Random access method, user equipment, source base station and target base station

A random access method for a UE, comprising:

• selecting a firstly detected first beam;
• selecting a first random access resource with an earliest transmission time from available random access resources in accordance with a random access resource configuration corresponding to the firstly detected first beam, to prepare to transmit a random access request;
• or randomly selecting an available first random access resource from a plurality of available random access resources within a first predetermined time period in accordance with the random access resource configuration corresponding to the firstly detected first beam, to prepare to transmit the random access request, wherein the first predetermined time period is a time period determined in accordance with a time for the random access resource with the earliest transmission time that is determined in accordance with the random access resource configuration corresponding to the firstly detected first beam;
• selecting a second beam detected before transmitting a random access request;
• selecting a second random access resource with an earliest transmission time from all of the available random access resources in accordance with the random access resource configuration corresponding to the first beam and a random access resource configuration corresponding to the second beam;
• or randomly selecting an available second random access resource from all of the available random access resources within a second predetermined time period in accordance with the random access resource configurations corresponding respectively to the first beam and the second beam, wherein the second predetermined time period is a time period determined in accordance with the time for the random access resource with the earliest transmission time that is determined in accordance with the random access resource configurations corresponding respectively to the first beam and the second beam;
• when the second random access resource is different from the first random access resource, transmitting the random access request through the second random access resource;
• and
• when the second random access resource is the first random access resource, transmitting the random access request through the second random access resource or the first random access resource.

A UE, comprising a memory, a processor, and a computer program stored in the memory and executed by the processor, wherein the processor is configured to execute the computer program to:

• select one or more beams after receiving random access resource configurations corresponding to a plurality of beams transmitted from a network side;
• and
• select a random access resource whose transmission time is a designated transmission time from available random access resources in accordance with a random access resource configuration of the random access resource configurations corresponding to the one or more beams, to transmit a random access request, wherein the available random access resources comprise a random access resource with an earlier transmission time and a random access resource with an earliest transmission time,
• wherein the random access resource whose transmission time is the designated transmission time is a randomly selected one of the available random access resources within a time period determined in accordance with a time for the random access resource with the earliest transmission time.