Increasing base station density does NOT always prevent handoff failure because

Cellular densification is a trade-off, not a pure gain. Shrinking cell radius (raising base-station density) improves average received signal strength, but it also raises the rate at which a moving mobile crosses cell boundaries. Every boundary crossing triggers a handoff, and every handoff consumes dedicated control- or signaling-channel resources rather than user-traffic capacity. So densification can shift the bottleneck from radio-link quality to control-channel signaling load, and a handoff can still fail even when the signal itself is strong.

1. Increasing base station density means the average distance between neighbouring base stations shrinks, so each cell covers a smaller geographic area.

2. A mobile moving at a given speed crosses more cell boundaries per unit time as the cell radius shrinks, so the handoff rate experienced by that user rises.

3. Each handoff event requires control-channel signaling to be exchanged and processed (channel request, measurement report, handover command) before the call is transferred to the new cell.

4. If the rate of these signaling events exceeds what the control channel can process, some handoff attempts are blocked or dropped -- a handoff failure -- independent of how strong the radio signal itself is.

• More towers place a mobile closer to its serving base station on average, which raises received signal power rather than reducing it, so that mechanism does not explain a handoff failure caused by densification.

• Densification shrinks cell radius; a larger cell footprint (the opposite change) is what would extend the maximum propagation distance to the base station and the shadowing variability along it, not the handoff-signaling load itself, so that mechanism runs against the premise of increasing density.

• Smaller cells generally raise overall network capacity through tighter spatial frequency reuse, so cell capacity does not decrease as base-station density rises.

The failure mode that densification does not remove is the load on the handoff-signaling path itself: frequent handoffs overload the control channel.