Abstract: Provided is a time division duplex (TDD) transceiver. A receiver chain processing received signals and a transmitter chain processing signals to be transmitted share an electronic component used in a circuit, such as an amplifier, a mixer, a filter, etc., so that the size of a semiconductor die needed to manufacture a radio frequency (RF) chip can be reduced.

Abstract: Provided is a method of changing a communication link between source devices and sink devices. The method includes in a first downlink period, broadcasting an uplink period allocation message to the sink devices and passive source devices by an active source device, which establishes a communication link with a primary sink device from among the sink devices; during a first uplink period, broadcasting by a primary passive source device a link set message for establishing a communication link with the primary sink device to all the source devices in the network; during a second downlink period, relaying the link set message to all the sink devices in the network, wherein the link set message is relayed by the active source device; and during a second uplink period, establishing a communication link between the primary sink device and the primary passive source device by the primary sink device.

Abstract: A method and apparatus for transmitting and receiving a digital signal using an orthogonal frequency division multiplexing (OFDM) communication system are provided. In this method, subcarriers are split into a plurality of subcarrier groups according to available frequency bandwidths and are respectively transmitted in a transmitting portion and the subcarrier groups are combined and are restored to the original signal in a receiving portion. Therefore, wireless resources may be used efficiently by combining with cognitive radio technology.

Abstract: Provided is a time division duplex (TDD) transceiver. A receiver chain processing received signals and a transmitter chain processing signals to be transmitted share an electronic component used in a circuit, such as an amplifier, a mixer, a filter, etc., so that the size of a semiconductor die needed to manufacture a radio frequency (RF) chip can be reduced.

Abstract: A method and apparatus for compensating for a mismatch in a radio frequency (RF) quadrature transceiver using a direct-conversion scheme is provided. The method includes setting an amplification gain for a baseband quadrature signal to be larger than an amplification gain for a baseband in-phase signal in a reception module; receiving only a baseband in-phase signal in a transmission module; and compensating for a phase mismatch on a basis of a signal output from a quadrature output port. The apparatus includes a phase mismatch compensator which sets an amplification gain for a baseband quadrature signal to be larger than an amplification gain for a baseband in-phase signal in a reception module, inputs only a baseband in-phase signal to a transmission module, and compensates for a phase mismatch on a basis of a signal output from a quadrature output port.

Abstract: Provided is a method of changing a communication link between source devices and sink devices. The method includes in a first downlink period, broadcasting an uplink period allocation message to the sink devices and passive source devices by an active source device, which establishes a communication link with a primary sink device from among the sink devices; during a first uplink period, broadcasting by a primary passive source device a link set message for establishing a communication link with the primary sink device to all the source devices in the network; during a second downlink period, relaying the link set message to all the sink devices in the network, wherein the link set message is relayed by the active source device; and during a second uplink period, establishing a communication link between the primary sink device and the primary passive source device by the primary sink device.

Abstract: Provided are a method and apparatus for communicating with a heterogeneous terminal, more particularly, a method and apparatus for communicating with a heterogeneous terminal in which the communication between terminals using different modulation methods can be initialized by transmitting throughout a network a preamble with a waveform that is commonly used in the network. The apparatus includes a preamble-generation unit which generates a preamble having a plurality of sequences corresponding to a combination of a modulation method and a waveform that are to be applied to a packet; and a communication unit which attaches the preamble to the packet and then transmits the packet.

Abstract: A method and apparatus for compensating for a mismatch in a radio frequency (RF) quadrature transceiver using a direct-conversion scheme is provided. The method includes setting an amplification gain for a baseband quadrature signal to be larger than an amplification gain for a baseband in-phase signal in a reception module; receiving only a baseband in-phase signal in a transmission module; and compensating for a phase mismatch on a basis of a signal output from a quadrature output port. The apparatus includes a phase mismatch compensator which sets an amplification gain for a baseband quadrature signal to be larger than an amplification gain for a baseband in-phase signal in a reception module, inputs only a baseband in-phase signal to a transmission module, and compensates for a phase mismatch on a basis of a signal output from a quadrature output port.

Abstract: A method and apparatus for transmitting and receiving a digital signal using an orthogonal frequency division multiplexing (OFDM) communication system are provided. In this method, subcarriers are split into a plurality of subcarrier groups according to available frequency bandwidths and are respectively transmitted in a transmitting portion and the subcarrier groups are combined and are restored to the original signal in a receiving portion. Therefore, wireless resources may be used efficiently by combining with cognitive radio technology.

Abstract: An apparatus and method for self-calibrating mismatching orthogonal signals and non-linearity of a circuit occurring in a mobile transceiver. For this, in a mobile terminal, a transmitter is used as a signal generator and a receiver is used as a response characteristic measurer. A base band processor calibrates mismatching signals and non-linearity in a reception side and a transmission side, based on a test signal received via the transmitter and a test signal received via the receiver.

Abstract: An apparatus and method for compensating for the frequency offset of a received signal in a receiving apparatus of a mobile communication system. In the present invention, a sine component is calculated by adding I and Q channel signals resulting from downconverting a training sequence inserted between data symbols, and a cosine component is calculated by subtracting the Q channel signal from the I channel signal. Using the cosine and sine components at two time points, tangent components for the two time points are computed and thus first and second phase values are obtained. The frequency offset is estimated by determining the slope of a second-order line derived from the first and second phase values. The frequency offset of the received signal is compensated for based on the estimated frequency offset.

Abstract: An apparatus and method for self-calibrating mismatching orthogonal signals and non-linearity of a circuit occurring in a mobile transceiver. For this, in a mobile terminal, a transmitter is used as a signal generator and a receiver is used as a response characteristic measurer. A base band processor calibrates mismatching signals and non-linearity in a reception side and a transmission side, based on a test signal received via the transmitter and a test signal received via the receiver.

Abstract: An apparatus and method for compensating for the frequency offset of a received signal in a receiving apparatus of a mobile communication system. In the present invention, a sine component is calculated by adding I and Q channel signals resulting from downconverting a training sequence inserted between data symbols, and a cosine component is calculated by subtracting the Q channel signal from the I channel signal. Using the cosine and sine components at two time points, tangent components for the two time points are computed and thus first and second phase values are obtained. The frequency offset is estimated by determining the slope of a second-order line derived from the first and second phase values. The frequency offset of the received signal is compensated for based on the estimated frequency offset.