Method for performing USTS handover and USTS mode switching in a mobile communication system

A handover controlling method in a Node B in a mobile communication system where an Uplink Synchronous Transmission Scheme (USTS) service occurs between a first Node B and a user equipment (UE) within a cell of the first Node B and the UE hands over when the UE is located in a handover area across cell areas of the first Node B and a second Node B, the cell area of the second Node B being adjacent to the cell area of first Node B, the method comprising the steps of:

• receiving handover information indicating that the UE is receiving the USTS service from an radio network controller (RNC), the handover information including a channelization code for a data transmission channel of the UE, a scrambling code used for the data communication, and a scrambling code time offset representing a time difference between a start point of the scrambling code and a start point of an uplink data frame;
• and
• transmitting a response message for the handover information to the RNC and assigning a handover channel according to the channelization code;
• and
• performing scrambling code synchronization by setting the start point of the uplink data frame relative to the start point of the scrambling code according to the scrambling code time offset.

A method of converting a non-Uplink Synchronous Transmission Scheme (USTS) mode to a USTS mode in a communication between a Node B connected to a radio network controller (RNC) and a user equipment (UE) within a cell area of the Node B, comprising the steps of:

• measuring by the Node B a round trip time (RTT) indicating a distance between the Node B and the UE;
• transmitting the measured RTT from the Node B to the RNC;
• transmitting from the RNC to the UE a scrambling code and a channelization code for use in the UE, and information representing a variance of a start point of a downlink data frame to be transmitted to the UE so that the downlink data frame starts at a position apart from a reference time point of the Node B by a multiple of a predetermined number of chips;
• and
• transmitting the scrambling code and the channelization code from the RNC to the Node B.

A method of converting from a non- Uplink Synchronous Transmission Scheme (USTS) mode to a USTS mode in a communication between a Node B connected to an radio network controller (RNC) and a user equipment (UE) within a cell area of the Node B, comprising the steps of:

• receiving a message including information representing a variance of a start point of an uplink data frame received from the UE to make the uplink data frame start at a position apart from a reference time point of the Node B by a multiple of a predetermined number of chips, and a channelization code and a scrambling code of a transmission channel on which the uplink data is transmitted from the RNC;
• calculating a scrambling code time offset if it is determined that the USTS mode conversion is possible for the UE, and transmitting a response message including the scrambling code time offset to the RNC;
• and
• assigning the received channelization code and scrambling code to the communication and determining the start points of the uplink data frame and the scrambling code according to the scrambling code time offset, and transitioning to the USTS mode.

A method of converting a non-Uplink Synchronous Transmission Scheme (USTS) mode to a USTS mode in a communication between a Node B connected to an radio network controller (RNC) and a user equipment (UE) within a cell area of the Node B, comprising the steps of:

• receiving a predetermined uplink signal from the UE, measuring a propagation delay of the received predetermined uplink signal, and transmitting the propagation delay measurement and a USTS mode conversion request to the RNC by the Node B;
• determining an additional delay based on the propagation delay measurement and transmitting the determined additional delay to the UE by the RNC;
• and
• starting to transmit an uplink data transmission channel signal by the UE after the propagation delay and the additional delay from reception of a downlink data transmission channel signal.