Wireless coverage is provided by a grid of cell towers in cellular networks. Mobile devices link to nearby cell towers. Moving may weaken your tower connection, therefore your device needs to relocate to a closer or stronger tower. To maintain connectivity, your device and cellular network must easily transition. Call this a handover or handoff. If your current tower's signal degrades or you're reaching its coverage area, the network will tell your device to switch to a neighboring tower with a stronger signal. 

A "Swiss cheese problem" is a pocket of poor connectivity when handover is not smooth. These locations must be prioritized to improve connectivity and enable the sharing economy in rural and urban communities.