Handoff system using an initial ranging scheme in a broadband wireless access communication system and method for controlling the same

An SS (Subscriber Station) handoff method in a communication system using an OFDM (Orthogonal Frequency Division Multiplexing), comprising the steps of:

• a) receiving neighbor BS (Base Station) information of a plurality of neighbor BSs associated with a plurality of cells adjacent to a cell and uplink-associated information needed for transmitting data from the SS to a first BS, from the first BS for controlling the cell currently containing the SS;
• b) requesting synchronization information needed for synchronizing the SS and the first BS, from the first BS;
• c) monitoring the plurality of neighbor BSs according to the neighbor BS information associated with the plurality of neighbor BSs;
• and
• d) establishing a handoff with a second BS, which is one of the plurality of neighbor BSs based on the monitored result.

A handoff method using an initial ranging process when an SS (Subscriber Station) is handed off from a first BS (Base Station) to which the SS currently belongs to a second BS in a communication system using an OFDM (Orthogonal Frequency Division Multiplexing) scheme, comprising the steps of:

• a) broadcasting, from the first BS and the second BS, neighbor BS information, downlink information including initial ranging information, and uplink information allocated to the SS;
• b) receiving, by the SS, the downlink information and the uplink information broadcast from the first BS;
• c) requesting, by the SS, an initial ranging process from the first BS using the initial ranging information and the uplink information;
• c) monitoring neighbor BSs in response to the neighbor BS information received from the first BS;
• d) receiving the downlink information and the uplink information broadcast from the second BS, when a specific state where a handoff state must be established with the second BS from among the neighbor BSs is detected during the monitoring time of the neighbor BSs;
• and
• e) requesting the initial ranging process from the second BS using the initial ranging information and the uplink information received from the second BS.

An SS (Subscriber Station) handoff method using an initial ranging process in a communication system using an OFDM (Orthogonal Frequency Division Multiplexing) scheme, comprising the steps of:

• a) receiving neighbor BS information broadcast from a first BS to which the SS currently belongs, downlink information including initial ranging information, and uplink information allocated to the SS;
• b) requesting an initial ranging process from the first BS using the initial ranging information and uplink information received from the first BS;
• c) monitoring the neighbor BSs in response to the neighbor BS information;
• d) if a specific state where a handoff state must be established with a second BS from among the neighbor BSs is detected during the monitoring of the neighbor BSs, receiving downlink information and uplink information broadcast from the second BS;
• and
• e) requesting an initial ranging process from the second BS using the initial ranging information and the uplink information received from the second BS.