OFDM signal transmission method and apparatus

• US 7,742,533 B2
• Filed: 03/10/2005
• Issued: 06/22/2010
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: Palmira Wireless AG
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Egashira, Yoshimasa, Seto, Ichiro, Takeda, Daisuke, Sakata, Ren, Aoki, Tsuguhide, Toyoda, Takehiko
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Ghulamali; Qutbuddin
• Application Number:
  US11/076,051
• Publication Number:
  US 20050201268A1
• Time in Patent Office: 1,930 Days
• Field of Search: 375/260, 375/261, 375/267, 375/326, 375/344
• US Class Current: 375/260
• CPC Class Codes: H04B 7/06 at the transmitting station
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/08 at the receiving station
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04J 11/0036 at the receiver
• CPC Class Codes: H04L 1/1829 Arrangements specially adapted for the receiver end
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2626 Arrangements specific to the transmitter only
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]

Abstract

An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus which transmits OFDM signals by using a plurality of transmission antennas includes a subcarrier setting device which sets signals for subcarriers so as to use some of the subcarriers of the OFDM signals as pilot subcarriers to transmit pilot signals and use the remaining subcarriers as data subcarriers to transmit data signals, the subcarrier setting device changing polarities of signals for the pilot subcarriers for each transmission antenna.

Claims

1. An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus for transmitting OFDM signals by using at least a first antenna and a second antenna, comprising:

a subcarrier setting device configured to set some of subcarriers of the OFDM signals to pilot subcarriers for transmitting pilot signals, and remaining subcarriers thereof to data subcarriers for transmitting data signals,

wherein the pilot signals to be transmitted include first pilot signals and second pilot signals, the first pilot signals to be transmitted by using a first pilot subcarrier of the pilot subcarriers have first polarities represented by first polarity data, the second pilot signals to be transmitted using a second pilot subcarrier of the pilot subcarriers have second polarities represented by second polarity data, the first polarities being different from the second polarities, the first polarity data corresponds to a first polarity pattern of a plurality of polarity patterns, the second polarity data is different from the first polarity data, the first pilot signals are generated by using a product of a sequence and the first polarity data, and the second pilot signals are generated by using a product of the sequence and the second polarity data, and

a transmitter for transmitting the first and second pilot signals to be transmitted using the first antenna and the second antenna in such a way that first ones of the first and second pilot signals which are transmitted by the first antenna and second ones of the first and second pilot signals which are transmitted by the second antenna have different polarities.

2. An apparatus according to claim 1, wherein the subcarrier setting device comprises a sequence generator which generates the sequence, a first memory which stores the first polarity data, a second memory which stores the second polarity data, a first multiplying unit which multiplies the sequence by the first polarity data to generate the first pilot signals, and a second multiplying unit which multiplies the sequence by the second polarity data to generate the second pilot signals.

3. An apparatus according to claim 2, wherein the subcarrier setting device comprises a subcarrier pattern controller which changes the first polarity pattern and a second polarity pattern different from the first polarity pattern when the data signals are a retransmission packet, and the second polarity data corresponds to the second polarity pattern.

4. An apparatus according to claim 2, wherein the first pilot signals are generated on the basis of a first sequence, and the second pilot signals are generated on the basis of a second sequence different from the first sequence.

5. An apparatus according to claim 1, wherein the data signals to be transmitted by the OFDM signal transmission apparatus are packetized in a plurality of packets, and the subcarrier setting device comprises a subcarrier pattern controller which changes the first polarity pattern and a second polarity pattern different from the first polarity pattern for each of the packets of the data signals, the second polarity data corresponding to the second polarity pattern.

6. An apparatus according to claim 1, wherein a first polarity of one of the pilot signals transmitted using one subcarrier and the first antenna is different from a second polarity of one of the pilot signals transmitted using the one subcarrier and the second antenna.

