The scope of this document includes service requirements for handover maintaining continuity of service to a wireless terminal as it moves between the radio coverage area, or "cells", associated with different base station sites. This functionality is called "handover". Handover can also occur due to change of radio resource providing a service without necessarily any change of the base stations involved. In particular, when the radio resources providing a service change from one of the UTRA radio access modes to the other (UTRA-FDD and UTRA-TDD), this is regarded as handover. Particular emphasis has been placed on the description of requirements for service continuity within UTRAN and between UTRAN and GERAN.

It is a key requirement to allow for dual or multi-mode terminals to handover traffic from UTRAN to GERAN and vice versa. This document describes the service requirements for intra- and inter- system handover.

The following subject areas are within the scope of these service requirements:

• User perceived performance that may be influenced by handover;
• Operational requirements relating to handover;
• Security requirements.

The requirements set forth in this document are service requirements, in that they fulfil the following:

• The requirements are independent of the implementation of the UTRAN;
• The extent to which the requirements are met are in principle verifiable using observables that are not internal to the UTRAN.