Transmitting a message in response to receiving a message

1. An apparatus comprising:

a receiver that receives a second message from a second remote unit, wherein the second message is transmitted from the second remote unit in response to the second remote unit receiving a first message from a first remote unit, and the second message indicates that the second remote unit is a unidirectional relay device or that the second remote unit is a bidirectional relay device; and

a transmitter that transmits a third message corresponding to the first message in response to receiving the second message, wherein transmitting the third message corresponding to the first message in response to receiving the second message comprises:

in response to the second message indicating that the second remote unit is the unidirectional relay device, transmitting the third message directly to the first remote unit; and

in response to the second message indicating that the second remote unit is the bidirectional relay device, transmitting the third message directly to the second remote unit.

2. The apparatus of claim 1 , wherein the transmitter transmits the third message to the second remote unit, and the second remote unit transmits the third message to the first remote unit.

3. The apparatus of claim 1 , wherein the transmitter transmits the third message to the first remote unit.

4. The apparatus of claim 1 , further comprising a processor that determines a transmission criterion for the second remote unit, wherein the transmitter transmits the transmission criterion to the second remote unit.

5. The apparatus of claim 4 , wherein the transmission criterion is received by the second remote unit and used by the second remote unit to determine whether to transmit the second message to the apparatus.

6. A method comprising:

receiving a second message from a second remote unit, wherein the second message is transmitted from the second remote unit in response to the second remote unit receiving a first message from a first remote unit, and the second message indicates that the second remote unit is a unidirectional relay device or that the second remote unit is a bidirectional relay device; and

transmitting a third message corresponding to the first message in response to receiving the second message, wherein transmitting the third message corresponding to the first message in response to receiving the second message comprises:

in response to the second message indicating that the second remote unit is the unidirectional relay device, transmitting the third message directly to the first remote unit; and

in response to the second message indicating that the second remote unit is the bidirectional relay device, transmitting the third message directly to the second remote unit.

7. The method of claim 6 , wherein the second message comprises a scheduling request, measurement information, or a combination thereof, and the third message comprises control signaling to schedule sidelink communication.

8. The method of claim 6 , wherein the second message comprises data and the third message comprises feedback corresponding to the data.

9. The method of claim 6 , wherein the second message comprises a scheduling request, measurement information, or some combination thereof.

10. The method of claim 9 , wherein the scheduling request comprises a traffic type, a traffic priority, a data size, a capacity, location information, or some combination thereof, and the measurement information comprises channel state information, power information, or some combination thereof.

11. An apparatus comprising:

a transmitter that transmits a first message to a second remote unit, wherein the second remote unit transmits a second message to a base unit, and the second message indicates that the second remote unit is a unidirectional relay device or that the second remote unit is a bidirectional relay device; and

a receiver that receives a third message corresponding to the first message in response to transmitting the first message, wherein receiving the third message corresponding to the first message in response to transmitting the first message comprises:

in response to the second message indicating that the second remote unit is the unidirectional relay device, receiving the third message directly from the base unit; and

in response to the second message indicating that the second remote unit is the bidirectional relay device, receiving the third message directly from the second remote unit.

12. The apparatus of claim 11 , wherein the receiver receives the third message from the second remote unit, and the second remote unit receives the third message from the base unit.

13. An apparatus comprising:

a receiver that receives a first message from a first remote unit;

a process that:

generates measurement information; and

determines whether a transmission criterion is satisfied based on the first message, measurement information, or some combination thereof; and

a transmitter that transmits a second message to a base unit in response to the transmission criterion being satisfied, wherein the second message indicates that the apparatus is a unidirectional relay device or that the apparatus is a bidirectional relay device;

wherein the receiver receives a third message from the base unit corresponding to the first message in response to transmitting the second message, wherein receiving the third message corresponding to the first message in response to transmitting the second message comprises:

in response to the second message indicating that the second remote unit is the bidirection relay device, receiving the third message directly from the base unit.

14. The apparatus of claim 13 , wherein the transmitter transmits a fourth message to the first remote unit, wherein the fourth message comprises control signaling to schedule the sidelink communication, feedback corresponding to data, or some combination thereof.

15. The apparatus of claim 13 , wherein the second message comprises data, a scheduling request, the measurement information, or some combination thereof, and the third message comprises control signaling to schedule sidelink communication, feedback corresponding to the data, the scheduling request, the measurement information, or some combination thereof.

16. The apparatus of claim 13 , wherein the second message comprises data and the third message comprises feedback corresponding to the data.

17. The apparatus of claim 13 , wherein the second message comprises data, a scheduling request, the measurement information, or some combination thereof.

18. The apparatus of claim 17 , wherein the measurement information comprises channel state information, measured power information, or some combination thereof.

19. The apparatus of claim 17 , wherein the scheduling request comprises a traffic type, a traffic priority, a data size, a capacity, location information, or some combination thereof.

20. The apparatus of claim 13 , wherein the transmission criterion is preconfigured by the base unit to configure the second remote unit to determine whether the second remote unit transmits the second message, the measurement information, or some combination thereof to the base unit.