Base station, mobile terminal, and communications method

• US 20090154378A1
• Filed: 09/25/2008
• Published: 06/18/2009
• Est. Priority Date: 12/18/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Sato, Naoto
• Granted Patent: US 7,978,660 B2
• Time in Patent Office: Days
• US Class Current: 370/280
• CPC Class Codes: H04W 74/002 Transmission of channel access control information
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access
• CPC Class Codes: H04W 74/0866 using a dedicated channel for access

Abstract

A base station, to which Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access is applied, communicates with a mobile terminal according to Time Division Duplex, in which a transmission frame includes a downlink subframe and an uplink subframe. The base station includes multiple antennas; a radio communications part configured to transmit the downlink subframe through a first one of the antennas and to receive an initial ranging code transmitted by the mobile terminal through a second one of the antennas during the transmission of the downlink subframe; and a ranging processing part configured to perform ranging based on the initial ranging code received by the radio communications part.

Claims

1. A base station to which Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access is applied, the base station communicating with a mobile terminal according to Time Division Duplex, wherein a transmission frame in Time Division Duplex includes a downlink subframe and an uplink subframe, the base station comprising:

a plurality of antennas;

a radio communications part configured to transmit the downlink subframe through a first one of the antennas and to receive an initial ranging code transmitted by the mobile terminal through a second one of the antennas during the transmission of the downlink subframe; and

a ranging processing part configured to perform ranging based on the initial ranging code received by the radio communications part.

2. The base station as claimed in claim 1, wherein the radio communications part is configured to receive the initial ranging code transmitted by the mobile terminal in a predetermined ranging region.

3. The base station as claimed in claim 2, wherein the predetermined ranging region is a region other than a preamble in symbols for transmitting information common to the mobile terminal and another mobile terminal.

4. The base station as claimed in claim 3, wherein the predetermined ranging region is adjacent to a frame control header.

5. A mobile terminal to which Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access is applied, the mobile terminal communicating with a base station according to Time Division Duplex, wherein a transmission frame in Time Division Duplex includes a downlink subframe and an uplink subframe, the mobile terminal comprising:

a plurality of antennas; and

a radio communications part configured to receive the downlink subframe through a first one of the antennas and to transmit an initial ranging code through a second one of the antennas during the reception of the downlink subframe.

6. The mobile terminal as claimed in claim 5, wherein the radio communications part is configured to transmit the initial ranging code using a ranging region predetermined in the downlink subframe.

7. The mobile terminal as claimed in claim 6, wherein the radio communications part is configured to retransmit the initial ranging code using the ranging region in response to no reception of a response to the initial ranging code.

8. The mobile terminal as claimed in claim 6, wherein the radio communications part is configured to, in a case of being informed of a configuration of the frame based on the downlink subframe, retransmit the initial ranging code using a ranging region determined by the configuration of the frame in response to receiving no response to the initial ranging code.

9. The mobile terminal as claimed in claim 5, wherein the initial ranging code is selected from one or more ranging codes predetermined for initial ranging codes.

10. A method of performing communications according to Time Division Duplex, to which method Orthogonal Frequency Division Multiplexing/Orthogonal Frequency Division Multiple Access is applied, wherein a transmission frame in Time Division Duplex includes a downlink subframe and an uplink subframe, the method comprising:

(a) a base station transmitting the downlink subframe through a first one of first antennas thereof;

(b) a mobile terminal receiving the downlink subframe through a first one of second antennas thereof;

(c) the mobile terminal transmitting an initial ranging code through a second one of the second antennas thereof;

(d) the base station receiving the initial ranging code transmitted by the mobile terminal through a second one of the first antennas thereof during the transmission of the downlink subframe; and

(e) the base station performing ranging based on the initial ranging code received in said step (d).