--- title: "Handover process and types of handover" subject: "Wireless Communication" chapter: 2 key: "semester_7/wireless_communication:handover-process-types" source: https://www.bctengineer.com/q/semester_7/wireless_communication/handover-process-types site: BCT Engineering --- # Handover process and types of handover Wireless Communication · Chapter 2: Cellular Mobile Communication Concepts - Asked in: 2074 Magh, 6 marks - Video: [Types of Handover | Soft Handoff vs Hard Handoff | MCHO | NCHO | MAHO](https://www.youtube.com/watch?v=Peh9qr96YJQ) — ECIT Engineering - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/wireless_communication/handover-process-types - Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-2 ## Question Explain handover process in cellular system. Mention various types of handover with application. ## Answer **Handoff (handover)** is the process of transferring an ongoing call from one channel or base station to another without interrupting the call, when the mobile moves into a different cell or the signal quality falls. #### Handoff process 1. The base station (or mobile) continuously monitors received signal strength (RSSI) and quality. 2. When the signal from the serving cell falls to a **handoff threshold** (Pr,handoff), a handoff is initiated. 3. Neighbouring base stations measure the mobile's signal (1G locator receiver) or the mobile measures neighbours' signals and reports them (MAHO in 2G). 4. The MSC selects the best target cell, finds a free channel there and instructs the mobile to retune. 5. The call is switched to the new base station before the signal reaches the **minimum usable level** (Pr,min); otherwise the call drops. ```text Power BS1 signal BS2 signal │ \ / │ \ ← Pr,handoff / │ \ Δ / │ \ ← Pr,min / └──────────────────────────── distance BS1 handoff BS2 ``` The margin Δ = Pr,handoff − Pr,min must be chosen carefully: too large causes unnecessary handoffs, too small causes dropped calls. #### Types of handover with applications 1. **Hard handover ("break before make")** – the old link is released before the new one is set up; the mobile changes frequency or time slot. Used in FDMA/TDMA systems: AMPS, GSM, LTE. 2. **Soft handover ("make before break")** – the mobile is connected to two or more base stations at the same time on the same frequency, and the MSC selects or combines the best signal. Used in CDMA systems: IS-95, CDMA2000, WCDMA. Fewer dropped calls. 3. **Softer handover** – between two sectors of the same base station in CDMA; signals combined at the base station. 4. **Intra-cell handover** – change of channel within the same cell due to interference; used in GSM. 5. **Inter-cell (intra-MSC) handover** – between cells under the same MSC. 6. **Inter-MSC / intersystem handover** – when the mobile moves to a cell controlled by another MSC or system (e.g. 4G to 3G when LTE coverage ends, or roaming). 7. **Mobile-controlled, network-controlled and mobile-assisted (MAHO)** handover – based on who measures and decides; MAHO is used in GSM, where the mobile reports neighbour cell power levels and the network decides. | Type | Systems | Key feature | |---|---|---| | Hard | GSM, LTE | Break before make | | Soft | IS-95, WCDMA | Make before break | | Softer | CDMA sectors | Same BS, different sector | | Intersystem | 4G ↔ 3G | Across networks | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. A handoff is triggered when: A. Signal falls below Pr,min B. Signal falls to Pr,handoff, above the minimum usable level C. The call ends D. The mobile powers on Answer: B. It must complete before Pr,min. (Key point: Handoff trigger) 2. Hard handover is: A. Make before break B. Connection to several base stations at once C. A change of sector at the same base station D. Break before make: the old link is released before the new one is set up Answer: D. Used in GSM, LTE. (Key point: Hard handover) 3. Soft handover is used in: A. CDMA systems (IS-95, WCDMA), connecting to several base stations at once B. GSM and AMPS C. LTE only D. 1G only Answer: A. It gives fewer dropped calls. (Key point: Soft handover) 4. Softer handover occurs: A. Between two MSCs B. Between 4G and 3G C. Between sectors of the same base station in CDMA D. Within a TDMA slot Answer: C. Signals are combined at the base station. (Key point: Softer handover) 5. Inter-MSC/intersystem handover occurs when: A. The channel changes in the same cell B. The mobile moves to a cell controlled by another MSC or network, e.g. 4G to 3G C. The mobile changes sector D. Two cells share the same MSC Answer: B. It involves extra signalling. (Key point: Intersystem handover) 6. In mobile-assisted handover (GSM): A. The mobile alone decides B. The base station measures only C. No measurement is made D. The mobile reports neighbour power levels and the network decides Answer: D. Who measures and who decides defines the type. 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