Diversity Transmission Method and Transmitter of a Base Station Using the Same in a Mobile Commmunication System

• US 20080214128A1
• Filed: 11/02/2005
• Published: 09/04/2008
• Est. Priority Date: 06/24/2005
• Status: Active Grant

• Current Assignee: Electronics and Telecommunications Research Institute, Hanaro Telecom., Inc., KT Corporation, Samsung Electronics Co. Ltd., SK Telecom Co., Ltd.
• Original Assignee: Electronics and Telecommunications Research Institute, Hanaro Telecom., Inc., KT Corporation, Samsung Electronics Co. Ltd., SK Telecom Co., Ltd.
• Inventors: Lim, Kwang-Jae, Yoon, Chul-Sik
• Granted Patent: US 7,941,104 B2
• Time in Patent Office: Days
• US Class Current: 455/101
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04L 1/0668 Orthogonal systems, e.g. using Alamouti codes
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

A diversity transmission method and a transmitter of a base station using the same is provided in a mobile communication system. For this purpose, the diversity transmission method for controlling power of transmit antennas when the transmitter transmits a signal to a mobile terminal using a plurality of antennas includes (a) receiving feedback information concerning the antenna having the best channel status from the mobile terminal, (b) increasing power allocation of a selected antenna according to the feedback information by a predetermined amount and decreasing power allocation of a non-selected antenna by a predetermined amount, and (c) transmitting the signal to the mobile terminal using the power allocation controlled in (b).

Claims

1. A diversity transmission method for controlling a power of transmit antennas when a transmitter of a base station transmits a signal to a mobile terminal using a plurality of antennas, comprising:

(a) receiving feedback information concerning the antenna having the best channel status from the mobile terminal;

(b) increasing power allocation of a selected antenna according to the feedback information by a predetermined amount and decreasing power allocation of a non-selected antenna by a predetermined amount; and

(c) transmitting the signal to the mobile terminal using the controlled power by the power allocation controlled in (b).

2. The diversity transmission method of claim 1, further comprising before (a), allocating the same power to the antennas.

3. The diversity transmission method of claim 1, wherein it is checked whether the mobile terminal is connected, and (a) to (c) are repeated for respective pre-determined times when the mobile terminal is connected.

4. The diversity transmission method of claim 1, wherein in (a), the feedback information has 1 bit when the transmitter uses two antennas.

5. The diversity transmission method of claim 4, wherein when the power rates for the respective antennas are respectively given as a real number β

₁ and β

₂ from 0 to 1, a transmit matrix is given as;

$\left[\begin{array}{cc}{\mathrm{\beta <br><br>}}_1<br><br>s_1& {\mathrm{\beta <br><br>}}_1<br><br>s_2\\ -{\mathrm{\beta <br><br>}}_2<br><br>s_2^{*}& {\mathrm{\beta <br><br>}}_2<br><br>s_1^{*}\end{array}\right],\mathrm{where}<br><br><br><br>{\mathrm{\beta <br><br>}}_1^2+{\mathrm{\beta <br><br>}}_2^2=1$

6. The diversity transmission method of claim 5, wherein in (b),

when a power allocation of the antenna increasing or decreasing by a pre-determined amount is given as Δ

, from 0 to 1,

when the first antenna is selected by the feedback information, the power allocation is given as

β

₁²(t)=β

₁²(t−

1)+Δ and

β

₂²(t)=β

₂²(t−

1)−

Δ

, and

when the second antenna is selected by the feedback information, the power allocation is given as

β

₁²(t)=β

₁²(t−

1)−

Δ and

β

₂²(t)=β

₂²(t−

1)+Δ

7. The diversity transmission method of claim 4, wherein

when signals received from the first antenna and the second antenna are respectively given as r₁ and r₂ and channel responses for the respective antennas are respectively given as h₁ and h₂, the mobile terminal detects data symbols as follows:

Ŝ

₁=β

₁h₁r₁+β

₂h₂r₂

Ŝ

₂=β

₂h₂r₁*+β

₁h₁*r₂

8. The diversity transmission method of claim 7, wherein when the transmission symbol energy is defined as E_S and the noise power density is defined as N₀, the signal-to-noise ratio (SNR) is calculated as follows:

$\mathrm{SNR}=\frac{E_s}{N_o}<br><br>\left({\mathrm{\beta <br><br>}}_1^2<br><br>{<br><br>h_1<br><br>}^2+{\mathrm{\beta <br><br>}}_2^2<br><br>{<br><br>h_2<br><br>}^2\right)$

9. A transmitter for controlling power of a transmit antenna when the transmitter of a base station transmits a signal to a mobile terminal using a plurality of antennas, comprising:

a feedback information checking unit for determining an antenna having the best channel status according to feedback information of the mobile terminal;

a power allocation unit for increasing power allocation of an antenna having the best channel status checked by the feedback information by a predetermined amount and decreasing power allocation of an antenna not having the best channel status checked by the feedback information by a predetermined amount; and

a power weight value controller for controlling power of the signal transmitted through the antennas according to the controlled power allocation.

10. The transmitter of claim 9, wherein the power allocation is controlled according to the received feedback information for respective predetermined times.

11. The transmitter of claim 9, wherein when a transmitter has n antennas, the power allocation unit increases the power allocation for the selected antenna by Δ

, and decreases the power allocations supplied to other antennas by

$\frac{\mathrm{\Delta <br><br>}}{n-1}$