Abstract: A method and an apparatus for transmitting and receiving a signal in a communication system are provided. The method includes transmitting a signal to a receiver through one of the antennas, receiving an antenna switching indicator indicating to switch the transmitting antenna from the receiver, and switching the transmitting antenna according to the antenna switching indicator, and transmitting a signal to the receiver through a switched antenna.

Abstract: A transmitting apparatus and method in a transmit diversity system, which transmits a plurality of block-coded symbols over a plurality of antennas are provided. The transmitting apparatus includes N+M antennas where N is an integer equal to or greater than two and M is an integer equal to or greater than one; a switch which forwards N-ary block-coded symbols to N-ary antennas of the N+M antennas; and a switch controller which controls switching of the switch, and when a receiving end which receives the N-ary block-coded symbols informs the switch controller of a poor reception state, the switch controller forwards the N-ary block-coded symbols to other N-ary antennas which include at least one antenna different from the N-ary antennas. The block-coded symbols can be transmitted by selectively using more antennas than block-coded symbols.

Abstract: Disclosed is a method for detecting a symbol using a trellis structure on a multiple input multiple output (MIMO) mobile communication system. The method includes the steps of: setting a plurality of states by grouping symbols producible from a receiving signal in the unit of sub-states; calculating metric values for paths inputted to the sub-states and selecting paths having the calculated metric values smaller than a preset first threshold, as first surviving paths; setting a second threshold based on an accumulated metric value of a path having the smallest accumulated metric in each of the states; and selecting paths having metric value smaller than the second threshold, as second surviving paths, among the first surviving paths selected for each state.

Abstract: A Multiple-Input Multiple-Output (MIMO) communication system and method. The MIMO communication system includes: an antenna number determination unit to determine a number of active antennas among a plurality of transmitting antennas based on a power of a transmission signal wherein the number of active antennas is at least one and the at least one active antenna transmits the transmission signal; and a beam generator to generate the transmission signal corresponding to the number of active antennas by using channel information wherein the channel information is fed back from each of a plurality of user terminals.

Abstract: System and method for code acquisition in a wireless communications system with a delay lock loop. A preferred embodiment comprises assigning a delay lock loop (DLL) to each path in a received signal with multipath, adjusting each DLL to maximize sample strength, grouping samples that are less than a first threshold apart into groups, adjusting DLL timing of samples in groups, regrouping groups that are less than a second threshold apart, applying a group decision to regrouped groups, and repeating the regrouping and applying until all groups are greater than the second threshold apart.

Abstract: System and method for detecting symbols wherein there may be a large frequency error. A preferred embodiment includes receiving an estimated frequency error, calculating a vector based on the estimated frequency error, buffering symbols from two symbol streams, rotating the symbols from the two symbol streams using the vector, estimating a channel gain for the symbols in the second symbol stream, and applying the channel gain to the rotated symbols from the second symbol stream.

Abstract: A method is provided for updating a check node in a low density parity check (LDPC) decoder, including: transmitting log-likelihood ratio (LLR) messages from variable nodes to a plurality of check nodes; decomposing the LLR messages in a plurality of node messages for each check node; and updating each check node using a modified function g(x), which is a function g?(x) comprising a sum operation of exponential functions based on the node messages.

Abstract: A transmitting apparatus and method in a transmit diversity system, which transmits a plurality of block-coded symbols over a plurality of antennas are provided. The transmitting apparatus includes N+M antennas where N is an integer equal to or greater than two and M is an integer equal to or greater than one; a switch which forwards N-ary block-coded symbols to N-ary antennas of the N+M antennas; and a switch controller which controls switching of the switch, and when a receiving end which receives the N-ary block-coded symbols informs the switch controller of a poor reception state, the switch controller forwards the-N-ary block-coded symbols to other N-ary antennas which include at least one antenna different from the N-ary antennas. The block-coded symbols can be transmitted by selectively using more antennas than block-coded symbols.

Abstract: A methodology of signal estimation over the generalized fading channel can be applied to any parameter whose dB value is required to be estimated. The estimator is shown to be asymptotically efficient in a number of samples and the amount of fading. Theoretical and simulation results confirm that the SINR estimator implemented using the methodology outperforms the sample-average estimator, which is currently used in most of systems and robust to the channel variation.

Abstract: System and method for code acquisition in a wireless communications system with a delay lock loop. A preferred embodiment comprises assigning a delay lock loop (DLL) to each path in a received signal with multipath, adjusting each DLL to maximize sample strength, grouping samples that are less than a first threshold apart into groups, adjusting DLL timing of samples in groups, regrouping groups that are less than a second threshold apart, applying a group decision to regrouped groups, and repeating the regrouping and applying until all groups are greater than the second threshold apart.

Abstract: System and method for detecting symbols wherein there may be a large frequency error. A preferred embodiment comprises receiving an estimated frequency error, calculating a vector based on the estimated frequency error, buffering symbols from two symbol streams, rotating the symbols from the two symbol streams using the vector, estimating a channel gain for the symbols in the second symbol stream, and applying the channel gain to the rotated symbols from the second symbol stream.

Abstract: A methodology of signal estimation over the generalized fading channel can be applied to any parameter whose dB value is required to be estimated. The estimator is shown to be asymptotically efficient in a number of samples and the amount of fading. Theoretical and simulation results confirm that the SINR estimator implemented using the methodology outperforms the sample-average estimator, which is currently used in most of systems and robust to the channel variation.