A method and apparatus for transmitting and receiving a preamble having sequence information for an OFDM system is provided. The preamble transmission method includes generating a preamble block including at least one frame having a header with a known sequence and a code block containing control information and transmitting the preamble block mapped to Orthogonal Frequency Division Multiplexing (OFDM) cells by repeating in frequency axis direction.

In a single-carrier frequency division multiple access (SC-FDMA) system that utilizes interleaved FDMA (IFDMA) or localized FDMA (LFDMA), a transmitter generates modulation symbols for different types of data (e.g., traffic data, signaling, and pilot) and performs code division multiplexing (CDM) on at least one data type. For example, the transmitter may apply CDM on signaling and/or pilot sent on frequency subbands and symbol periods that are also used by at least one other transmitter. To apply CDM to a given data type (e.g., signaling), the transmitter performs spreading on the modulation symbols for that data type with an assigned spreading code. CDM may be applied across symbols, samples, samples and symbols, frequency subbands, and so on. The transmitter may perform scrambling after the spreading. The transmitter generates SC-FDMA symbols of the same or different symbol durations for traffic data, signaling, and pilot and transmits the SC-FDMA symbols.

A wireless device transmits, during a first period, a first plurality of voice packets of a first talking period on a first plurality of subcarriers of a first carrier. The wireless device transmits, during a second period, a second plurality of voice packets of a second talking period on a second plurality of subcarriers of a second carrier. The wireless device transmits, in the first period and the second period, data traffic packets on a third plurality of subcarriers. There is at least one guard band between at least two subcarriers in the third plurality of subcarriers.

A method for mapping, by a base station, a channel state information reference signal (CSI RS) in a wireless communication system, the method comprising: generating the CSI for eight antenna ports; selecting a resource element (RE) set from a plurality of RE sets in a subframe using an extended cyclic prefix (CP), wherein the selected RE set includes four pairs of REs in consecutive orthogonal frequency division multiplexing (OFDM) symbols, and wherein the four pairs of REs are separated from each other by constant subcarrier spacing in the consecutive OFDM symbols; and mapping the CSI RS for the eight antenna ports to the selected RE set.

Methods and systems for obtaining improved joint channel estimates for a multi-user, frequency-multiplexed data transmission such as SC-FDMA or OFDM begins by estimating separate contributions of users (and/or other signal sources) to the received signal based on joint frequency domain channel estimates. A reduced data set is obtained by subtracting contributions of one or more users from the received data, leaving only the estimated contributions of the remaining users, with noise and residual estimation error signal. Time domain joint channel estimation is then performed on the reduced data set, which is feasible because the number of users has been reduced. In exemplary embodiments, the reduced data set includes only one estimated user contribution. This process is repeated to obtain time domain estimates for all of the users. The method can be repeated by using the TD channel estimates to re-estimate the user contributions and calculate revised TD channel estimates.

A Method for increasing coverage and robustness against frequency offsets in wireless networks, user device and computer program products In the method, a user device (171) that wirelessly communicates with a base station (172) through a wireless network employing a Single Carrier-Frequency Division Multiple Access, SC-FDMA, comprises: applying a number of calculated repetitions of a block of complex information symbols prior to a SC-FDMA modulator (176), said number of repetitions being an integer submultiple of a number of subcarriers scheduled for uplink transmission according to the expression: N.sub.sc.sup.UL=LM with L and M integers; and applying, when mapping to scheduled resources in the SC-FDMA modulator (176), a frequency shift equal to a subcarrier width multiplied by one half of said number of repetitions.

A receiving apparatus is provided. The receiving apparatus may include a receiver, a PN sequence remover, and a zero padding performing unit. The receiver may be configured to receive a frame signal. The PN sequence remover may be configured to remove a first PN sequence from a first frame detected from the frame signal corresponding to a first path to generate a PN removed first frame and remove a second PN sequence from a second frame detected from the frame signal corresponding to a second path to generate a PN removed second frame. The zero padding performing unit may be configured zero pad the first PN removed frame to a size of a discrete Fourier transform (DFT) and zero pad the PN removed second frame to the size of the DFT.

In a method for generating a data unit, it is determined whether the data unit is to be transmitted using single carrier (SC) modulation or orthogonal frequency division (OFDM) modulation. When it is determined that the data unit is to be transmitted using SC modulation, a header field of the data unit is generated using a first technique to indicate that the data unit conforms to a first protocol and/or whether the data unit conforms to a first PHY mode or a second PHY mode of the first protocol. When it is determined that the data unit is to be transmitted using OFDM modulation, the header field is generated using a second technique to indicate that the data unit conforms to the first protocol and/or whether the data unit conforms to the first PHY mode or the second PHY mode of the first protocol.

A method for mapping, by a base station, a channel state information reference signal (CSI RS) in a wireless communication system, and a user equipment (UE) for performing the method, are discussed. The method according to one embodiment includes selecting a resource element (RE) set from a plurality of RE sets in a subframe of a time division duplex (TDD) frame, wherein each of the plurality of RE sets includes a pair of consecutive orthogonal frequency division multiplexing (OFDM) symbol elements, and wherein the subframe uses an extended cyclic prefix (CP); and mapping the CSI RS to the selected RE set.

A wireless device transmits, during a first period, a first plurality of voice packets of a first talking period on a first plurality of subcarriers of a first carrier. The wireless device transmits, during a second period, a second plurality of voice packets of a second talking period on a second plurality of subcarriers of a second carrier. The wireless device transmits, in the first period and the second period, data traffic packets on a third plurality of subcarriers. There is at least one guard band between at least two subcarriers in the third plurality of subcarriers.