A system for maintaining wireless communication with a plurality of base stations in a communication network is disclosed. A portable terminal having a communication unit is configured to measure signal strength of a transmission signal for neighboring base stations in a frequency band being used by the communication unit, and create a first handoff candidate list in which one or more handoff candidates in a same frequency band are recorded. A handoff using the first handoff candidate list is performed by the portable terminal. Thereafter, the portable terminal measures signal strength of one or more base stations included in a second handoff candidate list. The result of the signal strength measurements are reported to the currently communicating base station, and a handoff is performed based on a response to the report at the portable terminal.