Random access method and apparatus and communication system

1. A network apparatus comprising:

processor circuitry configured to configure at least two uplink bandwidth parts (UL BWPs) and at least two downlink bandwidth parts (DL BWPs),

wherein the at least two UL BWPs and the at least two DL BWPs are of one-to-one correspondence based on value of BWP index;

a receiver configured to receive a preamble transmitted by a User Equipment (UE) at a time-frequency resource in a first UL BWP in the at least two UL BWPs;

controller circuitry configured to:

according to the received preamble, determine a first DL BWP in the at least two DL BWPs, the first DL BWP corresponding to the first UL BWP in which the preamble is received, the first DL BWP being configured with a same value of BWP index as the first UL BWP; and

control to cause the UE to switch, when an active DL BWP does not have a same value of BWP index as the first UL BWP, the active DL BWP to the first DL BWP corresponding to the first UL BWP; and

a transmitter configured to transmit a random access response (RAR) corresponding to the received preamble on the determined first DL BWP,

wherein the transmitter is further configured to:

transmit, via radio resource control (RRC) signaling or system information, first information indicating the first DL BWP, the first information including the BWP index configured for the first DL BWP, and

transmit, via RRC signaling or system information, second information indicating at least one time-frequency resource for transmitting preambles in the first UL BWP.

2. The network apparatus according to claim 1 , wherein the processor circuitry configured to control to cause the UE to monitor the RAR.

3. A terminal comprising:

processor circuitry configured to:

configure at least two uplink bandwidth parts (UL BWPs) and at least two downlink bandwidth parts (DL BWPs), wherein the at least two UL BWPs and the at least two DL BWPs are of one-to-one correspondence based on value of BWP index,

determine a first DL BWP in the at least two DL BWPs, wherein the first DL BWP corresponds to a first UL BWP in the at least two UL BWPs and comprising at least one time-frequency resource for transmitting preambles, the first DL BWP being configured with a same value of BWP index as the first UL BWP,

select a time-frequency resource in the at least one time-frequency resource for transmitting preambles in the first UL BWP, and

when an active DL BWP does not have a same value of BWP index as the first UL BWP, switch the active DL BWP to the first DL BWP corresponding to the first UL BWP; and

a transmitter configured to transmit a preamble, on the selected time-frequency resource, to a network device; and

a receiver configured to receive a random access response (RAR) on the first DL BWP,

wherein the receiver is further configured to:

receive, via radio resource control (RRC) signaling or system information, from the network device-first information indicating the first DL BWP, the first information including the BWP index configured for the first DL BWP, and

receive, via RRC signaling or system information, second information indicating at least one time-frequency resource for transmitting preambles in the first UL BWP.

4. The terminal according to claim 3 , wherein, the receiver switches to the first DL BWP, and monitors and receives an RAR in the first DL BWP.

5. The terminal according to claim 3 , wherein before the transmitter transmits the preamble on the selected time-frequency resource, the transmitter is further configured to switch to the first UL BWP.

6. The terminal according to claim 3 , wherein the RAR is a message 2 of a random access procedure.

7. A communication system, comprising;

a User Equipment (UE) configured to:

configure at least two uplink bandwidth parts (UL BWPs) and at least two downlink bandwidth parts (DL BWPs), wherein the at least two UL BWPs and the at least two DL BWPs are of one-to-one correspondence based on value of BWP index,

determine a first DL BWP in the at least two DL BWPs, wherein the first DL BWP corresponds to a first UL BWP in the at least two UL BWPs and comprising at least one time-frequency resource for transmitting preambles, the first DL BWP being configured with a same value of BWP index as the first UL BWP;

select a time-frequency resource in the at least one time-frequency resource for transmitting preambles in the first UL BWP;

transmit a preamble, on the selected time-frequency resource, to a network device; and

when an active DL BWP does not have a same value of BWP index as the first UL BWP, switch the active DL BWP to the first DL BWP corresponding to the first UL BWP; and

the network device configured to:

configure at least two UL BWPs and at least two DL BWPs wherein the at least two UL BWPs and the at least two DL BWPs are of one-to-one correspondence based on value of BWP index;

receive the preamble transmitted by the UE at a time-frequency resource in the first UL BWP in the at least two UL BWPs;

determine, according to the received preamble, the first DL BWP in the at least two DL BWPs, the first DL BWP corresponding to the first UL BWP in which the preamble is received, the first DL BWP being configured with a same value of BWP index as the first UL BWP; and

transmit a RAR corresponding to the received preamble on the determined first DL BWP,

wherein the network device is further configured to:

transmit, via radio resource control (RRC) signaling or system information, first information indicating the first DL BWP, the first information including the BWP index configured for the first DL BWP, and

transmit, via RRC signaling or system information, second information indicating at least one time-frequency resource for transmitting preambles in the first UL BWP.

8. The communication system according to claim 7 , wherein the time-frequency resource for transmitting preambles is a PRACH resource.