Communications method and device

1 . A communications method applied to a terminal device and comprising:

receiving, from a network device, a first message indicating a first cell and a second cell, wherein the first cell comprises a first downlink carrier and a first uplink carrier, wherein the second cell comprises the first downlink carrier and a second uplink carrier, wherein a first duplex mode of a band to which the first downlink carrier belongs is the same as a second duplex mode of a band to which the first uplink carrier belongs, and wherein the first duplex mode is different from a third duplex mode of a band to which the second uplink carrier belongs;

determining a common physical cell identifier based on at least one of a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) of the first downlink carrier;

determining a first physical cell identifier of the first cell and a second physical cell identifier of the second cell based on the common physical cell identifier, wherein the first physical cell identifier is different from the second physical cell identifier;

selecting the first cell or the second cell as a selected cell for access; and

communicating with the network device using the selected cell.

2 . The method of claim 1 , wherein the band to which the first downlink carrier belongs is the same as the band to which the first uplink carrier belongs, and wherein the band to which the second uplink carrier belongs is lower than the band to which the first uplink carrier belongs.

3 . The method of claim 1 , wherein selecting the first cell or the second cell for access comprises:

obtaining a downlink channel quality of the first cell;

selecting, when the downlink channel quality is greater than or equal to a first threshold value, the first cell for access; and

selecting, when the downlink channel quality is less than the first threshold value, the second cell for access.

4 . The method of claim 3 , wherein the first threshold value is preconfigured in the terminal device, and wherein the method further comprises receiving the first threshold value from the network device.

5 . The method of claim 1 , wherein selecting the first cell or the second cell for access comprises:

obtaining uplink load information of the first cell and the second cell;

selecting, when a first uplink load of the first cell is less than or equal to a second uplink load of the second cell, the first cell for access; and

selecting, when the first uplink load is greater than the second uplink load, the second cell for access.

6 . The method of claim 1 , wherein selecting the first cell or the second cell for access comprises:

selecting, when the terminal device supports access from the second cell, the second cell for access; and

selecting, when the terminal device does not support access from the second cell, the first cell for access.

7 . The method of claim 1 , further comprising receiving, from the network device, a second message instructing the terminal device to access the first cell or access the second cell, wherein the selecting the first cell or the second cell for access comprises selecting, by the terminal device based on the second message, the first cell or the second cell for access.

8 . The method of claim 1 , further comprising:

receiving, from the network device, a third message comprising one or more of a second threshold value, a third threshold value, a fourth threshold value, or a fifth threshold value, wherein the second threshold value and the third threshold value initiate first neighboring cell measurement and neighboring cell reselection performed on the first cell, and wherein the fourth threshold value and the fifth threshold value initiate second neighboring cell measurement and neighboring cell reselection performed on the second cell; and

starting, based on the third message, at least one of the neighboring cell measurement or neighboring cell reselection performed on the first cell or the second cell.

9 . The method of claim 1 , further comprising:

receiving, from the network device, a fourth message instructing the terminal device to hand over from a current cell to a target cell, wherein the fourth message indicates a configuration of the target cell comprising at least one of a physical cell identifier of the target cell or a lower-layer configuration, and wherein instructing the terminal device to hand over from the current cell to the target cell comprises instructing the terminal device to hand over from the first cell to the second cell or to hand over from the second cell to the first cell;

handing over to the target cell; and

applying at least one of the physical cell identifier of the target cell or the lower-layer configuration.

10 . The method of claim 9 , further comprising:

handing over, when the configuration of the target cell further comprises a cell radio network temporary identifier (C-RNTI) used in the target cell by the terminal device, to the target cell; and

applying at least one of the C-RNTI, the physical cell identifier of the target cell, or the lower-layer configuration.

11 . A communications method, comprising:

receiving, from a network device, a first message indicating a second cell, wherein the second cell comprises a first downlink carrier and a second uplink carrier, and wherein a first duplex mode of a band to which the first downlink carrier belongs is different from a second duplex mode of a band to which the second uplink carrier belongs;

determining a common physical cell identifier based on at least one of a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) of the first downlink carrier;

determining a second physical cell identifier of the second cell based on the common physical cell identifier, wherein the second physical cell identifier is different from a first physical cell identifier of a first cell;

accessing the second cell; and

communicating with the network device using the second cell.

