Abstract: In a cellular system in which OFDM is used, a forward link synchronization channel, a common pilot channel structure, an initial cell searching method of a mobile station, and an adjacent cell searching method for handover are required. A method of transmitting a forward synchronization signal in a wireless communication system according to the present invention includes generating a frame comprised of a plurality of sync blocks; and transmitting the frame through a forward link, wherein the frame comprises primary synchronization channel sequences which provide timing information of the sync blocks and a plurality of secondary synchronization channel sequences which provide timing information of the frame, wherein a cell identifier is specified by a combination of the primary synchronization channel sequence and a hopping code word specified by the plurality of the secondary synchronization channel sequences. Therefore, the cell searching time can be efficiently reduced in an OFDM system.

Abstract: A method of and an apparatus therefor searching a cell in a mobile station of a communication system in which a plurality of cells are grouped into a plurality of cell groups, and each cell group includes at least two cells. The method includes detecting a primary synchronization signal and a secondary synchronization signal from a received signal, and identifying a cell based on a combination of the primary synchronization signal and the secondary synchronization signal. The secondary synchronization signal is related to the cell group to which the mobile station belongs and the primary synchronization signal is related to the cell to which the mobile station belongs within the cell group.

Abstract: Provided is method of forming a signal in a wireless communication system in which a plurality of terminals commonly use a resource in the time domain and the frequency domain. The method includes multiplying a signal to be transmitted by a frequency domain orthogonal code symbol corresponding to a first cyclic shift index in a first slot to be transmitted to a base station, wherein the multiplying is performed by a first terminal and a second terminal; and multiplying information to be transmitted by a frequency domain orthogonal code symbol corresponding to a second cyclic index that is different from the first cyclic index of the first slot to be transmitted to the base station, in a second slot, wherein the multiplying is performed by the first terminal and the second terminal.

Abstract: Provided is a method of efficiently transmitting an acknowledgement/negative acknowledgement (ACK/NACK) bit supporting hybrid automatic repeat request (HARQ) in a wireless communication system supporting multi-user multi-input and multi-output (MIMO). The method transmits the same downlink code and in-phase/quadrature (I/Q) multiplexed ACK/NACK bit to two mobile stations using the same uplink resource block. Accordingly, the method can efficiently transmit the ACK/NACK bit for multi-user MIMO and efficiently use downlink radio resources.

Abstract: When a plurality of terminals share the same resources in a wireless communication system, and when control information such as acknowledgement/negative acknowledgement (ACK/NAK) information or scheduling information is transmitted, a method of efficiently performing code division multiplexing (CDM) is required to distinguish the plurality of terminals. In particular, it is necessary to develop a method by which a code sequence of CDM can be selected and used according to each cell condition. Provided is a method of forming a signal in a wireless communication system in which a plurality of terminals commonly share frequency and time resources. The method includes the operations of receiving condition information in a cell; selecting one of a plurality of time domain orthogonal sequences having different lengths, according to the condition information; and allocating the selected time domain orthogonal sequence to a control signal symbol block.

Abstract: Provided is a method of forming a signal in a wireless communication system in which a plurality of terminals commonly use time and frequency resources for efficient code hopping. The method includes allocating the same frequency-axis sequence and different time-axis sequences to a plurality of terminals by using a resource index according to a first slot in the first slot; and allocating different frequency-axis sequences and different time-axis sequences to the plurality of terminals by using a resource index according to a second slot in the second slot.

Abstract: Provided is a method of forming a random access preamble structure for an extended cell radius in a cellular system, the method including: generating a cyclic prefix (CP), which is the sum of a maximum delay spread and the maximum round trip delay according to the extended cell; generating a preamble sequence part. The method is used to form a preamble structure for an extended cell radius from among random access preamble structures transmitted when initial synchronization is achieved, when synchronization is lost, or when a handover is performed, during a random access process of the cellular system.

Abstract: A piece of user equipment (UE), which has received more than two synchronization codes at the same time, has a problem in that the UE may not confirm the synchronization codes due to an increase in inter-signal interference. As a result, the UE may not acquire a primary scrambling code (PSC). A method of transmitting a forward synchronization signal in a wireless communication system includes: each base station existing in a wireless communication system generating a frame according to a predetermined unit of frame timing by using a same external clock signal; and allocating different offsets to frames of adjacent base stations by using the external clock signal so that forward link common channels included in the frames do not overlap each other, and transmitting the frames.

Abstract: In a cellular system in which OFDM is used, a forward link synchronization channel, a common pilot channel structure, an initial cell searching method of a mobile station, and an adjacent cell searching method for handover are required. A method of transmitting a forward synchronization signal in a wireless communication system according to the present invention includes generating a frame comprised of a plurality of sync blocks; and transmitting the frame through a forward link, wherein the frame comprises primary synchronization channel sequences which provide timing information of the sync blocks and a plurality of secondary synchronization channel sequences which provide timing information of the frame, wherein a cell identifier is specified by a combination of the primary synchronization channel sequence and a hopping code word specified by the plurality of the secondary synchronization channel sequences. Therefore, the cell searching time can be efficiently reduced in an OFDM system.

Abstract: Provided are a sync channel of a forward link, a common pilot channel structure, and an initial cell search method and an adjacent cell search method for handover in a cellular system using orthogonal frequency division multiplexing (OFDM). A cell search method in an OFDM cellular system in which a primary sync channel and a secondary sync channel are configured based on time division multiplexing (TDM) includes acquiring sync block synchronization and a primary sync channel sequence number using a primary sync channel symbol included in a frame received by a terminal, detecting a boundary of the frame and a scrambling code group using the sync block and a secondary sync channel symbol included in the frame received by the terminal, and acquiring a scrambling code using the primary sync channel sequence number and the scrambling code group, thereby reducing cell search time with low complexity.