7. An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus for transmitting OFDM signals by using at least a first antenna and a second antenna, comprising:

a subcarrier setting device configure to set some of subcarriers of the OFDM signals to a plurality of pilot subcarriers for transmitting pilot signals, and remaining subcarriers thereof to data subcarriers for transmitting data signals,

the subcarrier setting device comprising a first sequence generator which generates a first sequence used for generating first pilot signals, and a second sequence generator which generates a second sequence used for generating second pilot signals, the first sequence and the second sequence differing between the first and the second pilot signals,

wherein the first sequence generator is configured to generate the first sequence for each of the first pilot signals, and the second sequence generator is configured to generate the second sequence for each of the second pilot signals, the pilot signals to be transmitted include the first pilot signals and the second pilot signals, the first pilot signals to be transmitted by using a first pilot subcarrier of the pilot subcarriers have first polarities represented by first polarity data, the second pilot signals to be transmitted using a second pilot subcarrier of the pilot subcarriers have second polarities represented by second polarity data, the first polarities being different from the second polarities, the first polarity data corresponds to a first polarity pattern of a plurality of polarity patterns, the second polarity data is different from the first polarity data, the first pilot signals are generated by using a product of the first sequence and the first polarity data, and the second pilot signals are generated by using a product of the second sequence and the second polarity data, and

a transmitter for transmitting the first and second pilot signals to be transmitted using the first antenna and the second antenna in such a way that first ones of the first and second pilot signals which are transmitted by the first antenna and second ones of the first and second pilot signals which are transmitted by the second antenna have different polarities.

8. An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus for transmitting OFDM signals by using at least a first antenna and a second antenna, comprising:

a subcarrier setting device configure to set some of subcarriers of the OFDM signals to a plurality of pilot subcarriers for transmitting pilot signals, and remaining subcarriers thereof to data subcarriers for transmitting data signals,

the subcarrier setting device comprising a first sequence generator which generates a first sequence used for generating first pilot signals, and a second sequence generator which generates a second sequence used for generating second pilot signals, the first sequence and the second sequence differing between the first and the second pilot signals,

wherein the first sequence generator is configured to generate a single first sequence having a value corresponding to each of the plurality of first pilot signals, and the second sequence generator is configured to generate a single second sequence having a value corresponding to each of the plurality of second pilot signals, the pilot signals to be transmitted include the first pilot signals and the second pilot signals, the first pilot signals to be transmitted by using a first pilot subcarrier of the pilot subcarriers have first polarities represented by first polarity data, the second pilot signals to be transmitted using a second pilot subcarrier of the pilot subcarriers have second polarities represented by second polarity data, the first polarities being different from the second polarities, the first polarity data corresponds to a first polarity pattern of a plurality of polarity patterns, the second polarity data is different from the first polarity data, the first pilot signals are generated by using a product of the first sequence and the first polarity data, and the second pilot signals are generated by using a product of the second sequence and the second polarity data, and

a transmitter for transmitting the first and second pilot signals to be transmitted using the first antenna and the second antenna in such a way that first ones of the first and second pilot signals which are transmitted by the first antenna and second ones of the first and second pilot signals which are transmitted by the second antenna have different polarities.

9. An orthogonal frequency division multiplexing (OFDM) signal transmission method of transmitting OFDM signals having a plurality of subcarriers orthogonal to each other by using a plurality of transmission antennas, comprising:

processing for transmitting the OFDM signals by using some of the plurality of subcarriers as pilot subcarriers for transmitting pilot signals and remaining subcarriers of the plurality of subcarriers as data subcarriers for transmitting data signals, the pilot subcarrier having a polarity given by

$\begin{array}{cc}{S}_k<br><br>\left(i\right)=\exp <br><br>\left(\frac{\mathrm{j\pi <br><br>}}{2}<br><br>\left(k-1\right)<br><br>i\right)<br><br><br><br>\mathrm{or}& \left(I\right)\\ S_k<br><br>\left(i\right)=-\exp <br><br>\left(\frac{\mathrm{j\pi <br><br>}}{2}<br><br>\left(k-1\right)<br><br>i\right)& \left(\mathrm{II}\right)\end{array}$

where s_k(i) represents each of the pilot subcarriers, j represents an imaginary unit, i represents a number of each of the pilot subcarriers, and k is an antenna number of each of the transmission antennas,

wherein, a pilot subcarrier of the pilot subcarriers that has a highest frequency has the polarity given by the equation (II), and the remaining pilot subcarriers have the polarity given by the equation (I).