12 . The method of claim 11 , wherein the band to which the second uplink carrier belongs is lower than the band to which the first downlink carrier belongs.

13 . A terminal device comprising:

a memory configured to store instructions; and

a processor coupled to the memory and configured to execute the instructions to cause the terminal device to:

receive a first message from a network device, wherein the first message indicates a first cell and a second cell, the first cell comprises a first downlink carrier and a first uplink carrier, the second cell comprises the first downlink carrier and a second uplink carrier, a first duplex mode of a band to which the first downlink carrier belongs is the same as a second duplex mode of a band to which the first uplink carrier belongs, and the first duplex mode of the band to which the first downlink carrier belongs is different from a third duplex mode of a band to which the second uplink carrier belongs;

determine a common physical cell identifier based on at least one of a primary synchronization signal (PSS) or a secondary synchronization signal (SSS) of the first downlink carrier;

determine a first physical cell identifier of the first cell and a second physical cell identifier of the second cell based on the common physical cell identifier, wherein the first physical cell identifier is different from the second physical cell identifier;

select the first cell or the second cell as a selected cell for access; and

communicate with the network device using the selected cell.

14 . The terminal device of claim 13 , wherein the band to which the first downlink carrier belongs is the same as the band to which the first uplink carrier belongs, and wherein the band to which the second uplink carrier belongs is lower than the band to which the first uplink carrier belongs.

15 . The terminal device of claim 13 , wherein the terminal device being configured to select the first cell or the second cell for access comprises the processor being further configured to execute the instructions to cause the terminal device to:

obtain downlink channel quality of the first cell;

select, when the downlink channel quality is greater than or equal to a first threshold value, the first cell for access; and

select, when the downlink channel quality is less than the first threshold value, the second cell for access.

16 . The terminal device of claim 13 , wherein the terminal device being configured to select the first cell or the second cell for access comprises the processor being further configured to execute the instructions to cause the terminal device to:

obtain uplink load information of the first cell and the second cell;

select, when a first uplink load of the first cell is less than or equal to a second uplink load of the second cell, the first cell for access; and

select, when the first uplink load is greater than the second uplink load, the second cell for access.

17 . The terminal device of claim 13 , wherein the terminal device being configured to select the first cell or the second cell for access comprises the processor being further configured to execute the instructions to cause the terminal device to:

select, when the terminal device supports access from the second cell, the second cell for access; and

select, when the terminal device does not support access from the second cell, the first cell for access.

18 . The terminal device of claim 13 , wherein the processor is further configured to execute the instructions to cause the terminal device to receive, from the network device, a second message instructing the terminal device to access the first cell or access the second cell, and

wherein the terminal device is configured to select the first cell or the second cell for access by being configured to select, by the terminal device based on the second message, the first cell or the second cell for access.

19 . The terminal device of claim 13 , wherein the processor is further configured to execute the instructions to cause the terminal device to:

receive, from the network device, a third message comprising one or more of a second threshold value, a third threshold value, a fourth threshold value, or a fifth threshold value, wherein the second threshold value and the third threshold value initiate first neighboring cell measurement and neighboring cell reselection performed on the first cell, and wherein the fourth threshold value and the fifth threshold value initiate second neighboring cell measurement and neighboring cell reselection performed on the second cell; and

start, based on the third message, at least one of the neighboring cell measurement or neighboring cell reselection performed on the first cell or the second cell.

20 . The method of claim 1 , wherein determining the first physical cell identifier of the first cell and the second physical cell identifier of the second cell comprises:

determining at least one of the first physical cell identifier or the second physical cell identifier based on a result of an offset of the common physical cell identifier using a physical cell identifier offset parameter;

receiving, from the network device in a broadcast manner, at least one of the first physical cell identifier or the second physical cell identifier; or

receiving, from the network device using radio resource control (RRC) dedicated signaling, at least one of the first physical cell identifier or the second physical cell identifier.