Why does a GSM network perform a handoff, and who initiates it?

Handoff reasons include a stronger signal at a new base station (better connectivity, less battery drain) and load balancing; GSM only standardizes HOW a handoff works (mechanism), not WHY it should happen (policy) — and the handoff is initiated by the old BSS.

The goal: route the call via a new base station without interruption.

Reasons for handoff:

• Stronger signal to/from a new BSS — better continuing connectivity AND less battery drain (the phone doesn't have to shout)
• Load balancing — free up a channel in the current, congested BSS

The mechanism/policy split (a classic protocol-design principle):

• GSM doesn't mandate WHY to perform a handoff — that's policy, left to the operator
• GSM only specifies HOW to do it — the mechanism

This separation lets each operator tune handoff behavior (aggressive vs. conservative, load-aware vs. signal-only) while all equipment interoperates on the same protocol.

Who starts it: the handoff is initiated by the old BSS — the network side, not the phone. The phone supplies measurements; the network decides.

Go deeper:

• Handover (Wikipedia) — the purposes of handover (coverage, congestion, interference) and the hard-vs-soft distinction.
• GSM handover (Electronics Notes) — Mobile-Assisted Handover: the phone scans and reports, the network decides.