WIRELESS COMMUNICATION METHOD

• US 20070243878A1
• Filed: 02/21/2007
• Published: 10/18/2007
• Est. Priority Date: 03/23/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Fujishima, Kenzaburo, Uwano, Koki, Taira, Masanori
• Granted Patent: US 7,627,298 B2
• Time in Patent Office: Days
• US Class Current: 455/450
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04W 16/24 Cell structures
• CPC Class Codes: H04W 16/28 using beam steering

Abstract

A terminal 211 measures pilot signals transmitted in directional (beam) patterns from an adjacent cell and an own cell, and estimates reception qualities with the presence (high)/absence (low) of the interference from the adjacent cell. The terminal 211 requests data rate request values (DRC1, DRC2) corresponding to the reception qualities with the presence/absence of the interference to the base station 201. The base station 201 shares beam direction schedule with an adjacent cell base station, and confirms the presence/absence of interference to the terminal 211 for each slot. In accordance with the presence/absence of the interference, the base station 201 selects a suitable one of the two values of the data rates requested from the terminal 211, and modulates the data and transmits it.

Claims

1. A wireless communication method in which a base station and a wireless terminal communicate with each other, including:

a step at which a first and a second base station each including a plurality of beam areas transmit, for each beam area, a pilot signal including identification information to identify the base station and the beam area, in a beam pattern;

a step at which the wireless terminal receives the pilot signals for each beam area from the first and the second base station and obtains received power of each pilot signal;

a step at which the wireless terminal causes one of the beam areas of the first base station to be a desired wave beam area;

a step at which the wireless terminal determines a first data rate based on the received power of a first interference beam area where the received power of the pilot signal from the second base station is highest or where the received power is a previously determined second threshold or higher and, the received power of the pilot signal of the desired wave beam area;

a step at which the wireless terminal determines a second data rate based on the received power of a second interference beam area which is one of beam areas where the received power of the pilot signal from the second base station is lower than the received power of the pilot signal of the first interference beam area and, the received power of the pilot signal of the desired wave beam area;

a step at which the wireless terminal transmits the determined first and second data rates and the identification information of the first interference beam area to the first base station;

a step at which the first base station assigns a slot to the wireless terminal;

a step at which the first base station refers to beam scheduling information including identification information of a beam pattern to be used in each slot by the second base station, selects, in a case where the identification information of the beam area to be used by the second base station in the slot assigned at the assigning step is coincident with the identification information of the first interference beam area received from the wireless terminal, the first data rate received from the wireless terminal, and selects, in a case where the identification information of the beam area to be used by the second base station is not coincident with the identification information of the first interference beam area, the second data rate received from the wireless terminal;

a step at which the first base station modulates data in accordance with one of the selected first data rate and second data rate, and transmits modulated data to the wireless terminal; and

a step at which the wireless terminal decodes the data received from the first base station using the first and/or second data rate.

2. The wireless communication method according to claim 1, wherein

the step at which the wireless terminal determines a first data rate and the step at which the wireless terminal determines a second data rate include:

a step at which the wireless terminal obtains a power ratio of desired signal to interference signal based on the received power of the pilot signal of the desired wave beam area and one of the received power of the first and the second interference beam area; and

a step at which the wireless terminal determines the first or the second data rate according to the obtained power ratio of desired signal to interference signal.

3. The wireless communication method according to claim 1, wherein

the step at which the first base station modulates data transmits to the wireless terminal includes modulating and transmitting a flag to confirm whether the data has been normally decoded, and

the step at which the wireless terminal decodes the data includes:

a step of decoding the data and the flag received from the first base station at both the first data rate and the second data rate; and

a step of referring to the respective flags decoded at the first and the second data rates and outputting the data in which the flag is detected.

4. The wireless communication method according to claim 1, wherein

the second interference beam area is the beam area where with respect to the pilot signal from the second base station, the received power of the pilot signal is large next to the received power of the pilot signal of the first interference beam area.

5. The wireless communication method according to claim 1, wherein

the second interference beam area is the beam area where with respect to the pilot signal from the second base station, the received power of the pilot signal is minimum within a range of a previously determined third threshold or more.

6. The wireless communication method according to claim 1, wherein

the second interference beam area is the beam area of the second base station and, is the beam area where the received power of the pilot signal is minimum in a plurality of beam areas each having a specified angle or less from the first interference beam area.