A quadrature amplitude modulation (QAM) transmitter separates an input digital level into I and Q components. In a variation, a QAM transmitter uses every other input digital level as an I or Q component. A QAM receiver receives a QAM modulated signal and outputs digital levels. A QAM transmitter for transmitting analog levels uses a pair of input analog levels as the I and Q components. A QAM receiver receives a QAM modulated signal and outputs analog levels. The digital and analog input levels are produced by encoding N samples using L orthogonal codes.

A quadrature amplitude modulation (QAM) transmitter separates an input digital level into I and Q components. In a variation, a QAM transmitter uses every other input digital level as an I or Q component. A QAM receiver receives a QAM modulated signal and outputs digital levels. A QAM transmitter for transmitting analog levels uses a pair of input analog levels as the I and Q components. A QAM receiver receives a QAM modulated signal and outputs analog levels. The digital and analog input levels are produced by encoding N samples using L orthogonal codes.

A computer implemented method for detecting data (y) comprised in a part (x) of a received signal (w) of a communication system (100), wherein the received signal (w) is associated with a population and where the part (x) of the received signal (w) is associated with a sub-population of the population, the method comprising: configuring (S1) a first function (ƒ1) to determine a context (c) of the received signal (w), wherein the context (c) is indicative of a state of the received signal (w), configuring (S2) a second function (ƒ2) to detect the data (y) based on the part (x) of the received signal, wherein the second function (ƒ2) is arranged to be parameterized by the context (c), and detecting (S3) the data (y) by the first (ƒ1) and second (ƒ2) functions.

A self-contained operation using a time-unit configuration taking into consideration HARQ processes is performed. In base station, transmission section transmits a downlink signal in a downlink transmission region in a time unit composed of the downlink transmission region, an uplink transmission region, and a gap interval that is a switching point from the downlink transmission region to the uplink transmission region; and reception section receives an uplink signal in the uplink transmission region in the time unit. Each time unit includes the downlink transmission region and the uplink transmission region for each of HARQ processes.

A self-contained operation using a time-unit configuration taking into consideration HARQ processes is performed. In base station, transmission section transmits a downlink signal in a downlink transmission region in a time unit composed of the downlink transmission region, an uplink transmission region, and a gap interval that is a switching point from the downlink transmission region to the uplink transmission region; and reception section receives an uplink signal in the uplink transmission region in the time unit. Each time unit includes the downlink transmission region and the uplink transmission region for each of HARQ processes.

A method of compensating for IQ mismatch (IQMM) in a transceiver may include sending first and second signals from a transmit path through a loopback path, using a phase shifter to introduce a phase shift in at least one of the first and second signals, to obtain first and second signals received by a receive path, using the first and second signals received by the receive path to obtain joint estimates of transmit and receive IQMM, at least in part, by estimating the phase shift, and compensating for IQMM using the estimates of IQMM. Using the first and second signals received by the receive path to obtain estimates of the IQMM may include processing the first and second signals received by the receive path as a function of one or more frequency-dependent IQMM parameters.

The disclosure relates to technology for compensating for I/Q imbalance. An apparatus includes I-path circuitry having a first analog filter configured to filter an I-path signal and Q-path circuitry having a second analog filter configured to filter a Q-path signal. An I/Q imbalance compensation circuit of the apparatus is configured to process digital versions of the I-path signal and the Q-path signal to compensate for mismatch between the I-path circuitry and the Q-path circuitry. A first circuit of the apparatus is configured to apply a coarse adjustment to at least one of the first analog filter or the second analog filter to reduce an initial mismatch between the I-path circuitry and the Q-path circuitry. The first circuit is configured to operate the I/Q imbalance compensation circuit to compensate for a residual mismatch between the I-path circuitry and the Q-path circuitry with the coarse adjustment applied.

A communication method and apparatus are provided. The method includes: A terminal device determines a first sequence whose length is Σ.sub.i=0.sup.M−1 K.sub.i, and sends the first sequence on M subcarrier groups, where an i.sup.th subcarrier group in the M subcarrier groups includes K.sub.i subcarriers on a same symbol, i=0, 1, . . . , M−1, and frequency domain positions of subcarriers included in any two of the M subcarrier groups are different and belong to different symbols; and a sequence carried in each of the M subcarrier groups is a fragment of the first sequence, and fragments carried in any two subcarrier groups are different. According to the method, the terminal device sends the first sequence on the M subcarrier groups, so that interference between different terminal devices is small when channel estimation is performed by combining M symbols. This can effectively improve accuracy of channel estimation.

A communication system includes a transmitter configured to transmit a modulated signal, a transmission line configured to carry the modulated signal, and a receiver coupled to the transmitter by the transmission line, and configured to receive the modulated signal. The transmitter includes a modulator configured to generate the modulated signal responsive to a data signal and a carrier signal. The receiver includes a demodulator configured to demodulate the modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit configured to adjust a gain of the filter, and to generate the set of control signals based on a voltage of the filtered first signal and a voltage of the first signal. The gain adjusting circuit includes a first peak detector coupled to the filter, and configured to detect a peak value of the voltage of the filtered first signal.

A communication system includes a transmitter configured to transmit a modulated signal, a transmission line configured to carry the modulated signal, and a receiver coupled to the transmitter by the transmission line, and configured to receive the modulated signal. The transmitter includes a modulator configured to generate the modulated signal responsive to a data signal and a carrier signal. The receiver includes a demodulator configured to demodulate the modulated signal responsive to a first carrier signal. The demodulator includes a filter and a gain adjusting circuit configured to adjust a gain of the filter, and to generate the set of control signals based on a voltage of the filtered first signal and a voltage of the first signal. The gain adjusting circuit includes a first peak detector coupled to the filter, and configured to detect a peak value of the voltage of the filtered first signal.