Communication device, communication method, and communication system

1 . A first communication device, comprising:

circuitry configured to:

acquire an end-to-end Hybrid Automatic Repeat Request (HARQ) process ID;

perform uni-directional relay communication based on the acquired end-to-end HARQ process ID, wherein

the uni-directional relay communication includes:

first uplink communication as relay communication between the first communication device and a second communication device via a relay station; and

first downlink communication as direct communication between the first communication device and the second communication device, or

second uplink communication as the direct communication between the first communication device and the second communication device via the relay station; and

second downlink communication as the relay communication between the first communication device and the second communication device,

the end-to-end HARQ process ID is different from at least one of a first HARQ process ID or a second HARQ process ID,

the first HARQ process ID is for communication between the second communication device and the relay station, and

the second HARQ process ID is for communication between the first communication device and the relay station; and

perform, based on the acquired end-to-end HARQ process ID, one of the first uplink communication or the second downlink communication with the second communication device.

2 . The first communication device according to claim 1 , wherein

the second communication device is a base station, and

the first communication device is a terminal device.

3 . The first communication device according to claim 2 , wherein

the acquired end-to-end HARQ process ID is different from the first HARQ process ID for the communication between the base station and the relay station and

the circuitry is further configured to perform, based on the acquired end-to-end HARQ process ID, the first uplink communication with the base station.

4 . The first communication device according to claim 3 , wherein the circuitry is further configured to:

perform, based on the acquired end-to-end HARQ process ID, communication with the relay station in the first uplink communication with the base station; and

receive, from the base station, one of a first acknowledgement corresponding to the acquired end-to-end HARQ process ID or a negative acknowledgement corresponding to the acquired end-to-end HARQ process ID.

5 . The first communication device according to claim 4 , wherein the circuitry is further configured to:

receive, from the relay station, a second acknowledgement corresponding to the acquired end-to-end HARQ process ID;

retain, independent of the reception of the second acknowledgement, transmission data corresponding to the acquired end-to-end HARQ process ID; and

delete the transmission data based on the reception of one of the first acknowledgement or the negative acknowledgement.

6 . The first communication device according to claim 4 , wherein

the circuitry is further configured to acquire, from the relay station, a grant for the first uplink communication, and

the grant for the first uplink communication including the end-to-end HARQ process ID.

7 . The first communication device according to claim 3 , wherein

the base station is a non-terrestrial base station.

8 . The first communication device according to claim 2 , wherein

circuitry is further configured to perform the first downlink communication with the base station based on the acquired end-to-end HARQ process ID.

9 . The first communication device according to claim 2 , wherein

the acquired end-to-end HARQ process ID is different from the second HARQ process ID, and

the circuitry is further configured to perform the first downlink communication with the base station based on the acquired end-to-end HARQ process ID.

10 . The first communication device according to claim 2 , wherein

the circuitry is further configured to perform the first uplink communication with the base station based on the acquired end-to-end HARQ process ID.

11 . The first communication device according to claim 1 , wherein

the second communication device is a terminal device, and

the first communication device is a base station.

12 . The first communication device according to claim 11 , wherein

the acquired end-to-end HARQ process ID is different from the first HARQ process ID, and

the circuitry is further configured to perform the first uplink communication with the terminal device based on the acquired end-to-end HARQ process ID.

13 . The first communication device according to claim 12 , wherein the base station is a non-terrestrial base station.

14 . The first communication device according to claim 11 , wherein

the circuitry is further configured to perform the first downlink communication with the terminal device based on the acquired end-to-end HARQ process ID.

15 . The first communication device according to claim 11 , wherein

the acquired end-to-end HARQ process ID is different from the first HARQ process ID, and

the circuitry is further configured to perform the first downlink communication with the terminal device based on the acquired end-to-end HARQ process ID.

16 . The first communication device according to claim 11 , wherein

the circuitry is further configured to perform the first uplink communication with the terminal device based on the acquired end-to-end HARQ process ID.

17 . The first communication device according to claim 1 , wherein the circuitry is further configured to:

determine that first communication data is user data;

perform the uni-directional relay communication with the second communication device based on the acquired end-to-end HARQ process ID and the determination that the first communication data is the user data;

determine that second communication data is control data; and

perform bidirectional direct communication with the second communication device, wherein the bidirectional direct communication includes:

third uplink communication as the direct communication between the first communication device and the second communication device; and

third downlink communication as the direct communication between the first communication device and the second communication device.

18 . A communication method comprising:

acquiring an end-to-end Hybrid Automatic Repeat Request (HARQ) process ID;

performing uni-directional relay communication based on the acquired end-to-end HARQ process ID, wherein

the uni-directional relay communication includes:

first uplink communication as relay communication between a first communication device and a second communication device via a relay station; and

first downlink communication as direct communication between the first communication device and the second communication device; or

second uplink communication as the direct communication between the first communication device and the second communication device via the relay station; and

second downlink communication as the relay communication between the first communication device and the second communication device,

the end-to-end HARQ process ID is different from at least one of a first HARQ process ID or a second HARQ process ID,

the first HARQ process ID is for communication between the second communication device and the relay station, and

the second HARQ process ID if for communication between the first communication device and the relay station; and

performing, based on the acquired end-to-end HARQ process ID, one of the first uplink communication or the second downlink communication with the second communication device.

19 . A communication system, comprising:

a first communication device;

a second communication device;

a relay station;

a terminal device; and

a base station configured to:

acquire an end-to-end Hybrid Automatic Repeat Request (HARQ) process ID;

perform, based on the acquired end-to-end HARQ process ID, uni-directional relay communication with the terminal device, wherein

the uni-directional relay communication includes:

first uplink communication as relay communication between the base station and the terminal device via the relay station; and

first downlink communication as direct communication between the base station and the terminal device, or

second uplink communication as the direct communication between the first communication device and the second communication device via the relay station; and

second downlink communication as the relay communication between the first communication device and the second communication device,

the end-to-end HARQ process ID is different from at least one of a first HARQ process ID or a second HARQ process ID,

the first HARQ process ID is for communication between the terminal device and the relay station, and

the second HARQ process ID is for communication between the base station and the relay station; and

perform, based on the acquired end-to-end HARQ process ID, the first uplink communication or the second downlink communication with the base station.

20 . The communication system according to claim 19 , wherein

the terminal device is configured to execute the first uplink communication with the base station via the relay station, to transmit uplink data,

the base station is further configured to disable, based on the execution of the first uplink communication via the relay station, an HARQ process between the base station and the relay station, and

the relay station is configured to:

transmit, to the base station, the uplink data from the terminal device; and

delete the uplink data based on the transmission of the uplink data to the base station.