LTE.
- **Soft handover** (make before break) – CDMA, WCDMA; connected to several base stations at once.
- **Intra-cell, inter-cell, inter-MSC (intersystem)** handover.

**Prioritising handover:** guard channels reserved for handoffs and queuing of handoff requests, because dropping a call is worse than blocking a new one.

**Practical issues:** umbrella cells for high-speed users, cell dragging, and dwell time variation due to fading.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Handover transfers an ongoing call:
   A. To the MSC
   B. To another channel or base station without interruption
   C. To a new user
   D. To a new frequency band only for data
   Answer: B. Done when mobile moves or quality falls. (Key point: Definition)

2. Handoff margin too large causes:
   A. Dropped calls
   B. No effect
   C. Zero interference
   D. Unnecessary handoffs
   Answer: D. Too small gives dropped calls. (Key point: Margin)

3. Soft handover differs from hard in that:
   A. Connection is made to several base stations before the old is released
   B. It breaks before making
   C. It is used in GSM
   D. It only occurs within a cell
   Answer: A. Soft is make before break. (Key point: Hard vs soft)

4. Guard channels are used to:
   A. Increase new-call capacity
   B. Reduce interference
   C. Reserve channels for handoffs, since dropping a call is worse than blocking a new one
   D. Lower transmit power
   Answer: C. Queuing of handoff requests also helps. (Key point: Prioritising)

5. In GSM, neighbour measurements are made by:
   A. Only base stations
   B. The mobile (MAHO)
   C. Only the MSC
   D. Nobody
   Answer: B. Mobile-assisted handoff. (Key point: MAHO)