Method for obtaining uplink synchronization and configuring uplink connection

A user equipment configuring an uplink connection with a BBU in a cloud radio access network (C-RAN) environment in which a remote radio head (RRH) and a baseband unit (BBU) are separated from each other, comprising:

• a transmitter,
• a receiver;
• and
• a processor configured to operate to configure an uplink connection in a manner of being connected with the transmitter and the receiver, the processor configured to control the receiver to receive a downlink signal from a plurality of RRHs, the processor configured to control the transmitter to transmit a random access preamble to a target RRH of which strength of the received downlink signal is equal to or greater than a threshold value among a plurality of the RRHs, the processor configured to control the receiver to receive a random access response message for indicating to configure an uplink connection with an RRH which is selected based on a difference between reception power of the random access preamble received by the target RRH and reception power of the random access preamble overheard by a neighboring RRH adjacent to the target RRH, the processor configured to configure an uplink connection with the selected RRH.

A method of configuring an uplink connection, which is configured by a BBU with a user equipment in a cloud radio access network (C-RAN) environment in which a remote radio head (RRH) and a baseband unit (BBU) are separated from each other, comprising the steps of:

• receiving a first random access preamble transmitted by the user equipment through a target RRH;
• receiving a second random access preamble delivered by a neighboring RRH adjacent to the target RRH by overhearing the first random access preamble;
• selecting an RRH to be connected with the user equipment from among the target RRH and the neighboring RRH based on a difference between reception power of the first random access preamble and reception power of the second random access preamble;
• and
• transmitting a random access response message for indicating to configure an uplink connection with the selected RRH to the user equipment.

A BBU configuring an uplink connection with a user equipment in a cloud radio access network (C-RAN) environment in which a remote radio head (RRH) and a baseband unit (BBU) are separated from each other, comprising:

• a transmitter;
• a receiver;
• and
• a processor configured to operate to configure an uplink connection in a manner of being connected with the transmitter and the receiver, the processor configured to control the receiver to receive a first random access preamble transmitted by the user equipment through a target RRH and a second random access preamble delivered by a neighboring RRH adjacent to the target RRH by overhearing the first random access preamble, the processor configured to select an RRH to be connected with the user equipment from among the target RRH and the neighboring RRH based on a difference between reception power of the first random access preamble and reception power of the second random access preamble, the processor configured to control the transmitter to transmit a random access response message for indicating to configure an uplink connection with the selected RRH to the user equipment.