Systems and methods for small cell uplink interference mitigation

A first base station comprising:

• a processor configured to determine a first timing advance;
• and
• a transmitter configured to transmit a second timing advance to a user terminal, the second timing advance determined, not based on a preamble received from the user terminal, to be the same as the first timing advance, the first timing advance for determining, by a user terminal, timing for uplink signal transmission to the first base station, the second timing advance for determining, by the user terminal, timing to transmit an uplink signal to a second base station before a handover of the user terminal from the first base station to the second base station is completed.

A user terminal comprising:

• a receiver configured to receive a first timing advance from a first base station where the first timing advance as been determined, not based on a preamble received from the user terminal, to be the same as a second timing advance, the second timing advance for determining, by a user terminal, timing for uplink signal transmission to the first base station, the first timing advance for determining, by the user terminal, timing to transmit an uplink signal to a second base station;
• and
• a transmitter configured to transmit, to the second base station, the uplink signal with a timing adjusted by the first timing advance before a handover of the user terminal from the first base station to the second base station is completed.

A base station comprising:

• a receiver configured to receive, from a user terminal, an uplink signal at a timing adjusted by the user terminal based on a first timing advance received at the user terminal from another base station, the first timing advance determined, not based on a preamble received from the user terminal, to be the same as a second timing advance determined by the another base station, the second timing advance for determining, by the user terminal, timing for uplink signal transmission to the another base station, the first timing advance for determining, by the user terminal, timing to transmit the uplink signal to the base station before completion of a handover of the user terminal from the another base station to the base station.

A method comprising:

• determining a first timing advance for uplink signal transmission timing from a user terminal to a first base station;
• transmitting a second timing advance to a user terminal, the second timing advance determined, not based on a preamble received from the user terminal, to be the same as the first timing advance, the second timing advance for determining, by the user terminal, timing for transmitting an uplink signal to a second base station before completion of a handover from the first base station to the second base station.