In a cellular system, mobile subscribers may move out of the coverage area of one base station while making a call. The process of transferring a mobile phone call from one base station to another as the subscriber crosses cell boundaries is known as handover. In CDMA networks, this transition can occur without changing frequencies, referred to as a soft handover. If the connection requires a frequency change, it is known as a hard handover. In American English, a handover is called a “hand-off.”