Apparatus for effectively transmitting in orthogonal frequency division multiple access using multiple antenna and method thereof

• US 20070171811A1
• Filed: 10/24/2006
• Published: 07/26/2007
• Est. Priority Date: 10/24/2005
• Status: Abandoned Application

• 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: Kwon, Dong-Seung, Lee, Yu-Ro
• Application Number:
  US11/585,481
• Publication Number:
  US 20070171811A1
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04B 7/068 using space frequency diversity space-frequency coding H04L1/0606
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only

Abstract

The present invention relates to a transmitting apparatus of an OFDMA system and a method thereof. The transmitting apparatus includes an encoder for modulating data to be transmitted into data or a preamble by using a desired modulation scheme; an S/P converter for converting serial data output from the encoder to parallel data; a preamble or pilot generator for generating a pilot or preamble; a multiplexer for multiplexing the data or preamble output from the preamble or pilot generator and the parallel data; an antenna selection controller for dividing an entire band of a signal output from the multiplexer into groups formed of neighboring symbols in time domain and neighboring subcarriers in frequency domain, and selecting a transmit antenna for each group; an IFFT unit for turning off subcarriers in groups selected by the antenna selection controller and subcarriers in unselected groups by the antenna selection controller and performing IFFT; for each antenna, a P/S converter for converting parallel signals transmitted from the IFFT unit into serial signals and inserting a cyclic prefix; and for each antenna, a D/A converter and filter for converting a digital signal transmitted from the P/S into an analog signal and filtering the analog signal, and transmitting the filtered analog signal through an antenna of an R/F end. Accordingly, when a transmitting end does not know a channel state of a transmit antenna, a transmit antenna is selected for an allocation unit and data is transmitted through the selected transmit antenna when a transmitting end of an OFDMA system using multiple antennas does not know a channel state, and accordingly a diversity gain can be acquired without making any changes in allocation of subcarriers according to the number of antennas, a transmission structure of a pilot of the transmitting end, an allocation structure of the transmitting end, and a receiving end. In addition, when the transmitting end does know the channel state, an antenna having the best channel state is selected for each group, and accordingly, performance degradation due to feedback delay of channel state information and inter-antenna interference due to an increase of mobility of the terminal can be prevented.

Claims

1. A transmitting apparatus of an orthogonal frequency division multiplexing access (OFDMA) system using multiple antennas, the transmitting apparatus comprising:

an encoder for receiving data and modulating data or a preamble according to a desired modulation scheme;

an serial to parallel (S/P) converter for converting serial data output by the encoder to parallel data;

a preamble or pilot generator for generating a pilot or a preamble signal;

a multiplexer for multiplexing the data or preamble output by the preamble or pilot generator and the parallel data;

an antenna selection controller for dividing an entire band of a signal output from the multiplexer into groups, each formed of neighboring symbols in the time domain and neighboring subcarriers in the frequency domain, and selecting a transmit antenna for each group;

an IFFT unit for turning off subcarriers in groups selected by the antenna selection controller and subcarriers in unselected groups by the antenna selection controller and performing inverse fast Fourier transform (IFFT);

for each antenna, a parallel to serial (P/S) converter for converting parallel signals transmitted by the IFFT unit into serial signals, and inserting a cyclic prefix therein; and

for each antenna, a digital to analog (D/A) converter and filter for converting a digital signal transmitted from the P/S converter into an analog signal and filtering the analog signal, and transmitting the filtered analog signal through an antenna of an R/F end.

2. The transmitting apparatus of claim 1, wherein, when a channel state is not known, the antenna selection controller divides the entire band of the signal into groups, each formed of neighboring symbols and neighboring subcarriers, and selects a transmit antenna by sequentially performing k mod M on allocated groups and transmits the groups (where n denotes the number of groups in a symbol domain, k denotes the k-th group, and M denotes the number of transmit antennas).

3. The transmitting apparatus of claim 1, wherein, when the channel state is not known, the antenna selection controller extends an antenna selection scheme for each group to the symbol domain, and selects a transmit antenna by using (k+n) mod M and transmits the groups.

4. The transmitting apparatus of claim 1, wherein, when the channel state is not known and the antenna selection scheme for each group is extended to the symbol and frequency domains and cyclic rotation is performed on K allocated groups among P groups in the frequency domain, the antenna selection controller selects a transmit antenna by using (k′

+n) mod M when k′

=(k+n) mod P (where n denotes a group number in the symbol domain, and k′

denotes a number of k moved by n).