10. An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus for transmitting OFDM signals by using at least a first antenna and a second antenna, comprising:

a subcarrier setting device configured to set some of subcarriers of the OFDM signals to pilot subcarriers for transmitting pilot signals, and remaining subcarriers thereof to data subcarriers for transmitting a data signal, and

a beam forming device which has a first mode to form a plurality of transmission beams in accordance with a channel response to an OFDM signal reception apparatus and a second mode to form the transmission beams regardless of the channel response, forms the transmission beams for the pilot subcarriers and data subcarriers in the first mode, and forms the transmission beams for only the data subcarriers in the second mode,

wherein the pilot signals to be transmitted include first pilot signals and second pilot signals, the first pilot signals to be transmitted by using a first pilot subcarrier of the pilot subcarriers have first polarities represented by first polarity data, the second pilot signals to be transmitted using a second pilot subcarrier of the pilot subcarriers have second polarities represented by second polarity data, the first polarities being different from the second polarities, the first polarity data corresponds to a first polarity pattern of a plurality of polarity patterns, the second polarity data is different from the first polarity data, the first pilot signals are generated by using a product of a sequence and the first polarity data, and the second pilot signals are generated by using a product of the sequence and the second polarity data, and

a transmitter for transmitting the first and second pilot signals to be transmitted using the first antenna and the second antenna in such a way that first ones of the first and second pilot signals which are transmitted by the first antenna and second ones of the first and second pilot signals which are transmitted by the second antenna have different polarities.

11. An apparatus according to claim 10, wherein for the pilot subcarriers, the beam forming device multiplies an input matrix representing the pilot subcarriers by a beam forming matrix for formation of the transmission beams in the first mode and multiplies the input matrix by an identify matrix in the second mode.

12. An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus which transmits OFDM signals by using a first transmission antenna, a second transmission antenna and a third transmission antenna, comprising:

a subcarrier setting device configured to set some of subcarriers of the OFDM signals to pilot subcarriers for transmitting pilot signals, and remaining subcarriers thereof to data subcarriers for transmitting a data signal,

wherein

(a) the subcarrier setting device causes a first pilot signal carried by pilot subcarriers of a first frequency to set a phase difference of 0°

between a first component of the first pilot signal transmitted through the first transmission antenna, and a second component of the first pilot signal transmitted through the second transmission antenna;

(b) the subcarrier setting device causes a second pilot signal carried by pilot subcarriers of a second frequency to set a phase difference of 180°

between a first component of the second pilot signal transmitted through the first transmission antenna, and a second component of the second pilot signal transmitted through the second transmission antenna;

(c) the subcarrier setting device causes a third pilot signal carried by pilot subcarriers of a third frequency to set the phase difference of 0°

between a first component of the third pilot signal transmitted through the first transmission antenna, and a second component of the third pilot signal transmitted through the second transmission antenna; and

(d) the subcarrier setting device causes a fourth pilot signal carried by pilot subcarriers of a fourth frequency to set the phase difference of 180°

between a first component of the fourth pilot signal transmitted through the first transmission antenna, and a second component of the fourth pilot signal transmitted through the second transmission antenna.

13. An orthogonal frequency division multiplexing (OFDM) signal transmission apparatus which transmits OFDM signals by using a plurality of transmission antennas, comprising:

a subcarrier setting device configured to set some of subcarriers of the OFDM signals to pilot subcarriers for transmitting pilot signals, and remaining subcarriers thereof to data subcarriers for transmitting a data signal,

wherein;

(a) the subcarrier setting device causes a first pilot signal carried by pilot subcarriers of a first frequency to set a phase difference of 0°

between a first component of the first pilot signal transmitted through a first transmission antenna and a second component of the first pilot signal transmitted through a second transmission antenna, and to set a phase difference of 180°

between the second component of the first pilot signal transmitted through the second transmission antenna and a third component of the first pilot signal transmitted through a third transmission antenna;

(b) the subcarrier setting device causes a second pilot signal carried by pilot subcarriers of a second frequency to set the phase difference of 180°

between a first component of the second pilot signal transmitted through the first transmission antenna and a second component of the second pilot signal transmitted through the second transmission antenna, and also between the second component of the second pilot signal transmitted through the second transmission antenna and a third component of the second pilot signal transmitted through the third transmission antenna;

(c) the subcarrier setting device causes a third pilot signal carried by pilot subcarriers of a third frequency to set the phase difference of 180°

between a first component of the third pilot signal transmitted through the first transmission antenna and a second component of the third pilot signal transmitted through the second transmission antenna, and to set the phase difference of 0°

between the second component of the third pilot signal transmitted through the second transmission antenna and a third component of the third pilot signal transmitted through the third transmission antenna; and

(d) the subcarrier setting device causes a fourth pilot signal carried by pilot subcarriers of a fourth frequency to set the phase difference of 0°

between a first component of the fourth pilot signal transmitted through the first transmission antenna and a second component of the fourth pilot signal transmitted through the second transmission antenna, and also between the second component of the fourth pilot signal transmitted through the second transmission antenna and a third component of the fourth pilot signal transmitted through the third transmission antenna.