Propagation path response estimation and interference canceling using spread-spectrum pilot signal in multi-feeder link of HAPS

A relay communication station that is incorporated in an aerial-staying type communication relay apparatus and relays radio communication of a terminal apparatus, comprising:

• a feeder-link communication section that transmits and receives relay signals different from each other on a same frequency in a feeder link to and from plural gateway stations that are time-synchronized with each other;
• and
• an interference suppression section that suppresses an interference between plural feeder links formed with the plural gateway stations,
• wherein the feeder-link communication section:
• transmits a plurality of spread pilot signals that are spectrally spread with a plurality of transmission-side spreading codes orthogonal to each other, to the plural gateway stations;
• and
• receives estimation results of plural propagation path responses between the gateway stations and an antenna for the feeder link of the communication relay apparatus in a transmission signal band of the feeder link, wherein the estimation results are estimated based on reception signals of a plurality of inverse-spread pilot signals that are spectrally inverse-spread with a reception-side spreading code corresponding to the transmission-side spreading code by any one of the plural gateway stations or a common apparatus common to each gateway station,
• wherein the interference suppression section:
• calculates a weight for suppressing an interference signal that causes an interference by a transmission signal transmitted from the relay communication station to a gateway station and received by another gateway station, based on the plural propagation path responses received from the any one of the gateway stations or the common apparatus, with respect to each of the plural gateway stations;
• and
• adds or subtracts, for the transmission signal to be transmitted to the gateway station, a transmission signal to be transmitted to another gateway station that is multiplied by the weight corresponding to the other gateway station, with respect to each of the plural gateway stations.

A relay communication station that is incorporated in an aerial-staying type communication relay apparatus and relays radio communication of a terminal apparatus, comprising:

• a feeder-link communication section that transmits and receives relay signals different from each other on a same frequency in a feeder link to and from plural gateway stations that are time-synchronized with each other;
• and
• an interference suppression section that suppresses an interference between plural feeder links formed with the plural gateway stations,
• wherein the feeder-link communication section:
• transmits a plurality of spread pilot signals that are spectrally spread with a plurality of transmission-side spreading codes orthogonal to each other, to the plural gateway stations;
• and
• receives reception results of the plurality of inverse-spread pilot signals, wherein the plural gateway stations spectrally inverse-spread a reception signal of the spread pilot signal with a reception-side spreading code corresponding to the transmission-side spreading code, and
• wherein the interference suppression section:
• estimates plural propagation path responses between the gateway stations and an antenna for the feeder link of the communication relay apparatus in a transmission signal band of the feeder link, based on the reception results of the plurality of inverse-spread pilot signals;
• calculates a weight for suppressing an interference signal that causes an interference by a transmission signal transmitted from the relay communication station to a gateway station and received by another gateway station, based on estimation results of the plural propagation path responses, with respect to each of the plural gateway stations;
• and
• adds or subtracts, for the transmission signal to be transmitted to the gateway station, a transmission signal to be transmitted to the another gateway station that is multiplied by the weight corresponding to the another gateway station, with respect to each of the plural gateway stations.

A relay communication station that is incorporated in an aerial-staying type communication relay apparatus and relays radio communication of a terminal apparatus, comprising:

• a feeder-link communication section that transmits and receives relay signals different from each other on a same frequency in a feeder link to and from plural gateway stations that are time-synchronized with each other;
• and
• an interference suppression section that suppresses an interference between plural feeder links formed with the plural gateway stations,
• wherein the feeder-link communication section:
• transmits a plurality of spread pilot signals that are spectrally spread with a plurality of transmission-side spreading codes orthogonal to each other, to the plural gateway stations;
• and
• receives a calculation result of a weight for suppressing an interference signal that causes an interference by a transmission signal transmitted from the relay communication station to a gateway station and received by another gateway station, wherein the weight is calculated based on reception signals of a plurality of inverse-spread pilot signals that are spectrally inverse-spread with a reception-side spreading code corresponding to the transmission-side spreading code by any one of the plural gateway stations or a common apparatus common to each gateway station, with respect to each of the plural gateway stations, and
• wherein the interference suppression section adds or subtracts, for a transmission signal to be transmitted to the gateway station, a transmission signal to be transmitted to the other gateway station that is multiplied by the weight corresponding to the another gateway station, with respect to each of the plural gateway stations.

An interference suppression method in a feeder link between a relay communication station and plural gateway stations, the relay communication station being incorporated in an aerial-staying type communication relay apparatus and relaying radio communication of a terminal apparatus, the plural gateway stations being time-synchronized with each other to transmit and receive relay signals different from each other on a same frequency, the method comprising:

• transmitting and receiving a plurality of pilot signals that are spectrally spread using a plurality of spreading codes orthogonal to each other between the relay communication station and the plural gateway stations;
• estimating a propagation path response between the plural gateway stations and an antenna for feeder link of the communication relay apparatus in a transmission signal band of the feeder link, based on reception results of spectral inverse-spreading the plurality of pilot signals;
• calculating plural weights respectively corresponding to the plural gateway stations based on the plural propagation path responses;
• and
• subtracting, from a signal to be transmitted and received via a directional beam corresponding to the gateway station, a signal to be transmitted and received via the directional beam corresponding to the other gateway station that is multiplied by the weight corresponding to the other gateway station, with respect to each of the plural gateway stations.