5. The transmitting apparatus of claim 4, wherein k′

=(k+b_n) mod P according to an offset b_n for moving the k-th group by n, and the antenna selection controller determines a transmit antenna for transmitting the (n,k′

)-th group by using (k′

+n) mod M.

6. The transmitting apparatus of claim 1, wherein, when the channel state is known, the antenna selection controller selects a transmit antenna a_k having the maximum channel power

$$

h k a k 

= max ⁡

( 

h k 0 

, 

h k 1 

, …

⁢

 

, 

h k M - 1 

)

for the k-th group in the transmitting end among multiple transmit antennas, and performs transmission.

7. The transmitting apparatus of claim 1 or claim 6, wherein, when the channel state is known, the antenna selection controller selects an antenna a_k having the maximum channel power for each group so as to guarantee performance in a middle and low speed environment, determines an average

${}^{}$

h 

2 = 1 K ⁢

∑

k = 0 K - 1 ⁢

( h k a k * ( h k a k ) * )

of a sum

${<br><br>h_k^{a_k}<br><br>}^2=\max <br><br>\left({<br><br>h_k^0<br><br>}^2,{<br><br>h_k^1<br><br>}^2,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},{<br><br>h_k^{M-1}<br><br>}^2\right)$

of a channel power of a transmit antenna selected for each group and a weight

$w_k^{a_k}=\frac{{\left(h_k^{a_k}\right)}^{*}}{<br><br>h<br><br>}$

of a transmission signal of each group, multiplies data to be transmitted through the selected transmit antenna a_k of each group by a weight of each transmission signal, and then transmits the multiplication result, the transmit antenna a_k being given as one of 0, 1, 2, and M−

1.

8. A transmission method of an orthogonal frequency division multiplexing access (OFDMA) system using multiple antennas, the transmission method comprising:

(a) modulating data or a preamble to be transmitted according to a predetermined modulation method;

(b) converting serially received modulated data into parallel data;

(c) generating a preamble and a pilot;

(d) multiplexing the preamble or pilot and the parallel data;

(e) dividing an entire band into groups, each formed of neighboring symbols in the time domain and neighboring subcarriers in the frequency domain, and selecting a transmit antenna for each group;

(f) for each transmit antenna, turning off subcarriers in groups selected by an antenna selection controller and subcarriers in groups unselected by the antenna selection controller and performing IFFT;

(g) for each transmit antenna, converting a parallel signal transmitted from an IFFT unit into a serial signal and inserting a cyclic prefix to the signal; and

(h) for each transmit antenna, converting and filtering a digital serial signal into an analog signal, and transmitting the analog signal through an antenna of an RF end.

9. The transmission method of claim 8, wherein, when a channel state is known, the selecting of the transmit antenna for each group comprises selecting a transmit antenna a_k having the maximum channel power

$$

h k a k 

= max ⁡

( 

h k 0 

, 

h k 1 

, …

⁢

 

, 

h k M - 1 

)

for the k-th group in a transmitting end among transmit antennas and performing transmission so as to prevent degradation of performance in an environment with high mobility and a large channel feedback delay.

10. The transmission method of claim 8 or claim 9, wherein, when a channel state is known, the selecting of the transmit antenna for each group comprises selecting an antenna a_k having the maximum channel power for each group so as to guarantee performance in a middle and low speed environment, determining an average

${}^{}$

h 

2 = 1 K ⁢

∑

k = 0 K - 1 ⁢

( h k a k * ( h k a k ) * )

of a sum

${<br><br>h_k^{a_k}<br><br>}^2=\max <br><br>\left({<br><br>h_k^0<br><br>}^2,{<br><br>h_k^1<br><br>}^2,\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>},{<br><br>h_k^{M-1}<br><br>}^2\right)$

of a channel power of a transmit antenna selected for each group and a weight

$w_k^{a_k}=\frac{{\left(h_k^{a_k}\right)}^{*}}{<br><br>h<br><br>}$

of a transmission signal to of each group, multiplying data to be transmitted through the transmit antenna selected for each group by the weight of each transmission signal, and transmitting the multiplication result, the transmit antenna a_k being given as one of 0, 1, 2, and M−

1.