Method, apparatus, device and network system for adding secondary serving cell

A method for adding a secondary serving cell, comprising:

• sending, by a primary base station, a random access resource allocation message and a secondary serving cell addition request message to a terminal and a secondary base station, the random access resource allocation message and the secondary serving cell addition request message comprise a serial number of a random access preamble code and a serial number of a physical random access channel mask code;
• receiving, by the primary base station, a time advance command (TAC) transmission message sent by the secondary base station, wherein the TAC transmission message is sent to the primary base station after the secondary base station receives a random access request message that is sent by the terminal and carries the random access preamble code obtained according to the serial number of the random access preamble code, and the TAC transmission message comprises a TAC obtained by the secondary base station according to the random access request message;
• and
• sending, by the primary base station to the terminal, a random access response message that carries the TAC, so that the terminal adjusts, according to the TAC, a time advance (TA) of the terminal on a secondary serving cell corresponding to the secondary base station.

A method for adding a secondary serving cell, comprising:

• receiving, by a secondary base station, a secondary serving cell addition request message sent by a primary base station, wherein the secondary serving cell addition request message comprises a serial number of a random access preamble code and a serial number of a physical random access channel mask code;
• receiving, by the secondary base station according to the secondary serving cell addition request message, a random access request message that is sent by a terminal and carries the random access preamble code obtained according to the serial number of the random access preamble code;
• and
• obtaining, by the secondary base station, a time advance command (TAC) according to the random access request message, and sending, to the primary base station, a TAC transmission message that carries the TAC, so that the primary base station sends, to the terminal, a random access response message that carries the TAC so that the terminal adjusts, according to the TAC, a time advance (TA) of the terminal on a secondary serving cell corresponding to the secondary base station.