A communication method, comprising: receiving, by a first terminal device, a first downlink control channel that is sent by a network device on a third time-frequency resource; and, (a), sending, by the first terminal device, a first uplink message to the network device on a first time-frequency resource based on the first downlink control channel, wherein transmission directions of the first uplink message and a second downlink message are different, and the second downlink message is a message that is sent by the network device and that the network device schedules, by using a second downlink control channel, a second terminal device to receive on a second time-frequency resource; or, (b), receiving, by the first terminal device based on the first downlink control channel and on the first time-frequency resource, a first downlink message sent by the network device, wherein transmission directions of the first downlink message and a second uplink message are different, and the second uplink message is a message that the network device schedules, by using the second downlink control channel, the second terminal device to send to the network device on the second time-frequency resource, wherein the first time-frequency resource and the second time-frequency resource comprise a same time domain resource and a same frequency domain resource, wherein before the receiving, by the first terminal device, the first downlink control channel that is sent by the network device on the third time-frequency resource, the method further comprises: receiving, by the first terminal device, indication information sent by the network device; and determining, by the first terminal device based on the indication information, to receive the first downlink control channel. receiving, by a first terminal device, a first downlink control channel that is sent by a network device on a third time-frequency resource; and, (a), sending, by the first terminal device, a first uplink message to the network device on a first time-frequency resource based on the first downlink control channel, wherein transmission directions of the first uplink message and a second downlink message are different, and the second downlink message is a message that is sent by the network device and that the network device schedules, by using a second downlink control channel, a second terminal device to receive on a second time-frequency resource; or, (b), receiving, by the first terminal device based on the first downlink control channel and on the first time-frequency resource, a first downlink message sent by the network device, wherein transmission directions of the first downlink message and a second uplink message are different, and the second uplink message is a message that the network device schedules, by using the second downlink control channel, the second terminal device to send to the network device on the second time-frequency resource, wherein (a), sending, by the first terminal device, a first uplink message to the network device on a first time-frequency resource based on the first downlink control channel, wherein transmission directions of the first uplink message and a second downlink message are different, and the second downlink message is a message that is sent by the network device and that the network device schedules, by using a second downlink control channel, a second terminal device to receive on a second time-frequency resource; or, (b), receiving, by the first terminal device based on the first downlink control channel and on the first time-frequency resource, a first downlink message sent by the network device, wherein transmission directions of the first downlink message and a second uplink message are different, and the second uplink message is a message that the network device schedules, by using the second downlink control channel, the second terminal device to send to the network device on the second time-frequency resource, wherein the first time-frequency resource and the second time-frequency resource comprise a same time domain resource and a same frequency domain resource, wherein before the receiving, by the first terminal device, the first downlink control channel that is sent by the network device on the third time-frequency resource, the method further comprises: receiving, by the first terminal device, indication information sent by the network device; and determining, by the first terminal device based on the indication information, to receive the first downlink control channel. receiving, by the first terminal device, indication information sent by the network device; and determining, by the first terminal device based on the indication information, to receive the first downlink control channel.