Wireless communication method, base station and, wireless communication system

• US 20070195736A1
• Filed: 08/23/2006
• Published: 08/23/2007
• Est. Priority Date: 02/23/2006
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Fujishima, Kenzaburo, Taira, Masanori
• Granted Patent: US 7,990,942 B2
• Time in Patent Office: Days
• US Class Current: 370/335
• CPC Class Codes: H04B 7/2643 using time-division multiple access [TDMA] H04B7/2615, H04B7/2618 take precedence

Abstract

Data transmission is performed using the most suitable data rate for the radiation pattern of an antenna. Using an individual pilot channel of a first slot, a base station transmits a pilot signal in a specified direction with a beam pattern having narrow directivity. A wireless terminal located in that direction receives the pilot signal and determines a data rate according to the reception quality of the pilot signal. The wireless terminal transmits to the base station a signal requesting the determined data rate. The base station receives that signal and, based on the requested data rate, transmits data to the wireless terminal with a beam pattern in the same direction as the direction in which the pilot signal was transmitted, using a data channel of a second slot, which occurs a predetermined number of slots after the first slot.

Claims

1. A wireless communication method in which a radiation pattern is specified for each channel in a time-division manner for communication between a base station and a wireless terminal, comprising the steps of:

in a first slot that includes a common pilot channel transmitted to the wireless terminal in an omnidirectional manner or in a directional manner corresponding to a sector, an individual pilot channel transmitted with a specific beam pattern among a plurality of beam patterns, and a data channel for transmitting data to the wireless terminal with the beam pattern, the base station performing control, including synchronization, using the common pilot channel of the first slot and transmitting a pilot signal with a radiation pattern including the beam pattern in the direction in which the wireless terminal is located, using the individual pilot channel of the first slot;

the wireless terminal, located in the direction, receiving the pilot signal and determining a data rate according to the reception quality of the pilot signal;

the wireless terminal transmitting to the base station a signal for requesting the determined data rate;

the base station receiving the signal and, based on the requested data rate, transmitting data to the wireless terminal with the radiation pattern, which includes the beam pattern in the same direction as the direction in which the pilot signal was transmitted, using a data channel of a second slot which is a predetermined number of slots after the first slot.

2. A wireless communication method according to claim 1,

wherein the base station comprises a plurality of sectors;

the base station operates at the same slot timing in each sector; and

a radiation pattern formed of beam patterns each of which is used by each of sectors for transmitting the pilot signal using the individual pilot channel of the first slot and a radiation pattern formed of beam patterns each of which is used by each of sectors for transmitting the data using the data channel of the second slot are the same.

3. A wireless communication method according to claim 2 wherein the separation between the first slot and the second slot is the same in each sector.

4. A wireless communication method according to claim 1,

wherein a plurality of the base stations operate at the same slot timing;

and

a radiation pattern formed of beam patterns each of which is used by each base station for transmitting the pilot signal using the individual pilot channel of the first slot and a radiation beam pattern formed of beam patterns each of which is used by each base station for transmitting the data using the data channel of the second slot are the same.

5. A wireless communication method according to claim 4, wherein the separation between the first slot and the second slot is the same in each base station.

6. A base station for communicating with a wireless terminal by specifying a radiation pattern for each channel in a time-division manner, comprising:

an array antenna for transmitting and receiving a pilot signal and data using a radiation pattern that is specified from among radiation patterns that include one of an omnidirectional manner and a directional manner according to a sector and a beam pattern;

a scheduler for specifying the radiation pattern and a beam direction;

a reverse-link beam controller for receiving a signal or data from the wireless terminal via the array antenna;

a demodulator for demodulating the signal or data received by the reverse-link beam controller;

a modulator for modulating a signal or data to the wireless terminal; and

a forward-link beam controller for transmitting the modulated data or signal to the wireless terminal via the array antenna,

wherein

the scheduler outputs to the forward-link beam controller radiation pattern information for transmitting the pilot signal in a direction in which the wireless terminal is located, using a beam pattern;

in a first slot that includes a common pilot channel transmitted to the wireless terminal in an omnidirectional manner or in a directional manner according to a sector, an individual pilot channel transmitted using a specific beam pattern among a plurality of beam patterns, and a data channel for transmitting data to the wireless terminal using the beam pattern, the forward-link beam controller performs control, including synchronization, using the common pilot channel of the first slot and, using the individual pilot channel of the first slot, the forward-link beam controller transmits, a pilot signal using a radiation pattern including the beam pattern in the direction in which the wireless terminal is located, based on the radiation pattern information from the scheduler;

the reverse-link beam controller receives, via the array antenna, a transmitted signal for requesting data rate determined by the wireless terminal located in the direction according to the reception quality of the pilot signal;

the demodulator demodulates the received signal to obtain the requested data rate;

a predetermined period after the first slot, the scheduler re-outputs the radiation pattern information to the forward-link beam controller and outputs to the modulator the data to be transmitted to the wireless terminal and the data rate obtained in the demodulator;

the modulator modulates the data to be transmitted to the wireless terminal according to the data rate from the scheduler, using a data channel of a second slot which occurs a predetermined number of slots after the first slot, and outputs the modulated data to the forward-link beam controller; and

the forward-link beam controller transmits to the wireless terminal the data in the data channel of the second slot, which is modulated by the modulator, using the radiation pattern including the beam pattern in the same direction as the direction in which the pilot signal is transmitted, based on the radiation pattern information from the scheduler.

7. A base station according to claim 6,

wherein the base station comprises a plurality of sectors;

the base station operates at the same slot timing in each sector; and

a radiation pattern formed of beam patterns each of which is used by each of sectors for transmitting the pilot signal using the individual pilot channel of the first slot and a radiation pattern formed of beam patterns each of which is used by each of sectors for transmitting the data using the data channel of the second slot are the same.

8. A base station according to claim 7, wherein the separation between the first slot and the second slot is the same in each sector.

9. A wireless communication system comprising:

a plurality of base stations according to claim 6,

wherein the plurality of base stations operate at the same slot timing; and

a radiation pattern formed of beam patterns each of which is used by each base station for transmitting the pilot signal using the individual pilot channel of the first slot and a radiation pattern formed of beam patterns each of which is used by each base station for transmitting the data using the data channel of the second slot are the same.

10. A wireless communication system according to claim 9, wherein the separation between the first slot and the second slot is the same in each base station.