Mobile terminal and base station involved in downlink channel operations including radio channel estimation based on demodulation reference signal

A base station, comprising:

• a processing circuitry which, in operation, assumes that a mobile terminal is configured to use for downlink control channel and corresponding demodulation reference signal receptions at the mobile terminal one of a plurality of reception beams;
• and
• a transceiver which, in operation, transmits a downlink control channel and a corresponding demodulation reference signal to the mobile terminal using one of a plurality of transmission beams corresponding to the assumed one of the plurality of reception beams;
• wherein, the processing circuitry, in operation, modulates the downlink control channel to be transmitted and generates a demodulation reference signal sequence to be transmitted as the corresponding demodulation reference signal,
• wherein, the demodulation reference signal sequence is generated observing an association which associates the generated sequence with the one of the plurality of transmission beams such that at least two of the plurality of transmission beams are associated with different demodulation reference signal sequences, and
• wherein, the demodulation reference signal sequence is generated from a base sequence corresponding to a scrambling identification including applying a cyclic shift to the demodulation reference signal sequence corresponding to a cyclic shift value which is associated with the one of the plurality of transmission beams.

A reception method for a mobile terminal, comprising:

• assuming that a base station is configured to use for downlink control channel and corresponding demodulation reference signal transmissions to the mobile terminal one of a plurality of transmission beams;
• receiving a downlink control channel candidate and a corresponding demodulation reference signal from the base station using one of a plurality of reception beams corresponding to the assumed one of the plurality of transmission beams;
• performing radio channel estimation based on the received demodulation reference signal and, depending on a radio channel estimation quality, demodulating the downlink control channel candidate using the radio channel estimation,
• wherein, the channel estimation is performed using a demodulation reference signal sequence which is generated observing an association which associates the generated sequence with the assumed one of the plurality of transmission beams such that at least two of the plurality of transmission beams are associated with different demodulation reference signal sequences, and
• generating the demodulation reference signal sequence from a base sequence corresponding to a scrambling identification including applying a cyclic shift to the demodulation reference signal sequence corresponding to a cyclic shift value which is associated with the assumed one of the plurality of transmission beams.

A transmission method for a base station, comprising

• assuming that a mobile terminal is configured to use for downlink control channel and corresponding demodulation reference signal receptions at the mobile terminal one of a plurality of reception beams;
• transmitting a downlink control channel and a corresponding demodulation reference signal to the mobile terminal using one of a plurality of transmission beams corresponding to the assumed one of the plurality of reception beams;
• modulating the downlink control channel to be transmitted and generating a demodulation reference signal sequence to be transmitted as the corresponding demodulation reference signal,
• wherein, the demodulation reference signal sequence is generated observing an association which associates the generated sequence with the one of the plurality of transmission beams such that at least two of the plurality of transmission beams are associated with different demodulation reference signal sequences,
• wherein, the demodulation reference signal sequence is generated from a base sequence corresponding to a scrambling identification including applying a cyclic shift to the demodulation reference signal sequence corresponding to a cyclic shift value which is associated with the one of the plurality of transmission beams.