A signal transmission method, comprising: receiving, by a terminal device, configuration information sent by a network device, wherein the configuration information is used to instruct the terminal device to send a reference signal, and a resource used to transmit the reference signal is determined based on a public cell identity of a cell to which the terminal device belongs; and sending, by the terminal device, the reference signal based on the configuration information by using the resource, wherein sending the reference signal comprises sending the reference signal to at least one other terminal device in a neighboring cell based on the configuration information by using the resource, and wherein the configuration information is further used to indicate whether the reference signal is used for interference/channel measurement between terminal devices, including the terminal device, and when the configuration information indicates that the reference signal is used for interference/channel measurement between the terminal devices, the configuration information is further used to indicate whether the terminal device is a sender or a receiver, and wherein the method further comprises: sending, by the terminal device, the reference signal when the configuration information is used to indicate that the reference signal is used for interference/channel measurement between the terminal devices, and the configuration information indicates that the terminal device is a sender, receiving, by the terminal device, the reference signal sent by another terminal device in a neighboring cell and performing interference/channel measurement between the terminal devices based on the reference signal, when the configuration information is used to indicate that the reference signal is used for interference/channel measurement between the terminal devices, and the configuration information indicates that the terminal device is a receiver, and sending an uplink reference signal or receiving a downlink reference signal based on the configuration information, by the terminal device, when the configuration information is used to indicate that the reference signal is not used for interference/channel measurement between the terminal devices. receiving, by a terminal device, configuration information sent by a network device, wherein the configuration information is used to instruct the terminal device to send a reference signal, and a resource used to transmit the reference signal is determined based on a public cell identity of a cell to which the terminal device belongs; and sending, by the terminal device, the reference signal based on the configuration information by using the resource, wherein sending the reference signal comprises sending the reference signal to at least one other terminal device in a neighboring cell based on the configuration information by using the resource, and wherein the configuration information is further used to indicate whether the reference signal is used for interference/channel measurement between terminal devices, including the terminal device, and when the configuration information indicates that the reference signal is used for interference/channel measurement between the terminal devices, the configuration information is further used to indicate whether the terminal device is a sender or a receiver, and wherein the method further comprises: sending, by the terminal device, the reference signal when the configuration information is used to indicate that the reference signal is used for interference/channel measurement between the terminal devices, and the configuration information indicates that the terminal device is a sender, receiving, by the terminal device, the reference signal sent by another terminal device in a neighboring cell and performing interference/channel measurement between the terminal devices based on the reference signal, when the configuration information is used to indicate that the reference signal is used for interference/channel measurement between the terminal devices, and the configuration information indicates that the terminal device is a receiver, and sending an uplink reference signal or receiving a downlink reference signal based on the configuration information, by the terminal device, when the configuration information is used to indicate that the reference signal is not used for interference/channel measurement between the terminal devices. sending, by the terminal device, the reference signal when the configuration information is used to indicate that the reference signal is used for interference/channel measurement between the terminal devices, and the configuration information indicates that the terminal device is a sender, receiving, by the terminal device, the reference signal sent by another terminal device in a neighboring cell and performing interference/channel measurement between the terminal devices based on the reference signal, when the configuration information is used to indicate that the reference signal is used for interference/channel measurement between the terminal devices, and the configuration information indicates that the terminal device is a receiver, and sending an uplink reference signal or receiving a downlink reference signal based on the configuration information, by the terminal device, when the configuration information is used to indicate that the reference signal is not used for interference/channel measurement between the terminal devices.