Message transmission method, user equipment, base station, and system

A message transmission method in a cell handover process in a cellular network, wherein the method comprises:

• receiving, by first user equipment, a measurement control signal from a source base station, and reporting a measurement report to the source base station after neighboring cell measurement;
• when handover is required, receiving, by the first user equipment, information that is about a contention resource and that is sent by a target base station, wherein the contention resource is a transmission resource obtained in an autonomous contention manner;
• and
• contending, by the first user equipment, for a transmission resource in a time window corresponding to the contention resource, and if the transmission resource is obtained, transmitting a message to second user equipment by using the obtained transmission resource.

First user equipment, comprising:

• a receiver, configured to receive information about a contention resource from a cellular network base station, wherein the contention resource is a transmission resource obtained in an autonomous contention manner;
• a processor, configured to contend, according to the information that is about the contention resource and that is received by the receiver, for a transmission resource in a time window corresponding to the contention resource;
• and
• a transmitter, configured to:
• when the processor obtains the transmission resource, transmit a message to second user equipment by using the obtained transmission resource.

A communications system, comprising first user equipment and a cellular network base station, wherein:

• the first user equipment comprises:
• a first user equipment receiver, configured to receive information about a contention resource from the base station, wherein the contention resource is a transmission resource obtained in an autonomous contention manner;
• a first user equipment processor, configured to contend, according to the information that is about the contention resource and that is received by the receiver, for a transmission resource in a time window corresponding to the contention resource;
• and
• a first user equipment transmitter, configured to:
• when the processor obtains the transmission resource, transmit a message to second user equipment by using the obtained transmission resource;
• and
• the base station comprises:
• a base station transmitter, configured to send the information about the contention resource to the first user equipment.